Response of the posterior corneal surface to myopic laser in situ keratomileusis with different ablation depths.

PURPOSE: To evaluate the posterior corneal surface response at a very early stage after myopic laser in situ keratomileusis (LASIK) with different ablation depths.

SETTING

Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA.

DESIGN

Cohort study.

METHODS

Healthy myopic eyes were divided based on the achieved ablation depth as follows: Group 1, more than 100 μm; Group 2, between 50 μm and 99 μm; Group 3, less than 50 μm. Posterior eccentricity and central (0.0 to 4.0 mm), paracentral (4.0 to 7.0 mm), and peripheral (7.0 to 10.0 mm) posterior corneal curvatures were measured with the Galilei system preoperatively and postoperatively after 1 day, 1 week, and 1 and 3 months.

RESULTS

Eighty eyes were evaluated. Posterior surface steepening and a shift toward prolateness occurred in all groups, with a peak within the first week before returning toward the original level after 1 month. The maximum change in the central posterior cornea occurred after 1 day in Group 1 and reached -0.106 diopter (D). This change was statistically significant (P=.03) and statistically greater than the change in Group 2 (mean -0.042 D; P = 0.02) and Group 3 (mean -0.026 D; P<.01). This change was not significant after 3 months (P = .5).

CONCLUSIONS

Posterior steepening and a shift toward prolateness of the posterior surface were observed very early after myopic LASIK, with a tendency to return toward the preoperative level between 1 month and 3 months. The degree of change was related to the amount of anterior tissue severed.

FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.