Paravascular defects and epiretinal membranes are seen on en-face slab OCT images in eyes with early glaucoma

Abstract

Purpose : Mechanical disruptions of the retinal nerve fiber layer (dRNFL) are easy to see with en-face slab analysis of optical coherence tomography (OCT) scans.[1,2] Here we examine the prevalence of dRNFL, specifically paravascular defects (PD) [1,3] and macular epiretinal membranes (ERM), in eyes categorized as mild glaucoma or glaucoma suspect.

Methods : 126 eyes of 126 patients (57.15 +/- 13.6 yrs) had abnormal or suspicious looking discs based upon stereo photographs, a mean deviation (MD) of better than -6dB on the 24-2 VF, and a spherical refractive error between +/-6D. Eyes were classified by 2 glaucoma specialists using 24-2 and 10-2VFs, disc stereo photographs, a custom inner retina report consisting of retinal nerve fiber and retinal ganglion cell layer thickness and probability plots superimposed with information,[4] and information from the patient's chart as requested. Of the 126 eyes, 71 eyes were classified as glaucomatous, 51 as suspects, and 4 as undecided, which were excluded. 68 eyes from 49 healthy individuals served as controls (55.6 +/- 9.6 yrs). All eyes had wide-field, swept-source OCT cube scans (9x 12 mm, 256 b-scans, 512 a-scans; DRI-OCT, Topcon, Inc). Using special purpose software (ATL 3D-Suite),[2] en-face slabs were generated, as previously described.[1] Two graders, masked as to eye classification, identified ERMs with separation from the internal limiting membrane and PDs on the en-face slab images using horizontal b-scans and derived vertical b-scans (Fig. 1).

Results : The prevalence of dRNFL in glaucomatous eyes (G) was significantly greater than than in suspects (S) and controls (C) [p =0.007]. 15 of 71 (21.1%) G, 1of 51 (2.0%) S, and 2 of 68 (2.9%) C eyes exhibited dRNFL. There were 11 eyes with PDs, 9 were G and 2 eyes were C. All PDs were adjacent to blood vessels. ERMs were identified in 8 eyes, 7 G eyes and 1 S eye and were associated with older age [p =0.10]. Although PDs are associated with ERMs,[1,3] only 3 of the 11 G eyes with PDs had ERMs.

Conclusions : Eyes with early glaucoma have a higher prevalence of dRNFL than suspects or controls and exhibit PDs even in the absence of ERM or high myopia.1. Hood, et al. IOVS. 2015; 2. Fortune et al. IOVS. 2014. 3. Muraoka et al. JAMA Ophth. 2015; 4. Hood & Raza BJO. 2014.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Fig. 1 En-face slab images with b-scan insets. A. PD B. ERM