Purpose: Amyotrophic lateral sclerosis (ALS) is characterized by a swift progression of neurodegeneration a!ecting upper and lower
motor neurons, as well as the extramotor nervous system. The retina, an expansion of the diencephalon, is commonly impacted in
neurodegenerative diseases. Research in ALS is limited and studies of retinal involvement have had conflicting results, however
histopathological studies have reported p62-positive cytoplasmic inclusions within layers of the retina with similar inclusions in the
cerebellum and hippocampus. The objective of this study is to evaluate the biomarker utility of non-invasive optical coherence
tomography imaging, through assessing the relationship between retinal thickness and disease severity in patients with ALS.
Study Design: Retrospective case-series.
Methods: Data from 14 patients (mean age 61 ± 9 years, 4 females and 10 males) with ALS, and no ocular comorbidities, were
collected from the Ontario Neurodegenerative Disease Research Initiative (ONDRI) database. Disease severity as measured by the
ALS Functional Rating Scale - Revised (ALSFRS-R, maximum score of 48 indicating normal function) and Forced Vital Capacity (FVC)
% predicted (clinical predictor of survival and disease progression in ALS) was assessed for correlations with spectral domain optical
coherence tomography (SD-OCT) measures of peripapillary retinal nerve fiber layer (pRNFL) thickness, central macular mean retinal
thickness (RT), and total macular volume (TMV).
Results: Mean pRNFL thickness, TMV, and RT were 98.4 ± 10.7μm, 8.5 ± 0.5mm3, and 274.8 ± 22.2μm, respectively. Patients had
a mean ALSFRS-R score of 38 ± 4, and mean FVC% of 98.4 ± 16.4% predicted. Spearman’s correlation analysis revealed a negative
correlation between mean TMV and FVC% (p=0.02, however not significant with Bonferroni adjustment). There were no significant
correlations between SD-OCT measures and ALSFRS-R.
Conclusions: In this study, high-resolution SD-OCT has shown that with greater macular volume ALS severity is worse as measured
by FVC%, a clinical test that assesses motor innervation of the diaphragm and is predictive of mortality. This may be secondary to
pathological retinal inclusions a!ecting macular volume in patients with a greater degree of measurable neurodegeneration. Further
studies on a larger cohort of ALS patients as well as further sublayer OCT analysis may help explain this finding. The ability to use
OCT as a biomarker in ALS could potentially allow for earlier diagnosis and act as a monitoring tool to follow disease progression.

Optical coherence tomography as a biomarker for disease severity in ALS

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