Читать книгу Essentials of Veterinary Ophthalmology - Kirk N. Gelatt - Страница 89

In the normal eye, IOP is generated by flow of AH against resistance, and is necessary to maintain the appropriate shape and optical properties of the globe. AH is a clear, colorless liquid that fills the anterior and posterior chambers as well as the pupil. It has a refractive index of 1.335, which is slightly denser than water, and is a critical constituent of the eye's optical system. As AH is formed by the ciliary body processes, it enters the posterior chamber and flows through the pupil into the anterior chamber, where it leaves the eye through the corneoscleral trabecular and uveoscleral outflow pathways. The rate of AH formation equals the outflow, so the IOP is maintained relatively constant, and the refractive surfaces of the eye are kept in a normal position.

This continuous flow of AH supplies the avascular cornea and lens with nutrients and also removes their waste products. A convection current exists within the anterior chamber whereby warm AH circulates from the pupil downward adjacent to the air‐cooled cornea and upward near the lens where the temperature is warmer. This thermal circulation is responsible for the deposition of cellular material – termed keratic precipitates – on the inferior aspect of the corneal endothelium.