Читать книгу Essentials of Veterinary Ophthalmology - Kirk N. Gelatt - Страница 85

Blood flow of the optic nerve head is usually provided primarily by branches from the short posterior ciliary arteries. In humans, cats, and rabbits, optic nerve head blood flow possesses autoregulation over a wide range of IOPs (∼30–75 mmHg), but in humans, this autoregulation is most efficient when IOP is 6–30 mmHg. Ocular perfusion pressure, the relationship between systemic blood pressure and IOP, determines blood flow in the optic nerve head. The autoregulatory capacity of optic nerve head blood flow is more susceptible to an ocular perfusion pressure decrease induced by lowering the blood pressure, compared with that induced by increasing the IOP. Studies of blood flow in the optic nerve head have been limited by the small tissue mass involved. The optic nerve head is subjected to several different pressures as well as to the tissue stress at the different levels of the scleral lamina cribrosa.