Rapid Retinal Nerve Fiber Layer Thinning in the Unaffected Contralateral Eyes of Patients with Unilateral Normal-Tension Glaucoma: A retrospective observational study

Purpose To observe the rate of progressive retinal nerve fiber layer (RNFL) thinning in the unaffected eyes of patients with unilateral normal-tension glaucoma (NTG), in comparison with that of healthy subjects, and to identify the factors associated with progressive RNFL thinning. Design Retrospective, longitudinal, observational study. Participants Ninety-five patients with unilateral NTG and 61 healthy controls Methods This study included unilateral NTG and healthy control subjects who were followed up for longer than 4 years and in whom at least 5 reliable RNFL thickness (RNFLT) measurements were performed using optical coherence tomography. Factors associated with the rate of thinning of the unaffected eyes of unilateral NTG patients were identified using regression analysis. Main Outcome Measures The rate of progressive RNFL thinning and the associated factors. Results RNFLT decreased significantly in both the unaffected eyes of unilateral NTG patients and the healthy eyes (both P<0.001). The RNFL thinning was significantly faster in the unaffected eyes of unilateral NTG patients than in the healthy eyes (P<0.001), specifically in the temporal-inferior sector (P=0.003). Factors associated with faster RNFL thinning in the unaffected eyes of unilateral NTG patients were thicker baseline RNFL of the unaffected eyes (P=0.002) and a worse visual field (VF) mean deviation (MD) in the NTG eyes (P=0.040). In the healthy controls, the rate of RNFL thinning in the contralateral eyes was the only factor associated with faster thinning (P=0.007). Conclusions The unaffected eyes of unilateral NTG patients showed faster RNFL thinning than healthy control eyes, more obviously in the temporal-inferior sector, and were likely to progress faster when they had a thicker baseline RNFL, and when the NTG eyes had a worse VF MD. In unilateral NTG patients, initiation of prophylactic treatment could be considered for the unaffected eyes when they are accompanied by a risk of developing glaucoma.