Predicting Visual Impairment of Cataract and Visual Outcome of Cataract Surgery Using Wavefront Aberrometry and Scheimpflug Photography

Abstract

Abstract: : Purpose:To determine objective predictors of visual impairment in subjects with cataract and possible predictors of improved visual outcome following cataract surgery in subjects free of additional ocular pathology. Methods: Subjects were recruited via a private ophthalmic institution, the Eye Institute, Auckland, with those exhibiting age–related cataract and no additional ocular pathology invited to participate. Subjects excluded could not obtain pharmacological mydriasis greater than 6mm, or were unable to physically comply with instrumentation. Assessment included: vision and visual acuity, autorefraction and full dilated–pupil clinical examination. Scheimpflug photography and wavefront aberrometry were performed under dim illumination, with mydriasis greater than 6 mm. Clinical subjective grading of cataract was performed by a single observer (NS) using the Lens Opacities Classification System (LOCS) III. Multivariate stepwise linear regression was used to determine predictors of visual impairment in subjects with cataract and visual outcome of cataract surgery. Results: The peak density of anterior embryonic nucleus accounted for 42.2% of variance in predicting spherical aberration (Z4,0). NO and NC scores in combination predict BSCVA pre–operatively, accounting for 63.0% of variation in the data, whereas average elliptical area of embryonic nucleus (Scheimpflug measure) accounted for 36.7% variation in predicting BSCVA. Coma (Z3,1) was the predictor of visual impairment due to cataract, accounting for only 10% of variation. The combination of elliptical area of the embryonic nucleus, with coma (Z3,1) and spherical aberration (Z4,0) accounted for 53.6% of variance predicting BSCVA pre–operatively. The pre–operative measures of elliptical area of the embryonic nucleus, the integrated density 1mm anterior the CND and tetrafoil (Z4,–4) predict change in BSCVA following cataract surgery (R²=.858, p<.001). Change in coma (Z3,1) and change in transparency for a 4mm pupil zone predict change in BSCVA following cataract surgery (R²= .770, p=.003). NO Score and change in coma (Z3,1) account for 92.3% of variation in predicting change in BSCVA following cataract surgery. Conclusions: Pre–operative objective measurements of wavefront aberrometry and scheimpflug photography can predict visual impairment in subjects with cataract, in addition to predicting visual outcome of uncomplicated cataract surgery in otherwise healthy eyes.

Keywords: cataract • visual acuity • refraction