Refractive surgery is any operation intended to alter the refractive state of the eye. Refractive corneal surgery refers to operations on the cornea that are intended to alter the refractive state of the eye. This type of surgery is popularly referred to as refractive keratoplasty, an appropriate term since keratoplasty means "to mold the cornea."
Lamellar refractive keratoplasty involves the placement of a lenticule on or within the cornea to alter its refractive power, usually by changing its anterior curvature.
Lamellar keratoplasty involves replacement of the patient's diseased anterior corneal stroma and Bowman's membrane with donor material. Host endothelium, Descemet's membrane, and a part of the deep stroma are preserved. The donor corneal disc becomes repopulated with host fibroblasts, and the recipient epithelium usually covers the anterior corneal surface. This procedure is technically more difficult than penetrating keratoplasty.
Lamellar keratoplasty has the advantage of being primarily an extraocular (outside the eye) procedure that preserves the host endothelium. The risk of rejection is therefore markedly diminished. The risks of wound leaks or flat anterior chambers associated with an intraocular procedure may be eliminated.
Microsurgical techniques have vastly improved the technique of lamellar keratoplasty, but they have also substantially improved the results with penetrating keratoplasty. The use of conjunctival flaps and therapeutic soft contact lenses has reduced the indications for lamellar keratoplasty.