Pachymetry Resources

Effect of Corneal Thickness on Measured IOP

Several studies, including most notably the Ocular Hypertension Treatment Study (OHTS), have determined a significant relationship between central corneal thickness (CCT) and intraocular pressure (IOP), and the need to adjust IOP applanation tonomtery readings by a factor to consider the effect of CCT in order to understand the "true" IOP. The Sonomed Pacscan series of pachymeters allows for the user to enter the measured IOP and then automatically apply the adjustment algorithm to display the "true" IOP.

For reference, the IOP correction values for various corneal thickness measures are shown in the table below:

uuuCorneal ThicknessuuuuuCorrection Value
uuuuuuuu[ um ] uuuuuuuuuuuuuu[ mmHg ]
u
uuuuuuuiiii445uuuuuuuuuuuuuuuuu+7
u
uuuuuuuiiii455uuuuuuuuuuuuuuuuu+6
u
uuuuuuuiiii465uuuuuuuuuuuuuuuuu+6
u
uuuuuuuiiii475uuuuuuuuuuuuuuuuu+5
u
uuuuuuuiiii485uuuuuuuuuuuuuuuuu+4
u
uuuuuuuiiii495uuuuuuuuuuuuuuuuu+4
u
uuuuuuuiiii505uuuuuuuuuuuuuuuuu+3
u
uuuuuuuiiii515uuuuuuuuuuuuuuuuu+2
u
uuuuuuuiiii525uuuuuuuuuuuuuuuuu+1
u
uuuuuuuiiii535uuuuuuuuuuuuuuuuu+1
u
uuuuuuuiiii545uuuuuuuuuuuuuuuuu 0
u
uuuuuuuiiii555uuuuuuuuuuuuuuuuu-1
u
uuuuuuuiiii565uuuuuuuuuuuuuuuuu-1
u
uuuuuuuiiii575uuuuuuuuuuuuuuuuu-2
u
uuuuuuuiiii585uuuuuuuuuuuuuuuuu-3
u
uuuuuuuiiii595uuuuuuuuuuuuuuuuu-4
u
uuuuuuuiiii605uuuuuuuuuuuuuuuuu-4
u
uuuuuuuiiii615uuuuuuuuuuuuuuuuu-5
u
uuuuuuuiiii625uuuuuuuuuuuuuuuuu-6
u
uuuuuuuiiii635uuuuuuuuuuuuuuuuu-6
u
uuuuuuuiiii645uuuuuuuuuuuuuuuuu-7