Evaluation of tonometric correction factors

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Corneal Biomechanics

Background:

• Intraocular pressure (IOP) measurement is crucial for diagnosing and managing glaucoma.
• Corneal properties, particularly central corneal thickness (CCT), significantly influence IOP readings.
• Existing correction factors aim to adjust IOP for variations in CCT, but their accuracy is debated.

Purpose of the Study:

• To evaluate the effectiveness of current correction factors in adjusting IOP measurements for corneal structural variations.
• To assess the accuracy of established models (Ehlers, Orssengo, Pye) in correcting IOP based on CCT.

Main Methods:

• Measured CCT and corneal radius of curvature in 324 individuals (normal and glaucoma/ocular hypertension groups).
• Recorded Goldmann applanation tonometer IOP and historical IOP data.
• Utilized regression analysis to correlate IOP, CCT, and corneal radius; calculated corrected IOP using Ehlers and Orssengo/Pye models.

Main Results:

• A significant positive correlation was observed between Goldmann IOP and CCT in both groups.
• No significant correlation was found between corneal radius of curvature and IOP.
• A significant negative correlation existed between CCT and corrected IOP, suggesting overestimation by the models.

Conclusions:

• The impact of CCT on IOP is less than predicted by Ehlers and Orssengo/Pye models.
• Current correction models may lead to erroneous IOP overcorrection, resulting in inaccurate assessments for patients with varying CCT.