Cup-to-disc ratio: Ophthalmoscopy versus automated measurement in a general population - The Rotterdam Study

Objective: To determine the correlations between ophthalmoscopic estimation s and the measurements with a semiautomated image-analysis device of the ve rtical cup-to-disc ratio (VCDR) in the human optic disc. Designs Population-based, cross-sectional study. Participants: All subjects 55 years of age and older from the population-ba sed sample of 6777 ophthalmologically examined subjects from The Rotterdam Study of whom gradable optic disc transparencies of at least 1 eye and opht halmoscopic data of the same eye were available. Main Outcome Measures: Ophthalmoscopic assessment of the VCDR and semiautom ated measurement of the VCDR. Methods: Indirect and direct ophthalmoscopy were performed in mydriasis to assess the VCDR, Optic disc transparencies made with a simultaneous stereos copic telecentric fundus camera were analyzed with a semiautomated measurem ent system (Topcon Imagenet). Results: In 5143 subjects, the mean ophthalmoscopic VCDR was 0.30 (standard error [SE], 0.0021; range, 0.00, 1.00) compared with a semiautomatically m easured VCDR of 0.49 (SE, 0.0019; range, 0.04, 0.86; difference, 0.19; P < 0.0001). The overall correlation between both methods was moderate (correla tion coefficient, 0.61; SE, 0.11) and lower in small optic discs. Semiautom ated optic disc measurements correctly identified 76% of the glaucoma cases las defined using visual field data and ophthalmoscopic data about the opt ic disc). Conclusion: Semiautomated measurements of the VCDR are larger than the opht halmoscopic VCDR estimate with a moderate correlation. The interobserver va riability using Imagenet was smaller compared with the ophthalmoscopic asse ssments, and Imagenet was better standardized, which is important for epide miologic surveys and follow-up studies.