Why do mice have red eyes? - briefly
Mice exhibit red eyes because they lack melanin in the iris and retina, so the underlying blood vessels are visible through the translucent tissue. This trait is typical of albino laboratory strains.
Why do mice have red eyes? - in detail
Mice that appear with red eyes lack ocular pigment. The absence of melanin in the iris and retinal pigmented epithelium allows blood vessels in the choroid to be seen through the transparent tissues, producing the characteristic red coloration.
The condition results from mutations that disrupt the tyrosinase enzyme, which catalyzes melanin synthesis. In laboratory strains such as BALB/c and C57BL/6 albino variants, the tyrosinase gene is either non‑functional or severely reduced, preventing pigment deposition during development. Consequently, the iris remains translucent, and the underlying choroidal vasculature reflects light, giving the eye its red hue.
Key biological consequences include:
- Increased light sensitivity due to reduced light‑absorbing pigment.
- Potential for visual acuity differences compared with pigmented counterparts.
- Use as a phenotypic marker in genetic studies; the red‑eyed trait is easily identifiable and often linked to other recessive alleles.
In pigmented mice, melanin granules within the iris absorb and scatter light, masking underlying vessels and resulting in brown, black, or gray eye colors. The contrast between pigmented and non‑pigmented eyes illustrates the role of melanin in ocular protection and visual function.