Intraocular pressure and ocular rigidity after LASIK

Purpose: To assess the intraocular pressure (IOP) and ocular rigidity (E) at 1, 3, 6 and 24 postoperative months in eyes that underwent LASIK. Methods: The IOP measured by Goldmann applanation tonometer (GAT) and by the 5.5 and 10 gm. weights of a standardized Schioetz tonometer (ST) and the E measured by differential tonometry (the 5.5 and 10 gm. of ST) were assessed before and after LASIK (at 1, 3, 6 and 24 month) in 23 eyes. The volume of the corneal indentation (Vc) and IOP with ST resting on the eye (tonometric pressure - Pt) were also evaluated. Results: The average IOP (GAT) at 6 and 24 months after LASIK was lower than at 1 and 3 months and before LASIK. A statistically significant difference of E was found at 1, 3, 6 and 24 months. The reduction of the central corneal thickness (CCT) by LASIK was the cause of increasing values of Vc and decreased values of Pt. In turn, the changes in Vc and Pt were responsible for the lower IOP measurements by GAT and E changes. Conclusions: LASIK reduces IOP readings by GAT but not the ones by ST (differential tonometry). LASIK also diminishes E. IOP (GAT) values are lower at 6 and 24 months. IOP evaluation by ST is more accurate than that by GAT. At 6 months, Vc, Pt and E parameters are stabilized (no changes relatively to 24 months measurements.