Functional Losses in Parkinson's Disease: Frequency Doubling Technology

Abstract

Abstract: : Purpose: Parkinson’s disease (PD) results in dopamine depletion in both the brain and retina. Horizontal cells and amacrine cells have been found to have dopamine receptor sites. Depletions in dopamine levels may impact the retinal ganglion cell function and lead to functional and structural deficits. Individuals with PD have losses in visual function including low spatial frequency contrast sensitivity. Methods: This project used Frequency Doubling Technology (FDT). The FDT measures low spatial frequencies and tests the central 20 degrees of the visual field. It is similar to a traditional visual field in that individuals respond when they see a target. The instrument is thought to isolate a subset of retinal ganglion cells in the magnocellular pathway by use of low spatial frequency sinusoidal gratings (<1 cycle/degree) that undergo a high temporal frequency counter–phase flicker at 15 Hz or greater. Results: Data using FDT was obtained from five PD participants who were free of any other ocular pathology and six control participants. The average age of the five PD participants included in the data analysis was 69 with an age range of 56 to 82 years. The average age of the control group was 77 with a range of 71 years to 81 years. The nasal quadrant of the right eye, the temporal quadrant of the right eye and the inferior quadrant of the left eye showed significant losses in the PD participants compared to the control participants. Conclusions: Further studies are warranted to determine if the deficits are consistent in Parkinson’s disease and to determine if the losses are the result of retinal pathology, are of neurological origin or a combination of the two in PD.

Keywords: contrast sensitivity • amacrine cells • neuro-ophthalmology: diagnosis