The Association of Spectral-Domain Optical Coherence Tomography Determined Ganglion Cell Complex Parameters and Disease Severity in Parkinson's Disease

Purpose: To evaluate the association between the retinal structural changes provided by spectral domain optical coherence tomography (SD-OCT) and disease severity in Parkinson's disease (PD). Materials and methods: Thirty-eight eyes of 20 patients with PD and 30 eyes of 30 healthy subjects were enrolled in this prospective study. The eyes ipsilateral (20 eyes) and contralateral (18 eyes) to the most affected body side in patients with PD were evaluated separately. SD-OCT (RTVue-100) was used to measure the macular ganglion cell complex thickness (mGCC), outer retinal thickness, and peripapillary retinal nerve fiber layer (RNFL) thickness. Disease severity was assessed using Unified Parkinson's Disease Rating Scale (UPDRS). Results: The differences in the nasal RNFL (p = 0.004), average mGCC (p = 0.014), superior mGCC (p = 0.007), inferior mGCC (p = 0.03) were significant between the ipsilateral eye group and controls. The differences in the nasal RNFL (p = 0.002), and superior mGCC (p = 0.038) were statisticallly significant between the contralateral eye group and controls. Inferior and average mGCC thicknesses of ipsilateral eyes were inversely correlated with UPDRS score (p= 0.001, r = -0.678 and p= 0.009, r = -0.568, respectively). Significant inverse correlation was demonstrated between UPDRS score and inferior RNFL of both eyes ipsilateral and contralateral to the most affected body side. Conclusions: There is significant thinning in mGCC parameters of the retina in PD. The SD-OCT derived mGCC parameters may improve the detection of PD progression.