Comparing retinal thickness in Parkinson’s disease, essential tremor and healthy controls
Reviewed by Lauren Hepworth

This study aimed to compare retinal findings in chronic essential tremor (ET), early Parkinson’s disease (PD) and healthy controls. Those recruited with ET had to have received a diagnosis a minimum of three years previous and those with PD had to have symptom duration of less than five years. Other exclusion criteria were previous ocular trauma, ocular surgery, ocular disease, increase intraocular pressure, media opacification and systemic conditions which can impair vision. All participants underwent a full neurological assessment and optical coherence tomography (OCT) using a standardised protocol. Both macular retinal thickness and peripapillary retinal fibre layer (RNFL) thickness were collected. A total of 23 patients with ET, 21 with PD and 17 healthy controls were recruited. There was greater than 10 years difference in the mean ages of the ET and PD groups, with the ET group being older. Differences in the tremor patterns of ET and PD participants were statistically significant. A total of six eyes were excluded from the OCT analysis due to poor image quality. The following layers were found to be significantly thinner in eyes of PD participants compared to ET, with an even greater difference to healthy controls; RNFL, ganglion cell layer, plexiform layer and inner nuclear layer. The authors acknowledge the small group sizes and cross-sectional design as limitations. A proposition that there is a continuum between ET and PD is made by the authors, and that OCT could provide a tool to facilitate differential diagnosis. Further research is required including longitudinal studies.

Retinal thickness in essential tremor and early Parkinson Disease: exploring diagnostic insights.
Terravecchia C, Mostile G, Chisari CG, et al.
JOURNAL OF NEURO-OPHTHALMOLOGY
2024;44:35–40.