New insights into structural and functional evaluation of the retina and optic nerve in Parkinson's disease

Abstract

Purpose : Parkinson’s disease (PD)-associated non-motor symptoms have gained importance in the last years, especially the retina given its easy structure and function in vivo evaluation. This prospective, observational clinical study aims to compare structural and functional findings of the retina and optic nerve in patients with PD with healthy controls (CT). We assessed, for the first time, retinal ganglion cell functioning in PD using the photopic negative response (PhNR) and the Bruch's membrane opening-minimum rim width using optical coherence tomography (OCT).

Methods : Forty-one eyes of 21 PD patients and 38 eyes of 19 CT underwent ophthalmic examination including contrast sensitivity test (CS), OCT, OCT angiography (OCTA), light-adapted full-field electroretinography (ffERG), and PhNR. In PD subjects, disease duration, severity, motor symptoms, and the use of antiparkinsonian drugs were assessed. OCT was used to obtain peripapillary retinal nerve fiber layer, peripapillary choroid, optic disc, macular and choroidal measurements. OCTA was used to access macular and peripapillary vascular complexes and analyzed to calculate vessel density and foveal avascular zone. Measurements were compared using generalized estimating equation and significance was set at p ≤ 0.05.

Results : PD group presented a significantly lower vascular density in deep vascular complex and deep capillary plexus, CS, oscillatory potentials amplitude, b-wave amplitude on ffERG, and PhNR (Table 1). There was no statistically significant difference in OCT data between groups. No correlation was found between statistically significant measurements and clinical data.

Conclusions : Functional abnormalities on CS, ffERG, and PhNR can be detected in PD even when structural damages are not observed on OCT. PD may also present structural abnormalities on macular OCTA in the setting of a normal OCT. Our findings indicate dysfunction of bipolar, amacrine, and retinal ganglion cells in PD, probably with a cellular dysfunction overcoming morphological damage.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Table 1. Mean values (± SD) of statistically significant measurements (p ≤ 0.05)