[Effects of central corneal thickness and corneal curvature on measurement of intraocular pressure with Goldmann applanation tonometer and non-contact tonometer].
OBJECTIVE
To investigate the effects of central corneal thickness (CCT) and corneal curvature (CC) on intraocular pressure (IOP) measurements by the Goldmann applanation tonometer (GAT) and the non-contact tonometer (NCT).


METHODS
One hundred and twenty patients were recruited from the clinic of Peking Union Medical College Hospital. The CCT was measured by ultrasound pachymetry and the mean radius of CC by using Canon PK-5 refractometer. The IOP of each eye was measured by both GAT and NCT. Linear regression was used to compare the measurements of GAT and NCT; multi regression was used to analyze the relationships between CCT, CC and the measurements of GAT and NCT. Bland-Altman method was used to compare the effect of NCT and GAT on the IOP measurements.


RESULTS
The results of the right eyes were reported in this paper. The mean and standard deviation of IOP measured by GAT and NCT was (18.4 + or - 4.0) mm Hg (1 mm Hg = 0.133 kPa) and (17.0 + or - 4.6) mm Hg, respectively, the difference was statistically significant (r = 0.835, P = 0.000). IOP measured using GAT increased by 0.039 mm Hg per microm increase in CCT. IOP measured using NCT increased by 0.064 mm Hg per microm increase in CCT. For an increase of 1 mm of mean corneal curvature there was decrease in IOP of 2.648 mm Hg measured by the GAT and of 3.190 mm Hg measured by the NCT. Compared to the GAT, NCT underestimated at low IOP level and overestimated at higher IOP level.


CONCLUSIONS
The IOP measurement obtained with both GAT and NCT varied with CCT and CC. CCT affected IOP measurements by NCT more than that by GAT.
Zhang
Yang
Y
Department of Ophthalmology, Peking Union Medical College Hospital, Peking Union Medical College, Eye Research Center of Chinese Academy of Medical Sciences, Beijing 100730, China. zhaojialiang@medmail.com.cn
Zhao
Jia-liang
JL
Bian
Ai-ling
AL
Liu
Xiao-li
XL
Jin
Yu-mei
YM
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003315:Cornea / Q000033:anatomy & histology*; D005260:Female; D005901:Glaucoma / Q000175:diagnosis; D006801:Humans; D007429:Intraocular Pressure; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D014065:Tonometry, Ocular / Q000295:instrumentation* / Q000379:methods*