IOP and biomechanical properties of the cornea before, 1 month and several years after LASIK

Poster Details

First Author: A.Grise-Dulac FRANCE

Co Author(s):    A. Saad   J. Febbraro   D. Gatinel        

Abstract Details

Purpose:

Refractive surgery by LASIK (Laser in Situ Keratomileusis) is a surgery booming, whether for the treatment of myopia, hyperopia and presbyopia. By modifying the thickness, the curvature and biomechanical characteristics of the cornea, Lasik makes IOP measurement by Goldmann applanation tonometer unreliable. The Ocular Response Analyzer® (Reichert, UK) can provide a measurement of IOP getting rid of these limitations. The objective of this study was to determine the values of IOP and the biomechanical characteristics of the cornea before, one month and several years after Lasik.

Setting:

Fondation Rothschild, Paris

Methods:

IOP and corneal biomechanical characteristics were measured by the ORA in 86 eyes of 43 patients before LASIK (group 1), one month after Lasik (group 2) and compared with those of 28 eyes of 14 patients who underwent Lasik on average 4 years ago (group 3). The parameters studied were: Goldmann IOP (IOPg), IOP compensated for the cornea (IOPcc), hysteresis coefficient (CH) and the corneal resistance factor (CRF). Central corneal thickness (CCT) was measured for all eyes included.

Results:

Age at the time of LASIK was not significantly different between groups (34.4 +/-9.18 and 33.66 +/- 9.38, p>0.05). Central corneal thickness before Lasik (564.06?m +/- 26.54) was significantly higher than in the two post-LASIK groups (p <0.001). Corneal thickness was not significantly different between the two post-LASIK groups (492.02 +/- 54.93 and 491.78 +/- 72.42). In group 3, Lasik was performed 4.64 +/- 2.08 years before inclusion. IOPg was significantly higher in group 1 (15.99 mmHg +/- 3.04) compared to group 2 (11.93 mmHg +/- 2.74) and group 3 (14.49 mmHg +/- 5.22). IOPcc was not significantly different between group 1 and 3 (15.35 mmHg +/- 3.33 mmHg and 16.31 +/- 4.07, p=0.85), whereas it was lower in group 2 compared to the 2 other groups (p<0.05). CH and CRF were significantly lower in the 2 post-LASIK groups compared to pre-LASIK group (p<0.0001). No significant variation of these two parameters was observed between groups 2 and 3 (p>0.05).

Conclusions:

IOP measurement and knowledge of the biomechanical behavior of the cornea several years after LASIK are essential for patients follow-up, especially to detect as early as possible the appearance of hypertony or glaucoma. More than 4 years after refractive surgery like LASIK, IOPcc was not different from the pre-operative IOPcc. This setting can help to monitor IOP after LASIK. The results of our study confirm the literature data on lowering of CH and CRF after LASIK and show that this effect is stable in time, even many years after surgery. FINANCIAL DISCLOSURE?: No