A New Tonometer System

Abstract

A tonometer, which involves no mechanical contact with the eye, has been designed and Is being tested. An air pulse generated from the ambient atmosphere with a reliable positive linear force‐time ramp impinges upon the cornea. The pulse causes a gradual curvature reduction, applanation, and finally a slight concavity before the decaying force‐time ramp permits restoration. Telecentric optical‐electronic monitoring of the corneal vertex specular reflection unlqueiy identifies, In time, the applanation event. Both human and animal testing have demonstrated a direct linear relationship between intra‐ocular pressure and the time interval to applanation. This permits Instantaneous digital readout in mm Hg. An optical‐spherometer type system is utilized to effect alignment of the pneumatic and monitoring systems with the cornea In the three dimensions. Following alignment and triggering, measurement in the normal range takes approximately 3 milliseconds, does not require lid retraction, and induces only a blink reflex with no discomfort.

The effects of lisuride, terguride and bromocriptine on intraocular pressure (IOP).

“…Using the non-contact tonometer (Grolman, 1972;Shields, 1980) in normal human volunteers, it has been shown that oral 1.25 mg bromocriptine produced a significant reduction in IOP (Mekki et al, 1983). A similar reduction was produced by 0.025% and 0.05% bromocriptine eye drops in normal human volunteers (Mekki et al, 1984).…”

Effect of cicloprolol in intraocular pressure in healthy volunteers.

“…Exercise heart rate was not measured at 1 h after dosing, i.e. only at times 0, 2, 3 and 6 h. Heart rate was measured by counting the radial pulse rate for 1 min, blood pressure by a standard mercury sphygmomanometer and IOP by non-contact tonometry (Grolman, 1972). Exercise heart rate was induced by exercising the subjects on an electrically-braked bicycle ergometer.…”

Local and systemic effects of pindolol eye drops.

“…Intraocular pressure was measured before and 1 h after instillation of the drop using non-contact tonometry (Grolman, 1972;Shields, 1980). Each subject had been screened in preliminary tests to ensure that six consecutive measurements of intraocular pressure showed a difference of less than 3 mm Hg.…”