Читать книгу Essentials of Veterinary Ophthalmology - Kirk N. Gelatt - Страница 120

The eye is not a perfect optical system. Two of the most significant optical problems that affect the eye are spherical and chromatic aberrations. Positive spherical aberrations occur because in both the cornea and the lens, rays passing through the periphery are refracted more than rays passing through the center. Therefore, rays passing through the periphery are focused closer to the cornea (or lens) than rays passing through its center. Obviously, as the image is not uniformly focused on the retina, the aberration causes blurred vision. A comparative study found significant degrees of spherical aberrations in the lenses of dogs, cats, and rats, but minimal lenticular aberrations in cows, sheep, and pigs.