New study identifies genetic disease that impairs night vision before retinal damage appears

A recent study conducted by researchers at University Hospital Bonn in Germany has identified a previously unknown form of inherited retinal disease. The condition reduces the ability to see in the dark before any visible structural damage appears, while leaving central visual acuity relatively preserved.

Published in the medical journal “JAMA,” the study links the condition to a specific genetic variant in the “EFEMP” gene, designated “p.Arg140Trp.” This variant primarily affects the outer regions of the retina and the light-sensitive cells responsible for vision in low-light conditions.

Early symptoms include difficulty seeing at dusk and in darkness, along with reduced peripheral vision. However, conventional examinations of the back of the eye reveal no abnormalities in the early stages, which can delay diagnosis.

To investigate this genetic variant in unrelated families, the researchers used genetic testing, high-resolution imaging and tests assessing the eye’s ability to adapt to darkness. Participants showed slower visual recovery after exposure to light despite having normal visual acuity, indicating that cellular dysfunction precedes structural damage.

The researchers noted that this pattern differs from conditions associated with previously known variants in the same gene, which affect the centre of the retina. In this case, the damage is concentrated in the periphery, while the central region remains preserved.

Maximilian Pfau, a researcher involved in the study, stressed that the findings demonstrate how different variants in the same gene can cause diseases with distinct clinical patterns. The discovery could help explain cases whose genetic cause had previously remained unknown.