Laser vision correction: LASIK, surface laser and SMILE explained

Short sight, long sight and astigmatism arise because the eye focuses light slightly in front of or behind the retina. NHS.UK lists these as reasons for laser or lens surgery. A Leeds page explains that the laser sculpts the cornea into the correct shape so glasses or contact lenses are no longer needed for the same accuracy of vision.

Nobody needs it for their health. Glasses and contact lenses correct the same errors, and the NHS page says surgery on the NHS is generally reserved for eye conditions that could lead to loss of vision, or for sight problems that cannot be corrected with glasses or lenses. If your reason is convenience, comfort with contact lenses or work, it is a lifestyle decision to be made with a full account of the risks.

LASIK uses two lasers. According to the Leeds page, quoting the Royal College, a femtosecond laser prepares a thin hinged flap that is lifted so that an excimer laser can remove a lens-shaped piece of tissue, after which the flap is smoothed back without stitches.

Surface treatments (PRK, LASEK, TransPRK) use the same excimer laser directly under the clear surface skin of the cornea. The Leeds page says the skin regrows over about a week and the visual recovery completes over the next three months. SMILE uses a femtosecond laser alone to cut a lens-shaped piece of tissue which is removed through a small incision, so there is no flap, and the page says end results are similar.

The specialist eye hospital page says all modern techniques produce similar visual results and that its surgeons choose between them according to the eye. It adds that surface treatments are often the best option for thinner corneas, and it describes visual recovery as slower than LASIK.

Before treatment NHS.UK says you should have a consultation with the surgeon covering what will happen on the day, what aftercare to expect and what to do about complications. Treat this as the main safety step: scans measure corneal thickness and shape, and the surgeon decides whether your eye is suitable.

The specialist eye hospital page gives three common reasons for being turned down. An unstable prescription means the eye is probably still changing, usually before the early twenties, and treatment would not be expected to last. A thin or irregular cornea can be made worse and may develop ectasia. Finally the prescription can be beyond the safe range, because the laser thins the cornea and there is a minimum thickness needed. Its guidance quotes limits of roughly -8 to -10 dioptres for short sight, but those figures vary by provider and individual cornea.

Providers set their own minimum ages and rules about pregnancy, breastfeeding and certain medicines. If you wear soft or hard contact lenses, ask when to stop wearing them before the scans.

• Bring your current glasses prescription and the name of any eye drops or medicines.

• Ask for the risks specific to your eye and prescription to be explained in writing.

• Ask what happens if you need an enhancement later, and who pays.

NHS.UK says local anaesthetic is usually given as drops, and that if both eyes need surgery they are usually done on the same day. The specialist eye hospital page says patients may feel pressure for around 30 to 40 seconds when the LASIK flap or SMILE lenticule is made, and mild discomfort for several hours afterwards. You go home the same day and the NHS page says not to drive yourself home.

NHS.UK says most people have some side effects: glare, halos, floaters, starbursts and ghost images, blurred vision, sore eyes similar to dry eyes and red blotches on the white of the eye, which normally improve within a few months. Complications named on the page include a detached retina, permanent serious loss of vision, needing a second operation, under-treatment or over-correction, and earlier cataracts, with the risks varying between types of surgery.

The specialist eye hospital page says fewer than 1 in 5,000 patients need further surgery to replace damaged corneal tissue, and it sets this against roughly 1 in 3,000 contact lens wearers developing a serious corneal infection each year. Those are one provider's figures, and they should be compared with the numbers your own surgeon quotes.

Expect lubricating drops, protective glasses if advised, and review visits. The Leeds page describes visits the day after and a week after surgery, then regular checks during the first year, with exercise and swimming avoided for two weeks and flying not planned for three weeks, though other clinics set different limits. NHS.UK also says not to drive at night until your eyes have recovered.

NHS.UK says to get help from NHS 111 if floaters suddenly appear or increase, you see flashes of light, a dark curtain or shadow moves across your vision, or vision suddenly becomes blurred. Contact the clinic that did the surgery if side effects are not improving, and treat severe pain or worsening vision as urgent.

Ask who performs each step, how many procedures the surgeon does, what the follow-up schedule is and what is included, how enhancements are handled, and what happens if there is a complication out of hours. Compare quotes on what they include rather than the headline figure.

Because NHS.UK describes this surgery as usually private, the choice is mostly about provider quality and aftercare rather than waiting times. Choose a provider where your surgeon sees you at the consultation and follow-up visits.