Effect of forward light scattering on visual function in eyes with cortical cataract

Abstract

Purpose: We examined correlations between forward light scattering (FLS) and visual function in cortical cataract (COR) and transparent (TP) eyes.

Methods: Of subjects in 2013 Monzen Eye Study and Kanazawa Medical University Hospital cataract surgery patients from July 2013 to March 2014, 39 COR eyes of 35 subjects (66.5±6.0 yrs) were compared with 42 TP eyes of 42 subjects (57.2±8.7 yrs) as control. Cases with ocular disease except for refractive error were excluded. COR was examined under maximal mydriasis by the same examiner, graded in 4 stages (Grade 0 to 3) according to WHO classification system, and categorized CEN+/- by opacity within/outside the central 3 mm diameter of the pupil. Opacity within this 3 mm diameter area was measured with transillumination imaging by anterior eye segment analysis system EAS-1000 (NIDEK). FLS was measured by C-Quant (OCULUS^®) and stray light correction level (Log(s)) was calculated. Total higher-order aberration (HOA) in the 4 mm pupil diameter, retinal image contrast (RIC) in the 3 mm entrance pupil, and 25% day and evening vision contrast visual acuity (CVA) were measured by KR-9000PW (TOPCON), PSF-1000 (TOPCON), and CAT-2000 (NEITZ), respectively.

Results: FLS was higher in COR (1.38±0.25) than in TP (1.13±0.22) (p<0.001). There was no significant correlation between FLS and age in COR or TP. FLS in COR increased with grade. CEN+ (1.45±0.20) had higher FLS than CEN- (1.26±0.30) (p<0.05) with CEN+ grade 1 (1.36±0.25), 2 (1.43±0.13), and 3 (1.51±0.24). There was a positive correlation between area of opacity of CEN+ and FLS (p<0.05). CEN- with COR grade 2 (1.37±0.32) had higher FLS than TP (p<0.05). In TP eyes, FLS was significantly correlated with decreased best corrected visual acuity (p<0.01), increased total ocular HOA (p<0.01) and total intraocular HOA (p<0.05), but not in COR eyes. There was no correlation between FLS and CVA in TP or COR, however, RIC in COR showed a negative correlation with FLS in low and intermediate frequency domains (p<0.05).

Conclusions: FLS in TP at age 40s-60s was little affected by aging. In COR, FLS increased with severity of opacity and opacity in the pupillary area, decreasing RIC. It was suggested that higher FLS is a major factor in decreased visual function.