It has long been appreciated that the maintenance of the ocular tension within a relatively narrow physiologic range is a fundamental necessity for the optimal function of the eye. A deviation of pressure below this norm is followed by morphologic changes in ocular structures that interfere grossly with optic performance. An elevation is attended with progressive pathologic alterations in ocular tissues associated with the syndrome complex of glaucoma.
Basically, the pressure within the globe is determined by the opposing forces of the semirigid wall of the eye and the encompassed structures—solid, semisolid and liquid. It is apparent that while the scleral coat and formed contents of the eye normally remain relatively constant, the circulating intraocular fluids—aqueous, blood and perivascular lymph—are potentially subject to changes in volume that establish them as basic determinants of intraocular pressure levels. Since the amount of lymph present in the eye is small, its effect