S160. Retinal involvement by optical coherence tomography and its correlation with disease severity in amyotrophic lateral sclerosis

Abstract

Non motor involvement in Amyotrophic lateral sclerosis is being increasingly recognized and studies on involvement of retina have conflicting results. Optical coherence tomography (OCT) as a tool for analysis of retinal neurons and axons has been used in various neurodegenerative disorders. Our aim was to study the involvement of retina by measuring the retinal nerve fiber layer and macular thickness in ALS and correlate with disease severity. Prospective cross sectional comparative study in patients diagnosed with ALS based on revised El-Escorial criteria. 50 subjects (25 cases; 25 age and gender matched controls) were recruited for the study. The disease severity was assessed using “Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS)” – Revised scale. Retinal nerve fiber layer thickness (RNFL) and macular thickness was measured using SD-OCT (Spectralis; Heidelberg Engineering). The mean age was 51.43 ± 11.2 years in cases, 48.8 ± 11.9 years in controls. There was no significant difference between the two groups and were comparable. The mean ALSFRS score was 31.96 ± 5.99. 24% had bulbar onset and the reminder had limb onset ALS. Mean duration of illness was 14.07 ± 7.8 months. Mean RNFL in cases was 102.2 ± 9.7 μm and in controls was 100.7 ± 7.2 μm which was not statistically significant. Average macular thickness in cases was 304.3 ± 12.7 μm in cases and 304.5 ± 11.2 μm in controls. Central foveal thickness was 253.5 ± 21.4 μm in cases and 256.2 ± 23.6 μm in controls. There was no positive/ negative correlation between ALSFRS and RNFL/ macular thickness. Mean RNFL, six sector RNFL, average macular thickness and nine segment Early Treatment Diabetic Retinopathy Study (ETDRS) grid macular thickness done in 25 patients (50 eyes) and 25 controls (50 eyes) did not show difference in thickness and there is no correlation between disease severity and retinal thickness. There was no difference in retinal thickness between bulbar onset or limb onset ALS. Retina is the window to the brain and our study attempted to look for possibility for any changes though retinal involvement may not be a part of ALS. Previous studies on OCT had shown conflicting evidence. Our study shows that retinal thinning may not be part of the non-motor involvement in ALS. Further studies may be required to validate on a large cohort.