Comparative evaluation of current ophthalmodynamometers.
Seventy-five patients under 40 years of age with no history of ocular, cardiovascular, or cerebrovascular disease were examined with four commonly used ophthalmodynamometers. There was a significant difference in the absolute values measured with each instrument and the ophthalmic to brachial artery pressure ratio. The standard deviations were comparable between 8.1 and 10.2%. The absolute value of the average percent difference between the right and the left eye ranged from 3.6% with the Galin unit to 6.7% with the Sisler unit. Limits of +/- 15% for ophthalmic artery to brachial artery pressure ratio and 10% for right to left pressure difference should be used for 95% confidence levels. There was a small but definite correlation between the ocular coefficient of rigidity and pressure differences between direct and indirect instruments.