Retinal changes in amyotrophic lateral sclerosis: looking at the disease through a new window

Amyotrophic lateral sclerosis (ALS) is the most frequent degenerative disease affecting motor neurons (MN). ALS has been traditionally considered as a pure motor system disease; however, there are currently sufficient evidences supporting the involvement of other non-motor systems. Recently, the development and the implementation of the optical coherence tomography (OCT) have provided new data regarding the ocular involvement in the disease. In this sense, alterations in retinal nerve fiber layer thickness (RNFL), other retinal layers thicknesses such as outer nuclear layer (ONL) and inner nuclear layer (INL) and changes in the retinal blood vessels have been described in ALS patients. Interestingly, the study of ocular alterations in ALS appears not only as new biomarker tool, but also as a new opportunity to deep into the pathogenesis of the disease. In this article we will review and standardize published studies regarding OCT and ALS, emphasizing both their strengths and weaknesses.