IOP & CCT Corrector — Complete User Guide
GAT IOP and CCT correction value reference estimation using square root ratio model, with AAO evidence-based notes and kPa/mmHg conversion.
IOP correctionCCT correctioncorneal thicknessGATCCT square root correctionkPa conversionglaucoma screening
Why CCT Correction is Needed?
Intraocular pressure (IOP) measured by Goldmann Applanation Tonometry (GAT) is affected by corneal thickness:
- Thicker cornea (>545μm) → GAT reading overestimates true IOP
- Thinner cornea (<545μm) → GAT reading underestimates true IOP
Correction Formula Explanation
Square Root Ratio Model (Used in This Tool)
Corrected IOP = Measured IOP × √(545 / Measured CCT)
Correction magnitude has a non-linear ratio relationship with corneal thickness deviation. This tool does not use any linear correction coefficients (such as Ehlers linear formula, Dresden formula) — linear coefficients vary greatly across literature sources and lack consensus values. The model direction is consistent with Orssengo-Pye corneal biomechanical analysis. Note: AAO guidelines explicitly recommend against using any CCT-based corrected IOP for clinical decision-making.
kPa to mmHg Conversion
- 1 mmHg = 0.133322 kPa
- 1 kPa = 7.50062 mmHg
References
- Ehlers N, et al. Corneal thickness and corneal applanation tonometry. Acta Ophthalmol. 1975.
- Orssengo GJ, Pye DC. Determination of the true intraocular pressure. Bull Math Biol. 1999.