Evaluation of Retinal Morphology and Contrast Sensitivity Function in Patients with Restless Legs Syndrome

Objective: The decreased number of dopamine receptors in the putamen are considered to play an important role in the pathophysiology of restless legs syndrome (RLS). Retinal dopamine plays an important role in contrast sensitivity (CS) by establishing communication between retinal cells. It is also suggested that retinal dopaminergic neurons protect other retinal neurons. In this study, we aimed to investigate the thickness of retinal layers and CS function (CSF) of patients with RLS.
Materials and Methods: A total of 68 participants were included in this prospective case-control study. The participants were divided into two groups as those with RLS (n=35) in group 1 and control subjects (n=33) in group 2. Optical coherence tomography was used to measure central macular thickness, retinal nerve fiber layer thickness (RNFL), and retinal ganglion cell inner plexiform layer thickness (GCIPL). RNFL thickness was measured as average and as sectoral (superior, inferior, nasal and temporal). Additionally, the CS test measured at all spatial frequencies of 1.5, 3, 6, 12 and 18 cycle per degree (cpd) was performed in all participants.
Results: The average and superior sectoral RNFL thicknesses in group 1 were statistically significantly thinner than group 2 (p=0.03 and p=0.01 respectively). However, the thicknesses of other RNFL sectors were not different between group 1 and group 2. There were no statistically significant differences between group 1 and group 2 regarding the thicknesses of GCIPL and central macula. The mean values of CSF at all spatial frequencies of 1.5 cpd, 3 cpd, 6 cpd, 12 cpd and 18 cpd were statistically significantly higher in group 2 in comparison to group 1 (p<0.001 for all spatial frequencies).
Conclusion: The decreased thickness of retinal layers and reduced CSF in patients with RLS support retinal dopaminergic dysfunction.