Effect of central corneal thickness and corneal hysteresis on tonometry as measured by dynamic contour tonometry, ocular response analyzer, and Goldmann tonometry in glaucomatous eyes.
OBJECTIVE
The dynamic contour tonometer (DCT; Pascal tonometer) and the Ocular Response Analyzer (ORA) are novel tonometers designed to measure intraocular pressure (IOP) independent of corneal properties and central corneal thickness (CCT), respectively. We wanted to compare the corneal compensated IOP (IOPcc) as measured by ORA with IOP values measured by DCT and Goldmann applanation tonometry (GAT) with respect to IOP readings and the influence of corneal hysteresis (CH) and CCT in glaucoma patients.


METHODS
In a study of 94 glaucomatous eyes, IOP measurements by ORA, DCT, and GAT were compared, and the effects of CCT and CH were analyzed. All measurements were taken by 1 of the authors only.


RESULTS
The Mean CCT was 550+/-44 mum and mean CH 10.24+/-3.3 mm Hg. The mean value for IOPcc was 17.94+/-5.9 mm Hg, 15.14+/-3.7 mm Hg for DCT, and 14.3+/-4.3 mm Hg for GAT. The mean difference was 3.65+/-3.85 mm Hg between IOPcc and GAT and 2.80+/-4.9 mm Hg between IOPcc and DCT (P<0.001) and -0.85+/-3.3 mm Hg between GAT and DCT (P=0.015). None of the methods was related to CCT. In contrast, CH was highly statistically significant related to IOPcc (P<0.0001), whereas GAT and DCT showed only weak relation to CH (P=0.05).


CONCLUSIONS
IOP measurements with the ORA are significantly higher than DCT or GAT with no apparent linear correction factor. To date, we cannot estimate the impact of differences in CH in relation to IOP and its measurement.
Hager
Annette
A
Department of Ophthalmology, Asklepios Klinik Nord-Heidberg, Tangstedter Landstr. 400, 22419 Hamburg, Germany. anhager@gmx.de
Annette
Hager
H
Loge
Kristina
K
Kristina
Loge
L
Schroeder
Bernd
B
Bernd
Schroeder
S
Füllhas
Mark-Oliver
MO
Mark-Oliver
Füllhas
F
Wiegand
Wolfgang
W
Wolfgang
Wiegand
W
D001696:Biomechanical Phenomena; D003315:Cornea / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004547:Elastic Tissue / Q000503:physiopathology; D005901:Glaucoma / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008875:Middle Aged; D014065:Tonometry, Ocular / Q000295:instrumentation*