Purpose
To evaluate the optic nerve and macula of patients with ALS compared with healthy controls using optical coherence tomography (OCT) and layer segmentation technology and to correlate findings with disease duration and clinical markers of severity. Ultimately, our goal is to correlate clinical OCT measurements with ALS specific histopathologic findings in donor eyes.
Methods
ALS patients underwent volumetric macular and retinal nerve fiber layer (RNFL) OCT imaging. Semi-automated retinal segmentation software was used to measure macular sub-layers in volumetric scans. Macular cube OCT scans from age- and gender-matched healthy subjects were provided by the OCT reading center. RNFL thickness was compared to normative data provided by the OCT software manufacturer. Clinical data including date of symptom onset and ALS functional scores were collected from the electronic medical records.
Results
OCT data from a total of 10 ALS patients and 10 controls were analyzed. Significant thinning of the macular nerve fiber layer (mNFL) was observed in ALS patients compared to controls (ALS mNFL = 35.1 µm, Control mNFL = 38.8 µm, p = 0.045). In this preliminary analysis, we did not find significant relationships between OCT measurements and ALS disease duration or clinical markers of ALS severity. We recently described ALS specific neuronal inclusions in inner nuclear layer (INL) bipolar cells of an ALS patient with a causative C9orf72 mutation (Image 1). Ongoing H&E and IHC study of donor eyes from additional patients is underway to explore similarities between retinal and other central nervous system cellular pathology in ALS, and to investigate if retinal histopathology correlates with specific layer involvement demonstrated on OCT analysis.
Conclusions
Using OCT, macular sublayer analysis and histopathologic study, we are further characterizing the ocular manifestations of ALS. ALS specific retinal pathology may explain the visual dysfunction seen in ALS patients and offer prognostic value. Additionally, delineating the progression of neuronal subtype involvement, inclusion accumulation and cell death through correlation between clinical and histopathologic findings may offer new insights into the neurodegenerative mechanism and neuronal subtype susceptibility in ALS.