Relative axial myopia induced by prolonged light exposure in C57BL/6 mice.

Ambient lighting is essential for ocular development in many species, however, disruption in diurnal lighting cycle can affect the development in refraction and axial growth of the eye. This study investigated the effects of prolonged daily lighting on refraction and various optical components of the eye by raising C57BL/6 mice under three different light/dark cycles (18/6, 12/12 and 6/18). Egr-1 mRNA expression, apoptosis and histology of the retina and size of the scleral fibrils were evaluated in these three lighting cycles. Results showed that there was a trend of myopic development, increasing vitreous chamber depth and thinning of the retina in eyes from 6/18 to 18/6 groups. Retinal Egr-1 mRNA expression and diameter of scleral fibrils were reduced with the prolongation of daily lighting from 6/18 to 18/6. However, retinal apoptosis was not detected in all the groups. These results suggest that prolonged lighting can induce axial myopia in inbred mice. This model, which uses mice with similar genetic backgrounds, provides an alternative to the currently available models and therefore is useful for evaluation of refractive errors caused by changes in environmental illumination.