Eyes - laser eye surgery

Laser corneal sculpting is a medical procedure that uses a laser to reshape the surface of the eye. It is done to improve or correct myopia (short-sightedness), hypermetropia (long-sightedness) and astigmatism (uneven curvature of the eye’s surface). The first laser sculpting procedures were performed more than 30 years ago.

The cornea is the transparent structure at the front of the eye, the part we see when we look into someone’s eye. It lets light enter the eye and is the first of two focusing systems in the eye. The second is the crystalline lens, which sits behind it.

During laser eye surgery, a computer-controlled excimer laser removes microscopic amounts of tissue from the cornea. The aim is to restore normal eyesight without the need for glasses or contact lenses.

How the surgery is performed#

There are several techniques:

• Photorefractive keratectomy (PRK): the thin outer layer of the cornea (the corneal epithelium) is removed and the underlying layers are reshaped with the excimer laser.
• Laser-assisted in situ keratomileusis (LASIK): a thin flap of corneal tissue is created, either with a femtosecond laser or with a fine-bladed instrument called a microkeratome. The flap is lifted aside, the excimer laser reshapes the underlying tissue, and the flap is replaced to cover the newly contoured surface.
• SMILE: a femtosecond laser creates an internal disc of tissue (a lenticule) within the cornea, along with a small incision at the edge. The surgeon separates the lenticule with a fine instrument and removes it through the incision.

The excimer laser is a “cool” laser. It does not burn tissue; instead it vaporises tiny amounts of the cornea each time a pulse is directed onto the eye. The beam diameter and the number of pulses are carefully controlled by computer so that the cornea is reshaped precisely.

Surgery is performed under local anaesthetic eye drops and takes around 5 minutes per eye, although the actual reshaping with the excimer laser usually takes less than a minute. If the procedure is successful, the cornea focuses light rays directly onto the retina at the back of the eye, rather than in front of or behind it.

Common sight problems#

Myopia (short-sightedness) is common in many populations. A person with myopia has no trouble focusing on close objects, but distant objects are blurry and hard to see.

Hypermetropia (long-sightedness) tends to cause vision problems later in life and is most often seen in people over the age of 40. A person with hypermetropia sees distant objects more clearly than close ones and often depends on glasses for up-close tasks such as reading.

Presbyopia is a common, age-related variation that usually begins when a person is in their 40s. People with presbyopia can see well in the distance but need to hold reading material further and further away to see it clearly. Presbyopia cannot usually be corrected with laser corneal sculpting. However, a laser procedure can be used to make one eye slightly short-sighted to reduce dependence on reading glasses, an approach known as monovision.

Reasons to consider laser eye surgery#

People may consider laser corneal sculpting because they:

• cannot wear contact lenses and would prefer not to wear glasses
• want to take part in work or leisure activities that are difficult to do while wearing glasses or contact lenses
• do not want the inconvenience of contact lens wear and the care it requires

Things to consider beforehand#

Before deciding on surgery, keep in mind that:

• it is best to be at least 20 years old before considering laser eye surgery
• your refractive error (your glasses prescription) should be stable
• people with very thin or abnormally shaped corneas, or a family history of keratoconus, should be especially cautious

These factors are easily assessed during preoperative testing, and an experienced refractive surgeon can advise you appropriately. Surgery carries extra risks if performed on people with abnormally shaped or very thin corneas.

After the operation#

Once you are home, you may want to rest or sleep. Some minor discomfort is normal. Your surgeon will guide you, but general suggestions include:

• use antibiotic and anti-inflammatory drops in the operated eye or eyes for a period after surgery
• wear plastic shields over the operated eye or eyes for several nights to prevent damage from rubbing
• do not rub the operated eye or eyes

Side effects and complications#

Possible side effects and complications include:

• Over- or under-correction – this may follow over- or under-treatment, and a second “enhancement” procedure may be needed for the best result.
• Dry eyes – you may need to use lubricating eye drops or have other treatment.
• Infection – this is extremely rare, but may require treatment with antibiotics.
• Superficial scarring – this may require a further procedure to correct.
• Excessive thinning of the cornea – this can lead to bulging of the cornea similar to keratoconus, and vision may deteriorate to the point of needing contact lenses or further surgery.
• Sensitive eyes – some people report increased sensitivity to glare, which can make driving dangerous.
• Blurred vision – “halos” or rings of fuzzy light may result from the treatment. This is no longer thought to be linked to large pupils, as was believed in the early days of laser vision correction.
• Regression – over time, some of the original refractive error can return, and an enhancement procedure may be needed.

Long-term outlook#

Some people who have laser eye surgery will still need glasses or contact lenses for the best possible vision, although their natural eyesight should be much improved. Most are free of glasses and contact lenses for many years. The long-term effects of laser corneal sculpting are believed to be minimal when the eyes are well suited to the procedure.

Other forms of vision correction#

Traditional ways of correcting myopia, hypermetropia and astigmatism include prescription glasses and contact lenses. There are also surgical alternatives that do not use an excimer laser, including the implantation of an intraocular lens and corneal incisions.

Intraocular lenses may be phakic lenses or the type used in people who have cataracts. Phakic lenses are a little like contact lenses, but are implanted inside the eye so they do not need to be removed.

Key points#

• Hypermetropia tends to cause vision problems later in life, most often after age 40.
• The most common age-related variation is presbyopia, which usually starts when a person is in their 40s.
• Laser eye surgery carries extra risks if performed on people with abnormally shaped or very thin corneas.
• Different sight problems require different treatments.
• Dry eyes after surgery may need lubricating eye drops or other treatment.

Where to get help#