How can mutations in the RHO gene affect vision?

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details of the mammalian eye — Photoreception The mammalian eye has a cornea and a lens and functions as a dioptric system, in which light rays are refracted to focus on the retina.

The RHO gene encodes rhodopsin, a sensory protein essential for converting light into electrical signals within the retina’s rod cells. Mutations in this gene disrupt the visual cycle, leading to hereditary eye diseases that impair the eye's ability to adapt to darkness.1

These mutations are primarily associated with two conditions:

Retinitis pigmentosa: This progressive condition typically begins in youth with the degeneration of rod cells and night blindness. Over time, it leads to the destruction of cone cells, eventually resulting in the loss of daytime vision.1
Autosomal dominant congenital stationary night blindness: Individuals with this condition are born with poor vision in dim light. Unlike retinitis pigmentosa, this form of night blindness is generally stable and does not typically worsen over time, with daytime vision usually remaining normal.1

In both cases, the underlying issue is a failure of the eye to properly adapt to low-light environments due to the dysfunction of the rhodopsin protein.1