LASIK is an acronym for "Laser in situ keratomileusis". A thin corneal flap is created using a mechanical microkeratome or a femtosecond laser (IntraLASIK).  The flap is lifted and another laser, the Excimer laser uses a cool ultraviolet light beam to change the shape of the cornea to correct refractive error (shortsight, farsight, astigmatism and now Presbyopia, the need for reading glasses). 

For shortsighted eyes, the cornea is flattened slightly in the centre.  Farsighted eyes are steepened slightly with the laser beam directed at the edges of the cornea.  Common misconceptions are that astigmatism and presbyopia cannot be corrected. LASIK can successfully correct astigmatism by altering the irregular shape of the astigmatic cornea and making it more normal in shape.

Correction or elimination of reading glasses can be accomplished by techniques such as Supracor Lasik or Monovision/Blended vision.

Once the cornea under the flap is reshaped, the flap is replaced and allowed to dry. Discomfort is experienced for about 4 hours and there may be some grittiness or foreign body sensation for the remainder of the day.  By the next morning, vision is typically very good with no discomfort.


Pre-Operative Evaluation

This involves a thorough consultation best performed by a consultant surgeon with expert/specialty knowledge of the cornea and refractive surgery.  LaserVisionForum only lists surgeons (and clinics) who meet this standard.  The evaluation at a minimum should include vision testing, refraction (testing for what power is required), pupil size evaluation in dim light, corneal mapping (ideally with 3 Dimensional topography), aberrometry (wavefront check), dry eye testing, intraocular pressure, corneal thickness and a dilated examination of the retina.  Other tests including corneal hysteresis, anterior segment ocular coherence tomography, ultrasound biomicroscopy, visual field analysis, macular OCT and retinal nerve fibre OCT, may all be performed in case your surgeon finds something during the examination that warrants closer evaluation. 

Wavefront and Customised treatments

 Each centre uses its own favored laser technology with which its surgeons are comfortable.   A variety of brand names are used, such as Zyoptix  and iLasik which can sometimes be confusing for the consumer.  Customised treatments are usually designed to provide the best possible outcome. Most evaluating surgeons will select the best option for the patient and if it is a customized treatment, there may be a slightly higher cost.  This is because the companies that provide the laser charge more for this type of treatment and the cost is passed on to the patient.

Risks and Complications

This type of procedure is highly successful with correct patient selection and evaluation and surgery by a speciality trained consultant.  Technology does need to be up to date and surgery performed in the correct environment backed up by a regular and appropriately trained team of nurses and technicians.

There are some issues you do need to be aware of and these should be discussed with you in advance of surgery. 

Under-correction, over correction or Regression

While all attempts are made to fully correct the refractive error, in a small number of cases there may be an over or undercorrection.  The human cornea is biologic tissue with its own individual response and propensity to heal.  Some patients may over or under respond to the treatment provided.  Additionally the treatment may be perfect in terms of outcome early on, but through individual healing there may be a regression where the power of the eye slips back a little (a small percentage of the original correction).  If the eye regresses or has an over or under-correction,  then a retreatment or enhancement may be required at 3 months or whenever the eye is deemed to be stable.

Dry eye

This is a listed side effect of LASIK and other laser eye surgery procedures.  There are multiple causes of dry eye following LASIK, the principle one being temporary anaesthesia of the corneal surface.  Creation of the LASIK flap involves cutting the fine nerve endings of the cornea. These have a role in providing sensation and alerting the eye to when it is dry and influencing tear production.  Nerves also have growth factors that influences the adjacent cells and promotes orderly growth.  Furthermore following LASIK, some of the drops used are highly concentrated and can be toxic to the surface of the eye.  This can worsen dry eye symptoms. 

To avoid prolonged problems with dry eye after LASIK surgery, it is important that any underlying dry eye problems or predisposition be identified and treated in advance of surgery.  This is best judged by an eye surgeon with specialty training in Cornea and the ocular surface.  Dry eye tests and evaluation of the lids for good closure, meibomian glands, tear production and staining of the surface are vital in advance of surgery as are specific tests (Schirmer’s and Tear Break Up Time)  

Halos and Glare

All patients experience some Halos soon after LASIK surgery, even following customised treatments to eliminate halos.  This is because of fluid in the flap which eventually disappears. Between a few days and a few weeks, patients report a marked reduction in halos.  Some patients do experience permanent halos, and this is often because their treatment has not been customised to suit their eyes and their optical problem.   Small zone treatments, incorrect correction and large pupils are some of the variable that can affect visual quality.  These are best addressed preoperatively by a specialist Cornea and Refractive Surgeon who will take all factors into consideration and plan a treatment that specific and individualised to each eye.


The risk of infection is very low with LASIK laser eye surgery and listed as less than 1:10,000 cases.  It is important that surgery is performed in the correct operating conditions with HEPA filtration and the correct room exchanges per hour.  This is to ensure the environment is free of bacteria and fungus.  Many clinics choose to operate in operating theatre environments which exceed the minimum requirement.  Very strong antibiotic drops are used before, during and after surgery to prevent infection.  Additionally instrumentation should be changed between eyes to minimise risk.  After surgery, it is important to follow your clinic / doctor’s instructions in terms of dos and don’ts to stay safe and avoid infection.


This is a condition where the cornea becomes unstable and starts to bulge following LASIK.  This is uncommon at laser centres where patients receive a thorough evaluation using good imaging instrumentation and corneal hysteresis (Ocular Response Analyser) and also where parameters for treatment are strictly followed to avoid excessive thinning of the cornea.  This condition occurs in corneas that are excessively elastic and can be identified using several parameters including 3 dimensional corneal mapping and corneal hysteresis. Again it is important that the evaluating surgeon be well versed with Corneal conditions to be able to accurately identify those at risk and avoid performing LASIK.  In some cases where there is a very slight risk, the surgeon may advise an alternative to LASIK such as PRK, LASEK or even implantable lenses.


Am I a candidate for LASIK/IntraLASIK?

To find out about your suitability for Lasik/IntraLASIK, it is best to contact a centre of your choice and arrange for a consultation preferably with an eye surgeon with special expertise in the Cornea and Refractive surgery.  The final decision about your suitability for this procedure will depend on findings at consultation. Typically this involves a very thorough 2 to 3 hour consultation with a clearly defined patient care pathway involving numerous checks This is followed by a complete eye examination by your surgeon who will determine if you are a candidate. Not everyone unfortunately is suitable for LASIK/IntraLASIK, however there are some basic requirements:

  • 0ver 18 years old (some clinics differ in requirement)
  • Stable spectacle prescription
  • Vision to a minimum level of 6/12 (20/40) with glasses
  • Healthy cornea

Am I too old to have LASIK/IntraLASIK?

There is no real top age for LASIK/IntraLASIK. A thorough eye examination is important to ensure that any visual problem is not caused by other problems such as cataracts or glaucoma. In certain age groups (>55) seom centres prefer to consider Refractive Lens Exchange over LASIK/IntraLASIK as this is a permanent correction that has the potential to provide a full range of correction and eliminate the need for reading glasses altogether.

Presbyopia is a condition where reading glasses are required. This occurs because the lens inside the eye becomes harder and no longer focuses sufficiently. Those with this condition need reading glasses. LASIK until recently did not address reading vision and patients over 45 undergoing surgery often required reading glasses.  There are now options available using lasers to reduce dependencuy on reading glasses. One option is monovision or blended vision where the non-dominant eye is left slightly shortsighted.  Another alternative where both eyes are treated similarly is called PresbyLASIK or “Supracor”.  This procedure corrects both eyes similarly for both distance and near.

The options for correction will depend on the eye and your surgeon will illustrate what is the best option for you. 

How safe is LASIK/IntraLASIK?

The procedure has been in use for over 20 years and is approved by the USA’s stringent Food and Drug Administration (FDA). The procedure is also approved by the UK’s National Institute of Clinical Excellence (NICE). The safety of the procedure is highly dependent on the Surgeon, the centre and its processes and environment as well as technology. 

Does LASIK/IntraLASIK hurt?

No. The treatment itself is painless. Large amounts of anaesthetic drops are used which completely numb the eye. You might feel a bit of pressure at the very beginning when the flap is being created. After the procedure some patients describe a gritty sensation like a lash in their eye. Some feel a bit of stinging and this lasts for a few hours. For this  patients are advised to have a nap for about 4 hours after the procedure. 

How long does it take to do LASIK/IntraLASIK?

The procedure is very quick and usually takes less than 10 minutes per eye. Althought he procedure is quick, plan on being at the centre for about 2 to 3 hours as time is required for preparation,  the procedure, recovery and discharge. 

How accurate is LASIK?

Based on clinical data from studies as well as that of regulatory authorities like the FDA, Lasik/IntraLASIK is highly accurate.   In spite of advanced technology and attention to detail, a small number of patients do require a touch-up or enhancement to achieve good unaided vision. This is because we are dealing with human tissue and there is some variation in how people respond and heal.

What if I blink or move during the procedure?

This is a commonly asked question. A delicate clip holds the eyelids open during the procedure and blinking is not possible. The head rests in a well or headrest where the head fits in snugly and does not move. The head will also often be held by the surgeon to ensure it does not move. All you will need to do is look at a blinking red light. Modern lasers also have tracking systems some using Iris recognition that follows the eye ensuring the laser shots are accurately delivered even with very fine and rapid movements of the eye. 

How soon after the surgery will I be able to see?

Vision recovers very quickly after the procedure and this is what makes the procedure so exciting. At 10 minutes after the most patients obtain vision close the standard required for drving. Although misty or foggy soon afterwards, this clears after a night’s sleep. Visual recovery in a few patients can take slightly longer than one day and in some can take up to 10 days. Although everyone is a little different, the vast majority of  LASIK patients achieve legal driving vision or better, the very next day. Note that vision may fluctuate a little in the first couple of weeks. This is a normal phenomenon and this will stabilize. 

When will I be able to drive?

On the day of your surgery it is important to have a driver take you home. You should be able to drive the next day, and best to check by testing your ability to read a number plate of a car at 25 yards/meters. 

What are the possible complications?

It is normal to be concerned about what can go wrong ! There are very small risks which will be outlined to you at your consultation. Problems that can cause problems are infection and severe inflammation following surgery. To prevent this strong medications are used before, during and after the procedure. It is important that the drop regimen be followed precisely as instructed.

Other complications include: Under or over correction, corneal flap healing problems, pain or discomfort, dry eye, hazy vision, sensitivity to light, glare at night, loss of best corrected visual acuity, or infection and these have been addressed under "Risks and Complications" above.

Does Lasik/IntraLASIK cause night vision problems?

Night vision problems such as starbursts, glare and halos at night have been reported.  There are several reasons for this problem and usually result from an incorrect choice of treatment for the eye involved. Each eye is individual and requires a bespoke treatment. Inadequate diameter area of the cornea treated, is one cause and we ensure we measure the pupil size in dim light conditions. Old technology and treatment profiles that are not Aspheric, are another cause of this problem.  For further information read the section about Halos and Glare under "Risks and Complications"

How long will the effect of LASIK last?

In the majority of cases, this treatment is permanent, especially if the spectacle prescription was stable at the time of the procedure. If some patients because of their genetic programming  are destined to have a change in their prescription then that will unfortunately happen. Although this is very uncommon, a retreatment can be performed many years later if needed.  The reason for a change is often an alteration of the lens inside the eye which can change the power of the eye.

Questions You Should Ask ...

1. Who is my surgeon and what are their qualifications ? Have they received specialist training in Cornea and refractive surgery?

Since this is an operation on the cornea, it is best that you be treated by someone who is well versed with this area. Ideally a surgeon who has had speciality training (Fellowship training) in Cornea and Refractive surgery will have good understanding and experience and be able to identify any issues of concern at the time of consultation and where possible address these in advance or exclude surgery as an option.

2. What is the experience of the treating institution ? How long have they or their surgeons performed LASIK surgery?

Understanding the track record of the institution and surgeon is useful. It is useful to also konw if the institution has a good track record. You want to be looked after by an institution that has a clear mission of looking after patients well and in businsess for the long haul.

3. What other procedures does the treating centre perform?

It is important that several options for vision correction be available. Laser eye surgery may not be the best option, however it is natural that boundaries are pushed if the treating facility is only able to provide one option. “If the only tool you have is a hammer, then everything starts to look like a nail”

4. What happens in case I have an emergency?

Although the likelihood of requiring care out of normal hours is extremely rare, It is useful to know what on-call arrangements are available. Is the centre available 24/7? Are calls answered by a person and if needed is an eye surgeon available to see patients?