Optıcal coherence tomography (OCT) and vısual evoked potentıals (VEP) fındıngs on multıple sclerosıs patıents

Multiple Sclerosis (MS) is a chronic disease that advances through episodes and that mostly affects young adults, causing axonal losses and demyelination in the central nervous system (CNS). Optic Neuritis (ON) is the most common ocular finding of MS and is reported as the presenting symptom in about 20% of the patients. ON can cause axonal losses resulting in thinner retinal neural fiber layer (RNFL) and abnormalities in visual evoked potentials (VEP). This study compares OCT with RNFL thickness, Ganglion Cell Complex (GCC) thickness, and macular thickness in MS patients and in the control group, and compares these parameters in patients with and without a clinical ON history and in healthy controls. This study also targeted to evaluate whether these values correlated with VEP findings and clinical findings and whether they can be used as a marker of axonal loss. The study included 49 MS patients (98 eyes) and 30 healthy control subjects (60 eyes) aged 18-55. All of the cases received detailed ocular examination to evaluate visual acuity and color vision, VEP and Fourier-Domain Optical Coherence Tomography (FD-OCT). Three groups were then created: eyes with ON history (38), eyes without ON history (68) and control eyes (60). OCT measurements were performed to see if there was any difference between the two groups, and understand the correlation between the values and VEP amplitude, latency values, EDSS, disease time, visual acuity and color vision. The study found a significant difference (p<0,05) in mean RNFL thickness, superior quadrant RNFL thickness, inferior quadrant RNFL thickness, mean GCC thickness, superior quadrant GCC thickness, and inferior quadrant GCC thickness values among MS patients with a history of ON and without a history of ON and control group eyes. Foveal thickness values were compared in patients with and without a history of ON and in control group eyes; the values were found to be thinner in both of the groups than the control group, and this comparison was statistically significant (p<0,05). A comparison of eyes with ON history and eyes without ON history found thinner foveal thickness in eyes with ON history, which was statistically insignificant. A comparison of macula thicknesses including temporal inner macula, superior inner macula, nasal inner macula, inferior inner macula, temporal exterior macula, nasal exterior macula, inferior exterior macula thickness in the control eye group and in eyes with ON history and eyes without ON history found a significant difference (p<0,05). There were no significant differences among the groups for superior exterior macula thickness. A comparison of VEP latency values among the groups found that P100 latency of VEP was meaningfully extended (p<0,05) in eyes with ON history and eyes without ON history compared with the control eyes. There was no significant difference (p>0,05) between eyes with ON history and eyes without ON history for P100 latency. VEP amplitude values showed no significant (p>0,05) differences between the groups. There were no statistically significant differences between the groups for mean cup/disk (c/d) rate, cup (c) area, disc (d) area, c/d horizontal rate, c/d vertical rate, and rim area. There was highly significant correlation between mean GCC thickness and mean RNFL thickness in eyes with a history of ON. In OCT measurements of MS patients, changes were found in RNFL, GCC thickness, fovea and macula parameters. Based on our findings, RNFL, GCC thickness, fovea and macula thickness were found to be thinner in eyes with a history of ON than eyes without a history of ON and the control group. Moreover, GCC thickness values correlate more with VEP latency than RNFL values in eyes without ON history. OCT parameters including RNFL thickness, GCC thickness, foveal thickness and macula thickness can be used as good markers in showing axonal degeneration and optic nerve involvement in the development of MS disease.