ABSTRACT
The most common indication for LASIK surgery in the present times is myopia, although it is also being increasingly utilized to treat hypermetropia and astigmatism.1-7 Other indications in which LASIK may be performed are anisometropia, induced refractive errors after other surgical procedures such as penetrating keratoplasty, radial keratotomy or cataract surgery.8 Recently, LASIK has also been undertaken to treat presbyopia although the option of mono vision is also possible in these patients and may be offered to them.9-12 Irrespective of the indications a patient who undergoes LASIK has certain basic requirements to be fulfilled (Table 2.1)
Myopia
Laser-in-situ keratomileusis (LASIK) has been used to treat myopia ranging from −1 to −29 dioptres.13 However the optimum correction is done for myopia up to −12.00 diopters since correction of myopia of more than −12 diopters (depending on the corneal thickness) entails excessive stromal ablation with a danger of producing corneal ectasia. It is important to remember that the amount of myopic correction possible in a particular patient is determined by the central corneal pachymetry and correction of myopic refractive errors in excess of −12 dioptres may not be possible if the central pachymetry is less than 500 µm. For myopia, we recommend that treatment be done up to −12 diopters, if corneal thickness allows the desired ablation with a residual bed thickness of 250 µm or preferably of 300 µm as cases ectasia has been noted in cases of residual bed thickness of >250 µm.14
