Studies Relating to Collagen Cross-Linking Therapy
Caporossi, A., S. Baiocchi, et al. (2006). "Parasurgical therapy for keratoconus by riboflavin-ultraviolet type A rays induced cross-linking of corneal collagen: preliminary refractive results in an Italian study." J Cataract Refract Surg 32(5): 837-45.
PURPOSE: To assess the effectiveness of riboflavin-ultraviolet type A rays induced cross-linking of corneal collagen in reducing progression of keratoconus and in improving visual acuity in patients with progressive keratoconus. SETTING: Department of Ophthalmology, Siena University, Siena, Italy. METHODS: This was a second-phase prospective nonrandomized open study. Starting in September 2004, 10 eyes of 10 patients (mean age 31.4 years) with bilateral keratoconus were treated by combined riboflavin-ultraviolet type A rays (UVA) collagen cross-linking. Radiant energy was 3 mW/cm2 or 5.4 joule/cm2 for a 30-minute exposure at 1 cm from the corneal apex. A complete ophthalmologic examination (uncorrected visual acuity [UCVA], sphere spectacles corrected visual acuity (SSCVA), best spectacle-corrected visual acuity [BSCVA]) was performed. Patients had corneal computerized topographic examination, linear scan optical tomography, endothelial cell count, ultrasound pachometry, intraocular pressure (IOP) evaluation, and HRT II system confocal microscopy at 1, 2, 3, and 6 months. After treatment, eyes were medicated and dressed with a soft contact lens. RESULTS: Comparative preoperative and postoperative results showed increases of 3.6 lines for UCVA (P = .0000112), 1.85 lines for SSCVA (P = .00065), and 1.66 lines for BSCVA (P = .00071). Topographic analysis showed a mean K reduction of 2.1 +/- 0.13 diopters (D) in the central 3.0 mm. Statistical analysis of IOP and endothelial cell count did not show significant differences. Topo-aberrometric analysis findings of corneal symmetry showed a trend toward increasing corneal symmetry with a major reduction in asymmetry between vertical hemimeridians. CONCLUSIONS: Refractive results showed a reduction of about 2.5 D in the mean spherical equivalent, topographically confirmed by the reduction in mean K. Results of surface aberrometric analysis showed improvement in morphologic symmetry with a significant reduction in comatic aberrations.
Mazzotta, C., C. Traversi, et al. (2006). "Conservative treatment of keratoconus by riboflavin-uva-induced cross-linking of corneal collagen: qualitative investigation." Eur J Ophthalmol 16(4): 530-5.
PURPOSE: To assess corneal tissue modifications after riboflavin-UVA-induced cross-linking of corneal collagen in patients with progressive keratoconus as well as regeneration of epithelium and subepithelial nerve plexus by in vivo HRT II system confocal microscopy in humans. METHODS: Ten patients with progressive keratoconus were treated by riboflavin-UVA-induced cross-linking of corneal collagen, involving assessment of ultrastructural modifications of the corneal epithelium and subepithelial nerve plexus by HRT II system confocal microscopy. Treatment included instillation of 0.1% riboflavin-20% dextrane solution 5 minutes before UVA irradiation and every 5 minutes for a total of 30 minutes. Radiant energy was 3 mW/cm 2 or 5.4 Joule/cm 2 and the source was dual UVA (370 nm) light-emitting LED. The protocol included the operation followed by antibiotic medication and eye dressing with a soft therapeutic contact lens. Changes in epithelium and subepithelial and stromal nerve plexus were assessed by HRT II system confocal microscopy in vivo. RESULTS: After 5 days of soft contact lens wearing, corneal epithelium has a regular morphology and density. Disappearance of subepithelial stromal nerve fibers was observed in the central irradiated area where, 1 month after the operation, initial reinnervation was microscopically observed. No changes in nerve fibers were observed in the peripheral untreated with a clear lateral transition between the two areas. Six months after the operation, the anterior subepithelial stroma was recolonized by nerve fibers with restoration of corneal sensitivity. CONCLUSIONS: HRT II system confocal microscopy confirms corneal epithelium restore and re-innervation after riboflavin-UVA-induced collagen cross-linking directly in vivo in humans.
Randleman, J. B. (2006). "Post-laser in-situ keratomileusis ectasia: current understanding and future directions." Curr Opin Ophthalmol 17(4): 406-12.
PURPOSE OF REVIEW: The aim of this article is to review the causes, risk factors, management, and future research directions for corneal ectasia after laser in situ keratomileusis. RECENT FINDINGS: Complex corneal biomechanical processes influence the integrity of the normal and postoperative cornea, and developing an understanding of these processes facilitates recognition of risk factors for ectasia after laser in-situ keratomileusis. Currently identified risk factors include keratoconus, high myopia, low residual stromal bed thickness from excessive ablation or thick flap creation, and defined topographic abnormalities such as forme fruste keratoconus and pellucid marginal corneal degeneration. Ectasia can also rarely occur in patients without currently identifiable risk factors, and future identification of at-risk patients may be facilitated by corneal interferometry and corneal hysteresis measurements. Utilization of intraoperative pachymetry measurements at the time of surgery and confocal microscopy prior to enhancement to measure residual stromal bed thickness should avoid unanticipated low residual stromal bed thickness. Management options for ectasia after laser in situ keratomileusis include intraocular pressure reduction, rigid gas permeable contact lenses, and intracorneal ring segments, in addition to corneal transplantation. In the future, collagen cross-linking may reduce corneal steepening and improve refractive error. SUMMARY: When ectasia develops, early recognition and proper management are essential to prevent progression, to promote visual rehabilitation, and to reduce the need for corneal transplantation for these patients.
Seiler, T. and F. Hafezi (2006). "Corneal cross-linking-induced stromal demarcation line." Cornea 25(9): 1057-9.
PURPOSE:: Corneal collagen cross-linking by UVA/riboflavin (X-linking) represents a new method for the treatment of progressive keratoconus and currently is under clinical study. To avoid UVA irradiation damage to the corneal endothelium, the parameters for X-linking are set in a way that effective treatment occurs only in the first 300 mum of the corneal stroma. Here, X-linking not only strengthens the biomechanical properties of the cornea but also induces keratocyte apoptosis. To date, the effectiveness of treatment could be monitored only indirectly by postoperative follow-up corneal topographies or using corneal confocal microscopy. Here we describe a corneal stromal demarcation line indicating the transition zone between cross-linked anterior corneal stroma and untreated posterior corneal stroma. The demarcation line is biomicroscopically detectable in slit-lamp examination as early as 2 weeks after treatment. METHODS:: X-linking was performed in 16 cases of progressive keratoconus, and corneas were examined biomicroscopically and by means of corneal topography and pachymetry before and after treatment. RESULTS:: In 14 of 16 cases, a thin stromal demarcation line was visible at a depth of approximately 300 mum over the whole cornea after X-linking treatment. CONCLUSION:: This newly observed demarcation line may result from differences in the refractive index and/or reflection properties of untreated versus X-linked corneal stroma and represents an effective tool to biomicroscopically easily monitor the depth of effective X-linking treatment in keratoconus.
Spoerl, E., G. Wollensak, et al. (2004). "Thermomechanical behavior of collagen-cross-linked porcine cornea." Ophthalmologica 218(2): 136-40.
PURPOSE: Collagen cross-linking using combined riboflavin/UVA treatment has been shown to increase the biomechanical rigidity of the cornea and has been used successfully for the treatment of progressive keratoconus. From morphological and biochemical investigations, a different degree of cross-linking for the anterior and posterior stroma by the treatment is suggested. The present study was undertaken to better evaluate this effect by testing the thermomechanical behavior. METHODS: Ten 10 x 5 mm corneal strips from porcine cadaver eyes enucleated within 5 h post mortem were cross-linked using the photosensitizer riboflavin and UVA irradiation (370 nm, irradiance = 3 mW/cm(2)) for 30 min and compared to ten untreated corneal strips and ten corneal strips cross-linked with 0.1% glutaraldehyde. The temperature in a water bath was raised from 60 to 95 degrees C with temperature increments of 1 degrees C per minute. The hydrothermal shrinkage of the corneal strips was measured in 2.5 degrees C steps using a micrometer. In addition, six 10-mm whole corneal buttons were cross-linked with riboflavin/UVA and immersed into water at 70 or 75 degrees C. RESULTS: The maximal hydrothermal shrinkage for the untreated control specimens and the posterior portion of the riboflavin/UVA-treated corneas was at 70 degrees C, for the anterior portion of the cornea cross-linked by riboflavin/UVA at 75 degrees C and for glutaraldehyde-cross-linked cornea at 90 degrees C. In the cross-linked corneal buttons, a typical mushroom-like shape was observed at 70 degrees C and a cylinder shape at 75 degrees C. CONCLUSIONS: The different degree of collagen cross-linking in the corneal stroma after riboflavin/UVA treatment is reflected by the differences in the maximal shrinkage temperature of the anterior and posterior portion. Therefore, in the corneas cross-linked with riboflavin/UVA a higher shrinkage temperature was observed for the anterior portion of the cornea (75 degrees C) compared to the posterior stroma (70 degrees C) due to the higher degree of cross-linking of the anterior stroma. The anterior localization of the cross-linking effect is advantageous for the endothelium and for the preservation of the anterior corneal curvature. Copyright 2004 S. Karger AG, Basel
Wollensak, G., E. Spörl, et al. (2003). "Behandlung von Keratokonus durch Kollagenvernetzung." Ophthalmologe 100(1): 44-9.
BACKGROUND: We were able to show a significant increase in corneal stiffness of rabbit and porcine eyes after combined riboflavin/UVA-induced collagen cross-linking. In this study,we tried to treat keratoconus patients with this method to stop the progression of corneal ectasia. PATIENTS AND METHODS: We treated 16 eyes of 15 patients with progressive keratoconus and mostly moderate keratectasia (48-56 dpt).After removal of the epithelium (7 mm X), riboflavin solution was applied on the cornea, which was irradiated with UVA (370 nm,3 mW/cm(2)) at a distance of 1 cm for 30 min.Post-operative follow-up controls were conducted every 3 months in the first year and then every 6 months, always including visual acuity testing, corneal topography and measurements of endothelial cell density.The follow-up time was between 1 and 3 years. RESULTS: Progression of keratectasia was stopped in all patients.Best corrected visual acuity and the maximal keratometry values improved slightly in about 50% of the cases. In all patients corneal transparency, the degree of keratectasia registered by corneal topography and the density of endothelial cells remained unchanged within the follow-up time.No negative side-effects were observed. CONCLUSIONS: Our results show that collagen cross linking might be a useful conservative treatment modality to stop the progression of keratoconus.By this means the need for keratoplasty might be significantly reduced.Given the simplicity of the technique and minimal costs of the treatment it might also be well suited for developing countries.Further studies are envisaged to exclude long-term side effects and to evaluate the long term durability of the mechanical stiffness effect.
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Contact Lens Research
Dominguez, C. E., A. Shah, et al. (2005). "Bitoric gas-permeable contact lens application in pellucid marginal corneal degeneration." Eye Contact Lens 31(5): 241-3.
PURPOSE: To evaluate the authors' experience fitting patients with pellucid marginal corneal degeneration (PMCD) with bitoric gas-permeable contact lenses. METHODS: The records of 11 patients with a confirmed diagnosis of PMCD were retrospectively reviewed. The numbers of diagnostic contact lenses at the first visit, office visits, and lenses ordered to complete the fitting; uncorrected, spectacle-corrected, and contact lens-corrected Snellen visual acuities; contact lens success or failure; and complications encountered were all assessed. These data were compared to historic data for patients with other corneal irregularities (keratoconus, penetrating keratoplasty, and refractive surgery). RESULTS: The mean number of diagnostic contact lenses used at the first visit was 1.09 +/- 0.302, and the number of lenses ordered to complete the fitting was 1.82 +/- 1.33. The number of visits during 4 months was 6.18 +/- 2.14. Uncorrected visual acuity (logMAR) was 0.957 +/- 0.398 (20/181 in Snellen); the best-corrected spectacle visual acuity (logMAR) was 0.231 +/- 0.309 (20/34 in Snellen); and the best contact lens-corrected visual acuity (logMAR) was 0.0424 +/- 0.06275 (20/22 in Snellen). Corrected vision in eyes with PMCD improved approximately two lines with bitoric gas-permeable contact lenses compared to that achieved with spectacles. Ten (91) of the patients met the criteria of contact lens success during the 4-month follow-up period. CONCLUSIONS: Bitoric gas-permeable contact lenses achieved a comfortable and visually successful fit in most eyes with PMCD. Patients with PMCD used the fewest contact lenses and had the fewest lens exchanges, but required more office visits than other groups of patients with various corneal irregularities.
Geerards, A. J., W. Vreugdenhil, et al. (2006). "Incidence of rigid gas-permeable contact lens wear after keratoplasty for keratoconus." Eye Contact Lens 32(4): 207-10.
PURPOSE: To review retrospectively the charts of all 190 patients who underwent penetrating keratoplasty for keratoconus in one hospital during a 5-year period (1995-2000), with special attention paid to contact lens fitting. METHODS: The frequency of postoperative contact lens use, the time to fit lenses after grafting, tolerance and visual acuity, and postoperative risks for the graft were studied. RESULTS: The authors successfully fitted large-diameter (12 mm) tricurve rigid gas-permeable contact lenses for 90 (47%) of 190 penetrating keratoplasty patients with good tolerance. There were nine dropouts, and 91 eyes were corrected in another way. Fitting contact lenses after grafting usually started after 8.5 months (range, 1-60 months). The average tolerance was 9.2 hours a day (range, 2-12 hours), and best-corrected visual acuity was 20/25 (range, 20/16-20/200). The average follow-up was at least half a year. The average age of the patient at the first lens fitting was 36.2 years (range, 14-75 years). There was no increased risk in graft rejection. CONCLUSIONS: Twelve-millimeter rigid gas-permeable contact lens wear was successful in 47% of patients who underwent penetrating keratoplasty for keratoconus. It does not interfere with the use of chronic postoperative topical medication, nor does it increase the risk of corneal graft rejection. It is necessary to recommend likely use of contact lenses to patients who have undergone grafting surgery.
González-Méijome, J. M., J. Jorge, et al. (2006). "Soft contact lenses for keratoconus: case report." Eye Contact Lens 32(3): 143-7.
PURPOSE: Contact lenses have assisted the refractive correction of keratoconus since the 19th century. In these case reports, the authors describe their experience with a new soft contact lens design. METHODS: The Soft K is a new soft lens comprising a thick fenestrated design to fit in patients with mild to moderate corneal distortion and fitting problems or physical intolerance to rigid gas-permeable (RGP) contact lenses. Three eyes with mild keratoconus from two 25-year-old patients (one man and one woman) were fitted with the Soft K contact lens. Both patients had previously worn other contact lens types. RESULTS: Improvements in comfort and quality of vision compared with previously worn RGP or soft toric contact lenses were the most remarkable advantages objectively observed and subjectively described by both patients. For one patient, a professional soccer player, the benefits were also important in terms of compatibility with the dynamic environment of his activity, satisfying the need for stable correction and constant full field-of-view demand without spectacles. No physiologic complications such as edema or neovascularization were observed during the follow-up period. CONCLUSIONS: This new soft lens design for irregular corneas is especially indicated for those with intolerance to RGP or other contact lenses and for patients for whom RGP lenses do not satisfy the dynamic environment inherent to some professional or leisure activities, particularly sport activity. This is a good option to consider in patients with mild to moderate keratoconus and good correction of slight or moderate irregular corneal astigmatism with good tolerance. Aftercare implications are also discussed.
McMonnies, C. W. (2004). "Keratoconus fittings: apical clearance or apical support?" Eye Contact Lens 30(3): 147-55.
PURPOSE: To examine the relative merits of apical support and apical clearance fitting of rigid gas-permeable contact lenses for keratoconus. METHODS: After an historic review of fitting approaches for keratoconus, a case report is described in which an adventitious apical clearance fitting for early keratoconus might have been associated with accelerated progress of the ectasia. DISCUSSION: The hypothesis that apical clearance fittings increase the risk of accelerating ectasia progression in early keratoconus is examined in counterpoint to the hypothesis that apical support fittings increase the risk of apical scarring. Reference is made to the responses of normal corneas to apical clearance fitting and to apical contact fittings used in orthokeratology fittings. The tendency for corneas to mold to contact lens curvature is reviewed. The possibility that reduced corneal thickness or tissue softening and associated changes to the biomechanical properties of the cornea in keratoconus may facilitate molding with apical clearance fitting is examined. CONCLUSIONS: Known and putative risk factors for fitting complications that are associated with apical clearance and apical touch contact lens fitting are given as a basis for the reader to draw conclusions about the management of contact lens fitting for keratoconus. The possibility of symptomless adverse responses is a strong indication for frequent routine aftercare reviews.
Moon, J. W., K. C. Shin, et al. (2006). "The effect of contact lens wear on the ocular surface changes in keratoconus." Eye Contact Lens 32(2): 96-101.
PURPOSE: To investigate the effects of contact lens wear or the keratoconic shape itself on the changes in the ocular surface in keratoconus. METHODS: Forty-two patients (84 eyes) were enrolled in this study and divided into four groups. Group 1 comprised 22 eyes with keratoconus that had been wearing rigid gas-permeable (RGP) contact lenses for an average of 5.54 +/- 2.11 years. Group 2 comprised 24 myopic eyes that had been wearing RGP contact lenses for 6.42 +/- 1.79 years. Group 3 comprised 20 eyes with keratoconus without any contact lens wear. Group 4 comprised 18 healthy eyes that were used as controls. The ocular surface changes were evaluated by determining the tear film breakup time and performing conjunctival impression cytology. The goblet cell densities, nucleus-to-cytoplasm ratio, and epithelial cell morphology in the four groups were compared with optical microscopy in the high-power field. RESULTS: The tear film breakup times in groups 1 and 2 were significantly lower than those in groups 3 and 4. The goblet cell densities were 5.49 +/- 1.75 and 5.82 +/- 1.63 in groups 1 and 2, respectively, which were significantly lower (P < 0.05) than the 8.79 +/- 1.42 and 10.24 +/- 2.10 in groups 3 and 4, respectively. There were no statistically significant differences in the goblet cell densities, nucleus-to-cytoplasm ratios, and epithelial cell morphologies between groups 1 and 2 and groups 3 and 4. CONCLUSIONS: The ocular surface changes in keratoconus may be directly related to contact lens wear and not to the keratoconic shape itself.
Pullum, K. W., M. A. Whiting, et al. (2005). "Scleral contact lenses: the expanding role." Cornea 24(3): 269-77.
PURPOSE: The purpose of this study was to describe the current indications for scleral contact lens (ScCL) management at Moorfields Eye Hospital, London. METHODS: A database of 1003 patients (1560 eyes) seen between September 1999 and May 2003, either assessed for an ScCL trial or to follow up previously issued lenses, was analyzed. RESULTS: The major contact lens indication groups were keratoconus or other primary corneal ectasia (PCE), corneal transplant, and ocular surface disease (OSD). The 3 main small groups were aphakia, myopia, and ptosis. A total of 538 patients continued lens wear in 1 or both eyes, for a total of 808 eyes. The total numbers of eyes for each contact lens indication were PCE, 496 (61.4%); corneal transplant, 150 (18.6%); OSD, 91 (11.4%); aphakia, 17 (2.1%); myopia 21 (2.6%); ptosis 14 (1.7%); and a miscellaneous indication, 19 (2.2%). The percentages were similar to those of the total group of 1560 eyes. Seven hundred twenty lenses (89.1%) were rigid gas permeable (RGP), 708 were nonventilated, and 12 were fenestrated; 88 (10.9%) were ventilated polymethylmethacrylate or ptosis props. CONCLUSIONS: ScCLs continue to play a significant role in the management of corneal abnormalities, especially PCE, corneal transplant, and OSD. The great majority of lenses in use were nonventilated RGP designs.
Rubinstein, M. P. and S. Sud (1999). "The use of hybrid lenses in management of the irregular cornea." Cont Lens Anterior Eye 22(3): 87-90.
The use of SoftPerm hybrid lenses was investigated as part of a 10 year retrospective audit of keratoconus in the Contact Lens Service at Nottingham University Hospital which serves a population of approximately one million. During this period, nine patients (14 eyes) were fitted with SoftPerm a lenses for keratoconus. Two further patients (two eyes) were included with a diagnosis of irregular astigmatism and one patient (one eye) was fitted post-corneal graft. Seven patients were regarded as successful hybrid lens wearers and five were regarded as unsuccessful wearers. Of the unsuccessful cases, one patient managed satisfactorily using a rigid gas permeable corneal on the unaffected eye, two patients subsequently had successful corneal grafts, one patient continued with restricted rigid gas permeable lens wear and one patient defaulted.
Sorbara, L., T. Chong, et al. (2000). "Visual acuity, lens flexure, and residual astigmatism of keratoconic eyes as a function of back optic zone radius of rigid lenses." Cont Lens Anterior Eye 23(2): 48-52.
The purpose of this study was to determine whether the visual acuity of keratoconic eyes was affected by alteration of back optic zone radii (BOZRs) of rigid gas permeable lenses (RGP) contact lenses. Visual acuity, spherical and sphero-cylindrical over-refraction and keratometry of the front surface of the RGP lenses of nine keratoconic eyes were measured. The BOZR of the five lenses varied from steeper to flatter than that habitually worn by the subjects. The steepest lenses produced significantly greater lens flexure and residual astigmatism (P < 0.002) and worse high and low contrast visual acuity with the spherical over-refraction (P < 0.05). There was no statistical difference in visual acuity across the range of BOZR when a sphero-cylindrical over-refraction was applied. Thus reduced visual acuity in keratoconus with steep lenses is likely due to uncorrected residual astigmatism from a combination of several possible sources.
Xie, P. Y., D. Wang, et al. (2005). "[The evaluation of visual quality in keratoconus eyes corrected by rigid gas-permeable contact lens]." Zhonghua Yan Ke Za Zhi 41(12): 1086-91.
OBJECTIVE: To evaluate the visual quality in keratoconus eyes corrected by rigid gas-permeable contact lens (RGPCL) and spectacles. METHODS: Corrected visual acuity, corneal topography, wavefront aberration and contrast sensitivity were measured in 27 keratoconus patients (54 eyes) before and after the fitting of RGPCL. RESULTS: The inclusive keratoconus eyes were diveded mild 30 eyes, moderate 13 eyes and sever 11 eyes. The average myopia and average astigmatism were (6.92 +/- 3.66) D and (5.75 +/- 1.85) D respectively. Uncorrected visual acuity (VA) in 96.3% keratoconus eyes was or= 0.6, while 100% by RGPCL. The VA in 20.4% of eyes corrected by spectacles were >or= 1.0, while 66.7% by RGPCL. Corneal topography study showed corneal toricity decreased to
Zhou, A. J., K. Kitamura, et al. (2003). "Contact lens care in keratoconus." Cont Lens Anterior Eye 26(4): 171-4.
PURPOSE: To quantify the complexity involved in fitting contact lenses on the eyes of patients with keratoconus. METHODS: The contact lens care of one randomly selected eye each of 38 keratoconus patients was retrospectively analyzed and compared to that of 38 gender and age matched controls. We evaluated the number of diagnostic contact lenses used to establish the initial contact lens order, number of ordered rigid gas permeable (RGP) contact lenses needed to complete the fit, number of office visits during the initial 4 months of care, best spectacle and RGP contact lenses corrected Log MAR visual acuities, complications encountered, and whether or not the patient was successful in contact lens wear. RESULTS: Keratoconic eyes statistically used more diagnostic lenses, more ordered lenses, and more office visits than did normal eyes. Visual acuities improved from an average of 20/40 with spectacles to an average of 20/20 by use of RGP contact lenses in keratoconic eyes. Visions were corrected to 20/20 with both spectacles and contact lenses in control eyes. Sixty nine percent (69%) of keratoconic eyes and 95% of controls were successful in contact lens wear. CONCLUSIONS: Contact lens care of keratoconic eyes is more challenging than care of normal eyes because of the need for more diagnostic and ordered contact lenses and the use of more professional time. Keratoconic eyes may suffer more complications than normals during contact lens care, but this does not affect the success rates, and such patients benefit from enhanced visual acuity with RGP contact lenses compared to that achieved with spectacles.
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Current Research on INTAC Rings
Alió, J. L., A. Artola, et al. (2005). "One or 2 Intacs segments for the correction of keratoconus." J Cataract Refract Surg 31(5): 943-53.
PURPOSE: To evaluate the effect of implanting 1 or 2 intracorneal rings (Intacs, KeraVision) as a device to correct, stabilize, and/or improve the best corrected visual acuity in patients with clear cornea keratoconus oriented by the preoperative corneal topography pattern. SETTING: Vissum/Instituto Oftalmológico de Alicante, Miguel Hernandez University, Alicante, Spain. METHODS: In this prospective comparative consecutive study, Intacs segments were implanted in 26 keratoconic eyes with clear central corneas of 19 consecutive patients (9 women and 10 men). Corneas were divided into 2 groups according to the topographic pattern of the cone. Group I included keratoconus not crossing the 180 degrees meridian and Group II included keratoconus crossing the 180 degrees meridian. The Intacs were horizontally placed through a lateral clear corneal incision. According to the corneal topography 1 segment was implanted 0.45 mm inferior in Group I, and 2 segments were implanted, 1 0.25 mm superior and the other 0.45 mm inferior, in Group II. All cases completed a minimum follow-up of 1 year. Differences between preoperative and postoperative uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, and keratometry were clinically and statistically evaluated. RESULTS: Spherical equivalent error and refractive astigmatism were significantly reduced. The mean keratometric values were reduced following Intacs insertion in both groups. At the end of the first year of the postoperative follow-up, Group I (1 segment) had an improvement in mean UCVA to 20/50 (0.4 +/- 0.22 decimal value), which was statistically significant when compared to the preoperative UCVA of 20/100 (0.2 +/- 0.13 decimal value) (P=.011). Mean BSCVA was 20/32 (0.62 +/- 0.24 decimal value), which was also statistically significant when compared to the preoperative BSCVA, which was 20/50 (0.4 +/- 0.21 decimal value) (P=.002). In Group II (2 segments), UCVA after 1 year was 20/63 (0.34 +/- 0.17 decimal value), which was statistically significant when compared to the preoperative UCVA of 20/400 (0.06 +/- 0.02 decimal value) (P=.001). Mean BSCVA was 20/32 (0.62 +/- 0.27 decimal value), which was significantly better than the preoperative UCVA of 20/50 (0.38 +/- 0.22 decimal value) (P=.001). In 4 eyes, the inferior segment was removed because of partial extrusion during the postoperative follow-up. CONCLUSIONS: Treatment of keratoconus with 1 or 2 Intacs segments oriented by the preoperative corneal topography used in this study proved to be effective in decreasing the corneal steepening and astigmatism and improving BSCVA. Further follow-up is needed to determine the final effect of Intacs on the progression of the corneal disease.
Alió, J. L. and M. H. Shabayek (2006). "Intracorneal asymmetrical rings for keratoconus: where should the thicker segment be implanted?" J Refract Surg 22(3): 307-9.
PURPOSE: To report a 20-year-old man who presented with monocular diplopia in the right eye with uncorrected visual acuity (UCVA) of 0.3 and best spectacle-corrected visual acuity (BSCVA) of 1.0 with -0.50 -3.00 x 45 degrees. METHODS: Clinical examination and corneal topography revealed grade I keratoconus in the right eye. Intracorneal ring segments (INTACS; Addition Technology, Des Plaines, III) were implanted in May 2004 without surgical complications at 415 microm (70% of the corneal thickness), with the 450-microm segment implanted superiorly and the 250-microm segment inferiorly. RESULTS: For 2 months postoperatively, BSCVA remained at 0.4 with +1.50 -4.50 x 25 degrees. The segments were reversed, implanting the 450-microm (thick) segment inferiorly and the 250-microm (thin) segment superiorly. One week later, UCVA was 1.0 and remained stable for 3 months after reimplantation. CONCLUSIONS: This report shows that implanting the thicker segment inferiorly provides better visual results.
Alió, J. L., M. H. Shabayek, et al. (2006). "Intracorneal ring segments for keratoconus correction: long-term follow-up." J Cataract Refract Surg 32(6): 978-85.
PURPOSE: To evaluate long-term results and stability of intracorneal ring segment (Intacs) implantation for keratoconus correction. SETTING: Vissum, Instituto Oftalmológico de Alicante and University of Miguel Hernandez, Alicante, Spain. METHODS: This retrospective study comprised 13 eyes operated on between April 2000 and December 2001 that had Intacs implantation for keratoconus correction. The outcomes were evaluated at 6, 12, 24, and 36 months in all eyes and at 48 months (6 eyes). RESULTS: Mean best spectacle-corrected visual acuity (BSCVA) increased from 0.46 (20/50) preoperatively to 0.66 (20/30) postoperatively (P< or =.001). Mean decrease of inferior-superior (I-S) asymmetry was 2.81 diopters (D) (P< or =.02), and the average K-value was 3.13 D (P< or =.001). Mean difference between 6 and 36 months (stability) showed no significant difference regarding BSCVA (P< or =.5) and I-S asymmetry (P< or =.6). Although a significant increase was noticed in the average K by 1.67 D (P< or =.002), at 36 months it did not reach the initial preoperative values. CONCLUSION: Intacs increased the BSCVA and decreased I-S asymmetry with stability up to 36 months. In spite of the decrease of the K-values at 6 months, a further significant increase was detected 36 months after surgery.
Alió, J. L., M. H. Shabayek, et al. (2006). "Analysis of results related to good and bad outcomes of Intacs implantation for keratoconus correction." J Cataract Refract Surg 32(5): 756-61.
PURPOSE: To evaluate factors influencing good and poor outcomes after intracorneal ring segment implantation to correct keratoconus. SETTING: Instituto Oftalmológico de Alicante (Vissum Corporation), University of Miguel Hernandez, Alicante, Spain. METHODS: A retrospective comparative study of the visual outcome, 25 eyes of 21 patients were implanted after intracorneal ring segments (Intacs, Addition Technology) as a method to correct keratoconus. Outcomes were evaluated 6 months after implantation based on the visual results. Group A comprised 20 eyes that gained 3 lines or more of best spectacle-corrected visual acuity (BSCVA) to correct keratoconus, and Group B comprised 5 eyes that lost 1 line of BSCVA. RESULTS: In Group A, the preoperative mean BSCVA was 0.43 (20/50) and the postoperative mean BSCVA, 0.82 (20/20) (P< or =.0001). In Group B, the preoperative mean BSCVA was 0.36 (20/63) and the postoperative mean BSCVA, 0.24 (20/80) (P< or =.02). The preoperative mean sphere power was 3.90 diopters (D) greater in Group B than in Group A (P< or =.007); the mean spherical equivalent was 4.36 D greater (P< or =.007), and the mean K-reading was 6.91 D greater (P< or =.001). The postoperative reduction in spherical dioptric power was 2.11 D (P< or =.027) and the mean spherical equivalent, 2.81 D (P< or =.003), significant only in Group A. The reduction in mean central K-readings was 4.30 D (P< or =.0001) in Group A and 6.19 D (P< or =.014) in Group B. The correlation of the preoperative mean K value to the postoperative BSCVA was significant at the .01 level by the Pearson test (-0.67). In Group A, all eyes (100%) had a mean K-reading < or =53 D. In Group B, 4 eyes (80%) had a mean K-reading > or =55 D. CONCLUSION: Intacs provided better results in visual acuity and corneal topography quality and significantly reduced the spherical equivalent in eyes with keratoconus with relatively low mean K values (< or =53 D) and a relatively low spherical equivalent. In advanced keratoconus (mean K-reading > or =55 D), poor results can be anticipated.
Boxer Wachler, B. S., J. P. Christie, et al. (2003). "Intacs for keratoconus." Ophthalmology 110(5): 1031-40.
PURPOSE: To evaluate the efficacy and safety of placement of Intacs in subjects with keratoconus. DESIGN: Retrospective, nonrandomized comparative trial. INTERVENTION: Intrastromal corneal ring segment implantation. PARTICIPANTS: Seventy-four eyes of 50 subjects (41 male and 9 female) were evaluated. The mean age of subjects in the study was 35 years, ranging from 20 to 73 years. Twenty-six subjects underwent single-eye treatment, and 24 subjects had both eyes treated. METHODS: A modified Intacs procedure was performed on subjects with keratoconus. Pachymetry was measured at the incision site, and the incision was made at 66% of the corneal thickness. A thicker ring segment was typically placed inferiorly, and a thinner segment was placed superiorly on the basis of a refractive nomogram. MAIN OUTCOME MEASURES: Differences between preoperative and postoperative uncorrected visual acuity, best spectacle-corrected acuity, and spherical equivalent. Changes in irregular astigmatism were evaluated with the inferior-superior value from comeotopographic maps, and differences in refractive cylinder groups were studied. RESULTS: Preoperative mean best-corrected logarithm of the minimum angle of resolution (LogMAR) visual acuity was 0.41 (20/50 - 1) (standard deviation [SD], +/-0.48), which improved to a postoperative mean of 0.24 (20/32 - 2) (SD, +/-0.31) (two lines of improvement). Preoperative mean uncorrected LogMAR visual acuity was 1.05 (20/200 - 2 1) (SD, +/-0.48), which improved to a mean of 0.61 (20/80-) (SD, +/-0.52) (four lines of improvement) at postoperative follow-up. Preoperative mean best-corrected LogMAR acuity in the corneal scarring group was 0.96 (20/200 + 2) (SD, +/-0.72), which improved to a mean of 0.54 (SD, +/-0.43) (20/63 - 2) (five lines of improvement). Uncorrected mean LogMAR acuity in the eyes with corneal scarring was 1.42 (20/400 - 4) (SD, +/-0.27), which improved to a mean of 1.03 (20/200 - 1) (SD, +/-73) (three lines of improvement). The mean spherical equivalent before surgery was -3.89 diopters (D) (SD, +/-5.16), which was reduced to a mean of -1.46 D (+/-4.11) at the postoperative follow-up. CONCLUSIONS: Asymmetric Intacs implantation can improve both uncorrected and best spectacle-corrected visual acuity and can reduce irregular astigmatism in corneas with and without corneal scarring.
Colin, J. (2006). "European clinical evaluation: use of Intacs for the treatment of keratoconus." J Cataract Refract Surg 32(5): 747-55.
PURPOSE: To evaluate the safety and efficacy of Intacs inserts in keratoconic eyes to alter corneal shape and refractive power and stabilize the progression of corneal ectasia. SETTING: Service d'Ophtalmologie, Bordeaux, France. METHODS: In this prospective study, 57 eyes with clear central corneas that were diagnosed with keratoconus and contact lens intolerant were followed for up to 1 year. The primary objectives were to assess the safety of Intacs and the visual outcomes by measuring uncorrected visual acuity (UCVA), best corrected visual acuity, manifest refraction spherical equivalent, keratometry, intraocular pressure (IOP), pachymetry, and patient satisfaction. The stability of the refraction, keratometry, and visual acuity measurements was also assessed. RESULTS: At the 6-month examination, 78% of patients showed improvement of 2 lines or more in UCVA (P<.001). Best corrected visual acuity of 20/40 or better improved from 53% of patients preoperatively to 74% of patients (P< or =.033). Manifest refraction spherical equivalent improved to 3.1 +/- 2.5 diopters (D) (P<.001) compared with the preoperative examination. Keratometry decreased a mean of -4.3 +/- 2.8 D from the preoperative readings (P< or =.002). These changes appeared to be stable over time. At 6 months, there were no adverse events, no clinically significant increase in IOP, and no decrease in central corneal thickness. In 7 of 57 eyes (12%), the Intacs were removed due to dissatisfaction with visual symptoms. There were no adverse effects or complications associated with the Intacs removal. CONCLUSIONS: Intacs were safe and effective for treating keratoconus. All patients demonstrated improved objective visual outcomes; functional vision was restored in most patients. Intacs were removed without permanent sequelae.
Colin, J., B. Cochener, et al. (2000). "Correcting keratoconus with intracorneal rings." J Cataract Refract Surg 26(8): 1117-22.
PURPOSE: To evaluate the potential of intrastromal corneal ring technology (Intacs, KeraVision) to correct keratoconus without central corneal scarring. SETTING: Department of Ophthalmology, Brest University Hospital, Brest, France. METHODS: In this prospective, noncomparative, interventional case series, Intacs segments were implanted in 10 keratoconic eyes with clear central corneas and contact lens intolerance after corneal pachymetry was checked. Segment thicknesses varied based on corneal topography analysis. RESULTS:No intraoperative complications occurred. The mean follow-up was 10.6 months. Postoperative results revealed a reduction in astigmatism and spherical correction and an increase in topographical regularity and increased uncorrected visual acuity. CONCLUSION: Intacs technology can reduce the corneal steepening and astigmatism associated with keratoconus.
Colin, J., B. Cochener, et al. (2001). "INTACS inserts for treating keratoconus: one-year results." Ophthalmology 108(8): 1409-14.
OBJECTIVE: To evaluate the use of INTACS micro-thin prescription inserts (Kera Vision, Inc., Fremont, CA) for the treatment of keratoconus. DESIGN: Prospective, nonrandomized (self-controlled) comparative trial. PARTICIPANTS/INTERVENTION: Ten patients from our prospective clinical study who had completed 12 months of follow-up were evaluated. All patients had keratoconus with clear central corneas and were contact lens intolerant. After reviewing corneal pachymetry and topography of individual patients, INTACS inserts of 0.45-mm thickness were placed in the inferior cornea to lift the cone and INTACS of 0.25-mm thickness were inserted superiorly to counterbalance and flatten the overall anterior corneal surface. MAIN OUTCOME MEASURES: Differences between preoperative and postoperative uncorrected visual acuity, best spectacle-corrected visual acuity, manifest refraction, and keratometry values were statistically assessed. Changes in corneal ectasia were evaluated by reviewing corneotopographic maps. RESULTS: No intraoperative complications occurred in this series of patients. Spherical equivalent error and refractive astigmatism were reduced with INTACS inserts treatment. Postoperative month 12 uncorrected visual acuity (logarithm of the minimum angle of resolution [logMAR] mean, 0.35, standard deviation [SD], 0.16 [approximately 20/50, approximately 2 lines]) was significantly better than preoperative (logMAR mean, 1.05; SD, 0.33 [approximately 20/200, approximately 3 lines]; P
Colin, J. and S. Simonpoli (2005). "Le kératocône: options chirurgicales actuelles." J Fr Ophtalmol 28(2): 205-17.
The treatment of keratoconus is in part dependant on the severity of the disease process. When contact lenses fail because of patient intolerance or insufficient acuity to meet the patient's needs, penetrating keratoplasty is the usual surgical modality considered for satisfactory visual rehabilitation. Keratoconus is considered to be a contraindication for incisional refractive surgery such as radial keratotomies or LASIK because of the corneal instability conferred by these procedures. When the cornea is transparent, INTACS implantation is a refractive modality that may improve visual function and in some instances prevent the need for corneal transplantation in select patients with keratoconus.
Colin, J. and S. Velou (2002). "Utilization of refractive surgery technology in keratoconus and corneal transplants." Curr Opin Ophthalmol 13(4): 230-4.
Keratoconus is considered a contraindication for refractive surgery because of the potential corneal instability following surgery. On the other hand, penetrating keratoplasty is the usual surgical modality when the keratoconic patient cannot tolerate a contact lens. In some selected cases, when the central cornea is still transparent, refractive surgical procedures, particularly Intacs implantation, may be used to help the patient to improve visual function.
Colin, J. and S. Velou (2003). "Implantation of Intacs and a refractive intraocular lens to correct keratoconus." J Cataract Refract Surg 29(4): 832-4.
We report a case of Intacs implantation for keratoconus followed by the implantation of an anterior chamber phakic refractive lens to correct a -8.25 diopter residual error.
Frost, N. A., J. Wu, et al. (2006). "A review of randomized controlled trials of penetrating keratoplasty techniques." Ophthalmology 113(6): 942-9.
PURPOSE: To assess the effects of variations in operative technique on the outcomes of penetrating keratoplasty (PK). METHOD: Systematic literature review of published randomized controlled trials of operative techniques in PK. MAIN OUTCOME MEASURES: Visual acuity, refractive error, endothelial cell density, graft rejection, intraocular pressure (IOP), and other surgical complications. RESULTS: Twenty-seven trials were identified. Many involved small numbers, some of which were probably compromised by inadequate statistical power. There was some limited evidence from a small number of studies (usually 1 or 2) for preoperative cauterization of the cone in keratoconus, excimer laser trephination, taking into account the effect of trephine sizing on postoperative IOP, taking into account the effect of trephine sizing on postoperative spherical equivalent, using sodium hyaluronate, avoiding vitrectomy if possible, using an iris-fixated posterior chamber lens implant in the absence of capsular support, and adjusting a single continuous suture intraoperatively if used. However, there was little convincing evidence for choosing interrupted suturing versus continuous suturing or for an effect of suturing on final sutures-out astigmatism. Likewise, there was no convincing evidence for the superiority of any lamellar alternative to PK for deep stromal disease. Overall, most of the effects of changing technique were small, and there was no evidence for the superiority of any specific technique in terms of improved quality of life or cost-effectiveness. CONCLUSIONS: There is a need for further studies with which to refine decision-making as regards the choice of operative techniques in PK.
Hellstedt, T., J. Mäkelä, et al. (2005). "Treating keratoconus with intacs corneal ring segments." J Refract Surg 21(3): 236-46.
PURPOSE: To assess the safety and efficacy of Intacs inserts for the treatment of mild to moderate keratoconus. METHODS: In a nonrandomized prospective clinical trial, 50 eyes of 37 patients with mild to moderate keratoconus were implanted with asymmetrical pairs of Intacs segments. Patients were interviewed and observed preoperatively and 24 hours, 1 week, 1, 3, 6, and 12 months postoperatively. Main outcome measures were uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, satisfaction with vision and trouble with vision, Visual Function-7 score, and surgically induced change in corneal astigmatism. RESULTS: Of the 50 operations performed, 92% were successful. Mean follow-up was 6.3 +/- 3.2 months. In 4 (8%) eyes, both Intacs segments were removed. In addition, 7 refractive adjustments in 7 eyes were performed successfully to improve visual and surgical outcome. Both BSCVA and UCVA improved throughout follow-up. Visual functioning index improved from 61.6 +/- 21.1 to 80.8 +/- 22.5, and the percentage of satisfaction with vision improved from 24.3% to 87.5% at 12 months. Vector analysis of astigmatism correction showed that the mean change in corneal astigmatism was 2.9 +/- 2.9 D at 6 months postoperatively. By selecting patients in whom astigmatism correction was best (index of success >0.5), an analysis was performed to determine individual factors important in successful surgery. Preoperatively these 11 (22%) eyes did not differ significantly from the remaining eyes and the only significant value was low K readings in the flat axis. CONCLUSIONS: Asymmetric Intacs placement improves BSCVA and UCVA and reduces astigmatism in patients with mild to moderate keratoconus. The procedure of Intacs placement is safe and effective. The change in astigmatism correction is unpredictable.
Hirsh, A., I. S. Barequet, et al. (2006). "[Wavefront-guided lasek after intacs in eyes with stable keratoconus]." Harefuah 145(3): 181-2, 247-8.
BACKGROUND: Keratoconus is a non-inflammatory, progressive thinning disorder of the cornea, resulting in a typical protrusion and in refractive errors and low visual acuity. Many of the patients with stable keratoconus encounter difficulties wearing glasses or contact lenses. PURPOSE: To evaluate the results of wave-front guided laser assisted subepithelial keratectomy (LASEK) for the correction of residual spherical and spherocylindrical myopia after INTACS insertion in patients with stable keratoconus. METHODS: Four eyes of keratoconus patents were treated with Zyoptix wavefront-guided LASEK for correction of residual myopia and astigmatism after insertion of INTACS. The refraction after insertion of INTACS was stable at least six months before the Zyoptix-LASEK. The mean pre-INTACS refraction was myopia of -2.37 D (range 0 to - 5.00 D) and astigmatism of -3.93 D (range -1.00 to -7.5 D). The mean refraction prior to Zyoptix-LASEK was myopia of -0.2 D and astigmatism of -2.71 D. The mean follow-up period after the Zyoptix LASEK was 8 months. RESULTS: Initially, prior to both surgeries, the mean uncorrected visual acuity was 6/240 (range count-fingers to 6/60) and at the final postoperative visit 6/12 (range 6/10 to 6/ 18). The preoperative mean best spectacle corrected visual acuity was 6/15 (range 6/10 to 6/24) and at the final postoperative follow-up visit 6/9 (range 6/8.5 to 6/12). CONCLUSION: Zyoptix wavefront-guided LASEK for correction of residual myopia and astigmatism in keratoconus patients after INTACS insertion and stable refraction provided excellent visual outcome, with no loss of visual acuity and no complications.
Hofling-Lima, A. L., B. C. Branco, et al. (2004). "Corneal infections after implantation of intracorneal ring segments." Cornea 23(6): 547-9.
PURPOSE: To report risk factors, clinical course, and outcome in patients with infectious keratitis following implantation of intracorneal ring segments (ICRS). METHODS: The records of 8 patients with culture-proven infectious keratitis after ICRS (Ferrara or Intacs) implantation were retrospectively reviewed. Age, gender, corneal findings, ocular abnormalities, the condition that led to ICRS implantation, immediate prior use of a contact lens, elapsed time between implantation and the onset of symptoms, previous medications, and systemic disorders were noted. RESULTS: Culture-positive infectious keratitis developed in 7 eyes of 7 patients (2 men and 5 women) with a mean age of 35 years who underwent Ferrara implantation for the treatment of keratoconus and in a 29-year-old man who underwent Intacs implantation for correction of low myopia. Contact lens use, diabetes, and trauma were factors possibly associated with the risk of infection in three cases. Microorganisms, identified in all cases, included Staphylococcus aureus, Streptococcus viridans, Streptococcus pneumoniae, Pseudomonas sp, Nocardia sp, Klebsiella sp, and Paecylomices sp. Onset of symptoms of infection varied from less than 1 week to 22 months postoperatively, depending on the infecting organism. CONCLUSIONS: Infectious keratitis following ICRS implantation is a sight-threatening complication for which early recognition and rapid institution of appropriate treatment may result in a better visual outcome.
Kanellopoulos, A. J., L. H. Pe, et al. (2006). "Modified intracorneal ring segment implantations (INTACS) for the management of moderate to advanced keratoconus: efficacy and complications." Cornea 25(1): 29-33.
PURPOSE: To evaluate the safety and efficacy of modified intracorneal ring segment implantation (INTACS) in the management of moderate and advanced keratoconus (KCN). METHODS: A modified procedure of intracorneal ring segment (INTACS) implantation was performed in eyes with moderate to advanced keratoconus that were intolerant to contact lens or spectacle correction. The main outcome measures were uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), refraction, and keratometry. The preoperative values were compared with the values 6 and 12 months postoperatively. RESULTS: Implantation was performed on 20 eyes of 15 patients; 9 were female and 6 were male. The mean age was 30.2 years (SD +/- 5.44; range, 23-40). At the 6-month follow-up, UCVA improved from 20/154 (SD +/- 0.11) preoperatively to 20/28 (SD +/- 0.21) postoperatively (P < 0.05); BCSVA improved from 20/37 (SD +/- 0.21) preoperatively to 20/22 (SD +/- 0.13) postoperatively (P < 0.05). Spherical refractive error improved from -3.38 D (SD +/- 3.12) to -1.15 D (SD +/- 1.84); cylindrical refractive error improved from -3.75 (SD +/- 2.04) preoperatively to -1.21 (SD +/- 0.84) postoperatively (P < 0.05); average keratometry decreased from 49.50 D (SD +/- 1.64) preoperatively to 46.35 D (SD +/- 1.50) postoperatively. The changes remained stable to the 12-month follow-up. There was 1 case of anterior chamber perforation. There were 6 eyes that had ring exposure secondary to corneal thinning over the implants 3-6 months postoperatively, and a dense corneal infiltrate developed in 1 patient at 7 months postoperatively. CONCLUSIONS: The procedure appears to be effective in improving UCVA and BSCVA of patients with clinical keratoconus. In our small study group, however, there were significant (6/20) postoperative problems with regards to thinning and ring exposure.
Kirkness, C. M. and L. A. Ficker (1992). "Risk factors for the development of postkeratoplasty glaucoma." Cornea 11(5): 427-32.
From a database of 1,122 penetrating keratoplasties performed under the care of the surgeons of the Corneal Clinic, Moorfields Eye Hospital (London, U.K.), 153 (14%) were identified as being complicated by postkeratoplasty glaucoma. The relative risk for its development varied with the indication for keratoplasty. Keratoconus had the lowest incidence along with some dystrophies, such as macular or granular dystrophy, and these were taken as the baseline for comparison. Anterior chamber dysgenesis syndromes had the highest risk among the indications for keratoplasty. Combined cataract or lens implant surgery was also found to be a risk factor, with anterior vitrectomy, anterior segment revision, and anterior chamber lens implant removal representing a greater risk than extracapsular extraction and posterior chamber lens implantation. Postkeratoplasty glaucoma was also strongly associated with peripheral anterior synechiae formation seen after keratoplasty.
Lai, M. M., M. Tang, et al. (2006). "Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes." J Cataract Refract Surg 32(11): 1860-5.
PURPOSE: To investigate intrastromal corneal ring segment depth with a high-speed corneal optical coherence tomography (OCT) system. SETTING: Doheny Eye Institute, University of Southern California, Los Angeles, California, USA. METHODS: A prospective observational case series comprised 4 eyes of 4 patients receiving Intacs intrastromal corneal ring segments (Addition Technology, Inc.) for keratoconus. Optical coherence tomography (OCT) was performed between 7 days and 43 days after implantation. RESULTS: The slitlamp impression of intrastromal corneal ring segment implantation depth did not correlate well with OCT measurements (r(2) = 0.68). The fractional implantation depth was correlated with several surgical variables using a stepwise multivariate regression model, and 2 statistically significant correlations were found. The position of the distal portions of the ring segments was shallower than that of the portion closer to the insertion site (P = .003). Segments placed in the inferior cornea (P = .008) experienced more distal shallowing. Shallower depth was associated with greater fractional anterior stromal compression (P = .04). CONCLUSIONS: Shallower placement of intrastromal corneal ring segments may result in more complications, such as epithelial-stromal breakdown and extrusion, because of the greater anterior stromal tensile strain. The distal and inferior portions of intrastromal corneal ring segments tended to be placed at a shallower depth. Optical coherence tomography provided precise measurement of ring segment depth and may help identify implants that pose a greater risk for depth-related complications.
Levinger, S. and R. Pokroy (2005). "Keratoconus managed with intacs: one-year results." Arch Ophthalmol 123(10): 1308-14.
OBJECTIVES: To describe the visual outcome of keratoconus managed with Intacs implantation (Addition Technology Inc, Fremont, Calif) and to define criteria that predict good outcome. METHODS: This retrospective, nonrandomized, comparative, consecutive case series studied 58 eyes of 43 patients with keratoconus managed by Intacs implantation. The outcome measures were analyzed pre-Intacs and 1 year post-Intacs. Preoperative parameters were correlated with outcome. MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, videokeratography, and patient questionnaires. RESULTS: Intacs were implanted in all eyes with no intraoperative complications. Six eyes underwent additional Intacs surgery. Post-Intacs, the mean +/- SD UCVA improved from less than 20/200 +/- 0.1 line to 20/50(-3) +/- 3.1 lines, the mean +/- SD BSCVA was unchanged at 20/32 +/- 2.0 lines, the mean +/- SD spherical equivalent improved from -3.88 +/- 1.64 to -1.04 +/- 1.51 diopters (D), and the mean +/- SD astigmatism improved from 3.34 +/- 2.23 to 1.97 +/- 1.51 D. Twenty-five eyes had a good outcome (UCVA> or =20/40). Multiple regression selected BSCVA, astigmatism, and spherical myopia as the preoperative predictors of outcome. CONCLUSIONS: Intacs improve myopia and regular astigmatism in keratoconus. Milder keratoconus (BSCVA>20/32(-2) and astigmatism<3.50 D) and significant spherical myopia (>-1.75) predict better outcome.
Nepomuceno, R. L., B. S. Boxer Wachler, et al. (2003). "Feasibility of contact lens fitting on keratoconus patients with INTACS inserts." Cont Lens Anterior Eye 26(4): 175-80.
PURPOSE: To demonstrate the feasibility of contact lens fitting in keratoconus patients with INTACS inserts. METHODS: A chart review was conducted of all patients with bilateral keratoconus who were treated with INTACS inserts on one eye and who were subsequently referred for contact lens fitting in a university based contact lens practice between April 2000 and April 2002. The study was a retrospective, non-comparative case series. The uncorrected and best spectacle corrected visual acuity (BSCVA) after INTACS implantation surgery, postoperative best contact lens-corrected visual acuity (BCLVA), number of diagnostic contact lenses used, number of contact lenses ordered within a 4-month follow-up period, contact lens complications encountered, final base curves, final lens powers, and final wearing times were determined. RESULTS: Three keratoconic patients meeting the selection criteria were found through the chart review. Prior to surgery, all patients had uncorrected visual acuity (UCVA) of 2.0 logMAR (counting fingers). This improved to a mean of 0.81+/-0.25 logMAR (20/125-1) after surgery. Mean BSCVA also improved from 0.51+/-0.30 logMAR (20/60-2) to 0.30+/-0.16 logMAR (20/40). The mean postoperative best contact lens-corrected visual acuity was 0.02+/-0.10 logMAR (20/20-1). The number of diagnostic lenses ranged from 1 to 7. The numbers of contact lenses ordered during the 4-month follow up period ranged from 1 to 3. Two eyes were fitted with larger than usual lens designs made of rigid gas-permeable material and one eye was fitted with a toric soft lens. The final lens power ranged from +1.25 to -21.0D with a mean spherical equivalent of -7.46+/-11.89 D. Final wearing times ranged from 2.5 to 12.0h. CONCLUSION: Fitting contact lenses on keratoconus patients who have INTACS inserts is feasible and has a role in augmenting their vision.
Rabinowitz, Y. S., X. Li, et al. (2006). "INTACS inserts using the femtosecond laser compared to the mechanical spreader in the treatment of keratoconus." J Refract Surg 22(8): 764-71.
PURPOSE: To determine the efficacy of INTACS insertion using a femtosecond laser in the treatment of keratoconus and to compare it to the technique using a mechanical spreader. METHODS: INTACS were inserted in 10 eyes using the mechanical spreader to create the channels and subsequently on another 20 eyes using the femtosecond laser. Uncorrected (UCVA) and best spectacle-corrected visual acuity (BSCVA), manifest refraction, and corneal topography were measured prior to surgery, at 6 months (femtosecond group), and 1 year (mechanical group). Pre- and postoperative data were analyzed to determine changes in the above parameters. RESULTS: Both groups showed significant reduction in average keratometry (K), spherical equivalent refraction, BSCVA, UCVA, surface regularity index (SRI), and surface asymmetry index (SAI). The laser group performed better in all parameters except change in SRI. Results of the laser versus the mechanical spreader were as follows: reduction in spherical equivalent refraction (3.98 vs 2.96), change in average K (2.91 vs 2.52), improvement in UCVA (4.13 vs 3.63), improvement in BSCVA (3.92 vs 1.63), change in SRI (0.37 vs 0.64), and change in SAI (1.00 vs 0.70). Statistical analysis, however, did not reveal any statistically significant differences between the two groups for any single parameter studied. The biggest improvement in the laser group versus the mechanical group was BSCVA (P=.09). Overall success, defined as contact lens or spectacles tolerance, was 85% in the laser group and 70% in the mechanical group. CONCLUSIONS: Inserting INTACS using the femtosecond laser to create the channels is as effective as using the mechanical spreader.
Sharma, M. and B. S. Boxer Wachler (2006). "Comparison of single-segment and double-segment Intacs for keratoconus and post-LASIK ectasia." Am J Ophthalmol 141(5): 891-5.
PURPOSE: To evaluate the efficacy of single-segment Intacs and compare with double-segment Intacs in subjects with post-LASIK ectasia and keratoconus. DESIGN: Retrospective comparative analysis. METHODS: setting: Boxer Wachler Vision Institute, Beverly Hills, California, USA. study population: Thirty-seven eyes of 28 patients with keratoconus and post-LASIK ectasia classified into two groups: single-segment group (17 eyes, 11 patients) and double-segment group (20 eyes, 17 patients). Both groups were matched for age, visual acuity (uncorrected, UCVA; best spectacle-corrected, BSCVA), refractive error (sphere, cylinder, spherical equivalent), and keratometry (K) value (flat, steep, average) by t test for equality of means. intervention: Single- or double-segment Intacs procedure with axis of incision for insertion in the steep axis of manifest refraction. main outcome measure: Improvement of acuity, refractive error, K values, and inferior-superior (I-S) ratio. RESULTS: There was more improvement in UCVA in the single-segment group (nine lines) than the double-segment group (2.5 lines), P < .01; in BSCVA in the single-segment group (2.5 lines) than the double-segment group (<1 line), P < .01; in steep K values in the single-segment group (2.76 diopters +/- 2.68) than the double-segment group (0.93 diopters +/- 2.01), P = .02; and in I-S ratio in the single-segment group (9.51 +/- 7.49) than the double-segment group (4.22 +/- 4.82), P = .01; and greater cylinder decrease after Holladay vector analysis in the single-segment group (5.69 diopters +/- 3.10) than the double-segment group (1.58 diopters +/- 3.09), P < .01. CONCLUSIONS: Single-segment Intacs improved both UCVA and BSCVA by differential flattening of inferior meridian and steepening of superior meridian as reflected by change in I-S ratio.
Siganos, C. S., G. D. Kymionis, et al. (2003). "Management of keratoconus with Intacs." Am J Ophthalmol 135(1): 64-70.
PURPOSE: To prospectively study the effects of the use of Intacs microthin prescription inserts for the management of keratoconus. DESIGN: Prospective nonrandomized clinical trial. METHODS: Thirty-three eyes of 26 keratoconus patients (17 males and 9 females) ages 21 to 51 years (mean age, 32 +/- 9.7 years) were included in the current study. All patients had clear central corneas and contact lens intolerance. Patients were excluded if any of the following criteria applied after the preoperative examination: previous intraocular or corneal surgery; history of herpes keratitis; diagnosed autoimmune disease; and systemic connective tissue disease. Two Intacs segments of 0.45-mm thickness were inserted in the cornea of each eye, aiming at embracing the keratoconus area to try to achieve maximal flattening. Preoperative examination included uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), manifest refraction, keratometric data, and corneal topography. RESULTS: Intacs were successfully implanted in all eyes. In one eye Intacs were removed after 3 months because of their improper (superficial) placement. The follow-up ranged from 1 to 24 months (mean: 11.3 months). The mean UCVA significantly improved from 0.13 +/- 0.14 (range, counting fingers [CF]-0.5) to 0.39 +/- 0.27 (range, CF-1.0) (P <.01). Of 33 eyes, 2 eyes lost 1 line of UCVA, and 3 eyes maintained the preoperative UCVA, whereas the rest (28 eyes) experienced a 1- to 10-line gain. The mean BCVA also improved from 0.47 +/- 0.31 (range
Tunc, Z., N. Deveci, et al. (2003). "Anneaux intracornéens (INTACS) pour le traitement de l'astigmatisme asymétrique du kératocône. Recul de plus de deux ans." J Fr Ophtalmol 26(8): 824-30.
OBJECTIVE: To evaluate the use of corneal ring segments (INTACS) for the treatment of asymmetrical astigmatism in keratoconus. MATERIAL AND METHODS: This prospective study involved nine eyes of seven patients who were operated on between December 1998 and June 2000. A case of keratoconus with opacified cornea was excluded from this study. The patients chosen were contact lens-intolerant. The surgical intervention was carried out under topical anesthesia. The INTACS (Addition Technology) corneal ring insert was inserted approximately 68% of the peripheral corneal depth and was centered to the cone of the cornea. RESULTS: No intraoperative complications occurred. We noted a flattening of the central cornea and a decrease in irregular astigmatism for all patients. Mean preoperative uncorrected visual acuity was less than 1/10. Postoperatively two eyes had an uncorrected visual acuity of 10/10, seven eyes showed an improvement from an uncorrected visual acuity of 2/10 to 7/10. CONCLUSION: We have observed that the flattening effect of INTACS inserts on the soft corneal keratoconic tissue and on the high astigmatic tissue seems greater than that produced in normal cornea. Implantation of INTACS resulted in a significant reduction in asymmetrical astigmatism of the keratoconus.
Twa, M. D., R. L. Kash, et al. (2004). "Morphologic characteristics of lamellar channel deposits in the human eye: a case report." Cornea 23(4): 412-20.
OBJECTIVE: To report the histologic characteristics of lamellar channel deposits after polymethyl methacrylate intrastromal corneal ring segments in a human eye. METHODS: A 34-year-old man previously diagnosed with keratoconus received photorefractive keratectomy in his left eye that exacerbated his corneal ectasia. To delay or possibly prevent corneal transplant, the patient elected to have intrastromal corneal segments implanted in the left eye. One year later the patient underwent corneal transplant. Before transplant, lamellar channel deposits were noted on clinical microscopic examination of the left eye. We performed histologic evaluation to assess changes to the patient's excised corneal tissue and to further characterize the observed lamellar channel deposits. RESULTS: Lamellar channel deposits in humans are histologically similar to our previous descriptions of deposits in rabbits. These deposits primarily consist of intracellular lipid accumulations that stain positively with oil red O and filipin but not periodic acid Schiff reaction. Immunohistochemistry of cells located in the deposit region stained positively with vimentin, suggesting that these cells were keratocytes. Stains for cytokeratins 3 and 12 and for CD68 were both negative, indicating that epithelial cells and macrophages were not present in the deposit region. CONCLUSION: Lamellar channel deposits are a common clinical finding after intrastromal corneal implants. This case provides further evidence to support our hypothesis that lamellar channel deposits in humans are a tissue response to corneal implants that consist of intracellular lipid accumulations. We use this case to propose a theoretical construct for the observation of stromal lipid accumulation in response to corneal injury.
Uçakhan, O. O., A. Kanpolat, et al. (2006). "Contact lens fitting for keratoconus after Intacs placement." Eye Contact Lens 32(2): 75-7.
PURPOSE: To describe a patient with keratoconus who underwent Intacs surgery to one eye with an unsatisfactory result and refused to undergo an Intacs removal procedure. METHODS: Case report. RESULTS: The patient's eye was fitted with a soft contact lens for visual rehabilitation 5 months after Intacs placement. CONCLUSIONS: Intacs, with the help of secondary refractive procedures or contact lenses, may still be considered as effective in postponing penetrating keratoplasty, even in patients with advanced keratoconus.
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