Techniques of intraocular pressure determination.

A variety of indentation or applanation tonometers are available for the measurement of intraocular pressure in conscious or anesthetized animals. The Schiøtz tonometer is a simple indentation tonometer, but unless used properly can give misleading values. Applanation tonometers include the air tonometer, pneumatonograph, and the Goldmann type (either slit-lamp or hand-held models). These flatten a small, fixed area of cornea and measure the resultant pressure. In anesthetized animals anterior chamber cannulation may be performed, although breakdown of the blood-aqueous barrier can ensue together with an alteration of intraocular pressure. Of importance is that all tonometers be calibrated for each species since scleral rigidity, ocular curvature, pressure/volume relationships, etc. all vary between species.