Quantitative analysis of optic disc structure and retinal nerve fiber layer thickness in patients with different degrees of Parkinson's disease

Objective To observe the changes of optic disc structure and retinal nerve fiber layer thickness (RNFL) in patients with different degrees of Parkinson's disease (PD). Methods Thirty eyes of 30 patients with primary PD and 20 eyes of 20 healthy subjects (control group) in Xuanwu Hospital of Capital Medical University from October 2016 to October 2017 were enrolled in this study. The patients were divided into mild to moderate PD group (15 eyes of 15 patients) and severe PD group (15 eyes of 15 patients). All the patients underwent OCT examination. The optic disc area, cup area, C/D area ratio, rim volume, disc volume, cup volume, rim area, C/D area, linear C/D, vertical C/D, the thickness of average RNFL, superior, inferior, temporal upper (TU), superior temporal (ST), superior nasal (SN), nasal upper (NU), nasal lower (NL), inferior nasal (IN), inferior temporal (IT), temporal lower (TL) quadrant RNFL thickness. Analysis of variance was performed for comparison among three groups. Minimum significant difference t test was performed for comparison between two groups. Results Optic disc structure parameters: there was no significant difference in the area of optic disc between the three groups (F=1.226, P>0.05). The other optic disc parameters were significantly different in the three groups (F=5.221, 5.586, 6.302, 5.926, 5.319, 5.404, 5.861, 6.603; P 0.05). The average thickness of RNFL, TU, IN, IT and TL in patients of the mild to moderate PD group and severe PD group were less than that in the control group (P<0.05). The thickness of the average RNFL, TU, IN, IT and TL in patients of the severe PD group were less than that in the mild to moderate PD group (P<0.05). With the increase of PD severity, the RNFL of TL and TU thinned most significantly. Conclusions With the increase of the severity of PD, the optic disc structure and RNFL thickness changes obviously, showing reduced optic disc area and volume, enlarged cup area and volume significantly enlarged C/D ratio. The average RNFL thickness of PD patients is significantly thinner than that of the controls, and it is the most obvious in the TU and TL quadrant. Key words: Parkinson's disease; Optic disk; Nerve fibers; Tomography, optical coherence