Digital Optic Nerve Photography in Assessing Cup-to-Disc Ratio:

The Experience in an Academic Institution

Naomi Goldberg, Lynda Z. Kleiman, Eric J. WolfEdward S. Harkness Eye Institute

Columbia University College of Physicians and SurgeonsNew York, NY

Purposes:1. To compare the level of agreement among

ophthalmic specialists in an academic institution in estimating cup-to-disc ratios from digital disc photographs.

2. To assess whether ophthalmology residents at different levels of training improve in interpreting cup-to-disc ratios from digital disc photographs.

3. To assess whether cup-to-disc ratios based on disc photographs are sufficient in communicating clinical data between practitioners.

Materials and Methods:

Digital optic nerve head images were obtained of five eyes from glaucoma or glaucoma-suspect patients and five eyes from normal patients. First, second, and third year ophthalmology residents, as well as attending ophthalmologists from the Cornea Service, the Retina Service, the Glaucoma Service and the Pediatrics Service were individually asked to determine vertical cup-to-disc ratios from the ten images.

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Conclusions:1. Among individual examiners, the maximal difference

between estimates is greater for glaucoma eyes (0.25-0.35) than for control eyes (0.2-0.3).

2. Individual examiners more strongly agreed in their assessments of control eyes rather than glaucoma eyes, and agreement was strongest regarding Eye H (standard deviation 0.06). Thus, there is strongest consensus in assessing non-glaucomatous nerves, especially those with smallest cup-to-disc ratios.

3. Individual examiners disagreed most in their assessments of the cup-to-disc ratio in Eye B (standard deviation 0.09). Among glaucoma eyes, however, examiners agreed most on Eye D (standard deviation 0.07). Thus, glaucomatous nerves were subject to the most disagreement, although there is a suggestion that there is less discrepancy with more highly cupped nerves.

Conclusions - continued4. There is more overall agreement between residents at different stages of

training than there is between specialists in determining cup-to-disc ratios. The discrepancies between sub-specialists’ estimates are more pronounced in glaucomatous eyes. There is no discernible trend in estimation of cup-to-disc ratio that is unique to a particular subspecialty; i.e. we cannot conclude that one group of specialists consistently over- or under-estimates cupping as compared to other specialists.

5. There was no trend toward graded improvement in residents’ assessments of cup-to-disc ratios.

6. In test eyes, residents tend to overestimate the degree of cupping relative to attending physicians.

7. The data here suggest that cup-to-disc ratio based on optic nerve photography may not be sufficient in communicating clinical information between practitioners. Further studies should be done to further clarify this issue.