Corneal higher order aberrations by Sirius topography and their relation to different refractive errors.

PURPOSE: To compare the root mean square (RMS) of anterior corneal higher-order aberrations (HOAs) in ametropic and emmetropic eyes. METHODS: This retrospective observational study was conducted at the Department of Ophthalmology, Tishreen University Hospital, Latakia, Syria. Study eyes were divided into four groups based on refractive error: mild-to-moderate myopia, hypermetropia, myopic astigmatism, and emmetropic eyes as controls. The following anterior corneal HOAs were evaluated using the Scheimpflug-Placido Sirius (CSO, Italy) tomographer over 6 mm pupil: Root mean square (RMS) total corneal HOAs, RMS trefoil, RMS coma and RMS spherical aberrations. RESULTS: RMS values of total HOAs, trefoil and coma showed statistically significant differences in all four groups (P < 0.05, all). HOAs were noted to be lowest in the control group (0.18 ± 0.09, 011 ± 0.08 and 0.09 ± 0.08 µm, respectively) and highest in the myopic astigmatism group (0.31 ± 0.16, 0.15 ± 0.12, 0.17 ± 0.14 µm, respectively). RMS spherical aberration was lowest in the astigmatism group (0.00 ± 0.16 µm) with a statistically significant difference from that in the control group (0.05 ± 0.07 µm, P = 0.049). CONCLUSION: The mean RMS values of total HOAs, trefoil and coma were highest in the astigmatism group and lowest in the control group. However, spherical aberration was minimal in the astigmatism group. A better understanding and targeted treatment of higher-order aberrations in ametropic human eyes, and in particular eyes with astigmatism, may enhance visual quality and performance in the treatment of refractive errors. Recognising atypical HOAs may also assist in the early detection of pathological conditions such as keratoconus.

Clinical Outcomes of Accelerated Corneal Cross-Linking for Pediatric Keratoconus.

AIM: To assess the efficacy and safety of accelerated corneal cross-linking in the treatment of pediatric keratoconus. METHOD: In this retrospective case series, 29 eyes of 20 pediatric patients with keratoconus underwent accelerated corneal cross-linking. Treatment was delivered at 10 mW/cm2 for 9 minutes with a total dose of 5.4 J/cm2. Clinical evaluation included visual acuities and refractive and Scheimpflug corneal tomography assessments. All patients with a minimum follow-up duration of 24 months were included in the study. RESULTS: Mean ± standard deviation age was 15.41 ± 2.13 years (range: 8 to 18 years). Uncorrected distance visual acuity improved significantly from 0.56 ± 0.28 to 0.42 ± 0.29 logMAR (P=0.0003), and corrected distance visual acuity improved significantly from 0.34 ± 0.23 to 0.28 ± 0.22 logMAR (P=0.014). The mean manifest refraction spherical equivalent value was significantly reduced (-0.59 ± 0.95 D, P=0.0024). While mean flat keratometry and steep keratometry values were not significantly altered (P > 0.05 for both), the mean maximum keratometry value was significantly decreased from 56.97 ± 5.24 D preoperatively to 55.84 ± 5.37 D at 24 months postoperatively (P=0.003). Maximum keratometry had progressed by >1 D in two eyes (6.89%). Permanent corneal haze was reported in one case (3.44%). CONCLUSION: Our 24-month follow-up demonstrated that accelerated corneal cross-linking appears to halt the progression of keratoconus in pediatric patients without apparent complications. Uncorrected and corrected distance visual acuities were also improved.