Researchers recently developed a new automated topographical evaluation method to corroborate structure and function tests—possibly offering greater insight than traditional methods for diagnosing glaucoma.
The study, presented last week at ARVO, enrolled 45 healthy control eyes/individuals with normal fundus exams and intraocular pressure of <22mm Hg and 53 eyes/patients with 24-2 mean deviation values that were better than -6dB. Investigators obtained widefield swept-source optical coherence tomography (OCT) scans, including the disc and macular regions, and 24-2 and 10-2 visual fields. The referring glaucoma specialist diagnosed the 53 eyes as “definite glaucoma” based on the performed tests. All individuals had a spherical refractive error between ±6D.
In addition to evaluating the standard metrics of the visual field (mean deviation, pattern standard deviation, glaucoma hemifield test) and OCT (global, quadrant and clock hour retinal nerve fiber layer thickness), researchers also assessed the topographical agreement between the 24-2 and 10-2 visual field total deviation probability maps and the OCT deviation probability maps. To obtain an objective, automated assessment of the latter, investigators developed a custom program with the following criteria that defined agreement: two abnormal points on the combined 24-2 and 10-2 probability map at ≤5% that fell upon a region ≤10% on the retinal ganglion cells and inner plexiform layer or retinal nerve fiber layer probability maps.
For the topographical agreement method, only 13.2% of the 53 eyes with early glaucoma failed to show agreement (misses), while two of the 45 healthy eyes showed agreement. Both of the latter were easily identified as mistakes, as the abnormal region of the visual field did not replicate, researchers noted. Without the 10-2, the misses for the topographical agreement method increased to 34%. The best visual field standard metrics (i.e., 24-2 glaucoma hemifield test or pattern standard deviation, or 10-2 pattern standard deviation) combined with best OCT (quadrants) had 30.2% misses, while omitting the 10-2 visual field resulted in 37.7% misses, investigators found.
Agreement between structural and functional damage can be improved by obtaining 10-2 and 24-2 visual fields and by comparing abnormal locations on the visual fields to abnormal retinal ganglion cell and retinal nerve fiber layer OCT regions, investigators said. As such, the addition of a 10-2 test adds significant, clinically useful information about early glaucoma, they added.
This objective, automated approach provides a novel way of providing structure/function corroboration of damage and serves as the underpinning for future artificial intelligence applications, researchers said.
|Hood DC, Tsamis EM, Bommakanti N, et al. Structure-function agreement in glaucomatous eyes is better than commonly thought if a topographical method is employed. ARVO 2019. Abstract 1782.