Not everyone is suitable for LASIK. Before planning a LASIK, patients have to undergo certain tests to evaluate if they are suitable for LASIK as it is performed only for patients with myopia of up to -10 dioptres, Hyperopia of up to 6 D and Astigmatism of up to 4 D. However, it is not just the refractive error that decides the suitability for LASIK. A thorough evaluation of the cornea on slit lamp to rule out any clinical signs of keratoconus, corneal scars or infiltrates is done. A corneal pachymetry of more than 490 microns is required for LASIK. A corneal topography is done to rule out any signs of sub clinical keratoconus. If any of the above criteria are not fulfilled, patients cannot undergo LASIK.