Comprehensive assessment of nuclear and cortical backscatter metrics derived from rotating Scheimpflug images
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PURPOSE: To quantify cataract in lens-backscatter metrics derived from Pentacam Scheimpflug photographs and determine the most predictive metrics for lens grading and visual performance measures. SETTING: Large tertiary referral hospital in South Australia. DESIGN: Evaluation of diagnostic test or technology. METHODS: In patients attending a cataract clinic between 2005 and 2008, standardized clinical assessments were performed and Scheimpflug photographs taken. Thirteen measures of cataract backscatter were drawn from the images of nuclear and cortical cataract, including new metrics for cortical cataract. The relationships between lens-scatter metrics, visual performance, and lens grades were determined with stepwise multiple linear regression. RESULTS: The study enrolled 342 eyes (177 patients). The Lens Opacities Classification System III (LOCS III) nuclear opalescence was best predicted by the average backscatter in the anterior half of the nucleus and the whole nucleus average (r(2) = 0.59). The LOCS III cortical grade was best predicted by the number of slices with significant cortical cataract (r(2) = 0.52), as was Pelli-Robson contrast sensitivity (r(2) = 0.16). Visual acuity was best predicted by the combined anterior half and whole nucleus averages (r(2) = 0.20). Pelli-Robson contrast sensitivity under glare was best predicted by a combination of the anterior half and whole nucleus averages and the calculated percentage of cortical cataract (r(2) = 0.16). CONCLUSIONS: Scheimpflug image-derived metrics of nuclear scatter were predictive of visual acuity and contrast sensitivity, whereas metrics of cortical cataract were predictive of visual performance under glare. Automated reporting of cataract severity from Scheimpflug images could be useful clinically and should include measurements of cortical cataract. FINANCIAL DISCLOSURE: Neither author has a financial or proprietary interest in any material or method mentioned.