Applanation and Schiotz tonometer standardizations for the owl monkey eye with a new technique for measuring episcleral venous pressure.

A Schi0tz Pi calibration by open manometer was performed on 18 owl monkey eyes cannulated in situ. Pi values for the owl monkey corresponded closely to those of the 1955 Friedenwald nomogram. The average ocular rigidity measured in 16 additional eyes with the use of clinical techniques was 0.0173 (± 0.0015). A manometric calibration for a 4 mm. diameter applanation face was done similarly on 21 eyes. The following standardization formula ivas generated: Pressure in mm. Hg = 0.641 (tonometric scale reading) + 2.56 mm. Hg. An attempt ivas made to compare the two tonometric pressure standardizations. In 16 intact eyes, Schi0tz PO pressures, corrected for ocular rigidity, averaged 0.77 ± 0.47 mm. Hg higher than corresponding applanation pressures. An improved method for measuring episcleral venous pressure, xoith the use of a new synthetic polyurethane pressure chamber membrane, is also reported.