LASEK has relatively little to go wrong as a surgical procedure.
The main complications are as follows:
1. Pain: The actual laser treatment itself is painless. However, 2-3 hours after treatment most patients will develop mild to moderate pain which usually lasts a few hours. Anaesthetic eye drops can relieve this. After the first day, the eye is usually just a bit gritty and the blank "bandage" contact lens is removed about 3 days post-op.
2. Corneal haze: Some patients can develop a mild degree of haze on the cornea over the treated area. This is maximal at 6 weeks post op and generally disappears within 3-6 months such that it can not be seen even with an operating microscope. This is a deposition of glycosoaminoglycans or "GAG"s. Most patients are unaware that they have ever developed any such haze and it is not visible to the naked eye. It only causes a visual problem in about 0.1% of patients overall, and even in these, it tends to go away with time even if bad. Haze leads to a slight loss of effect of the laser with a "myopic shift" and, as it clears, the refraction gets better. In the higher myopes, the risk of haze causing a visual problem is greater at about 3% (1 in 30). However, the prophylactic use of mitomycin-c in higher prescriptions and better lasers with smoother surfaces have reduced this risk even more.
3. Difference in refractive error between the 2 eyes (anisometropia): If one eye is treated at a time, then the untreated eye will be short sighted and the treated eye will be around zero. This is not usually a problem up to about -4 to -5 dioptres. However, above this the image sizes are too different for the brain to unite them into one image, and double vision results, with one big image from the treated eye and one smaller one from the eye with glasses. This problem can be avoided by wearing a contact lens in the untreated eye or by not wearing any glasses at all. Lower corrections can have both eyes treated at the same sitting. This has a slightly greater risk than doing the eyes separately and should be discussed with the treating doctor.
4. Refractive error: None of the lasers at present can measure what they are doing in "real time". This would not matter if all the patients were made of identical plastic. However, if one person's cornea is a little more or less dense than the average, then the laser will take off a little more or less tissue. People also vary in their healing characteristics. In general, the bigger the prescription, the bigger the spread of results. The great majority (less than 5 Dioptres) will get within 1/2 Dioptre of aim and the highest ones (6-9 dioptres) will be within 1 Dioptre of aim.
5. Loss of sharpness of vision: This can be caused by micro irregularities on the cornea due to healing problems, laser problems etc and can lead to loss of "best corrected spectacle vision" (BCSV). This means that the vision when corrected by glasses for any residual refractive error is not as sharp as it was prior to surgery. As a rule of thumb, there is a 1% chance of losing one line of vision on the Snellen chart for every one Dioptre of myopia. (Hence a -5 Dioptre prescription has a 5% chance of losing one line of BCSV). This would be for example a loss from 6/5 to 6/6. There is normally not noticeable to the patient. There is about a 1 in 1000 chance of losing 2 lines of BCSV, which is normally noticeable to the patient. A person with a very irregular cornea could probably be corrected with a gas permeable contact lens.
6. Infection: A very rare event with laser refractive surgery and which has not happed to me in 11,000 eyes treated. I have read of 4 infections in the world over the last 10 years leading to a corneal graft.