Intraocular pressure: Goldmann tonometry, computational model, and calibration equation.

Area of Science:

• Ophthalmology
• Biomechanical Engineering
• Medical Imaging

Background:

• Intraocular pressure (IOP) measurement accuracy is critical for glaucoma diagnosis.
• Goldmann applanation tonometry (GAT) assumes a thin corneal shell, potentially leading to inaccuracies.
• Corneal properties like thickness and curvature significantly influence IOP readings.

Purpose of the Study:

• To investigate the relationship between true IOP and tonometric IOP, considering corneal biomechanical properties.
• To develop a calibration equation for GAT to improve the accuracy of IOP measurements.
• To determine the range of corneal parameters for which GAT measurements are reliable.

Main Methods:

• Computational simulations using the finite element method (FEM) to model corneal mechanical behavior during applanation.
• Experimental validation using rabbit models to confirm GAT inaccuracies under specific conditions.
• Statistical multiple linear regression analysis to derive a calibration equation for GAT.

Main Results:

• A calibration equation was established relating true IOP to GAT measurements, external curvature radius (ECR), and central corneal thickness (CCT).
• GAT measurements show a linear dependency on the cornea's modulus of elasticity.
• The developed equation allows for correction of GAT measurements based on CCT and ECR for healthy corneas.

Conclusions:

• The study provides a method to enhance the accuracy of GAT IOP measurements.
• Corneal properties (CCT, ECR) are crucial factors in correcting tonometric IOP readings.
• Accurate IOP measurement is essential for effective glaucoma management and treatment.