Glaucoma Risk Underestimated by Ophthalmologists, Trainees

Ophthalmology trainees and comprehensive ophthalmologists who participated in an Internet-based multinational study to assess optic discs were about twice as likely to underestimate as to overestimate the likelihood of glaucoma, according to an article published online April 3 in JAMA Ophthalmology.

Evelyn C. O'Neill, MBBCh, MD, from the Centre for Eye Research Australia, University of Melbourne, East Melbourne, Victoria, and colleagues conducted the study involving training and practicing ophthalmologists from 22 countries who participated in the Glaucomatous Optic Neuropathy Evaluation (GONE) Project between December 1, 2008, and June 30, 2010.

GONE is a self-assessment program that presents 42 monoscopic optic disc photographs chosen from 2500 healthy and glaucomatous optic discs to represent a range of physiological and glaucomatous characteristics. Participants grade 9 topographic features and clinical features associated with the retinal nerve fiber layer. They then assess glaucoma likelihood, using a 4-point scale ranging from unlikely to possible, to probable, to certain. The program has a time limit of 90 seconds for each image.

Trainees and practicing ophthalmologists have learned about GONE through conference presentations, publications, and word of mouth. The current analysis includes participants who self-registered and completed assessment of the 42 discs between December 1, 2008, and June 30, 2010. Of 197 participants, 109 were trainees, 51 were comprehensive ophthalmologists, and 37 were glaucoma subspecialists.

For optic discs that glaucoma subspecialists graded as probable or certain glaucoma, ophthalmology trainees underestimated glaucoma likelihood in a mean of 22.1% of discs compared with comprehensive ophthalmologists, who underestimated the likelihood in a mean of 23.8% of discs.

For optic discs that glaucoma subspecialists graded as possible or unlikely glaucoma, trainees overestimated glaucoma likelihood in a mean of 13.0% of discs compared with a mean of 8.9% discs for comprehensive ophthalmologists.

4 Main Disc Characteristics

The researchers used multivariable linear regression analysis to determine which optic disc characteristics had the greatest effect on assessments. They found 4 characteristics that had the most influence: retinal nerve fiber layer loss, rim loss, hemorrhage, and vertical cup:disc ratio (P < .01).

When participants correctly assessed those 4 characteristics, underestimation of glaucoma likelihood fell to 10.9% for trainees and 3.1% for comprehensive ophthalmologists, and overestimation dropped to 2.9% and 1.6%, respectively.

However, when participants incorrectly assessed all 4 of these characteristics, the mean percentage of discs underestimated for glaucoma likelihood rose to 43.0% for trainees and 42.9% for comprehensive ophthalmologists, with no significant change in overestimation.

"The most important take-home message from this paper is the importance of accurate assessment of the optic nerve head and [retinal nerve fiber layer] in the diagnosis and monitoring of glaucoma. When these are inappropriately assessed, diagnoses may be missed," Dr. O'Neill told Medscape Medical News. "We all know population-based screening for glaucoma is not cost effective or efficient; thus, I would recommend improved awareness and case detection through screening of high-risk individuals and better assessment of the optic nerve head in all patients attending ophthalmic services."

She added, "One surprise result in this study was that small disc size did not increase the underestimation of glaucoma likelihood. This may have been due to sample size. However, it was unexpected."

"This paper outlines specific areas in optic nerve assessment that are associated with the grader making a false diagnosis," co-investigator Jonathan G. Crowston, PhD, MBBS, head of glaucoma research and managing director of the Centre for Eye Research Australia, and senior author, added. "In learning or teaching optic nerve assessment, we can focus on specific aspects of the examination that deserve special attention to avoid making a false diagnosis."

Underdiagnosis Is "Biggest Surprise"

"The results of the study weren't a huge surprise, in the sense that we already knew there was a lot of variability among different people who evaluate the optic nerve," Brian Song, MD, a glaucoma specialist at the Massachusetts Eye and Ear Infirmary and instructor in ophthalmology at Harvard Medical School, Boston, told Medscape Medical News.