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Keratoconus is a degenerative disease that affects adolescents and young adults and presents with variable thinning and conical deformation of the corneal apex. The resultant irregular astigmatism can progress to levels that can significantly affect everyday activities and overall quality of life. Therefore, stopping the progression of the disease is an essential part in managing patients with keratoconus. Corneal collagen cross-linking is a minimally invasive procedure that stiffens the anterior corneal stroma by creating strong covalent bonds between collagen fibrils. Over the past decade, many studies have proved its safety and efficacy in halting keratoconus progression in adults. This review of the literature highlights the growing trend towards using this treatment in pediatric keratoconic patients. In children, keratoconus tends to be more severe and fast progression is often encountered requiring closer follow-up intervals. Standard cross-linking shows comparable results in children with a good safety-efficacy profile during follow-up periods of up to three years. Further research is needed to standardize and evaluate transepithelial and accelerated cross-linking protocols as these could be of tremendous help in a population where cooperation and compliance are major issues.

Purpose: To test the hypothesis that spatially selective corneal stromal stiffening can alter corneal astigmatism and assess the effects of treatment orientation, pattern, and material model complexity in computational models using patient-specific geometries., Setting: Cornea and Refractive Surgery Service, Academic Eye Institute, Cleveland, Ohio, USA., Design: Computational modeling study., Methods: Three-dimensional corneal geometries from 10 patients with corneal astigmatism were exported from a clinical tomography system (Pentacam). Corneoscleral finite element models of each eye were generated. Four candidate treatment patterns were simulated, and the effects of treatment orientation and magnitude of stiffening on anterior curvature and aberrations were studied. The effect of material model complexity on simulated outcomes was also assessed., Results: Pretreatment anterior corneal astigmatism ranged from 1.22 to 3.92 diopters (D) in a series that included regular and irregular astigmatic patterns. All simulated treatment patterns oriented on the flat axis resulted in mean reductions in corneal astigmatism and depended on the pattern geometry. The linear bow-tie pattern produced a greater mean reduction in astigmatism (1.08 D ± 0.13 [SD]; range 0.74 to 1.23 D) than other patterns tested under an assumed 2-times increase in corneal stiffness, and it had a nonlinear relationship to the degree of stiffening. The mean astigmatic effect did not change significantly with a fiber- or depth-dependent model, but it did affect the coupling ratio., Conclusions: In silico simulations based on patient-specific geometries suggest that clinically significant reductions in astigmatism are possible with patterned collagen crosslinking. Effect magnitude was dependent on patient-specific geometry, effective stiffening pattern, and treatment orientation., Financial Disclosures: Proprietary or commercial disclosures are listed after the references., (Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)

Purpose: To report a novel application of collagen cross-linking (CXL) in refractive astigmatic enhancement of previously performed astigmatic keratotomy., Methods: A 28-year-old woman with prior history of bioptics correction of high myopic astigmatism with femtosecond laser-assisted astigmatic keratotomy followed by topography-guided LASIK showed long-term regression of the astigmatism 4 years later. A novel CXL application was employed in an attempt to reverse the regression of the astigmatic keratotomy., Results: The high fluence CXL intervention resulted in correction of 2 diopters of topographic and refractive cylinder. Uncorrected distance visual acuity changed from 20/50 to 20/20 and refraction from -0.50 -2.00 @ 90 to +0.25 -0.25 @ 90 at the 7-month follow-up., Conclusions: A possible novel application of high fluence CXL with refractive cornea effect is introduced. It may offer rapid and simple rehabilitation and its effect may be tapered., (Copyright 2013, SLACK Incorporated.)

Purpose: To compare the stability and predictability of the refractive outcomes in eyes treated with photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK) with and without postoperative use of topical cyclosporine A emulsion., Setting: Naval Medical Center San Diego Refractive Surgery Center, San Diego, California, USA., Design: Randomized clinical trial., Methods: Patients had PRK or LASIK and were randomized, pairwise, to a standard postoperative treatment regimen with or without the addition of topical cyclosporine A 0.05% emulsion twice daily for 3 months postoperatively. Visual acuity, mesopic contrast acuity, refractions, and ocular symptoms were assessed through the 3-month examination. Tear-film samples (cytokines and chemokines) were analyzed preoperatively and 1 week and 1 and 3 months postoperatively., Results: The PRK group comprised 70 patients and the LASIK group, 54 patients. The addition of topical cyclosporine A twice a day after PRK or LASIK did not confer special benefits in terms of achievement of target refraction, final uncorrected distance visual acuity (UDVA), or rate of visual recovery (all P>.05, multivariate analysis of variance [MANOVA]). There was no significant difference in tear-film composition based on measurement of matrix metalloproteinase-9, interleukin (IL)-6, or IL-8 recovery (all P>.05, MANOVA)., Conclusion: The addition of topical cyclosporine A twice daily for 3 months after PRK or LASIK did not provide a significant benefit in the rate of visual recovery, final UDVA, or patient symptoms, nor did it significantly change measured inflammatory mediators (cytokines) present in the tear film., (Published by Elsevier Inc.)

Purpose: To report the long-term results of combined collagen crosslinking (CXL) and toric phakic intraocular lens (pIOL) implantation to correct myopic astigmatism in patients with progressive mild to moderate keratoconus., Setting: Instituto de Microcirugia Ocular, Barcelona, Spain., Design: Case series., Methods: From November 2006 to July 2009, CXL was performed in eyes with proven progressive keratoconus. Once refraction and topography stabilized, toric Artiflex/Artisan pIOL implantation was performed to correct residual myopic astigmatism. A complete ophthalmologic examination, including manifest refraction, uncorrected (UDVA) and corrected (CDVA) distance visual acuities, biomicroscopy, tonometry, fundoscopy, keratometry, corneal tomography, and central endothelial cell count (ECC), was performed before each procedure and postoperatively at 3 months and at yearly intervals up to 5 years. Main outcome measures were accuracy and stability of the spherical equivalent (SE) and cylinder, keratometry, UDVA (efficacy), CDVA (safety), central ECC, and complications., Results: The median follow-up in the 9 patients (17 eyes) was 36.9 months ± 15.0 (SD). The median interval between CXL and pIOL implantation was 3.9 ± 0.7 months. Fourteen eyes (82%) were within ± 0.50 diopter (D) of the attempted SE correction and 13 eyes (76%) were within ± 1.00 D of the attempted cylinder correction. The mean difference in simulated keratometry between preoperatively and the last follow-up was 0.17 ± 0.45 D (range -0.55 to 1.45 D). The postoperative UDVA was 20/40 or better in 16 eyes (94%). No eye lost lines of CDVA. No significant decrease in central ECC occurred (P>.05)., Conclusion: Combined CXL and toric iris-claw pIOL implantation effectively and safely corrected myopic astigmatism in progressive mild to moderate keratoconus., Financial Disclosure: Dr. Güell is a consultant to Ophtec. No other author has a financial or proprietary interest in any material or methods mentioned., (Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the effect of laser in situ keratomileusis (LASIK) on tear secretion., Methods: A non-consecutive series of 42 eyes of 42 patients had LASIK for the correction of myopia and myopic astigmatism. The fellow eye served as a control. The mean preoperative spherical equivalent refraction was -5.25 +/- 1.00 D (range, -1.75 to -11.00 D). Attempted correction aimed at emmetropia. Schirmer I and II, and tear break-up time (BUT) tests were performed preoperatively and at 1, 3, and 6 months postoperatively. All tests were correlated to the amount of the attempted correction., Results: Preoperatively, mean values were Schirmer I: 16.2 mm, Schirmer II: 11.6 mm, and BUT: 16.3 sec. One month after LASIK, mean values were Schirmer I: 12.8 mm, Schirmer II: 9.2 mm, and BUT: 13.3 sec. At 3 months, mean values were Schirmer I: 15.76 mm, Schirmer II: 11.3 mm, and BUT: 14.15 sec. At 6 months, mean values were Schirmer I: 15.96 mm, Schirmer II: 11.66 mm, and BUT: 16.3 sec. No correlation to the amount of attempted correction was found. Fellow eye tests were not affected at any interval., Conclusions: Tear secretion following LASIK was decreased during 3 months after surgery and was normalized by 6 months.

Purpose: To investigate gender- and age-related differences in the corneal topography of a normal population., Methods: One hundred thirty-two topographic examinations were collected from 100 patients ranging in age from 23 to 83 years (average, 57.35+/-17.38 years). Data were segregated by gender and further divided into younger (less than 50 years) and older (50 years or more) age groups. The topographic indices of Surface Regularity Index, Surface Asymmetry Index, Irregular Astigmatism Index, Standard Deviation of Corneal Power, Corneal Eccentricity Index, Coefficient of Variation of Corneal Power, Simulated Keratometry 1 and 2, and Average Corneal Power were examined. The astigmatism pattern and corneal irregularity were determined and compared with respect to gender and age., Results: The corneas of older men were flatter than those of older women (p < 0.001). The vertical corneal meridian, but not the horizontal meridian, showed statistically significant gender-related changes with aging (p < 0.001). Older men had a significantly higher potential for against-the-rule astigmatism than women (p < 0.001). Corneal irregularity (measured in terms of the Surface Regularity Index and Irregular Astigmatism Index) increased with age (p < 0.001 and p < 0.001, respectively), although there was no gender-related difference. In the younger group, no gender-related differences in corneal curvature or astigmatism pattern were found., Conclusion: Aging influences changes in patterns of astigmatism differently in men and women. Decreases in levels of sex hormones may play a role in gender-related changes in corneal structure with age.

Purpose: To evaluate the effect of spherical and astigmatic excimer laser photorefractive keratectomy (PRK and PARK, respectively) on tear secretion., Setting: The Vlemma Eye Center, Athens, Greece., Methods: Forty-eight eyes of 48 patients had PRK (28 eyes) or PARK (20 eyes) for the correction of myopia and combined myopic astigmatism. The fellow eye served as a control. The mean preoperative spherical equivalent was -3.96 diopters (D) +/- 1.00 (SD) in the PRK eyes (range -2.00 to -6.50 D) and -3.45 +/- 0.50 D in the PARK eyes (range -1.75 to -6.00 D). Attempted correction aimed at emmetropia. Schirmer I and II and tear film breakup time (BUT) tests were performed preoperatively and 1, 3, and 6 months postoperatively. All tests were correlated to the amount of attempted correction., Results: In the PRK group, the preoperative mean values were Schirmer I, 16.20 mm; Schirmer II, 12.73 mm; and BUT, 16.46 sec. At 1 month, they were 12.23 mm, 8.46 mm, and 13.33 sec, respectively; at 3 months, 13.86 mm, 10.64 mm, and 14.42 sec, respectively; at 6 months, 14.32 mm, 11.32 mm, and 15.36 sec, respectively. In the PARK group, the mean Schirmer I, II, and BUT values were preoperatively 18.52 mm, 14.86 mm, and 17.42 sec, respectively; at 1 month, 14.5 mm, 10.4 mm, and 14.36 sec, respectively; at 3 months, 15.36 mm, 11.81 mm, and 14.72 sec, respectively; and at 6 months, 16.5 mm, 12.15 mm, 16.5 sec, respectively. No correlation to the amount of attempted correction was found. Fellow-eye tests were not affected at any interval., Conclusions: In the first 6 months after PRK and PARK, tear secretion test values decreased.

Purpose: The aim of this study was to evaluate the disruption of the blood-aqueous barrier (BAB) and the induced astigmatism following phacoemulsification, trabeculectomy and phacotrabeculectomy., Material and Methods: 141 eyes of patients who underwent different surgical procedures of the anterior segment were examined with the use of computer-assisted videokeratography. All maps were recorded preoperatively, and one and five days after surgery. We also applied a laser flare-meter in 41 eyes in order to quantify aqueous flare following these procedures., Results: The mean surgically-induced astigmatism following conventional trabeculectomy was 2.1 D and 1.4 D one and five days postoperatively, phacoemulsification with sutures 2.7 D and 1.9 D and phacotrabeculectomy 3.0 D and 2.4 D, respectively. Lower values of astigmatism obtained after sutureless phacoemulsification were 0.6 D and 0.3 D one and five days postoperatively, respectively (p < 0.05 vs Phaco+IOL+Trab. group, p < 0.01 vs other groups). It was found that aqueous flare values following phacotrabeculectomy were 58.0 photon counts/milisec.--one day, 39.3--3 days, 24.4--7 days, 20.4--10 days postoperatively. Significantly reduced values were observed after phacoemulsification--27.6 one day after surgery and 17.6--3 days later (p < 0.01 vs Phaco+IOL+Trab.group)., Conclusions: It could be concluded that induced astigmatism and the amount of inflammation were the highest after triple procedure and the lowest after phacoemulsification.

Background: One human pathology specimen has been studied previously following the use of the excimer laser for the correction of astigmatism. We report histopathologic findings following linear corneal excisions with the excimer laser., Methods: A 193 nm excimer laser was used to create symmetrical, transverse excisions in a human eye to correct astigmatism. Three months later, a full-thickness corneal transplant was performed due to unsatisfactory refractive results. The excised corneal button was examined with light microscopy, transmission electron microscopy and immunohistochemistry., Results: An area 10 to 20-micron wide was observed between the epithelial cells within the keratectomy and the sharply dissected stromal lamellae. This area stained positive for laminin and pro-collagen type III. Some epithelial cells showed processes reaching into this area. Descemet's membrane, immediately underneath the area of the keratectomy, contained atypically striated collagen fibers., Conclusions: These findings demonstrate wound healing changes similar to those reported following diamond knife keratotomy and photorefractive keratectomy for myopia. The changes in the posterior cornea are similar to those previously reported when an excimer laser beam approached Descemet's membrane.

This study used linear regression to analyze the correlation between the location of transscleral sutures and the postoperative visual acuity, refraction, and anterior chamber depth in eyes with posterior chamber intraocular lenses implanted by scleral fixation. The suture-to-limbus distance at the 12 o'clock and 6 o'clock positions averaged 2.4 mm and 1.7 mm, respectively. Suture location had no statistically significant relationship with postoperative acuity, spherical equivalent, astigmatism, or anterior chamber depth.

We show that normally a spherocylindrical lens will correct the local refractive error of any small area of the pupil. In general, however, the correction varies with position across the pupil. Plots are given to illustrate this variation for 2 typical individual eyes and for the average of 11 eyes, as calculated from the corresponding wavefront aberrations. The implications of these results for the design and use of objective optometers are briefly considered.