The influence of corneal properties on rebound tonometry.
OBJECTIVE
To determine the influence of corneal thickness, corneal hysteresis (CH), and corneal resistance factor (CRF) on intraocular pressure (IOP) measurements obtained using the iCARE rebound tonometer.


METHODS
Cross-sectional study.


METHODS
One hundred twenty-five eyes of 125 normal healthy subjects.


METHODS
Intraocular pressure was determined in all subjects using the iCARE at both central and temporal corneal regions. Corneal thickness at these 2 regions was determined by ultrasonic pachymetry. Corneal hysteresis and corneal resistance factor were measured using an ocular response analyzer. Goldmann applanation tonometry (GAT) was also performed on all eyes.


METHODS
Intraocular pressure, corneal thickness, corneal hysteresis, and corneal resistance factor.


RESULTS
Although the peripheral cornea was significantly thicker than the central cornea, IOPs obtained by the iCARE at the 2 regions were similar and significantly higher than GAT measurements. There were an overestimation at higher IOPs and an underestimation at lower IOPs relative to GAT measurements. Multiple regression analysis showed a significant correlation between the iCARE and CH (partial correlation r = -0.67, P<0.01) and CRF (partial correlation r = 0.82, P<0.01). The correlation between the iCARE and central corneal thickness was not significant.


CONCLUSIONS
Rebound tonometry is affected by corneal properties including CH and CRF but not corneal thickness.
Chui
Wan-sang
WS
School of Optometry, Hong Kong Polytechnic University, Hong Kong, China.
Lam
Andrew
A
Chen
Davie
D
Chiu
Roger
R
D000328:Adult; D001696:Biomechanical Phenomena; D003315:Cornea / Q000000981:diagnostic imaging / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D014065:Tonometry, Ocular / Q000379:methods*; D014463:Ultrasonography