Central corneal thickness and intraocular pressure relationship in eyes with and without previous LASIK: comparison of Goldmann applanation tonometer with pneumatonometer.

PURPOSE

To investigate central corneal thickness (CCT) and intraocular pressure (IOP) relationship in eyes with and without previous corneal laser refractive surgery and to compare the estimates of two different tonometers-Goldmann applanation and pneumatonometer.

METHODS

The study population included 234 glaucoma suspects who were referred to the glaucoma clinic with cup/disc ratios greater than 0.4, asymmetric cupping, and/or IOP greater than 22 mmHg during routine eye examination. Of those, 84 had previous myopic laser-assisted in situ keratomileusis (LASIK) (Group 1) while 150 of them did not (Group 2). CCT was measured by using optical coherence tomography (OCT) and IOP with both Goldmann applanation tonometer (GAT) and pneumatonometer (PT). In both groups, the difference between IOP estimates of two different tonometers and the relationship between CCT and IOP were analyzed.

RESULTS

In eyes with previous LASIK, GAT measured IOP significantly lower than PT (mean difference of 3.8+/-1.9 mmHg, p<0.0001). In eyes with virgin corneas, IOP estimates of GAT or PT were not different from each other (19.9+/-2.8 versus 19.9+/-2.2 mmHg, respectively, p=0.81). In both groups, there was a significant positive correlation between CCT and IOP estimates of GAT(R=0.29, p=0.007 in eyes with LASIK and R=0.38, p<0.0001 in those without), while no similar relationship was present between CCT with those of PT (R=0.03, p=0.76 in eyes with LASIK and R=0.03, p=0.69 in those without).

CONCLUSIONS

In eyes with previous LASIK, GAT measured IOP significantly lower than PT. Because IOP estimates of PT were found to be independent from CCT in all of the study eyes, this device was considered to be a more reliable method of IOP estimation than GAT in eyes with and without previous LASIK.