Novel Vertical Cup-to-Disc Classification to Identify Normal Eyes That Maintain Non-Glaucoma Status: A 10-Year Longitudinal Study.

Abstract

We propose a new classification model to serve as a control for future genomic studies of glaucoma by distinguishing normal subjects maintaining non-glaucoma status for 10 years using the vertical cup-to-disc ratio (VCDR). This study aimed to develop a classification for distinguishing subjects maintaining non-glaucoma status for 10 years using the VCDR. Among 842 volunteers 40 years and older, 421 volunteers participated in the second ophthalmic examination 10 years after their first examination. Each volunteer was diagnosed either as healthy normal or glaucoma suspect (GS) in the first glaucoma screening examinations. The former was further classified into the 3 grades of N1, N2, and N3. Specifically, N1 represented (1) VCDR <0.3; (2) no notching or nerve fiber layer defect; and (3) no undermining, N2 indicated 0.3≤VCDR<0.6 and conditions (2) and (3) of N1; and N3 represented 0.3≤VCDR<0.6 with undermining and condition (2), or 0.6≤VCDR<0.7 and condition (2) of N1. Glaucoma transition rates (GTRs) were evaluated in 421 volunteers who returned to participate after a 10-year period. GTRs were calculated as 1.3% in both N1 and N2, 3.9% in N3, and 18.2% in GS. The ratio of volunteers in the same category maintenance rate increased from N1 to N3. GTRs were lower in N1 and N2 than in N3 or GS during the 10-year study period. This novel classification of healthy non-glaucoma subjects may help identify those, especially Japanese males, who maintain a non-glaucoma status for an extended period of 10 years.