Ocular integrity after refractive surgery: Effects of photorefractive keratectomy, phototherapeutic keratectomy, and radial keratotomy

The effects on ocular integrity of three surgical techniques to correct refractive errors were compared. Ten matched pairs of eyes (right and left eyes) freshly enucleated from pigs underwent radial keratotomy (RK) (four incisions, 3.50-millimeter clear zone) in one eye and photorefractive keratectomy (PRK) with the 193-nanometer excimer laser (10.00-diopter myopic correction, 6.00-millimeter ablation diameter) in the fellow eye. Another 16 eyes underwent phototherapeutic keratectomy (PTK) at various depths; another 10 eyes were used as controls. All eyes were subjected to lateral compression by a bench press, with gradually increasing pressure applied until the globe ruptured. The rupture site was photographed. Of the 10 control eyes, 9 ruptured at the sclera and 1 ruptured at the optic nerve. All eyes that had undergone RK ruptured at the sites of the corneal incisions, whereas the eyes that had PRK ruptured at the sclera (P < .01). After PTK, corneal rupture upon compression occurred when ablations were about 40% depth or greater. Corneas that have been subjected to PRK thus appear less predisposed to rupture due to blunt trauma than do eyes that have undergone RK.