Читать книгу Essentials of Veterinary Ophthalmology - Kirk N. Gelatt - Страница 135

The dimensions of the ocular tissues also contribute to improved scotopic sensitivity in many species. For example, the mean diameter of the cornea in cats and humans is 16.5 and 11.7 mm, respectively. Consequently, much more light enters the cat's eye. Next, light must pass through the pupil. The diameter of a mydriatic pupil in cats and humans is about 12 and 8 mm, respectively, translating into a pupillary aperture of 113 and 50 mm², respectively. As a result, far more light passes through the cornea and pupil to reach the feline retina at night, when the pupil is fully dilated. Indeed, it has been calculated that a fully dilated pupil increases the amount of light reaching the retina by 135‐fold in the cat, compared to an 80‐fold increase in humans.