LASIK Surgery - Preoperative Tests
I have here below some of the preoperative tests that you will need to undergo prior to initiating the LASIK surgery procedure for myopia, hyperopia, or astigmatism. These tests are highly required in order to make certain that you obtain the most accurate and proper correction as well as follow up possible. These tests include, but are not limited to:
Complete Eye Examination
A complete eye examination, including pupil dilation, is required to decide the refractive power and health of your eye. It is especially used to determine the refractive error, which is verified with a cycloplegic or dilated technique. Along with this, several tests are made available to determine if you predisposed to Dry Eye Syndrome and related symptoms.
Usually, in this evaluation exam, you will be evaluated for your expectations of what refractive surgery will do for you. It is commonly suggested that if you wear contact lenses, you must stop wearing the lenses for a few weeks prior to the examination. The usual period range from:
- Three weeks for soft daily wear lenses
- Six weeks for gas permeable and extended wear soft contact lenses
- Eight weeks for hard plastic lenses on at least one eye and wear glasses or one contact lens during this period of time.
It is worth noting that the actual time needed for the removal of contact lenses may vary depending upon the recommendation of the doctor for your particular case. Also, the main purpose for the removal of the contact lenses during such period is to attain the most accurate measurements of your natural corneal curvature.
To further know this, you may be required to undergo some measurements which are taken every week for a number of weeks prior to the LASIK surgery. This is to make sure that your cornea is stable.
Experts say that if your cornea stabilizes sooner than expected after the removal of the contact lens, your LASIK surgery may be done sooner.
Computerized Topographical Analysis
This preoperative test is also known as Computerized Video Keratography and is a mapping of the surface of the eye by height as well as refractive power. In this kind of procedure, the more sophisticated machine is used to measure the thickness of the cornea, as well as the elevation of the front and back surfaces of the cornea.
This is usually performed to detect evidences of corneal thinning that are hidden, which might occur in the hidden form of kerataconus.
Tonometry
Before the refractive LASIK surgery, tonometry is taken for a certain purpose – to determine the intraocular pressure. Basically, this measurement is just a normal part of a complete eye examination.
Contrast Sensitivity Analysis
The contract sensitivity analysis may also be done prior to the LASIK surgery. This basically measures the capability of your eye to differentiate images under varying degrees of lighting.
It was found out that in some people, laser refractive surgery may cause a decrease in the ability to see at low light levels.
Pachymetry
There is only specific purpose for the consideration of this test – to determine the thickness of the cornea. According to some resources, the thickness of your cornea must be measured in order for the surgeon to identify your suitability for the LASIK surgery procedure.
As noted, the absolute minimum of residual thickness is 250 microns. So, if the depth of the ablation or the optical zone leaves less than 250 microns of residual corneal tissue, the danger of the cornea shape changing, or blowing out is greatly elevated.
Some of the refractive surgeons like to leave 270 to 275 microns of residual cornea in order to give a safety margin to allow for improvement.
If all these preoperative tests are taken, your surgeon and staff will proceed to analyzing the results to determine your chances of success with the LASIK Surgery procedure.