PhotoRefractive Keratectomy (PRK) and Laser in Situ Keratomileusis (LASIK) are forms of corrective eye surgery. They are used to correct hyperopia (farsightedness), myopia (nearsightedness), and astigmatism (an irregular shaped cornea). They cannot correct presbyopia, however, which a loss of flexibility that is a normal result of ageing.

The shape of the cornea affects how light is bent as it passes through, and how well it can be focused on the back of the eye, where it is transmitted to the brain. Other ways to compensate for this are to wear contact lenses or eyeglasses.

20/20, 20/40, 20/???

20/20 vision is not perfect vision, as many think. It is normal vision. What it means is that the level of detail and sharpness you see at 20 feet is the same as what the average person sees at 20 feet. 20/40 is usually the legal driving minimum. What it means is that the level of detail and sharpness that you see at 20 feet is what others can see at 40 feet. Your eye surgeon will usually shoot for 20/20, though there are no guarantees. However, many people end up with better than 20/20.

Your eye surgeon can sometimes under-correct one eye on purpose, which can help reduce or eliminate the need for reading glasses that most people need from their forties.

PRK or LASIK?

Why PRK?

With LASIK, there can be a complication in the creation of the flap that is cut, or the replacement of the flap after surgery; this occurs about 1 - 2% of the time. Also, some eye shapes are not eligible for LASIK. Some groups (some police agencies for example) do not allow LASIK corrected eyes. This is probably due to it being a newer procedure than PRK, and these policies may be changed soon.

Why LASIK?

In PRK, the top layer of cells is removed before the procedure. This layer takes about 4 days to regrow. In the meantime, a contact is applied as a bandage. It can be uncomfortable, and it delays the focus of vision. Each eye is usually done weeks apart, to account for the recovery time. Full healing requires 3-4 months. With LASIK, vision can be clear and focused in a day, and both eyes are generally done at the same time.

The Procedure for PRK

You will be awake for the entire procedure.

1. You may be given anti-anxiety medication.

2. You will have anesthetic drops in both eyes so you will not feel anything.

3. A speculum is placed in the eye, to hold the eyelids open; you can tell that they are there, but you do not feel them. You will actually feel like you are blinking normally.

4. The surgeon will prepare the surface of the eye by removing the top layer of cells.

5. Sometimes your eyes will be held in place by a suction ring; other times you just stare at a red dot while the laser tracks your eye.

6. You will hear a rapid clicking sound while the laser is in action, and you may notice a smell like burning hair.

7. The surface of the eye is then cleared, and a bandage - a soft contact lens - is applied.

The LASIK Procedure

The LASIK procedure is very similar to the PRK procedure. The difference is that instead of removing the top layer of cells, a machine will hold the eye in place by suction and use a blade to cut a circle almost all the way around the eye - this is called the flap. The laser then makes the corrections, after which the flap is folded back over the eye.

No contact is needed, because the flap will be held in place by the eye's natural suction. The cut around the eye heals in a few hours. Both eyes are done on the same day.

Post-Op

This is an outpatient procedure. You should have someone ready to drive you home after the procedure.

Medication in PRK

You will be given four types of drops to use in your eyes; antibiotics, anti-inflammatory, steroid, and moisturising eye drops. The antibiotic drops are for a week, while the top layer of cells grow back. The anti-inflammatory continues for one week. The steroid drops for 3 months, and the moisturising as needed. You may also get a prescription for Tylenol 3 to ease discomfort. If not, you should keep some regular Tylenol on hand.

Follow-ups for PRK

Several appointments will need to be made after the procedure:

• The next day - This is to check to make sure there are no infections, and to ensure that recovery is proceeding properly.

• Four days later - After four days, the top layer of cells should be regrown, and the contact is removed. Eyes are much more comfortable, and vision is clearer without the contacts.

• One week later (approx.) - Cornea smoothes out after removal of contact, and an accurate idea of your vision can be obtained.

• One month later - Vision is checked again, as almost all recovery has happened.

• Yearly thereafter - Standard yearly checkups to check up on eyes.

Complications

• Under- or Over-correction. Sometimes different people will heal differently, causing either of these problems. This can usually be fixed with another procedure.

• Problems with flap or errors in regrowth of top layer of cells. These can usually be fixed by either re-positioning the flap or removing the cells again and letting it regrow again.

• Infection while the top layer of cells is regrowing. An infection can occur, but eye drops usually prevent this.

These are the most likely problems but others can occur (ask your surgeon/doctor about these) such as halos. After the surgery, lights can have halos or starbursts at night, causing problems with night vision, especially driving at night. This typically goes away over six to nine months, but can be permanent.

In some cases, people have had permanently reduced vision after eye surgery. There is also a small risk of losing sight on one or both eyes.

Laser Eye Surgery - a Personal Perspective

Below you'll find a Researcher's own account of his experience with laser eye surgery:

I went in for a consultation, where I was told that my eyes were too flat for a suction machine to work properly, therefore I could not be a candidate for LASIK, and I decided to have PRK. About a month later (I had to wait until I was 21) I went in to have the procedure done. I opted to have both eyes done on the same day, since I could devote more time to recovery than most.

I was given the anti-anxiety pill and waited for it to take effect. In this time, an assistant explained all the follow-up medications, as well as reviewing what to expect during the surgery. I was brought into a the operating room (wear warm clothes, since the room is kept cold) and was told to lay down on the operating table. The drops were given to numb my eyes. When those took effect, the table was positioned under the laser, and I had to stare at a red dot of light.

The speculum was added - this was pain free - and blinking felt normal, though the speculum kept the eyes open. The surgeon removed the top layer of cells, and this felt like a wet paintbrush moving over the surface; once again there was no pain. The doctor has you stare straight ahead, and you hear a clicking sound as the laser fires. I could smell the burning cells, just like burnt hair. Not much, so it does not disgust you. Afterwards (it only takes 30 seconds under the laser) the contact was put in place, and the procedure was repeated on the other eye.

I was then brought into a dim room to recover. I was given my prescription for Tylenol 3, the eye drops, and a pair of dark wrap-around sunglasses. My eyes were sensitive to the light, as expected, so I wore the sunglasses all the time. They even have you wear then when you sleep, so you don't accidentally rub your eye. This procedure is easy, but it is also tiring. I slept for seven hours, had some food, then slept through the night. Eyes heal better when closed, so plan to spend a few days listening to music (or George Carlin CDs like I did).

The next day I was driven to the follow-up appointment. Most patients have only one eye done at a time, so they can drive themselves, but have a driver standing by just in case. No infection, so that threat was mostly gone. (The first 24 hours are the most risky; the risk is gone after the top layer grows back.) My eyes were not really bothering me by itching too much. How bad it is depends on your body and it's different for everyone. After four days, the contacts were removed and they felt like normal eyes again. I mostly stopped the moisturising drops then, and discontinued the antibiotics.

The week after appointment, my eyes were 20/20 or slightly better, with one problem. The scar tissue (normal, it goes away in time) caused a double vision in my right eye. This wasn't too bothersome, except in high contrast situations, such as lights at night driving, and black on white reading, writing and the computer. This went away in about a month, and I ended up with slightly better than 20/20 vision.

Advice

• Ask as many questions as you can, and research as much as you can online. Also ask others who have had the procedure, if you know any.

• Ask about the experience of your surgeon, as well as what results he usually gets, and what complications he has seen.

• Make your schedule as light as possible for the week following the procedure, especially the next 24 - 48 hours.

• Rest often; it helps the healing process.

• Clean up around where you will be resting - this lessens the chance of infections.

• Drink plenty of water as it can help keep the eyes moist.