Abstract
Purpose: :
To investigate whether retinal nerve fiber layer (RNFL) loss was related to disease duration in multiple sclerosis (MS) patients with or without a history of optic neuritis (ON).
Methods: :
RNFL thickness was measured using Stratus OCT3 in 133 MS patients (mean age 42.6 ± 10.3 yrs, MS duration 0-26 yrs, a median of 4 yrs). 95 eyes had a history of ON with last ON attack at least 3 months prior (ON eyes). Mean time from last ON attack was 5.9 ± 7.3 yrs. 135 eyes did not have ON (no-ON eyes). The generalized estimating equation (GEE) model was used to adjust for intrasubject intereye correlations and to examine whether factors such as age and MS duration were related to RNFL thickness. An eye’s RNFL was classified as abnormal if its thickness was significantly lower than the age-matched machine norms (P<5%). A subset of patients (n =76) also had multifocal visual evoked potential (mfVEP) tested. The mfVEP amplitude was considered abnormal if the interocular or monocular amplitude probability plot had 5 or more adjacent points with reduced amplitude P<5%.
Results: :
RNFL thickness decreased with MS duration with an average rate of -0.77 µm/yr (p=0.006) for ON eyes and -0.55 µm/yr (p=0.05) for no-ON eyes. When ON eyes were grouped based on MS duration, the mean RNFL thickness in the group with ≤3 yrs (n=38, 86.49±2.92 µm) was significantly greater compared to those >3 yrs: 3 to 6 yrs (n=23, 75.09±2.43 µm), 6 to 12 yrs (n=22, 73.51±2.85 µm) and >12 yrs (n=12, 72.04±4.13 µm) (p=0.002, ANOVA, Tukey post-hoc). The percent of eyes with abnormal RNFL thickness increased from 39% in the group ≤3 yrs to 70% in all >3 yrs (p = 0.002); the percent of abnormal mfVEP amplitude also increased (62% in ≤3 yrs vs 90 % in >3 yrs, p=0.025). Comparing no-ON eyes with duration ≤3 yrs to all those >3 yrs, the mean RNFL thickness was significantly greater (100.96 7± 1.40 vs 94.65±1.29 µm, p =0.00015). The percent with abnormal RNFL thickness and mfVEP amplitude increased but did not reach statistical significance (for RNFL, 4% vs 10%, p=0.181; for mfVEP, 11% vs 38%, p=0.06).
Conclusions: :
Greater retinal nerve fiber layer loss was observed in ON eyes (and to a lesser extent in no-ON eyes) of patients with longer duration of MS.
Keywords: neuro-ophthalmology: optic nerve • nerve fiber layer