Non surgical options for the correction of refractive errors include spectacles and contact lenses. Spectacles contain lenses that suitably refract the incoming rays of light and enable them to focus on the retina.
Contact lenses perform the same function but are placed on the cornea-the clear front portion of the eye. Hence, they provide better cosmesis and improved quality of vision in the higher refractory errors.
Surgical procedures attempt to eliminate the external aids like glasses and contact lenses. In Radial Keratotomy, where four to eight corneal incisions are made involving 95-99% of the corneal thickness, to flatten the central corneal. The weakened peripheral cornea is pushed outwards by the pressure within the eye. This results in a flattening of the central cornea which corrects a myopic refractive error.
Similar incisions when made in a hexagonal fashion in the mid-peripheral cornea result in a forward protrusion of the central cornea. This procedure is termed Hexagonal Keratotomy and is used to treat hyperopia. To correct astigmatism, straight or curved incisions are made in the mid peripheral cornea and the procedure is termed Astigmatic Keratotomy.
All incisional procedures weaken the structural integrity of the cornea. This theoretically results in an increased tendency of the cornea to rupture following trauma.
The use of the Excimer Laser in corneal refractive surgery has greatly increased the safety of the procedure as the refractive correction is achieved by the removal of as little as 10%-20% of the total corneal thickness. Excimer Photorefractive Keratectomy (PRK) is now a procedure used all over the world and has helped thousands of patients say goodbye to glasses.
A recent advance in the treatment of high refractive errors is a procedure termed Laser In-situ Keratomileusis (LASIK) which is often an adjunct to PRK.
These procedures are done as out-patient procedures and patients using topical anaesthetic drops and the patients can go home right after the procedure.
Thus, surgical procedures like PRK and LASIK are leading us towards a world without glasses.