High and Low Contrast Visual Acuity Are Not Affected in Amyotrophic Lateral Sclerosis

Abstract

The afferent visual system may be affected by neuro-degeneration in amyotrophic lateral sclerosis (ALS) based on observations of visual function impairment and retinal inclusions on histopathology in ALS patients. To test the hypothesis that visual acuity is impaired in ALS, we compared three measures of visual acuity in ALS patients (n = 25) attending a multidisciplinary ALS clinic and age matched control subjects (n = 25). Bilateral monocular and binocular visual acuities were assessed using high contrast (black letters on white background) and low contrast (2.5%, 1.25% grey letters on white background) visual acuity charts under controlled lighting conditions following refraction. Binocular summation was calculated as the difference between binocular and best monocular acuity scores. There were no associations between binocular or monocular high contrast visual acuity or low contrast visual acuity and amyotrophic lateral sclerosis diagnosis (generalized estimating equation models accounting for age). Binocular summation was similar in both amyotrophic lateral sclerosis and control subjects. There was a small magnitude association between increased duration of ALS symptoms and reduced 1.25% low contrast visual acuity. This study does not confirm prior observations of impaired visual acuity in patients with amyotrophic lateral sclerosis and does not support this particular measure of visual function for use in broad scale assessment of visual pathway involvement in ALS patients.

Validation of Simplified Visual Acuity Testing Protocols in Amyotrophic Lateral Sclerosis

“…All subjects had gold standard HCVA and LCVA within the range of that reported in a larger study of VA in ALS and control subjects. 7 Median HCVA and LCVA in ALS subjects in this study are similar to those reported in the larger study (HCVA: 49, LCVA: 28).…”

“…Although data have been conflicting, afferent visual system involvement in amyotrophic lateral sclerosis (ALS) is supported by studies showing decreased binocular LCVA and HCVA 4 and retinal changes on optical coherence tomography 5 and histopathology. 6 An association between afferent visual system deterioration and other markers of ALS has been demonstrated both with regards to function (LCVA and disease duration) 7 and structure (macular retinal nerve fibre layer and pulmonary function tests). 8 Larger clinical studies are needed to understand the extent of afferent visual pathway involvement in ALS, how it correlates with other markers of disease, and the functional implications of this.…”

Ocular Involvement Occurs Frequently at All Stages of Amyotrophic Lateral Sclerosis: Preliminary Experience in a Large Italian Cohort

“…Ferrari et al 21 demonstrated a corneal small-fiber sensory neuropathy in sporadic ALS patients using confocal microscopy, and found that bulbar function disability scores were significantly related to measures of anatomical damage to corneal nerve fibers. Recent visual acuity measurements by Moss et al 22 did not confirm previous observations of impaired visual acuity in ALS patients, and did not support the use of this particular measure of visual function in broad-scale assessments of visual pathway involvement in ALS. 23 …”

Amyotrophic Lateral Sclerosis: A Neurodegenerative Motor Neuron Disease With Ocular Involvement

“…Visual acuity in ALS patients is controversial. While a study found a lower visual acuity in ALS patients in both high-contrast and low-contrast (2.5% and 1.5%) visual acuity with Sloan charts ( Moss et al, 2012 ), in others, the visual acuity exam revealed no differences in monocular high-contrast visual acuity ( Volpe et al, 2015 ; Moss et al, 2016 ; Rojas et al, 2019 ) or low-contrast visual acuity ( Moss et al, 2016 ).…”