Case of autosomal dominant optic atrophy with relatively good visual function.

BACKGROUND

Dominant optic atrophy (DOA) is an inherited optic neuropathy caused by mutations of the OPA1 gene. Patients with DOA have a gradual loss of vision that is often detected in early life. While most cases stabilize at around a decimal best-corrected visual acuity (BCVA) of 0.1, some show mild impairments without visual field abnormalities. This then makes the diagnosis of DOA difficult. We report our longitudinal findings of a 56-year-old man with autosomal dominant DOA whose visual functions remained relatively good and genetic testing was needed for the diagnosis of DOA.

CASE PRESENTATION

The patient was first examined 7 years earlier when he was 49-year-old at the Saitama Medical University Hospital. His major complaint was blurred vision. He had no medical or family history of ocular disorders, and his decimal BCVA was 1.0 (Snellen 20/20) in both eyes (OU). The intraocular pressure (IOP) was 13.7 mmHg in the right eye and 14.0 mmHg in the left eye. Slit-lamp examination revealed mild cataracts OU, and fundus examination showed temporal pallor of the optic discs OU. Humphrey visual field analyzer (HFA) standard 30 - 2 white-on-white perimetry indicated that the sensitivity was not reduced. Five years later, the patient returned for further examination because his vision had worsened. The decimal BCVA was 0.8 in the right eye and 0.6 in the left eye, and the IOP was within normal limits OU. The critical fusion frequency (CFF) was 30 Hz in the right eye and 31 Hz (normal values > 39 Hz) in the left eye. Slit-lamp examination and ophthalmoscopy showed no intraocular changes. Optical coherence tomography (OCT) showed a thinning of the retinal nerve fiber layer temporal to the optic disc. The contrast sensitivity was slightly decreased in both eyes, and the Panel D-15 color vision test was normal. Goldmann visual field testing with HFA SITA standard 10 - 2 and 24 - 2 white-on-white perimetry showed no obvious scotomas. However, HFA SITA standard 24 - 2 blue-on-yellow perimetry showed a diffuse decrease of sensitivity. Full-field and focal macular electroretinograms (ERGs) were normal in both eyes. Genetic testing was performed with the patient's consent, and next generation sequencing analysis identified a new heterozygous c.2331+2T>G variant in the OPA1 gene (NM_130837.3). At the final follow-up examination at age 55 years, the decimal BCVA was still relatively good at 0.8 in the right eye and 0.6 in the left eye.

CONCLUSIONS

These findings indicate that relatively good visual function can be maintained until the late middle age in patients with DOA, and genetic testing should be considered when circumpapillary RNFL thinning is observed, even in patients with relatively good visual acuity.