Agreement among Optometrists, Ophthalmologists, and Residents in Evaluating the Optic Disc for Glaucoma

Purpose: To determine the agreement among optometrists, ophthalmologists, and ophthalmology residents in assessing glaucomatous optic nerve damage. The authors also determined the sensitivity of each group of observers for identifying glaucomatous optic nerve damage. Methods: Six optometrists, six general ophthalmologists, and six third-year ophthalmology residents evaluated 75 stereoscopic optic disc photographs. Observers estimated the vertical cup:disc ratio (C:D) and assessed the presence of glaucomatous damage. Agreement among and within observers was estimated by the kappa statistic (K_w, k). The sensitivity and specificity for the identification of glaucomatous optic nerve damage were determined for each group of participants. Results: lntraobserver agreement (K_w 0.69-0.79) was greater than interobserver agreement (K_w 0.56-0.68) in assessing the C:D ratio and glaucomatous optic nerve damage for optometrists, ophthalmologists, and residents. Interobserver agreement for ophthalmologists (K_w 0.68) was substantial and significantly higher than for optometrists (K_w 0.56) and residents (K_w 0.56) when estimating the C:D ratio. Ophthalmologists and residents had higher sensitivity (78%) in identifying glaucomatous optic nerve damage than did optometrists (56%). The specificity for all three groups was relatively poor (range, 47%-60%). Conclusion: The moderate interobserver agreement across all three groups of observers suggests the need to develop standardized criteria for assessing glaucomatous optic disc damage. Ophthalmologists in this study have a higher interobserver agreement in estimating the C:D ratio and are more sensitive than optometrists in assessing glaucomatous optic nerve damage.