Читать книгу Essentials of Veterinary Ophthalmology - Kirk N. Gelatt - Страница 137

Light adaptation is a process in which cone (and rod) sensitivity decreases, and threshold increases, in response to increased background light intensity and the resulting increased photopigment bleaching. This is a much faster process than dark adaptation. Our eyes begin light adaptation within seconds to a sudden increase in background light intensity, such as that experienced when exiting a dark room. Indeed, it is suggested that the reason for the initial photophobia exhibited when exiting a dark room is an attempt by the eye to preserve the dark‐adapted state of the retina. Several mechanisms account for light adaptation. One is the increased activity of phosphodiesterase, resulting in shorter turnover time for cGMP and accelerating the response kinetics of cones.