To analyze the postoperative intraocular pressure (IOP) underestimation measured with non-contact tonometry after corneal refractive surgery.

The postoperative IOP decrease measured with non-contact tonometry (NCT), regarded as IOP underestimation, was calculated in 253 LASIK patients and 281 LASEK patients. Multiple regression analysis was performed to determine the preoperative factors which affect postoperative IOP underestimation. The right eye results were reported in this paper.

The postoperative IOP decrease was affected by age (r = -0.0420, p = 0.03), corneal ablation depth (r = 0.0466, p < 0.01), and operation method (LASIK or LASEK) (r = 0.6006, p < 0.01). For every 100 µm decrease of corneal thickness by LASIK, the IOP decreased 6.29 ± 2.40 mm Hg in patients under 26 years of age and 6.12 ± 2.53 mm Hg in patients above 26 years of age ( p = 0.05). For every 100 µm decrease of corneal thickness by LASEK, the IOP decreased 5.77 ± 2.37 mm Hg in patients under 26 years of age and 5.44 ± 2.62 mm Hg in patients above 26 years of age ( p = 0.05).

The postoperative IOP underestimation measured with NCT was more prominent in younger-aged patients after LASIK than LASEK with deeper ablation depth.