Abstract
Purpose::
To correlate visual function with high-resolution structural imaging in a family with the NARP (neuropathy, ataxia, retinitis pigmentosa) syndrome.
Methods::
Best-corrected visual acuity (VA), Farnsworth D-15 color vision, Humphrey automated perimetry, Goldmann kinetic perimetry, fundus-guided microperimetry using a Nidek MP-1, and both full field and multifocal electroretinograms (ffERG and mfERG) were used to study retinal function in a family carrying the T8993C mitochondrial mutation. Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) imaging was performed to correlate macular structure with function in one patient.
Results::
The proband’s VA was correctable to 20/63 OD and 20/60 OS. Fundus exam revealed mild optic nerve pallor, retinal vascular attenuation and scattered retinal pigment epithelial (RPE) changes. Foveal thresholds were reduced at 25 dB OD and 27 dB OS, color vision was abnormal, visual fields showed a dense relative scotoma extending from 4-30 degrees OU and mfERG amplitudes were decreased with delayed timing OU; rod- and cone-ffERG amplitudes were near normal, although timing was delayed. The proband’s daughter’s VA was 20/50 OD and 20/63 OS; foveal thresholds were 32 dB OD and 34 dB OS and fundus findings were similar to her mother. Color vision was abnormal, visual fields were constricted to about 40 degrees centrally, and mfERG and ffERG rod- and cone-mediated amplitudes were reduced with delayed timing. Cones were readily imaged in the proband using AOSLO OS. Cone spacing was about twice that of a normal retina within 2 degrees of the fovea. Further from the fovea, cone coverage became patchy and RPE cells were visible in some places. Hyperreflective regions near the edges of the cone preserved area matched features on fundus photographs. Microperimetry results correlated well with observed structure in the AOSLO image, showing complete scotomas in regions where no cones were visible.
Conclusions::
AOSLO imaging demonstrated abnormalities in cone spacing which corresponded to reduced visual function in a patient in carrying the T8993C mitochondrial mutation associated with NARP. These high-resolution images provide the first in vivo measures of cone structure in patients with mitochondrial mutations.
Keywords: retinal degenerations: hereditary • imaging/image analysis: clinical • macula/fovea