Laser Eye Surgery Knowledge Hub

Everything you need to know. All in one place.

Essential Advice to Maintain Your Eye Health

Essential Advice on Eye Health

Last year, National Eye Health Week reminded us all of the importance of regular eye tests. It’s recommended we have our eyes examined at least every two years, not only to ensure they’re healthy, but also to check for changes to our current prescriptions….

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Top Tips: How to Eat Seasonally For Better Vision

Here at London Vision Clinic, as much as we love to see you, we encourage you to keep your eyes healthy by eating healthily for get a better vision. Your diet and choosing to eat the right foods can prevent long term eye problems later in life. In season vegetables can be incorporated into fun and inventive recipes that are both healthily delicious and good for your vision!…

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What to Expect: Before, During and After LASIK Surgery

LASIK is one form of corrective laser eye surgery. The procedure involves cutting a small flap of the cornea and laying it to the side in order to remove a small amount of the cornea with a laser. The flap is then set back in place and begins to immediately repair itself. …

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10 Amazing Eye Facts That Will Change How You See The World

Eyes are complex organs, so it’s really important to take care of them with the best specialists. Some scientists have even called them a wonder of nature. How they enable you to see is a fascinating biological process. We’d like to share with you 10 fascinating facts about your eyes that you might not know….

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London Vision Clinic’s Top Tips to Avoid Eye Strain

In this crazy, modern, techy world that we live in, we don’t take it easy on our eyes. Today many jobs require that we spend hours and hours in front of computer screens. Many people even elect to read on computer screens rather than actual books. With that being said, books are sometimes not much of an optical improvement. Eye strain can cause dryness, migraines and, later down the road, permanent vision problems….

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Your Eyes: Separating the Facts and the Fiction

The World Health Organisation states that 80% of the world’s blindness and serious visual impairment is preventable. There are certainly many myths and home-remedies about how to do just that. In fact, everybody has an idea about what is good or bad for your eyes but what is the truth behind it all? Here are some of the best-loved eye-related claims and the truth on the matter….

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What are the Finance Options for Laser Eye Surgery?

What are the Finance Options for Laser Eye Surgery? There’s no getting around it: High-quality Laser Eye Surgery isn’t cheap. So many people are relieved to find out that, as with many other investments, finance options are often available for Laser Eye Surgery – including here at the London Vision Clinic. Napoleon is widely credited with referring to England as a nation of shopkeepers (or l’Angleterre est une nation de boutiquiers); a comment that was meant to be derisive; however,…

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Your Eye Health: 5 Common Age-Related Eye Problems

Your Eye Health: 5 Common Age-Related Eye Problems Refractive errors are the leading cause of visual impairment worldwide with an estimated 43% of impairments attributed to errors including hyperopia, myopia, and astigmatism. For many people, refractive errors may worsen over time, increasing their need for higher prescription visual aids. However, even the lucky ones who have enjoyed clear, glasses-free vision for their whole lives could one day find their eye health deteriorating as they get older. Of course, just like…

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Laser Eye Surgery Technology: What is Spot Size? [VIDEO]

With the small size of an Excimer laser used for laser eye surgery, we will think of it as a paintbrush size. It is very difficult to do fine art with a house paintbrush. So obviously the smaller the brush you are using the more detail you can paint, you can carve. Of course the smaller the brush, the longer it will take you to paint an area. So there is an interplay between the spot size and the speed of the laser and that is all technical stuff but generally speaking small spot lasers are better than broad area lasers….

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The Evolution of Presbyopia Treatment

The Evolution of Presbyopia Treatment Declining vision is, unfortunately, an inevitability. Eventually, even those of us lucky enough to have enjoyed perfect vision for our whole lives will find ourselves in need of some sort of correction. In most cases, this will probably mean acquiring a pair of reading glasses – at least at first. But thankfully, over the last few decades, alternative options have been doing away with the need for reading glasses and contact lenses for presbyopia altogether…

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Can laser eye surgery treat the loss of reading vision?

Yes. The loss of reading vision occurs due to ageing, as the eye begins to lose its ability to ‘zoom’ from distance to near. This means that the close vision deteriorates. Some clinics choose to treat presbyopia by removing the natural lens inside the eye and replacing it with an artificial one.

However, there is also a laser eye surgery procedure called PRESBYOND® Laser Blended Vision, which is highly effective and much less invasive than lens replacement. With this technique, one eye is treated to view objects mainly at distance and a little up close, while the other is treated to view objects mainly up close and a little at distance. The brain learns to combine the two images, enabling the individual to see far and intermediate distances and up close, without effort. Studies have shown that 97% of people are suitable for PRESBYOND® Laser Blended Vision, and almost all are able to read normal newsprint without glasses after surgery.

Which procedure will I be suitable for?

The vast majority of patients undergoing laser eye surgery worldwide are suitable for LASIK, and most short-sighted patients are also candidates for SMILE. In the past, patients with thin corneas tended to be recommended for surface procedures (PRK, LASIK and Epi-LASIK) as these do not require the creation of a corneal flap.

Many of these patients can now be treated with SMILE – a totally ‘flap-less’, keyhole procedure, which was first introduced in the UK at London Vision Clinic in 2011. However, a small minority remain candidates for surface treatments only, and some patients may only be suitable for an intraocular lens procedure, either an ICL or CLE.

How long should I be out of contact lenses before the consultation with my surgeon (‘surgeon consultation appointment’)?
Contact lens typeLength of time lenses need to be out before the consent appointment with the surgeon
All soft contact lenses (including toric and extended wear)At least 1 week before
Rigid gas permeable (RGP)worn for 0-10 yearsAt least 4 weeks before
worn for 10-20 yearsAt least 8 weeks before
worn for 20-30 yearsAt least 12 weeks before
True hard lenses (polymethyl methacrylate)At least 12 weeks before
Are both eyes treated at the same time?

Yes. Large scale studies conducted over a decade ago demonstrated that there was no difference in safety between singleeye surgery and bilateral surgery. In fact, some evidence suggests that it is actually safer to treat the second eye immediately following the first eye. There are, of course, certain situations where your surgeon may suggest treating one eye at a time, but this would generally be due to specific medical issues.

What will I feel during and after the laser eye surgery procedure?

There is no pain involved during laser eye surgery. You will be given a topical anaesthetic to numb your eyes – most patients report feeling some pressure on the eye (which can be a strange sensation) but not pain. Many LASIK and SMILE patients do not experience any discomfort after surgery – although it is normal to experience some grittiness, light sensitivity and eye watering for the first 24 hours. After surface procedures (PRK, LASEK and Epi-LASIK), the eyes take a few days to heal. However, patients should not find the healing process painful, as they are given pain-relief medication and fitted with bandage contact lenses.

How long does laser eye surgery take?

The treatment takes only minutes and the laser itself is only active for seconds

What happens if I look away, blink, cough or sneeze during the procedure?

Nothing. Although your eye will move during surgery, eye tracking technology ensures your safety when this happens – the laser tracks your eye hundreds of times every second, and compensates for any movements. In the SMILE procedure, the eye is immobilised by the vacuum connection to the laser.

What is the risk of a complication during laser eye surgery?

Laser eye surgery is safe, but no surgery is entirely without some level of risk. Thankfully, an expert surgeon will have the knowledge to manage complications properly, and will usually be able to correct any complications that do occur. In the hands of an expert surgeon, the chance of something going noticeably wrong is around one in 1,000 procedures. The chance that such a surgeon would be faced with a situation he or she would not be able to correct satisfactorily is about one in 30,000.

Can I take a tranquiliser or sedative (e.g. Valium) prior to the procedure?

Rules about this will vary between clinics. Generally it is better to not use sedatives, as these can alter patient cooperation during the procedure. However, patients who suffer from anxiety disorders such as panic attacks, claustrophobia etc. may benefit from judicial use of sedatives. If this applies to you, your surgeon should discuss the risks and benefits of sedatives thoroughly with you, before surgery. Never self-medicate. Your medical team should provide the necessary required medical dose

Do laser eye surgery results differ between prescriptions?

Yes. In general, results decrease as prescriptions increase. Results also differ between short-sightedness and longsightedness. Therefore, when reviewing a clinic’s results, it is important to look at results for prescriptions that are similar to yours as these will provide you with a more accurate picture of your chosen clinic’s success rates.

What is wavefront?

Wavefront treatment has received a lot of publicity. However, it is important to remember that not all wavefront systems are as good as each other (see Technology section earlier). Wavefront sensors measure the unique optical imperfections of your eye, called ‘higher order aberrations’. These irregularities of your optical system affect the finer quality of your vision, beyond what glasses are able to correct. The most advanced wavefront technology can be used to customise your treatment to account for these higher order aberrations, meaning a safer and more accurate treatment

I have astigmatism, can I still have laser eye surgery?

Yes. Laser eye surgery can treat astigmatism at the same time as it corrects short or long-sightedness. No extra procedure is needed.

Is my prescription too high?

In most cases, having a very high prescription will not stop you having laser eye surgery. The range that any surgeon can treat depends on their technology and experience, but technology and expertise in the field is now so advanced that the vast majority of patients with very high prescriptions are now suitable for a ‘full correction’ and, for those patients with extremely high prescriptions, laser eye surgery can still be used to achieve a significant improvement in the vision, or an intraocular lens procedure could achieve a full correction, either an ICL or CLE. If you are turned away by a clinic, it is important to remember that this often does not mean that you are not suitable – it may simply mean that your chosen clinic does not have the technology or experience necessary to treat you safely

What range of prescriptions can be treated?

The majority of laser eye surgery is performed on patients with:

  • Myopia up to -8.00 D
  • Hyperopia up to +3.00 D
  • Astigmatism up to -4.00 D.

However, some surgeons have the expertise and technology that allows them to safely treat much higher prescriptions – a full correction is sometimes possible on prescriptions of:

  • Myopia up to -14.00 D
  • Hyperopia up to +6.50 D
  • Astigmatism up to -6.00 D.

If your prescription is higher than this, you should not be disheartened as it may be possible to significantly improve your vision with a partial correction. Alternatively, you can consider intraocular procedures such as an ICL or CLE, which can be used to correct almost any prescription.

Am I too old / too young?

Laser eye surgery patients must be at least 18 years old; there is no upper age limit

Does everyone get presbyopia?

Yes. Presbyopia typically develops during the 40s (although some patients do not begin to lose their reading vision until their mid-50s). When presbyopia develops, people begin to need glasses for reading even if they have never worn glasses before. People who previously wore glasses will need a different prescription for reading than for distance (e.g. bifocals).

What are the risks of laser eye surgery?

Laser eye surgery is, by any medical standard, a safe procedure. However, as with all surgical procedures, there are some risks to consider. Fewer than 3% of LASIK procedures result in any complications. The chance of having a serious complication is much less than 1% generally and probably less than 0.3% with an expert surgeon. The most common complications and sideeffects of laser eye surgery are as follows:

  • In about 1 in 1,000 LASIK cases, the flap is too short, thin or uneven. If this occurs, the flap is put back in place to heal. The surgeon will not use a laser on your eye and your vision will likely be unaffected, but you can try surgery again in a few months.
  • Wrinkles in the flap (striations) occur in about 1 in every 1,000 LASIK procedures. Striations can cause astigmatism. The most likely causes are either rubbing your eyes before they are fully healed, or the surgeon not lining up the flap properly when it is replaced. If the wrinkles are causing astigmatism, a second procedure can be done to lift and smooth out the flap. If they are not causing any problems they can be left untreated.
  • In about 1 in every 5,000 cases, patients develop irregular astigmatism after surgery. Contact lenses can usually correct this form of astigmatism (glasses will not). People who have very high prescriptions have a higher risk of this complication. Irregular astigmatism can happen even if the surgery is perfect, but your risk is increased if you have an inexperienced surgeon or one who does not use the best equipment.
  • Epithelial ingrowth is a potential complication of LASIK that occurs in less than 1% of cases, in which epithelial cells begin to grow and multiply under the corneal flap. The most common treatment is lifting the corneal flap, removing the cells, irrigating the interface and repositioning the flap. Most cases, if managed appropriately, have a good outcome.
  • Ectasia, which occurs in about 4 in 10,000 cases, is a progressive deformity that makes the cornea thinner and steeper. It can be treated with corneal crosslinking (CXL), by suturing (stitching) the flap to the underlying cornea, or in rare circumstances with a corneal transplant. When identified early, it is very unlikely to lead to further visual degradation with appropriate treatment. Ectasia is more likely to occur in eyes with a condition known as keratoconus. Therefore, it is important to undergo intensive and detailed screening for keratoconus before surgery. Currently, the most sensitive method for detecting keratoconus is to use thickness maps of the epithelium in combination with topography and tomography (see the sections on technology). This method was pioneered by Professor Reinstein and has become accepted by ectasia experts around the world as an important component to keratoconus screening. As with any surgical procedure, there is a risk of infection after laser eye surgery. The risk of a corneal infection is approximately the same as one year of soft contact lens wear (about 5 in 10,000 patients). As with any ophthalmic procedure there is a very remote risk, estimated as less than 1 in 4,000,000, of the loss of an eye, with partial or total blindness.
  • Most laser eye surgery patients experience some temporary dryness after treatment. In certain people, the condition is long-lasting. Eye drops can provide relief, but up to 5% of patients have persistent dry eye symptoms up to 1 year, and 1% longer than 1 year.
  • Glare and halos are probably the most common side-effect of laser eye surgery. Most patients indeed experience some level of glare and halos at first, but this generally goes away over a period of a few weeks to a few months. Those who do have lasting effects usually only experience symptoms at night, and most do not find them troublesome. Symptoms can usually be improved by further surgery. The causes are below.
What causes glare and halos and can it be treated?

There are several reasons why a patient might develop glare and / or halos after laser eye surgery:

If you have been ‘under-corrected’ (i.e. if the shape of your cornea has not been changed enough during your procedure), you may still be slightly short or long-sighted and/or still have a minor astigmatism.

A minor enhancement procedure can usually address this. For the small minority of patients who are not candidates for an enhancement, wearing glasses can generally get rid of any troublesome symptoms.

The size of your pupils can be another cause of glare and halos. If a patient’s pupils dilate (open) beyond the area of the cornea that has been treated during laser eye surgery, this can cause glare and halos in low light conditions. The risk of this can be mitigated by accurately measuring your dilated pupil size before surgery. The surgeon can determine whether or not they can effectively treat a large enough area of your cornea with the laser, and if this is not possible then the surgeon should decide not to treat you. Frequently Asked Questions

If you do have glare and halos at night because of your pupil size, there are a few techniques that can help. Some patients find that keeping the overhead light on inside their car when driving stops their pupils dilating so much that it affects their vision. There are also medicated eye drops that stop the pupil from dilating fully, and some patients find that these fully alleviate the problem. Alternatively, clinics with access to an excimer laser that includes a topography-guided treatment option can perform a second treatment that can reduce these symptoms.

Finally, glare and halos can be caused if the area of your cornea treated by the laser is off to one side (known as ‘off-centred ablation’ or ‘decentration’). Choosing a properly qualified and experienced surgeon can help to minimise the risk of this serious complication. Specialist clinics will be able to perform a topography-guided treatment to re-center the treated zone and improve the quality of vision.

In general, using advanced wavefront technology can significantly reduce the risk of glare, halos and night vision difficulties resulting from surgery (see Technology section for further detail).

How does the flap stay in place in LASIK?

Initially, the flap is kept in position by a vacuum effect. The cells lining the inner surface of your cornea – known as endothelial cells – pump water out to the inner part of the eye. This creates suction, which holds the flap in place. During the first few hours after surgery, the outer surface of the cornea – known as the epithelium – seals the edges of the flap. Over the ensuing weeks, natural substances inside your cornea bond the flap to the underlying tissue

What conditions may prevent me from having laser eye surgery?

The following list includes conditions or circumstances that prospective patients commonly ask about when discussing suitability for laser eye surgery

Condition or CircumstanceCan the person have laser eye surgery at the London Vision Clinic?
Older than 60?Yes. There is no upper age limit for laser eye surgery, as long as your eyes are healthy. Some older patients experience a longer healing period after laser eye surgery, but this can be discussed at your initial screening if it is likely to apply to you.
Pregnant or breastfeeding?No. Laser eye surgery is not recommended until 2 months after breastfeeding is complete. Increased hormonal activity during pregnancy and breastfeeding can affect visual outcomes and, while this is not dangerous, it increases your likelihood of being under- or over-corrected and therefore requiring an enhancement procedure. The medications used before, during and after laser eye surgery could also be transmitted to your unborn baby – this should be avoided.
Taking prescription drugs?Yes, probably. You should indicate which drugs you are taking (prescription or otherwise) during your initial screening. Occasionally, certain medications can prevent you from having laser eye surgery – however, this is rare.
Younger than 18?No. All laser eye surgery patients must be at least 18 years old before treatment.
Have amblyopia (lazy eye)?Yes. The aim of laser eye surgery is to achieve the same level of vision as you had with glasses before surgery. Having a lazy eye does not mean that you are unsuitable for laser eye surgery, and many patients with a lazy eye have had very successful overall outcomes – i.e. the surgery achieved the same level of vision as with glasses before surgery, but can also improve the peripheral vision. If you have ever been told that you have a lazy eye (also known as amblyopia) you should mention this at your initial screening, so that your options can be discussed in detail with your optometrist.
Have astigmatism?Yes. Laser eye surgery has been used to treat astigmatism since 1994.
Have a cataract?Yes. Whilst laser eye surgery does not ‘cure’ a cataract, a mild cataract (which is not significantly affecting the vision) should not prevent you from having laser eye surgery. Should the cataract worsen, you can still have successful cataract surgery after laser eye surgery (although you should be aware that cataract surgery after laser eye surgery is a specialist field, which may limit your choice of surgeon for your cataract procedure). In cases of cataracts that are already affecting the vision, you would usually be recommended to have cataract surgery (lens replacement), combined with a laser ‘top-up’ procedure to fully focus the vision if required.
Have a collagen vascular disease?Yes. You should indicate this when you are having an initial screening.
Have a compromised immune system?Perhaps. We assess this on a case-by-case basis and will provide you with an answer at your initial screening.
Have a connective tissue disorder (i.e. rheumatoid arthritis)?Perhaps. These conditions can be associated with altered healing responses by the body and therefore present a slightly higher risk of complications after laser treatment. However, if the connective tissue disorder is controlled, it is likely that you will be suitable. We assess this on a case-by-case basis and will provide you with an answer at your initial screening.
Have had a detached retina?Yes. However, it depends on the severity of your condition. Laser eye surgery does not treat a detached retina itself.
Have dry eyes?Probably. Your suitability for laser eye surgery will depend on the cause and severity of the dry eye, and it is likely that you would be recommended for SMILE rather than LASIK surgery (or occasionally for a surface procedure, if the dry eye is especially severe). To ensure optimum safety, serious dry eye conditions are sometimes monitored for several months (or even years) before surgery.
Have epilepsy?Yes.
Have glaucoma?Yes. Laser refractive surgery is not a treatment for glaucoma, but your surgeon will work in conjunction with your glaucoma specialist to ensure that your glaucoma management is not affected by your laser eye surgery.
Have hepatitis C?Yes. You should indicate this when you have your initial screening.
Have HIV?Yes. You should indicate this when you have your initial screening.
Have (or have ever had) herpes infection of the eye?Only if there has not been a reoccurrence of the infection for at least 12 months prior to having the procedure.
Have diabetes?Yes, if the diabetes is controlled and you don’t have any signs of active diabetic retinopathy. To be sure, you’ll need to be examined for this at your initial screening. Patients with uncontrolled diabetes are not suitable for laser eye surgery.
Have ever had iritis?Only if there has not been a reoccurrence of the condition for at least 12 months prior to having the procedure.
Have keloid scarring?Yes.
Have keratoconus?No. Keratoconus is a progressive disease that results in the thinning of the cornea. Therefore, removing corneal tissue with laser treatment is inadvisable as it will further destabilise the shape of the cornea. However, London Vision Clinic can successfully stabilise keratoconus – or protect patients from further progression – through a treatment called cross-linking. If you have ever been told that you may have keratoconus, please mention this as early as possible so that we can conduct the necessary investigations and direct you to the right treatment pathway.
Have large pupils?Yes. With our custom programmed treatments, we have successfully treated patients with very large pupils without inducing night vision disturbances.
Have macular degeneration?Yes. However, it should be noted that laser eye surgery does not treat macular degeneration itself. If your central vision is significantly reduced as a result of macular degeneration, laser eye surgery may provide little improvement to your uncorrected central vision (although it is likely to improve your uncorrected peripheral vision).
Have night vision disturbances?Yes.
Have nystagmus (involuntary eye movements)?Yes. Laser eye surgery will not treat the nystagmus, but can be safely performed with the use of sensitive eye tracking systems (which are now fitted to most modern lasers).
Have only one good eye?Yes. But have to consider the greater risk.
Have prism?Yes. However, you may still need prism glasses if you have double vision with contact lenses or without the prism in your spectacles.
Have strabismus (squint)?Yes. However, laser eye surgery techniques alone will not resolve a strabismus problem, unless the strabismus is a fully accommodative squint (this is seen in some longsighted people whose eye turns in without their glasses or contact lenses but is perfectly straight with glasses or contact lenses). In general, laser eye surgery is unlikely to be able to restore vision beyond that which is attainable with glasses or contact lenses.
Have systemic lupus erythematosus?Yes, if it is well controlled. Your surgeon will assess your suitability on a case-by-case basis.
Have thin corneas?Perhaps. If you have been turned down for laser surgery due to corneal thickness, it is worth having a complete preoperative assessment with us, including a VHF digital ultrasound examination with the Artemis, to rule out keratoconus. If you have thin corneas but do not have keratoconus, you will likely still be a candidate for laser eye surgery using SMILE or a surface procedure.

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