Risks of Laser Eye Surgery
What are the risks of laser eye surgery?
Risk is present in every surgical technique, no matter how small, and it would be foolish to pretend otherwise. There is indeed a very small risk that laser eye surgery may compromise the vision so that neither glasses nor contact lenses are able to sharpen vision back to a pre-surgery state. Regardless of where you go to have laser eye surgery, it is important to:
- Choose an expert surgeon who can minimise the risks, and has the experience to handle any foreseen or unforeseen complications or side effects during or after surgery
- Appreciate that all surgery has an element of risk
- Understand how clinics and surgeons manage risk
- Assess the possibilities of complications
- Put long term outcomes into context
- Learn about the risks and their relative chances of occurring
Should you then consider laser eye surgery to be as straightforward as a visit the dentist? We think not. In expert hands, laser eye surgery is a safe experience that enhances the patient’s life. However, clinics and the standards they employ differ greatly and it is certainly wise to choose your practitioner carefully.
All surgery has an element of risk
Although the vast majority of our patients experience a significant improvement in their vision, neither your laser eye surgeon, your optometrist, London Vision Clinic nor its staff, can guarantee that the procedure will be 100% effective or free from complications.
During your pre-operative examination, we will communicate your likely outcome (e.g. the chances of you seeing well without glasses or contact lenses after surgery) to you based on the level of your particular refractive error.
Laser eye surgery safety
The key to managing risk lies in the rigorous application of safety protocols. Those in place at London Vision Clinic are the direct results of Professor Reinstein’s earlier work in the USA, training and controlling the quality of 58 surgeons in 28 clinics, all operating under standardised protocols defined by his research.
It was by studying the work of these 58 surgeons that he was able to determine exactly what allowed some surgeons to perform better than others did did. Both he and Mr. Carp now apply that knowledge to their own practice at London Vision Clinic.
The possibility of complications
There is a very small possibility that the procedure or a complication arising from the procedure could cause your vision to be blurred, doubled, distorted, or to have halos or other disturbances, and that these would NOT be correctable with glasses or contact lenses.
London Vision Clinic enjoys an exceedingly low complication rate. In the event that a complication should occur, your laser eye surgeon will discuss and offer you advice on further treatment, which may involve medications or more surgery.
In the remote chance, that a surgeon cannot correct the outcome by medications or an enhancement, the only way of restoring the vision may be a corneal transplant.
How London Vision Clinic keeps it’s complication rates so low
At London Vision Clinic, we pride ourselves in knowing that we have never discharged a patient from our care with unresolved issues. This is because Professor Reinstein’s protocols ensure that both he and Mr. Carp deal with any possible complications in the most prompt and expert fashion.
In addition, we continue to offer aftercare to our patients for life. This ensures that if any questions ever arise in the future, we will not abandon you to find appropriate expert help on your own. Once you have had surgery at London Vision Clinic, we consider you our patient for life, even if you should require specialised ophthalmic care that unrelated to your laser eye surgery, we could refer you to the appropriate specialist.
Long term outcomes of laser eye surgery
It is necessary to mention that there are no published very long-term outcomes of laser eye surgery. However, corneal flaps have been created in the cornea for approximately over 50 years (in procedures such as keratomileusis as described and performed by Barraquer since the 1950’s), the excimer laser has been used for almost 20 years in the cornea and there have been approximately 17 million procedures performed to date worldwide.
Professor Reinstein was one of the key contributors to the National Institute of Health and Clinical Excellence (NICE) Guidance Document on LASIK (2006), which determined that the “current evidence suggests that photorefractive (laser) surgery for the correction of refractive errors is safe and efficacious for use in appropriately selected patients.” Furthermore, the Guidance Document did not mention any serious concerns about the long-term safety of the procedure if performed with the latest technology and techniques.
Laser eye surgery risks
Like any surgical procedure, laser eye surgery (LASIK and PRK / LASEK) involve risks of unsuccessful results, complications, or serious injury, from unknown and unforeseen causes.
Laser eye surgery risks described
Although it is not possible to list every potential risk or complication that may result from the procedure, we describe the most relevant risks below. At first glance, it becomes apparent that there are many possible risks to surgery. This is why it is so important that you ensure that you are choosing a highly trained, competent surgeon to avoid them from happening. In addition, in the unlikely event of a complication occurring, your having chosen the care of the best possible surgeon using the latest technology ensures that any possible issues are dealt with promptly and expertly to maximise your final outcome.
Complications that can occur during surgery
|Condition||Probability of Occurrence||Solution|
|Under-correction or over-correction||More common with higher prescriptions||Mitigated by planned 2-stage treatments; correctable with an enhancement|
|Corneal flap complications||Rare in expert hands (1 in 1000)||Mitigated by expert use of equipment; correctable with an enhancement|
|Debris under the corneal flap||Rare in expert hands and will likely not affect visual result||Mitigated by stringent adherence to superior safety protocols; correctable with an enhancement|
|Diffuse Lamellar Keratitis, or “Sands of the Sahara”||Rare in expert hands (1 in 500)||Mitigated by stringent adherence to superior safety protocols; correctable with an enhancement|
|Equipment malfunction||Extremely rare in expert hands||Mitigated by stringent adherence to superior safety protocols; correctable with an enhancement|
|Vascular occlusion||1 in 1 million|
Risks and complications that can develop after surgery
|Condition||Probability of Occurrence||Solution|
|Dry Eyes||Common, but generally temporary||Can be mitigated with dry eye testing prior in assessment; managed with lubricating drops|
|Regression||More common in higher prescriptions||Correctable with an enhancement|
|Night vision – glare, starbursts and halos||Extremely rare, mostly temporary||Can be avoided through the use of newer lasers and high resolution wavefront aberrometers; correctable with an enhancement|
|Light sensitivity, fluctuating vision||Very rare, mostly temporary||Will decrease in time|
|Infection||Very, very rare (1 in 5,000), extremely low chance of affecting visual result||Can be avoided through stringent safety protocols; can be managed with antibiotics|
|Excessive corneal haze||Part of the healing process in surface procedures ( PRK / LASEK); higher risk in higher prescriptions||Dependent on smoothness of the surface created by the laser; will often disappear; correctable with an enhancement|
|Fragility on impact||Part of healing process 3 months after LASIK||Can be mitigated by following aftercare instructions|
|Corneal ectasia||Extremely rare||Can be mitigated by screening for keratoconus or unusually thin corneas using Artemis|
|Epithelial erosion||Rare (1 in 500), more in older patients||Can be identified prior to surgery; can be managed by a bandaged contact lens|
|Epithelial ingrowth||Rare (1 in 100)||Can be corrected with an enhancement|
|Other extremely rare complications||Extremely rare (1 in 50,000)||Dependent on complication|
Under-correction or over-correction
Although often classed as a ‘complication’, under- or over-correction of the prescription strictly speaking is not a complication. A complication is results in the blurring or doubling of vision that is not correctable with glasses.
In under- or over-correction, the vision may be blurred or double, but glasses can correct the vision to the level of sharpness that was present before surgery with glasses. Despite all precautions and the highest standard of care, the healing response of the eye can lead to slight inaccuracies in the final correction.
Your laser eye surgeon would be able to advise you before your initial surgery of the likelihood that you would not have sufficient remaining corneal tissue for enhancements.
The chances of under- or overcorrection increase for older lasers and lasers with less strict maintenance schedules. Furthermore, clinics that do not employ a digital statistical system for fine-tuning the treatment parameters may risk having more complications.
Corneal flap complications
The corneal flap may be too thin, too thick, uneven, and too short, may wrinkle, become displaced or may not heal properly. This condition could be temporary, requiring the surgeon to postpone LASIK be until they can create a new corneal flap.
Quoted corneal flap complication rates in the medical literature range from 0.3% to 1.0%. In contrast, London Vision Clinic’s corneal flap complication rate is closer to 0.1%.
Debris under the corneal flap
There can sometimes be a small amount of debris or tissue under the corneal flap after the surgeon has completed the LASIK procedure. Debris can result from the instruments used or consist of tear-film oil or floating material.
Your laser eye surgeon may decide in the immediate post-operative period to irrigate beneath the corneal flap to remove this debris. Small amounts of debris can generally be left in place and monitored without surgical intervention. In almost all cases, debris under the corneal flap does not affect the patient’s visual result.
Diffuse Lamellar Keratitis or “Sands of the Sahara”
One in 500 patients experience a temporary inflammatory reaction beneath the corneal flap. This condition has been called “Sands of the Sahara” or Sporadic Diffuse Lamellar Keratitis (also known as “Sporadic DLK”).
Patients with DLK may not show any symptoms at all or may experience blurred vision and tearing, which can last from several days, up to several weeks, which can delay the healing process.
Surgeons manage DLK by the use of supplemental topical steroid eye drops. Usually with aggressive management, there are no longer-term effects of DLK. However, significant levels of DLK may reduce the accuracy of the vision correction, so the likelihood of requiring an enhancement is increased.
All equipment in laser eye surgery should be maintained according to manufacturer specifications. However, despite this regular maintenance, the microkeratome or the excimer laser could malfunction, requiring the surgeon to stop the procedure before completion. In some instances, this could result in a rescheduling of the procedure, or damage to the vision. Clearly, the modernity, maintenance, and quality of the equipment influence the likelihood of equipment malfunction.
When the suction ring is applied to the eye during the corneal flap-making process, the pressure in the eye increases significantly and many patients will notice that the light will dim or go out completely in the eye. When the suction ring is removed, the vision is restored to the eye within a few seconds.
There is an extremely remote risk that when the suction ring interrupts the blood supply to the eye, permanent damage to the retina (the film of the eye camera) or blood vessels in the retina can take place, with loss of vision. This possible occurrence has a theoretical probability of less than 1 in 1,000,000.
Dry eye is a common, but generally temporary, complication arising from LASIK or LASEK / PRK. This condition can usually be treated with lubricating eye drops and occasionally with temporary inserts or “plugs” that prevent the normal drainage of tears into the nose. Dry eye generally improves within a few months after surgery, but in rare instances can continue for longer periods of time, and may require long-term use of lubricant drops and permanent plugs. Patients who have dry eyes before LASIK or LASEK / PRK are likely to experience dry eyes after the procedure.
Regression is the loss of some of the vision correction effect originally achieved. The cornea is living tissue. Once the laser removes tissue from the cornea during the procedure, the surface epithelium (“skin”) can thicken to compensate for the change in shape that has occurred. This happens to a variable degree among treated patients, accounting for the reason why some patients have a stable immediate result (minimal epithelial thickening) and others regress (more significant epithelial thickening).
Regression is more likely to occur in patients with higher prescriptions. In the majority of cases, the patient can have another treatment to improve their vision.
The ability to perform further surgery will depend on safety parameters set by Professor Reinstein and Mr. Carp.
Glare, starbursts and halos
Some patients do not see as clearly at night or in dim light and may notice an optical effect called a “halo” or a “starburst” around lights and illuminated objects after the procedure. We can help patients who notice these effects with glasses to drive at night.
These effects are temporary, typically lasting between two weeks and three months. Increases in night glare and halo could be permanent; however, this is mainly a feature of treatments performed with older lasers that do not have the most sophisticated software (known as aspheric profiles).
These effects are more likely to occur in patients with high levels of shortsightedness or longsightedness and for patients with larger-than-average pupil size.
One of Professor Reinstein’s main research focuses over the last 8 years has been the correction (and prevention) of night vision disturbances. Professor Reinstein has developed protocols for correcting and preventing halo and starburst effects even when treating very high prescriptions and patients with large pupils.
Zeiss incorporates many of Professor Reinstein’s findings in the commercially available Carl Zeiss Meditec MEL80 excimer laser system, in use at the clinic today. It is therefore extremely rare for patients in our practice to end up with night vision disturbances. We believe that we have the most sophisticated systems in place for preventing or treating night vision disturbances.
Light sensitivity, fluctuating vision
Patients may experience increased sensitivity to light or find that their visual acuity fluctuates after the procedure. These conditions are generally temporary and usually resolve within the first few weeks to months after the procedure. It is very rare for these to persist longer.
Infections in corneal laser eye surgery are very, very rare. Reported series quote rates of approximately 1 in 5,000, but these of course can be higher, depending on the technique and conditions of practice of individual surgeons.
In the rare event that they do occur, if spotted early, we can manage most infections by administering antibiotics with full resolution and with an extremely low chance of affecting the outcome.
Preventative measures as well as protocols for the detection of these rare infections after surgery are the key. Neither Professor Reinstein nor Mr. Carp have, to date, had a patient suffer from a compromised outcome due to infection.
Excessive corneal haze
Corneal haze is part of the normal healing process in the corneal surface procedures (PRK/LASEK), and gradually subsides with little or no permanent effect on vision.
However, if the haze is excessive or does not go away, the patient may need additional treatment either with medications to reduce the haze or further laser surgery to physically remove the haze or both. Haze is extremely unusual in LASIK.
The risk of haze in PRK/LASEK increases the higher the prescription to be treated, but is also dependent on the smoothness of the surface created by the laser as well as the protocols for postoperative management of the cornea.
Fragility on impact
For about three (3) months after LASIK, surgeons consider the corneal flap somewhat susceptible to direct trauma. After the first month, the level of direct trauma that would be required to displace the corneal flap would be somewhat severe.
When participating in sports or other activities involving possible contact with the eye during this period, you should wear protective eyewear.
It’s important to leave a certain amount of corneal tissue under the flap after the procedure; this relates to the long-term stability of the cornea. In very rare cases, less tissue remains than intended. This can produce a situation where there is forward bulging of the cornea (reversing the intended flattening effect), or it can lead to progressive deformity of the cornea, with thinning and increasing curvature changes. This progressive deformation is called ectasia. It can be treated with corneal collagen cross-linking (CXL), by suturing (stitching) the flap to the underlying cornea, or in rare circumstances with a corneal transplant.
The probability of progressive ectasia, given our protocols and technology is estimated to be 1 in 20,000.
The epithelium is the surface layer of cells that protects the cornea as the “skin” over the stromal layer of the cornea. If a surgeon cuts or removes the epithelium, it generally grows back.
In LASIK, the surgeon creates a corneal flap, consisting of epithelium and stroma, and holds the corneal flap back while performing the laser treatment. In some people, there is less attachment between the epithelium and the underlying stroma; such eyes are at increased risk for epithelial scratches or epithelial sliding, especially as the corneal flap-maker (microkeratome) passes over the corneal surface to create the corneal flap.
In some cases, we can identify eyes at risk and advise about the increased risks associated with surgery. There are, however, rare patients where there are no pre-operative clues; the likelihood of having a scratch during LASIK with no preoperative warning signs is approximately 1 in 500. In addition, older patients are more likely to have areas of weakened surface epithelium during corneal flap creation.
In such instances, the surgeon places a bandage contact lens over the cornea after LASIK to assist in healing and to reduce discomfort. Patients who experience an epithelial slide, abrasion or erosion may experience a longer recovery period and may be at risk for complications including infection, inflammation, recurrent erosions, corneal flap wrinkles or epithelial ingrowth.
In the event of a severe epithelial scratch, your laser eye surgeon will still typically be able to lift the corneal flap and perform laser treatment. However, he may recommend delaying the LASIK procedure on the second eye until the vision has improved in the first eye. This would be the case for the 1 in 500 patients at risk for significant scratches.
Your laser eye surgeon may recommend against LASIK in the second eye if he considers you predisposed to epithelial scratches. In such cases, LASEK / PRK would be a viable alternative to glasses or contact lenses.
Epithelial ingrowth is a condition in which epithelial cells from the surface of the cornea grow under the edge of the corneal flap. The vast majority of these cells regress on their own.
However, if the cells continue to grow, they can affect the underlying tissue causing astigmatism, corneal flap edge thinning and reduction of vision. A surgeon will generally treat this condition with medication and observation, although further surgery to remove the epithelial cells from the interface may be necessary. This occurs in less than 1% of cases.
Other extremely rare complications
Intraocular haemorrhage, permanent corneal swelling, retinal detachment, venous or arterial blockage, drug reaction, and others have been either documented or theoretically proposed as risks of laser eye surgery. We estimate the probability of one of these contributing to significant visual damage, for expert practices, to be in the range of one in 50,000. From all available information, we estimate the risk of partial or total blindness due to laser eye surgery in expert practice to now be range of about 1 in 4 million (about the same probability of dying on a commercial airliner).
Of course, the very best way to discuss your specific questions about risk and find out if you are a good candidate for a procedure is with a complimentary initial screening.
- Reinstein DZ, Srivannaboon S, Archer TJ, Silverman RH, Sutton HF, Coleman DJ. Probability Model of the Inaccuracy of Residual Stromal Thickness Prediction to Reduce the Risk of Ectasia after LASIK Part II: Quantifying Population Risk. J Refract Surg 2006;(In Press).
- Reinstein DZ, Rothman RC, Couch D, Archer TJ. Artemis VHF digital ultrasound guided repositioning of a Free cap following Laser in Situ Keratomileusis. J Cataract Refract Surg 2006;(In Press).