Rates of Retinal Nerve Fiber Layer Loss in the Contralateral Eyes of Glaucoma Patients Showing Unilateral Progression by Conventional Methods

Abstract

Purpose: To determine whether progressive retinal nerve fiber layer (RNFL) loss occurs in the contralateral eye of patients with glaucoma showing unilateral progression according to conventional diagnostic methods.

Methods: This was an observational cohort study involving 346 eyes of 173 patients (118 eyes with glaucoma and 228 eyes with suspected glaucoma at baseline) recruited from the Diagnostic Innovations Glaucoma Study (DIGS). Average follow-up time was 3.5 ± 0.7 years. All subjects had standard automated perimetry (SAP, HFA) and spectral- domain optical coherence tomography (SD-OCT; Heidelberg Engineering, Heidelberg, Germany) in both eyes at 6-month intervals, with a minimum of 5 SAP and 5 SD-OCT examinations in each eye. Eyes were determined as progressing by conventional methods if there was progression on masked grading of optic disc stereophotographs or SAP guided progression analysis (GPA, “likely progression”). Rates of change in SD-OCT average RNFL thickness were obtained by linear mixed effects model.

Results: 39 subjects had evidence of unilateral progression by GPA and/or disc photographs during follow-up. Mean ± SE rate of RNFL loss in eyes progressing by conventional methods was −0.89 ± 0.22 μm/year; P < 0.001. The contralateral eyes of these subjects also showed significant loss of RNFL over time (−1.00 ± 0.20 μm/year; P < 0.001). 134 subjects did not show progression by conventional methods in either eye. These eyes also had significant decline over time in average RNFL thickness (−0.71 ± 0.09 μm/year; P < 0.001), however, the rate of change in these eyes was slower than the contralateral eye of patients showing unilateral progression (P < 0.001).

Conclusions: Significant RNFL thickness loss was seen in the contralateral eyes of glaucoma patients showing unilateral progression by conventional methods. These findings indicate that assessment of RNFL thickness by SD-OCT may show progressive glaucomatous damage that is not detected by visual fields or optic disc stereophotography.