Relation of Dynamic Light Scattering (DLS) Cataract Detection Device parameters to Visual Acuity

Abstract

Purpose: : To evaluate the relation between Dynamic Light Scattering (DLS) parameters and visual acuity (VA).

Methods: : Persons with normal lenses or with cataract were examined under an NEI IRB–approved cross–sectional clinical study. Subjects gave informed consent, then had a complete eye examination including clinical grading of the lens using the AREDS nuclear cataract grading scheme. VA (number of letters correctly read) was measured using the ETDRS protocol. The NASA–NEI DLS clinical device was then used to non–invasively sample a small volume of the lens nucleus. This device uses A–scan measurements of axial length and anterior chamber depth to precisely sample the central lens. The DLS device measures the light intensity scattered by the diffusion of protein particles within the lens over a short time interval. This information is used to derive an autocorrelation curve, from which the distribution of lens protein particle sizes can be estimated. This distribution was typically bimodal. Summary parameters were computed to describe the relative intensity of the two peaks and the median particle size. The relation of DLS parameters to VA was assessed, adjusting for age and nuclear lens grade, using mixture models (SAS version 9.1).

Results: : 343 eyes of 212 patients were studied. Age ranged from 18–86 years. Nuclear lens grades ranged from 0.0 through 3.8 (mean 0.75). VA ranged from 14–95 letters (approximately 20/600 – 20/20). After adjustment for age and nuclear grade, lens particle size was significantly associated with VA (for each log–unit increase in median particle size, VA was 6.3 letters smaller (95% CI, –10.3 – –2.4, p=.002). Borderline significant relationships were found between worse VA and greater proportion of particles in the second "peak", and between worse VA and greater log particle diameter in the second "peak".

Conclusions: : Greater lens protein particle size as measured by DLS was associated with worse VA, even after adjustment for clinical cataract status.

Keywords: clinical (human) or epidemiologic studies: systems/equipment/techniques • cataract • visual acuity