The next part of the preoperative evaluation involves a series of eye tests and examinations that provide the necessary data before a LASIK procedure. These may be conducted at your surgeon’s office or by your regular eye doctor.
In either case, the physician will measure your refractive error and determine which of your eyes is dominant. Next, he or she will measure your cornea with a corneal topographer, an instrument that uses computerized analysis to arrive at an extremely accurate three- dimensional map of your cornea. This test will reveal whether you have a structurally abnormal cornea, which could disqualify you as a candidate for LASIK.
The thickness of your cornea will be measured with a pachymeter. Because a certain amount of tissue will be surgically removed, or ablated, during the LASIK procedure, your cornea must be thick enough for remaining tissue to retain its structure and shape. If your cornea is too thin, you would not be a good LASIK candidate.
The surgeon will examine your eyes with a special microscope called a slit lamp. This allows examination of the cornea in microscopic detail. The doctor will be checking for abnormalities that could be symptomatic of eye disease.
The intraocular pressure of your eyes will be measured with a tonometer. This tests the pressure exerted by the fluid (aqueous humor) within the eyeball that gives it a round, firm shape. Increased pressure could be an indication of glaucoma.
Next, drops may be put in your eyes. These drops temporarily relax focusing muscles, dilating the pupil. The doctor may measure your refractive error again and will examine the back of the eye, including the retina and the optic nerve. In nearsighted patients, these dilating eye drops will not affect distance vision, which is needed for driving, but will blur near vision for about four to six hours. Both near and distance vision may be affected in farsighted patients.