Researchers have identified criteria using optical coherence tomography (OCT) and visual field testing that can define glaucomatous optic neuropathy (GON) objectively, according to a study published in the British Journal of Ophthalmology.
The researchers used a combination of data from OCT retinal nerve fiber layer (NFL) imaging and visual fields testing, specifically the Glaucoma Hemifield Test (GHT), to establish the criteria. Their study aimed to determine criteria that could be used, at a single point in time, to diagnose GON in open-angle glaucoma eyes.
The investigators studied images and perimetry results from 2580 eyes (of 1531 patients) submitted to an online database. Data was compiled from 9 centers, across 5 continents.
Each eye was graded by a glaucoma specialist as “definite GON,” “probable GON” or “not GON.” The criteria that the researchers developed identified 75% of the patients glaucoma experts had deemed as having GON, while effectively excluding those without GON.
The team established that using only OCT data or field data alone had inadequate specificity (<90%). The best definitional choice for data from either the most recent or the preceding OCT/field pair had 77% sensitivity at 98% specificity and consisted of abnormal OCT superior or inferior NFL quadrant with matching, opposite, abnormal GHT.
The study relied on a dataset of representative eyes, including from patients older than 21 years, for whom at least two reliable OCT scans and visual field tests were available, the most recent of each within 12 months. Eyes that had any secondary cause for GON, such as uveitic or neovascular disease, or eyes with non-open angle glaucoma (non-OGA) diseases that might distort the data, were excluded.
There were no significant age or gender differences between the definite GON and not GON groups in the study. Women made up 52% of patients in the definite GON group, but also 56% of patients in the not GON group.
While the combined OCT and perimetry criteria outlined in the study might not include some eyes considered to have early glaucoma damage, researchers stated the criteria’s strength was its objectivity, high specificity, easy implementation and widespread availability.
Iyer JV, Boland MV, Jefferys J, Quigley H.. Defining glaucomatous optic neuropathy using objective criteria from structural and functional testing. Br J Ophthalmol. Published online September 22, 2020.doi: 10.1136/BJOPHTHALMOL-2020-316237