Before LASIK can be performed, you must have a thorough eye examination to ensure that you are an ideal candidate for the procedure. An ideal LASIK candidate meets the following criteria:
- Vision correction - Your existing vision must fall within an acceptable correction range and must not have changed significantly within the last two years. The differences in vision are measured in diopters, which are a measure of prescription. A normal eye falls within the diopter range of - 0.50 to +0.50. Here are the diopter ranges that LASIK can treat:
- Myopia (-0.75 to -14.00)
- Hyperopia (+0.75 to +5.00)
- Astigmatism (+/- 0.75 to +/- 5.00)
- Cornea thickness - Studies have shown that a cornea that is too thin after surgery can have difficulties later. With removal of each diopter of prescription an amount of cornea is removed. During your examination a measurement of the thickness of your corneas will be performed. Using this information Dr. Davis will determine if your corneas are thick enough for a refractive procedure.
In addition to the list above, certain conditions are considered risky and can prevent a person from being an ideal candidate:
- Pregnancy – If you are pregnant or nursing
- Severe heart problems - Particularly if you must wear a pacemaker
- Certain systemic and eye diseases -Severe Auto-immune diseases (rheumatoid arthritis, lupus), vascular disease, eye diseases (severe glaucoma, cataracts, ocular herpes), severe diabetes
- Certain drugs - Acutane (acne), Imitrex (migraines), immune-system medications
- Keratoconus and Pellucid Marginal Degeneration - Conditions characterized by a thinning of the cornea
Your eyes are thoroughly checked during a scheduled pre-op (short for preoperative) visit. This visit is necessary to fully access your candidacy and to ensure that we get as accurate a prescription as possible. During your preoperative visit, you may have scans performed using some of the very sophisticated diagnostic equipment listed below.
A number of machines are used to determine the shape and condition of your eyes. These include:
Auto-refractor - This machine measures the prescription in the eyes using a cone of infrared light. The infrared light is not visible to you. It is directed into your eye by the auto-refractor while you attempt to focus on an image within the machine's viewfinder. The auto-refractor changes the magnification of the image until it comes into focus for you.
The auto-refractor has sensors that detect the reflections from the cone of infrared light. These reflections are used to determine the size and shape of a ring at the back of the eye called the ocular fundus. This is the part of the eye directly across from the pupil's opening. By measuring the ocular fundus, the auto-refractor can determine when your eye properly focuses on the image you are staring at. The auto-refractor monitors the magnification setting and calculates the approximate level of vision correction needed. This information can then be fed into the phoreopter for refinement of the prescription.
Corneal Topographer and Wavefront Analyzer
Corneal topographer - The corneal topographer maps the cornea, determining its exact shape. You look into a purple, spiraled cone (sort of looks like a hypnotist's prop). Within the cone are sensors that detect infrared light. It collects the light from several hundred points across the eye. The topographer's mapping software then "connects the dots" to create an outline of the cornea's shape. This procedure is very accurate and can find anomalies in the cornea undetectable by other means.
Wavefront analyzer - This machine use technology borrowed from astronomers who use it to improve images coming from outer space. It is able to measure all of the optical irregularities in your eye. This includes not only nearsightedness, farsightedness, and astigmatism but also the smaller irregularities that are peculiar to each eye that can blur your vision. This information can then be passed on to the excimer laser in order to perform custom or Wavefront LASIK.
OPD Scan- This machine is one of the most advanced Wavefront analysis systems available. This machine measures up to 1440 points across the pupil and has the capability of evaluating even severely irregular corneas. Once all of the measurements are done, Dr. Davis can determine if you are a candidate. If you are considered a candidate, then the next step is the procedure.
Prior to the day of your procedure you should obtain and sign an informed consent. This is a document that states that you are aware of the risks involved with laser eye procedures and agree that you willingly assume those risks. On the day of your procedure, Valium is offered to lessen your anxiety and nervousness.
Please arrange for someone to drive you home after your procedure.
When its time for your procedure, an assistant will take you to a preparation room and put an anesthetic drop in your eyes. These drops have a numbing effect that lessens the chance of any discomfort. Then you are taken to the procedure room. We lay you down on a cushioned platform that is rotated until your head is under the laser. The laser technician will instruct you to move your head until you're in the correct alignment. During the procedure, you cannot close the operated eye. To keep this from happening, the LASIK technician that works with Dr. Davis will use a couple of items.
- Special tape that holds the your eyelashes out of the way
- An eyelid holder will be used to keep your eyes open
Once the eye is prevented from closing, a shield is placed over the eye not being operated on. Dr. Davis will make tiny marks on the cornea to indicate proper alignment of the corneal flap when the flap is replaced. The corneal flap is created either using a device called a microkeratome or using a laser. Dr. Davis uses a small suction ring to hold your eye steady and quickly creates a flap. As soon as Dr. Davis has folded the corneal flap out of the way, you are told to focus on a colored light above you. Then the excimer laser is activated and the procedure is carried out while you're watching a colored light. The laser will pulse for a few seconds. Once the laser is done, Dr. Davis will replace the corneal flap and administer a small amount of antibiotic drops. The amazing thing about the cornea is that it begins to heal immediately, so there is typically no need for stitches or any other agent to hold the flap in place. As soon as one eye is done, the shield is placed over that eye. Then the procedure will be repeated on the opposite eye. The entire procedure happens very quickly, generally taking less than 15 minutes from the moment that you enter the operating room until both eyes have been treated. Normally there is no pain involved but there can be a certain amount of pressure and discomfort.
Shields with tiny holes in them will be taped over each eye. This allows you to see just enough to get around, but prevents you from touching your eyes at all. You will be instructed to wear these for the remainder of that day and to sleep in them that night. You can take them off before your examination the next morning. The night of your procedure you will have blurry vision while your eyes heal. You will also need to put drops in your eyes:
- Preservative Free Rewetting drops are similar to the ones used by people who wear contacts to keep the eyes from drying out. These are normally used every half an hour while awake for the first day. Then as directed by Dr. Davis. Anti-inflammatory steroid (Pred Forte or Econopred) drops are used differently depending on what procedure you have done. If you have the Intralase laser, you will use the drops four times a day for one week and every hour while awake the first day. With the microkeratome, you will use the drops four times a day for a week. These drops reduce inflammation. Antibiotic drops are typically used four times a day for seven days.
The Day After
The day after your procedure your vision may still be somewhat blurry, your eyes may be red and sensitive to light. This can be expected for a couple of weeks as your eyes continue to heal.
The follow-up appointments typically are scheduled on a progressively lengthening basis:
- One day after surgery
- One to two weeks after surgery
- Three months after surgery