Enhancing the Automated Detection of Implantable Collamer Lens Vault Using Generative Adversarial Networks and Synthetic Data on Optical Coherence Tomography.

PURPOSE: To investigate the efficacy of incorporating Generative Adversarial Network (GAN) and synthetic images in enhancing the performance of a convolutional neural network (CNN) for automated estimation of Implantable Collamer Lens (ICL) vault using anterior segment optical coherence tomography (AS-OCT). METHODS: This study was a retrospective evaluation using synthetic data and real patient images in a deep learning framework. Synthetic ICL AS-OCT scans were generated using GANs and a secondary image editing algorithm, creating approximately 100,000 synthetic images. These were used alongside real patient scans to train a CNN for estimating ICL vault distance. The model's performance was evaluated using statistical metrics such as mean absolute percentage error (MAPE), mean absolute error (MAE), root mean squared error (RMSE), and coefficient of determination (R2) for the estimation of ICL vault distance. RESULTS: The study analyzed 4,557 AS-OCT B-scans from 138 eyes of 103 patients for training. An independent, retrospectively collected dataset of 2,454 AS-OCT images from 88 eyes of 56 patients, used prospectively for evaluation, served as the test set. When trained solely on real images, the CNN achieved a MAPE of 15.31%, MAE of 44.68 µm, and RMSE of 63.3 µm. However, with the inclusion of GAN-generated and algorithmically edited synthetic images, the performance significantly improved, achieving a MAPE of 8.09%, MAE of 24.83 µm, and RMSE of 32.26 µm. The R2 value was +0.98, indicating a strong positive correlation between actual and predicted ICL vault distances (P < .01). No statistically significant difference was observed between measured and predicted vault values (P = .58). CONCLUSIONS: The integration of GAN-generated and edited synthetic images substantially enhanced ICL vault estimation, demonstrating the efficacy of GANs and synthetic data in enhancing OCT image analysis accuracy. This model not only shows potential for assisting postoperative ICL evaluations, but also for improving OCT automation when data paucity is an issue. [J Refract Surg. 2024;40(4):e199-e207.].

Use of a support vector machine for keratoconus and subclinical keratoconus detection by topographic and tomographic data.

PURPOSE: To define a new classification method for the diagnosis of keratoconus based on corneal measurements provided by a Scheimpflug camera combined with Placido corneal topography (Sirius, CSO, Florence, Italy). DESIGN: Retrospective case series. PARTICIPANTS: We analyzed the examinations of 877 eyes with keratoconus, 426 eyes with subclinical keratoconus, 940 eyes with a history of corneal surgery (defined as abnormal), and 1259 healthy control eyes. METHODS: For each group, eyes were divided into a training and a validation set. A support vector machine (SVM) was used to analyze the corneal measurements and classify the eyes into the 4 groups of participants. The classifier was trained to consider the indices obtained from both the anterior and posterior corneal surfaces or only from the anterior corneal surface. MAIN OUTCOME MEASURES: Symmetry index of front and back corneal curvature, best fit radius of the front corneal surface, Baiocchi Calossi Versaci front index (BCV(f)) and BCV back index (BCV(b)), root mean square of front and back corneal surface higher order aberrations, and thinnest corneal point were analyzed. The diagnostic performance of the classifier was evaluated. RESULTS: The accuracy of the classifier was excellent both with and without the data generated from the posterior corneal surface and corneal thickness because the number of true predictions was greater than 95% and 93%, respectively, in all classes. Precision improved most when posterior corneal surface data were included, especially in cases of subclinical keratoconus. Using the data from both anterior and posterior corneal surfaces and pachymetry allowed the SVM to increase its sensitivity from 89.3% to 96.0% in abnormal eyes, 92.8% to 95.0% in eyes with keratoconus, 75.2% to 92.0% in eyes with subclinical keratoconus, and 93.1% to 97.2% in normal eyes. CONCLUSIONS: The classification algorithm showed high accuracy, precision, sensitivity, and specificity in discriminating among abnormal eyes, eyes with keratoconus or subclinical keratoconus, and normal eyes. Including the posterior corneal surface and thickness parameters markedly improved the sensitivity in the diagnosis of subclinical keratoconus. Classification may be particularly useful in excluding eyes with early signs of corneal ectasia when screening patients for excimer laser surgery.

Comparison of LASEK and LASIK with thin and ultrathin flaps after excimer laser ablation with the SCHWIND Aspheric ablation profile.

PURPOSE: to compare visual, refractive, and wavefront aberration outcomes of laser epithelial keratomileusis (LASEK), thin-flap LASIK (flap thickness 110 to 130 microm), and ultrathin-flap LASIK (flap thickness <110 microm) after excimer laser ablation with an aspheric ablation profile. METHODS: a retrospective analysis of 97 eyes of 56 patients with myopia <6.00 diopters (D) sphere (30 eyes, alcohol-assisted LASEK; 30 eyes, LASIK 110; and 37 eyes, LASIK 130) was conducted. Surgery was performed using the SCHWIND ESIRIS Aberration-Free aspheric ablation profile and the Carriazo-Pendular microkeratome. RESULTS: groups were comparable preoperatively except for lower astigmatism and ocular trefoil (3,+3) in the LASIK 130 group and lower corneal thickness in the LASEK group. At 6 months postoperative, the groups were comparable for uncorrected and corrected distance visual acuity, efficacy index, safety, and refractive predictability. All groups demonstrated improved contrast sensitivity. All groups demonstrated a significant change in spherical aberration compared to preoperative levels. The induced spherical aberration was 0.057 microm/D in the LASEK group, 0.039 microm/D in the LASIK 110 group, and 0.044 microm/D in the LASIK 130 group. Other higher order aberrations did not show significant change except for a reduction in corneal trefoil (P=.034) in the LASEK group and increased ocular trefoil (P=.002) in the LASIK 110 group. The extent of change in higher order aberrations was not significantly different among groups. CONCLUSIONS: the aspheric ablation profile is safe, effective, and predictable and produces similar visual and refractive results with three different surgical approaches of LASEK, thin-flap LASIK, and ultrathin-flap LASIK. The ablation profile demonstrated a low induction rate of higher order aberrations regardless of surgical approach.

Decision Assistant Wizard to standardize optimal outcomes in excimer laser refractive corneal surgery.

PURPOSE: To assess a decision tree analysis system to further optimize refractive surgery outcomes. METHODS: A 5-step decision tree, the Decision Assistant Wizard, based on previous experience with the SCHWIND AMARIS laser, was applied for selecting a customized refractive surgery treatment mode (aspheric aberration neutral, corneal wavefront-guided, or ocular wavefront-guided) to eliminate or reduce total aberration. RESULTS: Using the Decision Assistant Wizard, 6467 LASIK treatments were performed over a 30-month period; 5262 and 112 for myopic and hyperopic astigmatism, respectively, using aspheric aberration neutral (AF) profiles, 560 using corneal wavefront-guided profiles, and 533 using ocular wavefront-guided profiles. Twenty-two (0.3%) retreatments were performed overall; 18 (0.3%) and 0 (0%) after myopic and hyperopic astigmatism, respectively, using AF, 3 (0.5%) after corneal wavefront-guided profiles, and 1 (0.2%) after ocular wavefront-guided profiles. CONCLUSIONS: Decision Assistant Wizards may further optimize refractive surgical outcomes by providing the most appropriate ablation pattern based on an eye's anamnesis, diagnosis, and visual demands. The general principles may be applied to other laser systems; however, specifics will depend on manufacturers' specifications.

LASIK for myopia and astigmatism using the SCHWIND AMARIS excimer laser: an international multicenter trial.

PURPOSE: To assess the efficacy, predictability, and safety of LASIK for the surgical correction of low to moderate myopia with astigmatism using the SCHWIND AMARIS excimer laser. METHODS: Six international study sites enrolled 358 eyes with a manifest refraction spherical equivalent (MRSE) from -0.50 to -7.38 diopters (D) (mean sphere: -3.13+/-1.58 D) with up to -5.00 D of astigmatism (mean: -0.69+/-0.67 D). All eyes underwent treatment with the nonwavefront-guided aspheric algorithm of the SCHWIND AMARIS excimer laser. All eyes were targeted for emmetropia. Refractive outcomes and corneal higher order aberrations were analyzed pre- and postoperatively. Visual quality was assessed using photopic and mesopic contrast sensitivity. Six-month postoperative outcomes are reported. RESULTS: At 6 months postoperative, the MRSE for all eyes was -0.21+/-0.20 D, and 96% (343/358) of eyes had MRSE within +/-0.50 D. Uncorrected visual acuity was 20/20 or better in 98% (351/358) of eyes, and no eyes lost 2 or more lines of best spectacle-corrected visual acuity. The total corneal higher order aberrations root-mean-square increased by 0.09 microm, spherical aberration increased by 0.08 microm, and coma increased by 0.04 microm postoperatively. Photopic and mesopic contrast sensitivity did not change 6 months postoperatively. CONCLUSIONS: Treatment of myopia with astigmatism using the SCHWIND AMARIS excimer laser is safe, efficacious, predictable, and maintains visual quality.

Clinical outcomes of LASIK for myopia using the SCHWIND platform with ocular wavefront customized ablation.

PURPOSE: To evaluate the clinical outcomes of aspheric ocular wavefront ablation profiles in LASIK treatments. METHODS: Thirty eyes treated by ocular wavefront were retrospectively analyzed at 6-month follow-up. Custom Ablation Manager (CAM) software was used to plan wavefront-customized aspheric treatments, and the ESIRIS system was used to perform ablations (SCHWIND eye-tech-solutions). Outcomes were evaluated in terms of efficacy, predictability, refractive outcome, safety, and pre-and postoperative wavefront aberration analysis (SCHWIND Ocular Wavefront Analyzer). RESULTS: At 6 months postoperatively, 47% of eyes achieved uncorrected visual acuity 20/20 or better. Average defocus was reduced from -3.49+/-2.38 diopters (D) preoperatively (range: -10.63 to 0.00 D) to -0.14+/-0.31 D postoperatively (range: -1.75 to 0.00 D). Astigmatism was reduced from -0.81+/-1.15 D (range: -4.25 to 0.00 D) to -0.25+/-0.37 D (range: -1.25 to 0.00 D). Eighty-six percent of eyes were within +/- 0.50 D. Best spectacle-corrected visual acuity (logMAR) improved from +0.12+/-0.08 (range: 0.0 to +0.2) to -0.05+/-0.13 (range: -0.2 to +0.2) (P=.04). The treatment did not change coma or spherical aberration, and reduced the trefoil from 0.21+/-0.13 microm (range: 0.05 to 0.53 microm) to 0.08+/-0.13 microm (range: 0.01 to 0.39 microm) (P=.002). CONCLUSIONS: The study results indicate that the aspheric ocular wavefront customized CAM approach for planning ablation volumes is safe and effective.

Central ablation depth and postoperative refraction in excimer laser myopic correction measured with ultrasound, Scheimpflug, and optical coherence pachymetry.

PURPOSE: To compare measurements of ultrasound, Scheimpflug, and optical coherence pachymetric techniques to describe ablated depth after myopic astigmatic corneal laser refractive surgery and achieved refractive correction. METHODS: Ninety-six myopic astigmatism treatments using LASIK or LASEK in 58 patients with 3-month followup were retrospectively analyzed. In all cases, standard examinations, pre-/postoperative corneal topography, ocular aberrometry, and pachymetry were performed. SCHWIND Custom Ablation Manager (CAM) software and the ESIRIS laser were used for planning treatments and performing ablations. Outcomes were evaluated in terms of predictability, safety, and wavefront aberration. Pachymetry was taken before treatment (ultrasound [DGH Pachette 2], Scheimpflug [Oculus Pentacam HR], and optical coherence pachymetry [OCP] [Heidelberg-Engineering OCP]), after lifting the flap (Pachette 2, OCP), immediately after finishing ablation (Pachette 2, OCP), and at 3-month follow-up (Pachette 2, Pentacam HR). RESULTS: At 3 months, 87 (91%) of eyes achieved 20/20 UCVA, and 89 (93%) of eyes were within +/-0.50 diopters (D). Postoperative mean spherical equivalent refraction was -0.15 +/- 0.30 D. Best spectacle-corrected visual acuity improved in 30 (31%) of eyes. Differential pachymetry correlated to intended central ablation depth for all techniques: r2 = 0.60, P < .0001, slope 0.81 for ultrasound; r2 = 0.75, P < .0001, slope 0.97 for Scheimpflug; and r2 = 0.76, P < .0001, slope 1.03 for OCR Relative differential pachymetry correlated only marginally to achieved refractive correction for ultrasound and OCP. CONCLUSIONS: Differential pachymetry is a metric useful for describing intended central ablation depth but not for achieved refractive correction. The rotating Scheimpflug technique offers the best estimation (closest slope to 1) and OCP offers the best correlation (closest r2 to 1) for describing intended central ablation depth achieved. The three techniques give different measurements for ablation depth, with OCP being substantially different from ultrasound and Scheimpflug. Only borderline correlations were obtained for achieved refractive correction with ultrasound and OCP.

LASIK for myopia with Aspheric "aberration neutral" ablations using the ESIRIS laser system.

PURPOSE: To evaluate the clinical outcomes of LASIK using optimized "aberration neutral" ablation profiles. METHODS: Laser in situ keratomileusis was performed in 231 eyes (120 patients) with a mean spherical equivalent refraction of -4.12+/-2.26 diopters (D) (range: -0.37 to -9.50 D) using a SCHWIND Pendular microkeratome with a 130-microm cutting head and the SCHWIND ESIRIS excimer laser. In all cases, pre- and postoperative autorefractor measurements, manifest refraction, best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA), topography and corneal wavefront analysis, and ocular wavefront analysis as well as complications were analyzed. Ablations were calculated using the ORK-CAM software. Clinical outcomes were evaluated in terms of efficacy, predictability, stability, refractive outcome, safety, and wavefront aberrations. RESULTS: At 3 months, mean spherical equivalent refraction was -0.10+/-0.33 D (range: +0.86 to -1.18 D). Of 231 eyes, 201 (87%) were within +/-0.50 D of attempted correction. Uncorrected visual acuity was 20/16 or better in 71% (164 eyes), 20/20 or better in 92% (213 eyes), and 20/32 or better in 100%. Average root-mean-square higher order aberrations increased 0.05 microm after treatment, mean spherical aberration increased 0.08 microm after treatment, and mean coma increased 0.04 microm after treatment (all for 6.0-mm analysis diameter). CONCLUSIONS: Our results show that non-customized "aberration neutral" ablation profiles derived from wavefront analysis are able to minimize the amount of induced aberrations of both the cornea and the eye.

Clinical outcomes of corneal wavefront customized ablation strategies with SCHWIND CAM in LASIK treatments.

PURPOSE: To evaluate the clinical outcomes of aspheric corneal wavefront (CW) ablation profiles in LASIK treatments. METHODS: Thirty eyes treated with CW ablation profiles were included after a follow-up of 6 months. In all cases, standard examinations including preoperative and postoperative wavefront analysis with a CW topographer (Optikon Keratron Scout) were performed. Custom Ablation Manager (CAM) software was used to plan corneal wavefront customized aspheric treatments, and the ESIRIS flying spot excimer laser system was used to perform the ablations (both SCHWIND eye-tech-solutions, Kleinhostheim, Germany). Clinical outcomes were evaluated in terms of predictability, refractive outcome, safety, and wavefront aberration. RESULTS: In general, the postoperative uncorrected visual acuity and the best corrected visual acuity improved (p < 0.001). In particular, the trefoil, coma, and spherical aberrations, as well as the total root-mean-square values of higher order aberrations, were significantly reduced (p < 0.05) when the pre-existing aberrations were greater than the repeatability and the biological noise. CONCLUSIONS: The study results indicate that the aspheric corneal wavefront customized CAM approach for planning ablation volumes yields visual, optical, and refractive results comparable to those of other wavefront-guided customized techniques for correction of myopia and myopic astigmatism. The CW customized approach shows its strength in cases where abnormal optical systems are expected. Apart from the risk of additional ablation of corneal tissue, systematic wavefront-customized corneal ablation can be considered as a safe and beneficial method.

Clinical outcomes of laser in situ keratomileusis with an aberration-neutral profile centered on the corneal vertex comparing vector planning with manifest refraction planning for the treatment of myopic astigmatism.

PURPOSE: To evaluate clinical outcomes of laser in situ keratomileusis (LASIK) with an aberration-neutral profile centered on the estimated visual axis (considering 70% of the pupil offset toward the corneal vertex) comparing vector planning with manifest refraction planning for the treatment of myopic astigmatism. SETTING: Muscat Eye Laser Center, Muscat, Sultanate of Oman, Muscat, Oman. DESIGN: Retrospective case series. METHODS: The outcomes were evaluated at a 6-month follow-up in eyes showing ocular residual astigmatism (ORA) over 0.75 diopters (D) preoperatively. RESULTS: Eighty-five treatments were based on manifest astigmatism (preoperative sphere -2.11 D ± 1.3 [SD], cylinder -0.90 ± 1.0 D), and 79 treatments were based on vector planning (preoperative sphere -2.46 ± 1.5 D, cylinder -0.78 ± 0.79 D). At a 6-month follow-up, 128 patients (164 eyes) were evaluated and no significant differences were observed between the 2 groups in terms of difference between corrected distance visual acuity and uncorrected distance visual acuity (UDVA) (P = .1, t test and Fisher exact test Snellen lines 1 or better, P = .4) and postoperative UDVA (P = .05, t test and Fisher exact test for UDVA 20/16 or better, P = .3). Significant differences were observed between the 2 groups in terms of achieved spherical equivalent (P = .04), corneal toricity, and ORA (P < .001, t test and Fisher exact test for ORA ≤0.75 D, P < .001). CONCLUSION: Performing LASIK for myopic astigmatism with the vector planning approach resulted in comparable visual outcomes to manifest refraction planning.

Nidek MK 2000 microkeratome clinical evaluation.

PURPOSE: To evaluate flap dimension, flap thickness, hinge size, and cut deterioration with second blade use with the Nidek MK 2000 automatic microkeratome. METHODS: The Nidek MK 2000 with different head options (130 and 160 microm) and suction rings (8.5 and 9.5 mm) was used during 328 consecutive LASIK procedures, reusing the blade for the second eye in the same patient. Flap diameter and hinge size were measured under microscopy with a Castroviejo caliper and thickness was calculated using the Pachete ultrasonic pachymeter. RESULTS: The mean flap thickness was 116.03 +/- 19.26 microm using the 130-microm head and 147.7 +/- 21.74 microm using the 160-microm head. The average vertical flap size was 8.56 +/- 0.36 mm with the 8.5-mm suction ring and 9.45 +/- 0.32 mm with the 9.5-mm ring. The hinge size was 4.7 +/- 0.72 mm. The second cut was thinner than the first; 14.7 microm average using the 130-microm head, and 19.1 microm average using the 160-microm head. CONCLUSION: The Nidek MK 2000 microkeratome was simple, safe, predictable, and reliable for LASIK.

Six-month clinical outcomes of customized treatments minimized for depth and time in laser corneal refractive surgery.

PURPOSE: Evaluating the application of 2 methods for minimizing the ablated tissue upon objective minimization of depth and time of Zernike-based customized ablations. SETTING: Muscat Eye Laser Center, Muscat, Sultanate of Oman. METHODS: Recently developed algorithms for selection of Zernike terms in customized treatments for refractive surgery were used. Clinical outcomes and tissue-saving attributes were evaluated on 2 groups [minimize depth (MD) and minimize volume (MV); 30 eyes each], plus a control group [corneal wavefront (CW); 30 eyes] with conventional customized approach. Clinical outcomes were evaluated in terms of predictability, safety, and contrast sensitivity and tissue-saving attributes in terms of saved depth and time for each condition (in micrometers, seconds, and percentage) and whether minimized depth or time were less than required for equivalent noncustomized treatments. RESULTS: Ninety-three percent of treatments in the CW group, 93% in the MD group, and 100% in the MV group were within 0.50 diopters of spherical equivalent (SEq) postoperatively. Forty percent of treatments in the CW group, 34% in the MD group, and 47% in the MV group gained at least 1 line of best spectacle-corrected visual acuity postoperatively. Tissue-saving attributes showed an average saved depth of 8 µm (1-20 µm) and a saved time of 6 seconds (1-15 seconds) in the MD group and 6 µm (0-20 µm) and 8 seconds (2-26 seconds) in the MV group. Proposed corrections were always less deep and shorter than full wavefront corrections. In 43% of the MD cases, corrections were less deep, and in 40% of the MV cases, corrections were shorter than equivalent aberration-free treatments. CONCLUSION: The minimization techniques compared here effectively reduced depth and time needed for ablation (up to a maximum of 50% and by 15% in average) without negatively affecting clinical outcomes postoperatively, yielding results equivalent to those of the full customization group.

The SCHWIND AMARIS Total-Tech Laser as An All-Rounder in Refractive Surgery.

PURPOSE: To describe and argument an overview of the main features and unique technical points of AMARIS Total-Tech Laser, coupled with patient outcomes supporting the decision to perform LASIK treatments with maximised outcomes. SETTINGS: Dr. M.C. Arbelaez, Muscat Eye Laser Center, Muscat, Sultanate of Oman. METHODS: The findings collected during 18-month experience using SCHWIND AMARIS Total-Tech Laser have been reviewed to provide arguments for supporting the decision to perform LASIK treatments with maximised outcomes. For updated clinical outcomes, the last 100 myopic astigmatism treatments, the last 100 hyperopic astigmatism treatments, the last 30 ocular-wavefront-guided treatments, and the last 30 corneal-wavefront-guided treatments, all with 6-month follow-up, were included. For all those, LDV femtosecond system was used to prepare the flaps, and AMARIS flying spot system was used to perform ablations. Clinical outcomes were evaluated in terms of predictability, refractive outcome, safety, wavefront aberration, and contrast sensitivity. RESULTS: 6-month postoperatively, mean defocus was -0.14+/-0.31D and astigmatism 0.25+/-0.37D. 70+/- eyes were within +/-0.25D of emmetropia. 43+/- eyes gained lines of best spectacle-corrected visual acuity. For Aberration-Free treatments, none of the aberration metrics changed from pre- to postoperative values in a clinically relevant amount. For ocular-wavefront-guided treatments, the surgery did not change coma or spherical aberration, and reduced trefoil (p<0.005). For corneal-wavefront-guided treatments, the trefoil, coma, and spherical aberrations, as well as the total root-mean-square values of higher order aberration, were significantly reduced (p<.05) when the pre-existing aberrations were greater than the repeatability and the biological noise. CONCLUSIONS: Although this review does not allow for evidence-based conclusions, following our strategy, LASIK results were excellent. LASIK surgery with AMARIS system yield excellent outcomes. Refractions were reduced to subclinical values with no induction of High-Order-Aberrations. Neither adverse events nor complications were observed.

Excimer laser correction of moderate to high astigmatism with a non-wavefront-guided aberration-free ablation profile: Six-month results.

PURPOSE: To evaluate the postoperative clinical outcomes and higher-order aberrations (HOAs) in eyes with astigmatism greater than 2.00 diopters (D) that had laser in situ keratomileusis (LASIK) using a non-wavefront-guided aberration-free ablation profile. SETTINGS: Private practice. METHODS: This retrospective study evaluated the 6-month results of LASIK for astigmatism greater than 2.00 D. Standard examinations and preoperative and postoperative wavefront analyses were performed. Aspheric treatments with a non-wavefront-guided ablation profile were planned using software integrated into the Amaris flying-spot excimer laser system, which was used to perform the ablations. The LASIK flaps were created using an LDV femtosecond laser. Clinical outcomes were predictability, refractive outcomes, safety, efficacy, and wavefront aberration. RESULTS: At 6 months, 84% of the 50 eyes evaluated achieved 20/20 or better uncorrected distance visual acuity (UDVA) and 40% achieved 20/16 or better UDVA. Forty-four percent of eyes were within +/-0.25 D of the attempted astigmatic correction, and 78% were within +/-0.50 D. The mean SE was -0.12 D +/- 0.25 (SD) and the mean astigmatism, 0.50 +/- 0.26 D. Corrected distance visual acuity (CDVA) improved in 36% of eyes; 4% of eyes lost 1 line of CDVA. The predictability slope for astigmatism was 0.97 and the intercept, -0.15 D. There were no clinically relevant changes in any aberration metric from preoperatively to postoperatively. CONCLUSIONS: Excimer laser LASIK using a non-wavefront-guided aberration-free ablation profile yielded excellent visual outcomes. The preoperative astigmatism was reduced to subclinical values with no clinically relevant induction of HOA.

Collagen cross-linking with riboflavin and ultraviolet-A light in keratoconus: One-year results.

BACKGROUND: The aim of this study is to evaluate the safety and effectiveness of riboflavin-ultraviolet type A (UV-A) light rays induced cross-linking of corneal collagen in improving visual acuity and in stabilizing the progression of keratoconic eyes. The method of corneal cross-linking using riboflavin and UV-A light is technically simple and less invasive than all other therapies proposed for keratoconus. It is the only treatment that treats not only the refractive effects of the condition but the underlying pathophysiology. MATERIALS AND METHODS: In this prospective, nonrandomized clinical study, 20 eyes of 19 patients with keratoconus were treated by combined riboflavin UV-A collagen cross linking. The eyes were saturated with riboflavin solution and were subjected for 30 min under UV-A light with a dose parameter of 3 mW/cm(2). Safety and effectiveness of the treatment was assessed by measuring the uncorrected visual acuity, best corrected visual acuity, manifest cylinder/sphere, keratometry, pachymetry, posterior and anterior elevations from Pentacam and corneal aberrations at 6 months and 1 year post-treatment. RESULTS: Comparative analysis of the pre-operative and 1 year post-operative evaluation showed a mean gain of 4.15 lines of UCVA (P= 0.001) and 1.65 lines of BCVA (P= 0.002). The reduction in the average keratometry reading was 1.36 D (P= 0.0004) and 1.4 D (P= 0.001) at the apex. Manifest refraction sphere showed a mean reduction of 1.26 D (P= 0.033) and 1.25 D (0.0003) for manifest cylinder. Topo-aberrometric analysis showed improvement in corneal symmetry. CONCLUSION: Cross-linking was safe and an effective therapeutical option for progressive keratoconus.

Clinical outcomes of corneal vertex versus central pupil references with aberration-free ablation strategies and LASIK.

PURPOSE: To compare the clinical outcomes of aberration-free ablation profiles based on the normal corneal vertex (CV) and the pupil center (PC) in relation to laser in situ keratomileusis. Aberration-free aspheric ablation treatments were performed in all cases. METHODS: Two myopic astigmatism groups (CV centered using the offset between pupil center and normal corneal vertex and PC centered using the pupil center) comprising 24 and 29 eyes (16 and 19 patients), respectively, with a 6-month follow-up, were included. All enrolled eyes had <0.65 mum RMS-higher order aberration (HOA) for 6.00 mm analysis diameter and pupillary offset >200 mum. In all cases, standard examinations, and preoperative and postoperative wavefront analysis were performed. Custom ablation software was used to plan aberration-free aspheric treatments and a flying spot excimer laser system was used to perform ablations. The clinical outcomes were evaluated for predictability, refractive outcome, safety, ocular wavefront aberration, and asphericity. RESULTS: Of the CV eyes, 38% had improved best spectacle-corrected visual acuity (BSCVA) compared with 24% of the PC eyes (comparison CV/PC P = 0.38). Induced ocular coma was on average 0.17 mum in the CV group and 0.26 mum in the PC group (comparison CV/PC P = 0.01 favoring CV). Induced ocular spherical aberration was on average +0.01 mum in the CV group and +0.07 mum in the PC group (comparison CV/PC P = 0.05 favoring CV). Change in asphericity was on average +0.56 in the CV group and +0.76 in the PC group (comparison CV/PC P = 0.05 favoring CV). No significant shift was observed in the pupillary offset after treatments. CONCLUSIONS: In myopic eyes with moderate to large pupillary offset, CV-centered treatments performed better in terms of induced ocular aberrations and asphericity, but both centrations were identical in photopic visual acuity.