Quantitative detection of glaucomatous damage at the posterior pole by retinal thickness mapping. A pilot study

Abstract

Objective: The posterior pole ganglion cell bodies form a substantial fraction of the retinal thickness, prompting the authors to study the feasibility of detecting, by scanning retinal thickness analysis, retinal changes at the posterior pole due to glaucomatous damage.

Study design: Nonconsecutive case series.

Participants: One or both eyes of patients with chronic open-angle glaucoma who presented with either a superoinferior asymmetry in visual fields or a localized field loss or a nerve fiber layer defect visible on photography were recruited. Twenty-nine eyes of 18 patients were studied.

Interventions: A laser slit was projected on the retina and scanned, in 400 msec, across a 2- x 2-mm area of the fundus, yielding optical cross-sections that were digitally recorded. Nine such scans covered the central 20 degrees of the fundus. The optical cross-sections were analyzed by an operator-free algorithm to yield a three-or two-dimensional color map. The asymmetry (difference) between the visual sensitivity of the upper and lower hemifields was compared with the asymmetry in retinal thickness deviation from normal.

Results: Large losses (up to 34%) in retinal thickness were detected at the posterior pole of patients with glaucoma due to the loss of ganglion cells and nerve fibers. A statistically significant correlation was found between the asymmetry in visual sensitivity loss and the asymmetry in deviation from normal thickness (r = 0.72; P < 0.0005).

Conclusions: Mapping of the retinal thickness may provide a sensitive method for the detection and monitoring of early glaucomatous tissue loss in the posterior pole, which is unique due to the combination of (1) the direct measurement of neuroretinal loss in the central field of vision; (2) the mapping capability; and (3) the rapid image acquisition.