Abstract
Purpose: :
The purpose of our study was to evaluate and understand the relationship between central corneal thickness (CCT) and Goldmann applanation tonometry GAT) and dynamic contour tonometry (DCT)measurements in patients with open angle glaucoma.
Methods: :
This was a cross–sectional retrospective study. The charts of 43 open angle glaucoma patients submitted to complete ophthalmologic exam, Goldmann applanation tonometry (GAT), dynamic contour tonometry (DCT) and central corneal thickness measurements (CCT) were reviewed. One eye of each subject eligible for the study was enrolled. Differences in IOP measurements between the two instruments were evaluated for all subjects and for groups of patients based on different ranges of central corneal thickness.
Results: :
There was a significant difference in mean IOP measurements performed with GAT and DCT (16.2 ± 4.0 mmHg and 18.1 ± 3.7 mmHg, respectively, p = 0.02) in all subjects. DCT measurements were higher than GAT measurements in eyes with thinner corneas and also in eyes with thicker corneas. Median difference between GAT and DCT in eyes with CCT <536 µm was 2.7 mm Hg ( interquartile range [25th–75th percentile] = 1.0 – 2.5 mm Hg ) and 1.0 mm Hg ( interquartile range [25th–75th percentile] = 0.3 – 1.9 mm Hg ) in eyes with CCT >576 µm. This difference between groups was significant (p=0.03) GAT measurements were closer to DCT measurements in eyes with thicker corneas compared to eyes with thinner corneas.
Conclusions: :
Glaucomatous eyes with thinner corneas could lead to unreliable IOP measurements in a larger proportion than eyes with thicker corneas. In eyes with elevated corneal thickness, IOP may not be necessarily overestimated.
Keywords: intraocular pressure • cornea: clinical science • clinical (human) or epidemiologic studies: systems/equipment/techniques