Читать книгу Essentials of Veterinary Ophthalmology - Kirk N. Gelatt - Страница 115

The pupillary aperture is not considered to be a classic refractive structure as it has no refractive index, but it does make an important contribution to the resolving power of the eye. As the pupil dilates in dim light, the number of photons entering the eye increases, resulting in increased retinal illumination. However, there is “a price to be paid” for this increased illumination, as mydriasis also decreases the depth of focus of the eye. This means that as the pupil dilates, the range of distances at which objects remain in focus decreases.