VA loss, RNFL thinning characterize MS

September 1, 2013

Visual loss and progressive thinning of the retinal nerve fiber layer (RNFL) occur over time in patients with multiple sclerosis (MS), according to results from a longitudinal study.

Take-Home:

Visual loss and progressive thinning of the retinal nerve fiber layer (RNFL) occur over time in patients with multiple sclerosis (MS), according to results from a longitudinal study.

 

Moster

Philadelphia-Visual loss and progressive thinning of the retinal nerve fiber layer (RNFL) occur over time in patients with multiple sclerosis (MS), according to results from a longitudinal study of visual function and optical coherence tomography (OCT).

“Axonal and neuronal loss are common in (the disease) and have been shown pathologically in the anterior visual pathway, even in patients with no history of optic neuritis,” Stephen Moster, MS, said of the study’s results.

“The introduction of OCT has allowed researchers to capture the structure/function correlations in MS and has brought the anterior visual pathway to the forefront as a model for testing new therapies,” he said.

The baseline data from the longitudinal study showed that the baseline RNFL in the eyes of patients with MS was 91 µm compared with 104 µm in healthy controls.

The initial 3-year study, said Moster, who is a fourth-year medical student at the University of Pennsylvania, Philadelphia, showed significant progressive RNFL thinning from baseline to 3 years.

Using time-domain OCT, Moster and colleagues extended the study to determine if the RNFL thinning continued and was associated with visual loss in patients with MS.

About the study

(Figure 1) Patients were followed every 6 to 12 months after baseline evaluation. Compared with baseline, at 5 to 7 years the retinal nerve fiber layer decreased by -9.2 μm (p < 0.001).

In this multicenter study, patients were followed every 6 to 12 months after the baseline evaluation. The patients underwent high- and low-contrast visual acuity (VA) testing and measurement of the RNFL (Stratus OCT-3, Carl Zeiss Meditec).

The study included 196 patients (mean age, 44 years; 379 eyes); three quarters of patients were women. More than 80% had the relapsing/remitting form of MS. Forty-three percent of patients had a history of optic neuritis.

The results, Moster said, showed a trend in RNFL thinning over time.

“Notably, the trend continued past the 3-year time point and did not level off,” he said.

Compared with baseline, at 5 to 7 years the RNFL decreased by -9.2 µm (P < 0.001).

An evaluation of the subgroup that had 153 patients with a history of optic neuritis also indicated the same trend in the thinning of the RNFL.

The same thinning was seen in the patients without a history of optic neuritis.

“When we compared the amount of RNFL thinning between eyes with and without a history of optic neuritis, there was no significant difference in the amount of thinning between the two groups,” Moster said.

The thinning of the RNFL progressed by an average of about 1.9Ó µm annually at the 7-year time point, which agreed with the rate of progression at 3 years.

(Figure 2) Thinning of the retinal nerve fiber layer progressed by an average of ~ 19 μm annually at the 7-year time point, agreeing with the rate of progression at 3 years (Figures courtesy of Stephen Moster, MS).

In healthy controls, the annual rate of RNFL thinning was about 0.16 µm.

“These results indicated that there is a steady subclinical axonal loss in the anterior visual pathway in patients with MS that continues beyond 3 years,” Moster said.

The percentage of patients with RNFL loss also increased from 19% at 1 to 2 years after baseline, to 56% at 5 to 7 years after baseline.

A history of optic neuritis was not predictive of the amount of RNFL thinning over time.

Visual acuity

Regarding VA loss, the study found that patients with greater visual loss had greater thinning of the RNFL. The percentage of patients with visual loss by low-contrast acuity testing increased from 7% during the early years of follow-up-to 40% from 5 to 7 years after baseline.

A notable finding was that patients with visual loss over time did not have differences in the baseline RNFL thickness compared with the patients with steady vision, Moster said.

“The eyes with low-contrast visual loss over time had significant (P < 0.001) differences in the amount of thinning of the RNFL over time compared with eyes with steady vision,” he said.

Based on these findings, the study concluded that visual loss and thinning of the RNFL occur as a function of time in MS, and thus there is a steady decrease in the RNFL thickness over time. This suggests progressive axonal loss in the anterior visual pathway that continues beyond 3 years after baseline.

The study findings also supported the use of OCT and low-contrast VA testing in MS trials.

Stephen Moster, MS

E: smoster@gmail.com

Mr. Moster has no financial interest in the subject matter.

 

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