Deepa Viswanathan

Wavefront-guided versus wavefront-optimized laser in situ keratomileusis: Contralateral comparative study

PURPOSE: To compare the outcomes of wavefront‐guided and wavefront‐optimized treatment in fellow eyes of patients having laser in situ keratomileusis (LASIK) for myopia. SETTING: Medical and Vision Research Foundation, Tamil Nadu, India. METHODS: This prospective comparative study comprised 27 patients who had wavefront‐guided LASIK in 1 eye and wavefront‐optimized LASIK in the fellow eye. The Hansatome (Bausch & Lomb) was used to create a superior‐hinged flap and the Allegretto laser (WaveLight Laser Technologie AG), for photoablation. The Allegretto wave analyzer was used to measure ocular wavefront aberrations and the Functional Acuity Contrast Test chart, to measure contrast sensitivity before and 1 month after LASIK. The refractive and visual outcomes and the changes in aberrations and contrast sensitivity were compared between the 2 treatment modalities. RESULTS: One month postoperatively, 92% of eyes in the wavefront‐guided group and 85% in the wavefront‐optimized group had uncorrected visual acuity of 20/20 or better; 93% and 89%, respectively, had a postoperative spherical equivalent refraction of ±0.50 diopter. The differences between groups were not statistically significant. Wavefront‐guided LASIK induced less change in 18 of 22 higher‐order Zernike terms than wavefront‐optimized LASIK, with the change in positive spherical aberration the only statistically significant one (P = .01). Contrast sensitivity improved at the low and middle spatial frequencies (not statistically significant) and worsened significantly at high spatial frequencies after wavefront‐guided LASIK; there was a statistically significant worsening at all spatial frequencies after wavefront‐optimized LASIK. CONCLUSION: Although both wavefront‐guided and wavefront‐optimized LASIK gave excellent refractive correction results, the former induced less higher‐order aberrations and was associated with better contrast sensitivity.

Wavefront aberrations in eyes with decentered ablations

PURPOSE: To compare the refractive and functional outcomes and wavefront profiles in eyes with decentered ablations and eyes with well‐centered ablations. SETTING: Medical Research Foundation, Chennai, Tamil Nadu, India. METHODS: This retrospective analysis comprised eyes with topographically diagnosed decentered ablations after laser in situ keratomileusis (LASIK). Refraction, contrast sensitivity, and ocular wavefront aberrations were measured preoperatively and 1 month postoperatively. The induced aberrations in these eyes were compared with those in eyes with well‐centered ablations. RESULTS: Forty‐six eyes (38 patients) had decentered ablations and 60 eyes (32 patients), well‐centered ablations. The mean decentration in the study group was 0.86 mm ± 0.29 (SD) (range 0.35 to 1.61 mm). There was no significant correlation between decentration and attempted refractive correction. There was, however, a statistically significant (P<.05) linear correlation between the distance of decentration and the magnitude of induced tilt (r = −0.31), coma (r = −0.41), and secondary astigmatism (r = 0.36). The induced changes in tilt, oblique astigmatism, vertical coma, and spherical aberration were statistically significantly higher in eyes with decentered ablations than in eyes with well‐centered ablations. A statistically significantly higher percentage of eyes (87%) with well‐centered ablations than eyes with decentered ablations (70%) had a postoperative uncorrected visual acuity (UCVA) of 20/20 or better. There was no significant difference in contrast sensitivity between groups. CONCLUSION: Eyes with decentered ablations had a significantly higher magnitude of induced aberrations and lower UCVA than eyes with well‐centered ablations.

Prospective longitudinal study of corneal collagen cross-linking in progressive keratoconus.

Collagen cross‐linking has been reported to be effective in treating progressive keratoconus, and this study aims to evaluate the long‐term efficacy of this procedure.Background Collagen cross-linking has been reported to be effective in treating progressive keratoconus, and this study aims to evaluate the long-term efficacy of this procedure. Design Prospective longitudinal interventional study of patients with progressive keratoconus who underwent cross-linking in a tertiary referral hospital. Participants Thirty-five patients (51 eyes) who underwent cross-linking with a mean follow-up of 14.38 ± 9.36 months (range 6–48) were compared with a control group of 25 fellow eyes that did not undergo the procedure. Methods Cross-linking was performed using 0.1% riboflavin (in 20% dextran T500) and ultraviolet A irradiation (370 nm, 3 mW/cm2, 30 min). Main Outcome Measures Maximum keratometry in dioptres, logMAR best spectacle-corrected visual acuity, cylindrical power, manifest refraction spherical equivalent and central corneal thickness. Results Analysis of the treated group demonstrated a significant flattening of maximum keratometry by 0.96 ± 2.33 dioptres (P = 0.005) and a significant improvement in visual acuity by 0.05 ± 0.13 logMAR (P = 0.04). In the control group, maximum keratometry increased significantly by 0.43 ± 0.85 dioptres (P = 0.05), and visual acuity decreased by mean 0.05 ± 0.14 (P = 0.2). No statistical differences were noted regarding cylindrical power, spherical equivalent or corneal thickness in both groups. Conclusions Results indicate that corneal collagen cross-linking using riboflavin and ultraviolet A is effective as a therapeutic option in cases of progressive keratoconus by reducing the corneal curvature and by improving the visual acuity in these patients.

Bilateral femtosecond laser–enabled intrastromal astigmatic keratotomy to correct high post-penetrating keratoplasty astigmatism

A 35-year-old man presented with bilateral high astigmatism following penetrating keratoplasties performed for advanced keratoconus. Femtosecond laser-enabled intrastromal astigmatic keratotomy was performed, resulting in a significant reduction in corneal astigmatism. At 4 months, the corneal astigmatism continued to decrease. The visual acuity, refraction, and serial corneal topographic data are presented.

Longitudinal effect of topical antiglaucoma medications on central corneal thickness

Background To determine the change in central corneal thickness over time and whether the use of long-term topical antiglaucoma medications influences central corneal thickness. Design Case control study with retrospective and prospective data collection. Participants One hundred eighty-seven eyes of 187 glaucoma patients (mean follow up 6.92 ± 1.67 years) being treated with topical antiglaucoma medications (at least 3 years) with no history of surgery or laser were included and compared with 100 eyes of 100 age–matched, untreated control subjects (mean follow up 6.58 ± 1.93 years) who were glaucoma suspects with normal intraocular pressure not on any treatment. Methods Demographic data, central corneal thickness and intraocular pressure were collected at initial glaucoma diagnosis and at most recent visit, and findings were compared between two groups. Main Outcome Measures Mean change in central corneal thickness in microns (μm). Results Central corneal thickness fell significantly (P < 0.0001) in treated eyes but not in control eyes (P = 0.18); mean central corneal thickness reduction was 12.29 ± 13.65 μm in treated eyes and 1.17 ± 8.75 μm in controls. Among treated eyes, central corneal thickness reduction was significant (P < 0.0001) in those treated with either prostaglandins or a combination of prostaglandin and beta-blockers, while no significant reduction occurred in eyes treated with only beta-blockers (P = 0.15) when compared with control eyes. Conclusions Prostaglandins appear to be associated with a small but significant central corneal thickness reduction over time. Serial central corneal thickness measurements might be helpful in glaucoma patients, particularly those on prostaglandins.To determine the change in central corneal thickness over time and whether the use of long‐term topical antiglaucoma medications influences central corneal thickness.

Comparative analysis of corneal measurements obtained from a Scheimpflug camera and an integrated Placido‐optical coherence tomography device in normal and keratoconic eyes

To assess the agreement between a Scheimpflug camera (Pentacam) and a combined Placido‐optical coherence tomography device (Visante OMNI) in measuring corneal curvature, thickness and elevation values in normal and keratoconic eyes.

Outcome of Corneal Collagen Crosslinking for Progressive Keratoconus in Paediatric Patients

Purpose. To evaluate the efficacy of corneal collagen crosslinking for progressive keratoconus in paediatric patients. Methods. This prospective study included 25 eyes of 18 patients (aged 18 years or younger) who underwent collagen crosslinking performed using riboflavin and ultraviolet-A irradiation (370 nm, 3 mW/cm2, 30 min). Results. The mean patient age was 14.3 ± 2.4 years (range 8–17) and mean followup duration was 20.1 ± 14.25 months (range 6–48). Crosslinked eyes demonstrated a significant reduction of keratometry values. The mean baseline simulated keratometry values were 46.34 dioptres (D) in the flattest meridian and 50.06 D in the steepest meridian. At 20 months after crosslinking, the values were 45.67 D (P = 0.03) and 49.34 D (P = 0.005), respectively. The best spectacle corrected visual acuity (BSCVA) and topometric astigmatism improved after crosslinking. Mean logarithm of the minimum angle of resolution (logMAR) BSCVA decreased from 0.24 to 0.21 (P = 0.89) and topometric astigmatism reduced from mean 3.50 D to 3.25 D (P = 0.51). Conclusions. Collagen crosslinking using riboflavin and ultraviolet-A is an effective treatment option for progressive keratoconus in paediatric patients. Crosslinking stabilises the condition and, thus, reduces the need for corneal grafting in these young patients.

Relationship of Structural Characteristics to Biomechanical Profile in Normal, Keratoconic, and Crosslinked Eyes.

Purpose: To evaluate the correlation of corneal biomechanical parameters with structural characteristics in normal, keratoconic, and collagen crosslinked eyes. Methods: A prospective observational study that included 50 normal, 100 keratoconic, and 25 crosslinked eyes. All eyes were imaged using a Scheimpflug camera and an ocular response analyzer. The main outcome measures analyzed were central corneal thickness (CCT), corneal volume (CV), maximal keratometry (Kmax), corneal hysteresis (CH), and corneal resistance factor (CRF). Results: Significant differences were noted among all 3 groups of eyes for CCT, CV, Kmax, CH, and CRF values (P < 0.05 by analysis of variance). CH and CRF correlated negatively (CH, r = −0.40; CRF, r = −0.44; both P < 0.0001) with the Pentacam topographic keratoconus classification. Both CH and CRF correlated positively with CCT and CV for the normal, keratoconic, and crosslinked eyes. In contrast, significant negative correlations were observed between CH, CRF, and Kmax in the keratoconic eyes (CH, r = −0.43; CRF, r = −0.53; both P < 0.0001), whereas no association was noted for the normal and crosslinked eyes. Conclusions: CH and CRF are influenced by the corneal structure, with higher values noted in corneas with greater thickness and volume. Corneal biomechanical parameters progressively decrease as the severity of keratoconus increases. After collagen crosslinking, the relationship of the corneal curvature to the biomechanical profile is similar to normal eyes.

Corneal collagen crosslinking for post-lasik ectasia: an Australian study

Purpose: Post laser‐assisted in situ keratomileusis (LASIK) ectasia is a rare and unpredictable complication after LASIK. Corneal collagen crosslinking (CXL) has emerged as a promising technique to address this complication. Our study evaluates the long‐term efficacy of CXL for post‐LASIK ectasia in an Australian setting. Design: Retrospective review of post‐LASIK ectasia patients referred to and treated at 3 corneal refractive surgery institutions in Sydney, Australia. Methods: Eleven patients (14 eyes; mean age, 39.7 ± 12.6 years) underwent epithelium‐off CXL with follow‐up ranging from 12‐78 months. Best spectacle‐corrected visual acuity (BSCVA), simulated keratometry, corneal topography indices, and higher‐order aberrations (HOAs) [mean ± standard error of the mean (SEM)] were measured with a rotating Scheimpflug camera (Pentacam, Oculus). Comparisons between baseline measurements and postoperative outcomes were performed using paired t test analysis. Results: At last follow‐up, BSCVA improved significantly by 0.2 ± 0.06 logMAR (P = 0.01), and 12 of 14 eyes showed no keratometric deterioration. Of the corneal topography indices, index of height asymmetry showed a trend toward a significant improvement (P = 0.05). There was no progression of corneal HOAs. Central corneal thickness was not significantly altered (P = 0.6). No major postoperative complications were observed. Conclusions: In the Australian setting, CXL has proven effective at stabilizing the progression of post‐LASIK ectasia, inducing corneal regularity, and improving visual acuity.

Comparative study of long-term outcomes of accelerated and conventional collagen crosslinking for progressive keratoconus

PurposeTo compare the long-term outcomes of accelerated corneal collagen crosslinking (CXL) to conventional CXL for progressive keratoconus.Patients and methodsComparative clinical study of consecutive progressive keratoconic eyes that underwent either accelerated CXL (9 mW/cm2 ultraviolet A (UVA) light irradiance for 10 min) or conventional CXL (3 mW/cm2 UVA light irradiance for 30 min). Eyes with minimum 12 months’ follow-up were included. Post-procedure changes in keratometry readings (Flat meridian: K1; steep meridian: K2), central corneal thickness (CCT), best spectacle-corrected visual acuity (BSCVA), and manifest refraction spherical equivalent (MRSE) were analysed.ResultsA total of 42 eyes were included. In all, 21 eyes had accelerated CXL (20.5±5.5 months’ follow-up) and 21 eyes had conventional CXL group (20.2±5.6 months’ follow-up). In the accelerated CXL group, a significant reduction in K2 (P=0.02), however no significant change in K1 (P=0.35) and CCT (P=0.62) was noted. In the conventional CXL group, a significant reduction was seen in K1 (P=0.01) and K2 (P=0.04), but not in CCT (P=0.95). Although both groups exhibited significant reductions in K2 readings, no noteworthy differences were noted between them (P=0.36). Improvements in BSCVA (accelerated CXL; P=0.22 and conventional CXL; P=0.20) and MRSE (accelerated CXL; P=0.97 and conventional CXL; P=0.54) were noted, however were not significant in either group.ConclusionAccelerated and conventional CXL appear to be effective procedures for stabilising progressive keratoconus in the long-term.