Variation and Magnitude of Ocular Light Scatter in Keratoconic Corneas
Evaluate the ocular light scatter of keratoconic corneas and correlate with the severity of corneal ectasia as compared to normal corneas undergoing LASIK.
Retrospective study of patients with keratoconic corneas undergoing ocular light scatter analysis. Patient corneas undergoing LASIK were used as normal controls. The objective scatter index (OSI), which quantifies the intraocular light distribution over the retina, was collected by the Optical Quality Analysis System (OQAS) for ectatic and pre-LASIK corneas. Baseline data for each patient included refractive error, mean central corneal power, mean central corneal pachymetry, presence of corneal scarring, and lens status. OSI was correlated to severity of corneal ectasia, as measured by the Keratoconus Severity Score (KSS) and Amsler-Krumeich (AK) stage.
Mean OSI for keratoconic corneas (n=27) was 6.2 ±5.4, and mean OSI for pre-LASIK controls (n=14) was 0.96 ± 0.56. Two sample t-Test showed a statistically significant difference between mild and severe keratoconic corneas: (1) corneas with a KSS of 1-2 and AK stage of 1-2 had a mean OSI of 1.7 and 3.8, respectively; (2) corneas with a KSS of 3-5 and AK stage of 3-4 had a mean OSI of 8.8 and 11, respectively. ANOVA single factor analysis showed the OSI variance in keratoconic corneas was dependent on the KSS (p-value 0.001) and the AK stage (p-value 0.0002).
Ocular light scatter was more severe in keratoconic corneas versus pre-LASIK controls. Moreover, the KSS and AK stage of the keratoconic corneas predicted much of the variation in ocular light scatter. Corneas with subclinical or early disease had lower OSI recordings than those with moderate to severe keratoconus.