Time Course of Changes in Corneal Forward Shift After Excimer Laser Photorefractive Keratectomy

Open Access
Publisher Website
Google Scholar
Abstract
EXCIMER LASER refractive surgery modifies the refractive power of the cornea by means of photoablation of the corneal tissue. There is concern that the cornea is structurally compromised by the surgical tissue subtraction and by the loss of integrity of the Bowman membrane after excimer laser surgery.1 Several cases of iatrogenic keratectasia after excimer laser surgery have been documented.2-10 In a series of patients undergoing laser in situ keratomileusis, forward shift of the posterior corneal surface has been demonstrated, which correlated with the residual corneal bed thickness11 and the amount of laser ablation.12 Increases in posterior corneal curvature resulting from forward bulging of the cornea after photorefractive keratectomy (PRK)13,14 and laser in situ keratomileusis15 also have been reported. The long-term course of these changes, however, has not been studied. Considering the expected longevity of patients undergoing refractive surgery, it is critical to investigate whether progressive anterior protrusion of the cornea occurs after refractive surgery. In addition, forward shift of the cornea can cause myopic regression after excimer laser surgery.13-15 Thus, longitudinal assessment of the corneal geometric changes in relation to refractive regression after PRK is also important. We conducted a prospective study to evaluate the time course of changes in anteroposterior movement of the cornea after PRK.