Glaucoma Specialist Optic Disc Margin, Rim Margin, and Rim Width Discordance in Glaucoma and Glaucoma Suspect Eyes.

Purpose

To quantify the variability of 5 glaucoma specialists' optic disc margin (DM), rim margin (RM), and rim width (RW) estimates.

Design

Inter-observer reliability analysis.

Methods

Clinicians viewed stereo-photographs from 214 subjects with glaucoma or ocular hypertension and digitally marked the DM and RM. For each photograph, the centroid of each clinician's DM was calculated, and an averaged DM centroid was determined. The axis between the DM centroid and the fovea was used to establish 12 30-degree sectors. Measurements from the DM centroid to each clinician's DM (DM radius ) and RM (RM radius ) were used to generate a RW (DM radius -RM radius ) and cup-to-disc ratio (CDR) (RM radius /DM radius ) by sector. Parameter means, standard deviations, and coefficient of variations (COVs) were calculated across all clinicians for each eye. Parameter means for each clinician, and intraclass correlation coefficients (ICC), were calculated across all eyes by sector.

Results

Among all eyes, the median COV by sector ranged from 3% to 5% for DM radius , 20% to 25% for RM radius , and 26% to 30% for RW. Sectoral ICCs for CDR ranged from 0.566 to 0.668. Sectors suspicious for rim thinning by 1 clinician were frequently overlooked by others. Among 1724 sectors in which at least 1 clinician was suspicious for rim thinning (CDR ≥ 0.7), all 5 clinicians' CDRs were ≥ 0.7 in only 499 (29%), and 2 of the 5 clinicians failed to detect rim thinning (CDR < 0.7) in 442 (26%).

Conclusion

In this study, glaucoma specialist RM, DM, and RW discordance was frequent and substantial, even in sectors that were suspicious for rim thinning.