Evaluation of retinal alterations in Parkinson disease and tremor diseases

Optical coherence tomography (OCT) has been suggested as a method for detection of retinal alterations in neurodegenerative diseases. The usefulness of OCT as a diagnostic tool to differentiate Parkinson's disease (PD) from other tremor diseases, remains unknown. We aimed to evaluate morphological changes of the retina in patients with PD, essential tremor (ET), essential tremor-Parkinson's disease (ET-PD) using OCT. Forty-two eyes of 21 patients with PD, 24 eyes of 12 patients with ET, 24 eyes of 12 patients with ET-PD and 44 eyes of 22 age-matched healthy controls were included in the study. All participants underwent detailed neurological and ophthalmological examination. Measurements in all quadrants of macula and retinal nerve fiber layer (RNFL) thickness using OCT were recorded. There was no significant difference among the groups regarding age, sex. The average RNFL thickness was thinner in PD patients than that of ET (p = 0.032). The RNFL thickness in superior quadrant was lower in PD group compared with the ET and control group (p = 0.001, p = 0.016). Significant differences were observed in most of the macular thickness parameters excluding foveolar and foveal thickness (p = 0.865, 0.394). Correlations were found among several OCT parameters and disease duration or severity in all patient groups (p > 0.05). Retinal alterations were found in PD patients compared to ET. However, no significant retinal changes were detected by OCT in patients with ET and ET-PD compared to controls. According to our data, retinal assessments by OCT do not seem to be satisfactory for differentiation of these disorders.