Baseline, one and three month changes in the peripapillary retinal nerve fiber layer in acute optic neuritis: Relation to baseline vision and MRI

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Abstract

Objective

Retinal nerve fiber layer (RNFL) loss occurs with MS or after optic neuritis. Acute RNFL alterations at presentation and changes over time have not been well documented. We analyzed regional RNFL changes using 2 methods, ocular coherence tomography (OCT) and scanning laser polarimetry (SLP), to study initial edema and early RNFL loss.

Methods

40 subjects with unilateral acute optic neuritis, had prospective OCT and SLP RNFL thickness values organized into 4 quadrants. We compared affected with normal fellow and control eyes to determine RNFL thickening (≥ 10% of 95th percentile of controls) and thinning (≥ 10 μ less than fellow eye) at presentation, 1 and 3 months.

Results

RNFL thickening occurred in 27/33 eyes (82%) by OCT and in 21/34 eyes (62%) by SLP at baseline. At 1 month, RNFL thickening was common even as thinning developed in 15/23 (65%) of eyes by OCT and in 15/28 eyes (54%) by SLP. At 3 months, RNL was thinned by OCT in 14/24 (58%) and by SLP in 15/25 (60%) affected eyes (58%). Neither MRI optic nerve lesion nor vision at baseline correlated with optical image findings or vision outcome.

Conclusions

RNFL swelling, most likely due to axoplasmic stasis from blockade at the lesion site in optic neuritis, is seen with OCT better than SLP. RNFL swelling in some quadrants and loss in others occur at 1 month and is well seen with interocular comparison by both methods. Optical imaging provides pathophysiologic as well as quantitative information regarding axonal changes.

Introduction

Swelling of the optic disc is seen on clinical examination in approximately one third of eyes at presentation of acute optic neuritis. Available methods for imaging of the optic disc and peripapillary retinal nerve fiber layer (RNFL) can be utilized to demonstrate and quantify RNFL swelling and subsequent thinning due to demyelination. An earlier small case series showed a trend of thickening in the RNFL in eyes with acute optic neuritis eyes when compared with fellow asymptomatic eyes [2]. OCT studies performed months or longer after the onset of optic neuritis revealed reduction in the global mean RNFL that was more prevalent in eyes with persistent visual deficits [3], [4]. Until recently, no large case series study of acute optic neuritis with ocular imaging at the time of presentation had been reported [5].

Although OCT is the most commonly used optical imaging modality to evaluate the RNFL, scanning laser polarimetry (SLP) studies also show RNFL losses in eyes with glaucoma and in multiple sclerosis (MS) patients [6], [7], [8]. Scaling differences between the two imaging techniques account for larger RNFL thickness measurements seen with OCT compared with SLP, but both are comparable for uncovering RNFL loss due to disease [9], [10]. The temporal RNFL, possibly the quadrant most often disturbed in optic neuritis, was difficult to image with older SLP methods, and is seen better using newer methodology, called enhanced corneal compensation [11], [12]. We prospectively investigated eyes with acute optic neuritis to further elaborate the RNFL changes at presentation, 1 and 3 months and to explore the relationship of these findings to changes in vision and MRI demonstrated lesions of affected optic nerves. Further, we sought to improve the sensitivity of uncovering more subtle abnormalities or alterations in the RNFL results by utilizing interocular comparisons and evaluating all 4 quadrants of collected data. We also explored whether additional or distinguishing features in RNFL alteration could be uncovered by comparing the measured OCT thickness and SLP retardation results at baseline 1 and 3 months.

Section snippets

Methods

We selected subjects with first-time unilateral acute demyelinating optic neuritis in the affected eye and vision loss less than 21 days. All study subjects had typical features of optic neuritis including a relative afferent pupillary defect in the affected eye [1]. None of the eyes had significant optic disc swelling or peripapillary hemorrhages or exudates on ophthalmoscopy. Mild swelling of the optic disc, noted by comparison to the fellow eye with smaller cup to disc ratio, was permitted.

Results

We studied 40 subjects, 6 men and 34 women, with a mean age 32 years (median 31.6 years) at an average of 6.4 days (sd 4.0) after the onset of vision loss. Twelve subjects had relapsing remitting MS, diagnosed by Poser criteria, for a mean of 1.4 years (sd .69, range 1–3 years) and 10 were taking interferon or glutarimer acetate. Prior optic neuritis in the fellow eye occurred in 9 subjects (7 of who had MS). Affected eye baseline and follow up visual performance are detailed in Table 1. Intravenous

Discussion

Quadrant analysis and comparison to fellow eye measurements revealed RNFL thickening, suggestive of swelling, in 82% by OCT and 62% by SLP of acutely affected eyes at presentation with first time optic neuritis. OCT was clearly superior to SLP in demonstrating the extent of RNFL baseline thickening. Interocular comparison of RNFL thickness is superior to the typically-used difference in quadrants from age-matched controls in industry databases for OCT and SLP and for OCT values obtained from

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    Supported in part by grants from Pearle Vision Foundation, Teva Pharmaceutical, Veterans Administration (Merit Grant; Rehabilitation Division) and Research to Prevent Blindness (New York, New York). MJK had grants from Pearle Vision Foundation and Teva, neither of which designed, conducted or analyzed any aspect of this study. There are no conflicts of interest.

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