Abstract
Purpose:
Previous reports of ocular abnormalities in Huntington’s disease (HD) have detailed eye movement disorders. Mitochondrial dysfunction is a feature of HD, and diseases affecting mitochondrial function frequently manifest neuro-ophthalmic signs and symptoms including optic neuropathy. However, these changes have not been reported in HD. The objective of this case-control study was to investigate optic nerve and macular morphology in HD using optical coherence tomography.
Methods:
A total of 26 HD patients and 29 controls underwent a thorough neuro-ophthalmic examination including digital retinal photography and spectral domain optical coherence tomography (OCT) scans of the macula and peripapillary retinal nerve fibre layer (RNFL). Genetic testing results, disease duration, HD disease burden scores and unified HD rating scale (UHDRS) motor scores were acquired for HD patients.
Results:
Of the 26 patients with HD, 13 were women; the mean age was 52.0 years (range 33 - 68). The control group was matched for age and gender. The range of the CAG repeat expansion size was 38-48 repeats. Amongst the 52 HD patient eyes, eight were excluded from macular and/or RNFL analysis due to poor scan quality. After statistical analysis confirmed no significant difference in the measurements from both eyes of each participant, 22 right eyes were included in OCT analysis. Temporal RNFL thickness was significantly reduced in the HD group (62.3 (± 7.3) μm vs. 69.8 (±10.8) μm, p = 0.005). There was no significant difference in total macular volume between HD patients and controls (8.57 (± 0.38) mm³ vs. 8.62 (±0. 31) mm³), p = 0.63). There was, however, a significant negative (p < 0.05) correlation between macular volume and UHDRS motor scores (R2 = -0.56), and disease duration (R2 = -0.57).
Conclusions:
The temporal RNFL is preferentially thinned in HD patients. This could implicate mitochondrial dysfunction as the temporal RNFL is reduced in other conditions where mitochondrial function is impaired, including Leber’s hereditary optic neuropathy. The correlation between the decrease in macular volume and increasing motor disability suggests that ocular coherence tomography may be a useful biomarker for disease progression in HD. Larger, longitudinal studies are required in order to corroborate these findings.