You are most likely to be suitable for laser vision correction if your glasses prescription, which can be provided to you by your optician/optometrist, is in the range:
- Up to -10.00D of myopia or short sight
- Up to +4.00D of hyperopia or long sight
- Up to ±6.00D of astigmatism
Laser vision correction can be effective for higher prescriptions in some patients. Conversely, some patients with lower prescriptions may be better suited to lens implantation techniques.
The different LASER techniques
All laser vision correction procedures are performed using eye-drop anaesthetic, and a spring clip to allow you to blink safely during surgery. You will be lying down throughout. It is usual to operate on both eyes, and the surgery typically takes about half an hour. You can return home on the same day as surgery.
LASIK
LASIK (laser in situ keratomileusis) is typically performed using 2 lasers: one (femtosecond laser) to prepare a thin protective layer (the LASIK flap), which is lifted up before a second (excimer laser) removes a lens shaped piece of tissue to reshape the cornea beneath. The protective layer is then smoothed back and sticks in place and without stitches. IntraLASIK is the technique commonly used now.
SMILE
SMILE (Small Incision Lenticule Extraction) uses a femtosecond laser of the same type used to create a LASIK flap to define a lens shaped piece of tissue that is removed by the surgeon through a small incision to correct focus. This is like LASIK without the LASIK flap, but the thickness of tissue removal is slightly greater and the tissue may be removed from slightly deeper in the cornea. End results are similar to those for LASIK and surface laser treatments.
Surface laser treatments
Surface laser treatments (PRK, LASEK, and TransPRK) use the same excimer lasers to perform an identical removal of a lens shaped piece of tissue immediately beneath the clear skin layer of the cornea. The clear skin layer regrows over a period of about a week, then smooths off optically to complete the visual recovery over the next three months. While the skin layer is regrowing, the eye surface is normally very sore. This is one of the main differences between surface laser treatments and LASIK or SMILE, which both aim to keep the corneal skin layer intact. All surface laser treatments produce similar results, and the only difference between them is the way in which the corneal skin layer is removed. In PRK and LASEK the skin layer is removed by the surgeon – in LASEK dilute alcohol is applied to loosen the skin layer first. Some modern excimer laser systems are able to remove the skin layer as part of the reshaping treatment.
This is called TransPRK. The area of skin layer removal in TransPRK is reduced to the minimum required for reshaping the cornea beneath, shortening recovery time by 1 to 2 days in comparison with PRK and LASEK.