German study identifies genetic cause of night vision loss without visible retinal damage

A recent study by researchers at the University Hospital Bonn in Germany has revealed a new form of inherited retinal disease that can cause night vision impairment before any obvious retinal damage is detected.

The research team explained that the condition is linked to a mutation in the EFEMP1 gene, which primarily affects the outer edges of the retina and the light-sensitive cells responsible for vision in low-light conditions. Early symptoms include difficulty seeing at dusk or in darkness, and a gradual decline in peripheral vision, while central visual acuity may remain intact and standard retinal examinations appear normal. This can delay diagnosis of the disease.

The study involved unrelated families carrying the same genetic mutation. Researchers used genetic testing, retinal imaging, and assessments of vision and the eye’s ability to adapt to darkness. The findings, published in the journal JAMA, showed that four members of one family with the mutation experienced slow recovery of vision in the dark after exposure to light, despite having normal visual acuity and no visible changes in the back of the eye.

Details of the genetic mutation and its effects

The researchers identified the disease-causing mutation as p.Arg140Trp, noting that it differs from another known mutation in the same gene that affects the center of the retina. The newly identified form mainly impacts the peripheral retina, while the central area remains relatively preserved.

Study co-author Maximilian Pfau noted that the results suggest different mutations in the same gene can lead to diseases with varying patterns, which may explain some previously unexplained hereditary cases.