Background: The visual system of desert rodents demonstrates a rather high degree of development and specific features associated with adaptation to arid environment. The aim of this study is to carry out a descriptive investigation into the most relevant features of the sand rat eye. Results: Light microscopic observations revealed that the eye of Psammomys obesus diurnal species, appears similar to that of others rodent with characteristic mammalian organization. The eye was formed by the three distinct layers typical in vertebrates: fibrous tunic (sclera and cornea); vascular tunic (Iris, Ciliary body, Choroid); nervous tunic (retina). Three chambers of fluid fundamentals in maintaining the eyeball's normal size and shape: Anterior chamber (between cornea and iris), Posterior chamber (between iris, zonule fibers and lens) and the Vitreous chamber (between the lens and the retina) The first two chambers are filled with aqueous humor whereas the vitreous chamber is filled with a more viscous fluid, the vitreous humor. These fluids are made up of 99.9% water. However, the main features, related to life style and arid environment, are the egg-shaped lens, the heavy pigmentation of the middle layer and an extensive folding of ciliary processes, thus developing a large surface area, for ultrafiltration and active fluid transport, this being the actual site of aqueous production. The ciliary muscle is poorly developed and the dilator pupillae is not apparent. Conclusions: The ocular globe of sand rat demonstrates a high degree of development and several specific features associated with adaptation to life style and arid environment.

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