When do mice open their eyes? - briefly
Laboratory mice usually open their eyes between 12 and 14 days after birth, most commonly around day 13. The precise timing can differ slightly among strains.
When do mice open their eyes? - in detail
Neonatal mice keep their eyelids sealed for the first few days after birth. The typical species used in laboratory research, Mus musculus, opens its eyes between post‑natal day 12 and day 14. This range reflects slight variations among strains, litter size, and environmental conditions such as temperature and lighting.
Key factors influencing the exact timing:
- Genetic background (e.g., C57BL/6 vs. BALB/c)
- Maternal care and nest temperature
- Nutritional status of the pups
- Light exposure in the rearing environment
Physiologically, eyelid opening coincides with maturation of the visual system: photoreceptor development, synaptic refinement in the retina, and the establishment of cortical connections. Behavioral markers, such as the emergence of visual orienting responses, become observable shortly after the lids separate.
Researchers monitor this milestone to schedule experiments that require functional vision, adjusting protocols to the specific window when the eyes first become visible.