Reduction in intraocular pressure after excimer laser photorefractive keratectomy. Correlation with pretreatment myopia.

PURPOSE

The authors relate the observed reduction in intraocular pressure (IOP) after excimer laser treatment to the degree of myopia treated.

BACKGROUND

Intraocular pressure, measured by both Goldmann applanation and noncontact tonometry, has been reported to decrease after excimer laser photorefractive keratectomy (PRK). However, IOP readings after excimer laser PRK might be inaccurate as a consequence of changes in both the thickness and curvature of the cornea.

METHODS

Baseline IOP readings were measured by noncontact tonometry in each eye of a group of 1320 patients at the time of their initial consultation. These were compared to readings obtained before treatment of the second eye, which took place a minimum of 4 months later. The untreated eyes served as controls. The paired Student's t test was used for statistical analysis.

RESULTS

After PRK, a decrease was observed in the IOP of treated eyes that was related to the degree of myopia treated. A significant difference was observed between treated and untreated eyes (P < 0.0000).

CONCLUSIONS

The IOP measured after PRK for myopia may be reduced because of changes in corneal thickness (absence of Bowman's membrane and central thinning) and topography. This is of particular relevance when monitoring the IOP of those patients who are given steroid drops to prevent regression. It also may be of importance in the management of any future glaucoma.