Table 1.

Formulae to adjust intraocular pressure measured by tonometry for central corneal thickness.

Formula Name (adjusted for IOP)	Formula
Ehlers11	$\text{IOP}-\left[\frac{5.0\ast \left(\frac{\mathit{CCT}}{1000}-0.520\right)}{0.070}\right]$
Whitacre12	$\text{IOP}-\left[\frac{2.0\ast \left(\frac{\mathit{CCT}}{1000}-0.520\right)}{0.100}\right]$
Orssengo/Pye13	$\text{IOP}=\frac{\mathit{IOP}}{K}$, where
i.	$\text{K}=\left(\frac{B1-C1+C}{B}\right)$
ii.	$\text{B}1=0.6\ast \pi \ast 7.8\ast \left(7.8-\frac{0.580}{2}\right)\ast \left(\frac{\sqrt{(1-{0.49}^2)}}{{0.580}^2}\right)$
iii.	$\text{B}=0.6\ast \pi \ast 7.8\ast \left(7.8-\frac{\mathit{CCT}}{1000\ast 2}\right)\ast \left(\frac{\sqrt{1-{0.49}^2}}{{\left(\frac{\mathit{CCT}}{1000}\right)}^2}\right)$
iv.	$\text{C}1=\pi \ast 7.8\ast {\left(7.8-\frac{0.580}{2}\right)}^2\ast \left[\frac{(1-0.49)}{7.35\ast 0.580}\right]$
v.	$\text{C}=\pi \ast 7.8\ast {\left(7.8-\frac{\mathit{CCT}}{1000\ast 2}\right)}^2\ast \left[\frac{(1-0.49)}{7.35\ast \frac{\mathit{CCT}}{1000}}\right]$
Doughty14	$\text{IOP}-\left[\frac{2.5\ast \left(\frac{\mathit{CCT}}{1000}-0.535\right)}{0.05}\right]$
Kohlhaas15	$\text{IOP}+(23.28-0.0423\ast \text{CCT})$

IOP = intraocular pressure; CCT = central corneal thickness, π = 3.14159265