LASIK is not for everyone. The ideal candidate would have a good overall health status because various conditions can slow down the healing of the cornea after LASIK surgery. These include auto-immune conditions as well as those that require medication that slow down the healing process. Slowed healing whether by condition or age can increase the likelihood of complications to develop.
Pregnancy is a phase that is also not ideal for LASIK surgery. This is because eye shape can be temporarily altered by the hormonal changes involved during pregnancy.
Some corneas are simply too thin to undergo LASIK surgery. If too much tissue is cut in such instances, the remaining corneal tissue is not sufficient to provide integrity to the refractive process. LASIK in such cases may worsen rather than improve vision. The alternative possibility is LASEK, a procedure that does not involve a blade cutting a corneal flap.
Some corneas are too irregular in shape for LASIK to work successfully. This can arise from a condition known as keratoconus whereby the cornea steepens into a cone shape. Some irregularities of the cornea that occurs in mild to moderate levels of astigmatism are  usually acceptable and can be treated successfully with LASIK.
Naturally large pupils may actually exceed the size of the small and circular corneal area treated by the excimer laser in LASIK surgery. This results in various visual problems like halos that can occur particularly during the night when the pupils are at their largest.
Eyes that are already considered dry by medical standards prior to LASIK are predisposed to delay healing after the surgery. The quality of vision is hence affected regardless of the outcome of the procedure. The condition of dry eyes is also a significant side effect associated with LASIK surgery. Chronic dry eyes may result from LASIK surgery when performed on eyes that are already considered dry or are likely to become dry.
The various conditions that reduce suitability for LASIK can be diagnosed and assessed by a good LASIK surgeon using specific quantitative tests.
Advances in the LASIK process are constantly expanding the scope of the procedure. Hence, some of the disqualifications to the procedure today may not be applicable in the future. Other contraindications may be circumvented by procedures like LASEK and corneal transplantation.
LASIK surgery has developed as an effective means for sight enhancement for the qualified candidate. A lack of suitability to undergo the procedure however, does not imply an end to the quest for perfect vision.
