IOP Measurement Using Corneal Vibrations Parameters Analysis in Humans

Abstract

Purpose: A novel non-contact, non-invasive Vibration Tonometry technology with excitation of corneal vibrations and their correlation to GAT IOP was tested in a large clinical trial from which partial results are reported herein.<br />

Methods: 470 eyes form 236 volunteers from various ethnic origins at a suburban Paris hospital eye clinic and in the St Joseph Paris Glaucoma Institute were studied. History, vibration tonometry measurements in triplicate GAT, NIDEK air puff IOP, refractometry, keratometry and Tomey or Lenstar non-contact pachymetry. Algorithm discovery was performed by random draw splitting runs into a discovery sample and a separate validation sample performed 10 times separately on males and females.

Results: In 236 patients, 34.6% of eyes had glaucoma, 51% of which females. 1311 of 1772 (76%) vibration tonometry measurement runs were in correct position. Population aged 20-92 yo with 48.7% females with mean of 62.1(+/-13.5) in females and 62.5 (+/-12.7) in males. CCT mean was 531.2µ (+/-37.3) in females and 534.8µ (+/-38.5) in males. First 207 patients AL mean was 23.29 mm (+/-1.68) in females and 23.73 mm (+/-1.68) in males. GAT IOP ranged from 5.3 to 34 mm Hg, mean was 15.2 mm Hg (+/-3.1) in females and 15.2 (+/-3.52) in males. None of these differences were significant. No adverse events were reported during or post trial. Algorithm for women yielded 98,6% of IOP mean within 5 mm Hg of mean GAT IOP and 86% within 3 mm Hg. For men 96.4% of IOP mean was within 5 mm Hg of mean GAT IOP and 84.2% within 3 mm Hg from GAT IOP mean. Using the mean of 2 closest measures further improved results and could easily be implanted into the tonometer algorithm.

Conclusions: Current algorithm seems to show no evidence of effect of CCT on measurement precision. Vibration tonometry is a valuable method for non-invasive measurement of IOP without contact with reasonable precision and good reproducibility and independently of CCT. It may thus prove to be a valuable tool for IOP measurement in thin and surgical corneas.