Retinal Nerve Fiber Layer among Multiple Sclerosis Patients with or without Optic Neuritis and Normal Controls

To compare peripapillary retinal nerve fiber layer (RNFL) thickness among multiple sclerosis (MS) patients with or without a history of optic neuritis (ON) and a healthy control group. In this retrospective case-control study, 59 MS patients were recruited from a neurology clinic of Imam Hossein hospital. Of which, 36 patients had at least one episode of ON and 23 others had no history of ON. Control group included 30 healthy individuals. Peripapillary RNFL thickness was measured in all cases using Stratus spectral domain optical coherence tomography (OCT). Average RNFL thickness was significantly lower in MS patients with a history of ON compared to MS patients without ON (86.6±11.81 vs. 95.04±11.29 microns, respectively; P<0.001). Both patient groups had lower mean RNFL thickness as compared to the control group (105.83±8.32 microns; P<0.001). The greatest difference was observed in the inferior quadrant followed by the superior quadrant. Patients with unilateral ON demonstrated thinner RNFL (81.52±12.31 microns) in the affected eyes compared to the contralateral unaffected eyes (93.83±10.46 microns, P<0.001). Furthermore, patients with progressive MS had thinner RNFL compared to those with a relapsing remitting course, although the difference was not statistically significant (86.2±13.38 vs. 89.79±12.46 microns, respectively; P>0.05). Patients with the disease lasting between 1 and 5 years had thinner RNFL than those with a duration less than one year (88.87±12.5 vs. 99.07±8.19 microns, respectively; P<0.05). RNFL thickness did not differ in patients with only one ON attack from those with multiple attacks (88.48±12.59 vs. 84.31±10.87 microns, respectively; P>0.05). Measuring RNFL can quantitatively provide an index of axonal damage in MS patients and estimate disease progression and subsequent disabilities.