Optical coherence tomography as a tool to evaluate retinal changes in Parkinson's disease

Though Parkinson's disease (PD) is primarily a disease of the basal ganglia, recent evidence suggests that PD affects the retina.

The study was designed to evaluate the thickness of retinal nerve fiber layer (RNFL) and thickness and volume of the macula in PD and hence explore the utility of optical coherence tomography (OCT) in studying retinal changes in PD.

A prospective, hospital based evaluation of 30 patients with PD and 30 healthy controls was carried out. Various parameters such as RNFL, central macular thickness (CMT), central and total macular volumes (TMV) and retinal thickness were analyzed using OCT.

(a) RNFL thickness was not significantly different between the patients and controls. A significant negative correlation was found between the RNFL thickness in the right nasal superior sector and the UPDRS motor score. (b) CMT was found to be significantly reduced in the right eye and a negative correlation with the UPDRS motor score was noted. (c) TMV was significantly greater in patients compared to the controls. (d) The outer retinal layer in the right nasal quadrant and the right inferior quadrants were found to be significantly thinner in patients with PD.

We did not find any significant abnormality in the RNFL thickness in patients with PD. Decreased CMT in patients with PD and a significant negative correlation of RNFL thickness and CMT with severity of PD suggest a remote possibility of dopaminergic depletion in the retina. However long term studies are warranted to validate our findings.