Like all surgical procedures, there are potential complications and side effects associated with LASIK. Some of these, such as seeing halos around objects, were much more common with the early laser machines which treated a much smaller area than the lasers that are used today.
Your surgeon should discuss your individual risk for any side effects alongside the benefits of the procedure so you can make an informed decision about whether to proceed. 

The following side effects have been reported after LASIK:

Reduction in quality of vision
There is a risk (between 2.7% and 4.8%) of a reduction in the quality of vision following LASIK. People who are affected may be able to read two lines less on an optician’s reading chart, even when they are wearing the right prescription of glasses.

Minor over- or under-correction of refractive error
People’s eyes heal in different ways and at different rates and this may mean that the expected visual correction is not achieved. If this happens, you may be offered a second procedure (known as an enhancement), or you may need to wear glasses or contact lenses for some tasks.  Enhancement rates vary from 5% to 15%.

Presbyopia is the difficulty reading without glasses that usually occurs naturally in the early- to mid-40s. People who are short-sighted may not require glasses for reading when they develop presbyopia as simply removing their distance glasses provides the right level of visual correction.  However, a short-sighted person who has their distance vision corrected using LASIK will effectively become normal sighted, and it is likely that they will need to wear reading glasses for tasks such as reading as they reach their 40s.

Difficulty wearing contact lenses
If further visual correction is needed after laser eye surgery, it may be more difficult to wear contact lenses as the cornea has been reshaped.

Instability of the cornea
If the cornea is weakened through the removal of too much tissue during LASIK, the centre of the cornea may bulge, making the eye surface irregular and resulting in poor quality vision.  At your pre-operative assessment, your surgeon will take measurements to ensure that 250 microns depth of corneal tissue remains untouched following LASIK, as this is generally accepted as a safe level. 

Decreased night or low light vision
Problems with night vision include glare, halos and starbursts seen around objects at night or in dim light and for some people these symptoms can interfere with daily activities, especially with driving at night.  Reduced night vision is often temporary, lasting about four to six weeks, but some continue to experience the symptoms in the longer term.  These problems are more common in people with particularly large pupils.

Eye sensitivity
For the first few months after surgery, it is quite common for the eye to be slightly more sensitive to touch, but it is rare for this to be severe.  The problem persists in less than 1% of patients.

Dry eye
Most people experience dry eye symptoms immediately after laser eye surgery because the surface nerves have been cut. The use of lubricating drops will usually relieve the irritation, but in very severe cases a temporary plug may be placed in the opening of the tear duct to slow tear drainage.

Retinal detachment
People with short sight have a greater risk of retinal detachment and this risk is not reduced by laser eye surgery.

  • Other rare problems include:
  • incomplete cut of the corneal flap (usually remedied by a repeat procedure after several months)
  • loss or extensive damage to the corneal flap
  • unattached corneal flap, which may require stitches to hold it in place
  • inflammation caused by debris or fibres under the corneal flap
  • growth of the surface layer (epithelial tissue) of the cornea under the corneal flap
  • wrinkling of the corneal flap
  • bleeding or blocking of the retinal artery or other blood vessels
  • penetration of the eye by the microkeratome and possible loss of the eye due to haemorrhage or infection (very rare).