Purpose
To study the relationship between central corneal thickness (CCT) and intraocular pressure (IOP) in a healthy population.
Methods
This study is a retrospective chart review of 91,024 patients (174,666 eyes) who underwent pre-operative pachymetry and IOP measurement before refractive surgery. Patients with glaucoma were excluded. Central corneal thickness was measured using a standard pachymetry instrument. IOP was measured using non-contact tonometry. A multivariable regression analysis was performed to determine the relationship between CCT and IOP, and association with other covariates.
Results
The study population ranged from ages 18 to 72 (mean age = 38.6 ± 11.9 years). Myopic patients represented 83% of the study population. The refractive errors ranged from -12.125 diopters (D) to +6.125 D. Among myopic patients the average refractive error was -3.21 ± 1.9 D, while among hyperopic patients the average refractive error was +1.91 ± 0.80 D. The average CCT measurement was 546 ± 33 µm, ranging from 410 to 700 µm. The average IOP was 15.2 ± 2.9 mmHg, ranging from 9 to 27 mmHg. A statistically significant linear relationship was found between IOP and CCT (p < 0.0001). Controlling for age, average keratometry, and mean spherical equivalent, it was found that for every 10 µm change in CCT, measured IOP changed by 0.3 mmHg.
Conclusions
This is the largest study of healthy eyes to identify a linear relationship between CCT and IOP. This data suggests that a correction of IOP measurement can be made based on CCT.
Keywords: 568 intraocular pressure