The commercially available Perkins applanation tonometer was evaluated in laboratory and clinic. In the laboratory, this tonometer was linear over its full range, free from hysteresis, and free from significant temperature effects over the range 9 to 57 C. Force produced by the arm never deviated more than 3% of full scale from the expected force, regardless of scale setting, position with respect to gravity, or position of the arm with respect to the body of the tonometer. In its clinical evaluation, the tonometer was found to be conveniently constructed, easy to use, and acceptable to patients. When compared to Goldmann applanation tonometer readings, the root mean square difference between the two instruments was 1.4 mm Hg. No systematic difference was detected. The endpoint for the Perkins applanation tonometer was difficult to see in a brightly illuminated room.
Dunn JS, Brubaker RF. Perkins Applanation TonometerClinical and Laboratory Evaluation. Arch Ophthalmol. 1973;89(2):149-151. doi:10.1001/archopht.1973.01000040151020