Morphologic Changes and Functional Retinal Impairment in Patients with Parkinson Disease without Visual Loss

Abstract

Purpose: TO investigate the anatomic and electrophysiologic changes of the macula and the optic nerve in patients with Parkinson disease (PD) without visual impairment. Methods: Thirty-two eyes of 16 patients with PD (group A) without visual impairment were tested. Visual acuity was 20/20 or better and visual fields as well as color vision testing results were normal. Also, no retinal lesions were assessed. Patients in group B (40 eyes of 20 patients) were age- and sex-matched control subjects. All study participants underwent a comprehensive ophthalmic examination, multifocal electroretinogram (mfERG) recording, and optical coherence tomography (OCT) scan. Thickness of retinal nerve fiber layer (RNFL) along a 3.4-mm-diameter circle centered on the optic nerve head was evaluated using third-generation OCT. Results: The mean P1-response density amplitude of ring 1 of mfERG was 136.69 nV/deg² in patients with PD and 294 nV/deg² in control subjects and the difference was highly significant. On the contrary, these values in ring 2 and 3 did not differ statistically between controls and patients with PD. The mean inferior and temporal RNFL thickness was significantly lower in patients with PD than in control subjects (p<0.0001 and p=0.0045, respectively). Conclusions: In patients with PD with normal vision, we found a decrease in the electrical activity of the fovea as well as in the thickness of the RNFL. Multifocal electroretinogram and OCT scan objectively detect early subclinical PD-associated visual functional impairment.