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Scanning Tonometer for Eye Pressure (STEP™)
Problem
Measurement of eye pressure by Goldmann applanation tonometry
is a technique first embodied in the late 1950’s. Tonometry is
faced with a number of unknown variables including elastic
resistance of the cornea, surface tension of tears on the eye, and
changes in eye pressure with cardiac and respiratory pulse.
Solution
Goldmann and instantaneous (air-puff) measures of intra-ocular
pressure are always flawed by time bound (0.5 to 12 seconds)
changes in eye pressure. The Scanning Tonometer for Eye
Pressure (STEP™) overcomes all the above limitations of state-ofthe-art tonometry and provides information on corneal integrity.
STEP™ Glaucoma Assessment
The standard technique for Goldmann applanation
tonometry is automated to enable inclusion of variables
that change the reading as a function of tear volume,
corneal elastic resistance, and the cardiac and respiratory
pulse.
References
Whitacre MM, Stein R. Sources of error with use of
Goldmann-type tonometers. Survey of
Ophthalmology 1993 July-August; 38(1):1-30.
2. Aggarwala KR. On the short-term variability of
measurements of intraocular pressure. Optometry
and Vision Science. 1995 October; 72(10):753-5.
3. Lam AK, Lam CH. Effect of breath-holding on
pulsatile ocular blood flow measurement in normal
subjects. Optometry and Vision Science 2004
August; 81(8):597-600.
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