Evaluation of retinal fiber thickness and visual pathways with optic coherence tomography and pattern visual evoked potential in different clinical stages of obstructive sleep apnea syndrome

Purpose To investigate the possible changes in retinal nerve fiber layer (RNFL) by optic coherence tomography and in the amplitudes and peak times (PTs) in pattern visual evoked potential (pVEP) and to compare them in obstructive sleep apnea syndrome (OSAS). Methods This prospective study included patients with mild OSAS ( n = 30), severe OSAS ( n = 30), and 30 control subjects. All patients were assessed after obtaining the approval from our hospital’s ethics committee. Results There was no difference in age and gender between the groups ( p = 0.184, p = 0.954). By analysis of variance, there was a significant difference in RNFL values among patients with mild OSAS, severe OSAS, and control for three measures of RNFL (average p = 0.044, nasal p = 0.003, inferior p = 0.027). In severe OSAS group, nasal and inferior quadrants of the RNFL were found to be thinner than the control group ( p = 0.008, p = 0.031). We showed that the PT of P100 and N145 was prolonged in severe OSAS compared to the control group ( p < 0.001) and that PT of P100 was prolonged in mild OSAS compared to the control group ( p < 0.05). The amplitude of N75-P100 was significantly decreased in patients with both severe OSAS and mild OSAS compared to the control group ( p < 0.001). Correlation of RNFL and pVEP values showed that the inferior quadrant RNFL thickness is correlated with both P100 and N145 PTs ( r = 0.271*, p = 0.036 and r = 0.290*, p = 0.043, respectively) and N75-P100 amplitude ( r = 0.378**, p = 0.003) in severe OSAS group. Conclusions In mild and severe stages of the disease, edema and inflammation were evident and VEP PT and amplitudes were affected in both groups. Furthermore, thinning in RNFL in the severe stage of the disease might be associated with higher atrophy levels and prolonged exposure to hypoxia.