ABSTRACT
Purpose: To determine the applicability of central corneal thickness [CCT] based correction factor for non-contact tonometer [NCT] measured intraocular pressure [IOP] readings
Method: A prospective, non-randomized study involved 346 eyes of 173 consecutive patients with age >/=21 years undergoing laser-assisted in situ keratomileusis [LASIK] for myopia and/or myopic astigmatism. The CCT and IOP were measured before and after the LASIK procedure. The IOP pre and post-LASIK was compared after applying the correction factor for CCT. Patients not completing the 3 month postoperative follow-up were excluded
Results: The median spherical equivalent before undergoing LASIK was -4.25D [inter-quartile range, -3.25D]. The mean preoperative CCT was 536.82 +/- 33.71 micro m which reduced to 477.55 +/- 39.3 micro m [p < 0.01] post-LASIK. The mean IOP reduced from a preoperative value of 14.6 +/- 2.32 mmHg to 10.64 +/- 2.45 mmHg postoperatively [p < 0.01]. On applying correction for the corneal thickness, the pre and postoperative IOP was 15.14 +/- 2.8 mmHg and 15.37 +/- 2.65 mmHg [p = 0.06] respectively with a strong positive correlation [r = 0.7, p < 0.01]. Three hundred eyes [86.7%] had an absolute difference in IOP of less than 3.0 mmHg post-CCT correction which is within the retest variability of NCT. Only 46 eyes [13.3%] had an absolute difference of more than 3.0 mmHg
Conclusion: The modified Ehler's correction algorithm used in this study can be effectively applied in the normal IOP range in a majority of patients