Glaucomatous Optic Neuropathy Defined Using OCT, Perimetry

Glaucomatous optic neuropathy (GON) can be diagnosed using objective metrics, according to study results published in the British Journal of Ophthalmology. The criteria include a combination of visual field analyses and optical coherence tomography (OCT) images. 

Researchers from Johns Hopkins School of Medicine sourced data from the online management system REDCap. Eyes (N=2580) from 1531 patients evaluated at 9 centers. With input from 176 experts, multiple criteria were used to categorize eyes as definite GON, probable GON, or not GON.

Patients were 54% women, 29% pseudophakic, and had a mean age of 66.2±12.2 years.

Eyes were classified as definite GON (54%), probable GON (22%), and not GON (24%). No significant patterns were observed for age or gender on the basis of category.

The median deviation of definite eyes was -5.55 dB and pattern standard deviation was 6.43 dB, indicating that most eyes with GON exhibited half of the damage expected according to published literature.

Among more recent, more precise OCT scans, abnormal superior quadrants were observed among 56% of definite, 31% of probable, and 7% of not GON eyes and inferior quadrants for 69%, 28%, and 4%, respectively. An abnormal reading in either quadrant was observed for 1-2 hours among 81% of definite, 38% of probable, and 10% of not GON eyes.

In the Glaucoma Hemifield Test (GHT), eyes were normal 8%, 49%, and 67% of the time for definite, probable, and not GON cohorts. Eyes had both upper and lower GHT abnormalities among 39%, 8%, and 3%, respectively.

On the basis of these findings, the investigators assessed the predictive power of 4 criteria. They found the abnormal OCT quadrant with matching superior/inferior GHT abnormality criteria performed best, demonstrating 98% specificity and 77% sensitivity.

These GON diagnostic criteria require external validation to confirm the utility in clinical practice. The study authors say that objective criteria were able to detect 75% of eyes with GON and that these criteria would be of utility in the clinical and research settings.

Reference

Iyer JV, Boland MV, Jefferys J, Quigley H. Defining glaucomatous optic neuropathy using objective criteria from structural and functional testing. Br J Ophthalmol. 2021;105(6):789-793. doi:10.1136/bjophthalmol-2020-31623