Risks and Complications of Laser Eye Surgery

Laser eye surgery was first performed in 1987, since then millions of people across the globe have undergone this impressive procedure. With constantly evolving technology and increasingly sophisticated techniques, the surgery is more popular now than ever. One of the most common misconceptions about laser eye surgery is that it is too risky. We’ve previously debunked other laser eye surgery myths such as “laser eye surgery is painful” or “it can only correct short sightedness”. In this article, Dr. Andrew Logan explores the potential risks and complications of the operation.

How does laser eye surgery work?

All laser eye surgery procedures (LASIK, SMILE^Ⓡ or PRK) work in the same manner. That is by reshaping- the clear part of the eye in front of the iris, also known as the cornea. This changes the eye’s focal point, focusing it neatly onto the back of the eye and giving a clear image.

Short sightedness is when the focal point sits inside the eye. For clear vision, the focal point needs to sit on the back of the eye. Short sighted eyes are therefore either too long or the cornea is too curved. Whereas long sightedness is caused by the eye being too short or the cornea too flat. In this scenario the focal point ends up behind the eye. Short sighted vision is corrected by flattening the cornea to reduce the refractive power. This has the effect of pushing the focal point back onto the retina at the back of the eye. For long sighted eyes, the cornea is steepened. This increases the refractive power and and moves the focal point back inside the eyeball.

Before you get to surgery, you have a comprehensive medical exam with the Wellington Eye Centre team. This examination checks the health and well-being of your eyes and the physical qualities of the cornea. During this examination you will meet one of our technicians, our Optometrist and our surgeon, Dr Andrew Logan. This appointment is to help us ensure that it would be safe for you to receive laser eye surgery.

On the day of surgery

You are with us for around one and a half hours. First, you will have a pre-operative talk with one of our team members. During this talk, you will go over the post-surgery instructions, medications and what to expect during and after the surgery. You will then have local anaesthetic drops applied to the surface of the eye. These ensure that the surface of the eye is numb. These anaesthetic drops still allow you to control the movement of your eye. You are then taken into our theatre for your surgery.  

Immediately after your surgery, Dr Logan checks your eyes, before sending you home to rest. The healing time for each surgery is slightly different. The expected recovery experiances will be discussed with you before your surgery. You will be provided with paracetamol to ease any discomfort following surgery. This discomfort is normally most pronounced for the first 8-12 hours after. It can feel like you have something in your eye, and/or a slight burning sensation for a few hours. This will quickly pass. You will be on a busy regime of eye drops while you are awake, often having a drop every 1-2 hours. Following your immediate recovery, you will have regular follow-up care (day one after surgery, one week, one month, three months, six months and one year) to ensure your recovery is going well.

Is laser eye surgery safe?

Studies carried out in the United States have shown that the most common reason that eligible people do not have laser eye surgery performed is not the cost, but fear of the procedure itself. The safest way to correct your vision is to wear glasses. Glasses provide eye protection from physical injuries and reduce UV light exposure. Glasses can easily be updated.

Contact lenses are another alternative to correct vision. However, although contacts do not use surgery to correct vision, they may not be as safe long-term. A study in 2006 found that the risk of significant vision loss following LASIK was 0.001% but contact lens wearers had a 1% risk of developing a serious contact lens associated corneal infection and 0.02% risk of significant vision loss over 30 years of contact lens wear⁽¹⁾. Since that time, both contact lens technology and laser eye surgery technology have improved enormously but the relative risks remain similar. 

To put things into perspective, in the United States the most common occupational group to have laser eye surgery performed is ophthalmologists. I, Dr Andrew Logan, had LASIK surgery performed on my eyes over 23 years ago using the much less sophisticated technology available then, and I would have the procedure performed again today without any hesitation.

What are the risks of laser eye surgery?

The vast majority of people who have had laser eye surgery have had excellent outcomes and no significant complications. However, laser eye surgery is like any other surgical procedure in the sense that it is not “risk-free”. With any surgery it is important, that you are aware of the risks. You need to be comfortable with the low (but not non-existent) level of risk. 

Postoperative corneal infection

Infection, whilst the most serious complication after laser eye surgery, it is very uncommon. If infection occurs, it can potentially cause severe corneal scarring which could require a corneal transplant to restore vision. However, the largest study on infection following LASIK surgery reported from Spain in 2010 and included over 200,000 individual eyes treated with LASIK⁽²⁾. Infection occurred in only 82 eyes across 63 patients, a risk of just over three per 10,000 procedures or 0.03%. Of these patients, 93% of the affected eyes maintained good vision after successful treatment of the infection. No patients required a corneal transplant. 

I, Andrew Logan, have seen just one patient who developed corneal infections in both eyes following LASIK surgery. Their LASIK procedure was not performed in Wellington. The patient was treated successfully in Wellington hospital. And they luckily retained perfect vision after the infection had resolved.

The risk of corneal infection following SMILE laser eye surgery seems to be lower than with LASIK. Very few cases have been reported. By mid-2019 over 2 million SMILE procedures had been performed worldwide. But I have only been able to find five reports of corneal infections in medical literature. Two patients were reported with bacterial infections affecting both eyes, and one patient developed a fungal infection in one eye. It is likely, that the risk of infection following SMILE is up to 10 times less than after LASIK surgery. This is due to the quick healing time of SMILE compared to LASIK, as it is a keyhole surgery.

Dry Eyes

Dry eyes are very common in the first few months after having laser eye surgery. This is because there is a temporary decrease in tear production, due to reduced corneal sensation which occurs as a result of the surgery. This is usually more of an issue after LASIK than after SMILE or PRK. For the first six months or so after your surgery, your eyes may feel unusually dry as they heal, but in almost all cases the problem will resolve after 6 to 12 months. 

Some people are more prone to getting dry eyes after laser eye surgery. This includes people with pre-existing dry eyes prior to having laser eye surgery, people with inflamed eyelid margins (blepharitis), post-menopausal women, and people with autoimmune diseases such as Sjogren’s syndrome, lupus and rheumatoid arthritis. 

Managing dry eyes usually involves the regular use of artificial tears. Taking an Omega 3 oil supplement, such as Krill oil, can be very helpful. Some people may need to have temporary plugs placed in their tear ducts to slow the drainage of tears from the surface of the eyes. Other treatment options include Low-Level Light Therapy, also known as LLLT.

Dry eyes can reduce the quality of your vision so it is important to manage it before and after surgery.

Glare and halos

Many people who have had laser eye surgery experience glare and halos at night, especially in the first few weeks after their surgery, but these days it is very uncommon for this to be a longer-term problem. Glare and halos are the terms we use to describe when street lights and headlights at night appear brighter and larger than usual or appear to have a ring around the light source. 

Persistent problems with night vision were more common in the 1990s, the early years of laser eye surgery. These issues were more common then because they used smaller treatment zones. And these night time vision issues were also more common for people with higher prescriptions. In recent years, our improved understanding of why these problems occurred has resulted in improved laser treatment patterns which have meant that night vision problems are much less common, even with larger corrections.

Undercorrection and overcorrection

Laser eye surgery, whether it is LASIK, SMILE or PRK, is not completely predictable. Every eye is slightly different, and some eyes over or under respond to a given amount of laser treatment. This means that you can end up slightly short sighted or long sighted after your laser vision correction surgery. This can occur even though the correct measurements were fed into the laser. This happens more frequently with bigger corrections and long sighted patients. 

In 2016, a literary review of 97 published articles was released. These articles covered the clinical outcomes of LASIK between 2008 and 2015. This review represented 67,893 eyes⁽³⁾. It was found that 98.6% of eyes were within ±1.0 dioptre of the target refraction. SMILE surgery has been shown to be slightly more predictable than LASIK. 

If an undercorrection or overcorrection has occurred, in most cases a retreatment can be performed. Retreatments have a good success rate of improving the vision. You need to wait at least 6 months after your first procedure, before having any retreatments.

Astigmatism

Astigmatism is the term used to describe distortion of the cornea. This type of distortion happens regularly in the general population, and is correctable with glasses, contact lenses and laser vision surgery. Eyes with astigmatism are often described as having a “rugby ball” shape (slightly more curved on one axis, slightly less curved on the other). Corneas with no astigmatism are “soccer ball” shaped (equally curved on all axes). In rare cases astigmatism can develop after laser surgery. 

This is a similar outcome to being under or overcorrected, an irregular astigmatism may also result in double vision. Residual astigmatism may require a retreatment surgery, glasses or contact lenses.

Flap problems

FemtoLASIK surgery involves creating a thin flap of corneal tissue using a femtosecond laser. This flap is then lifted out of the way and an excimer laser is used to reshape the tissue under the flap. The reshaping of this tissue is what corrects the vision. The flap is then returned to its original location. The corneal flap heals slowly, meaning it can be displaced in the first few weeks after surgery. This is most likely to happen if the eye is rubbed. 

If the flap shifts, the eye will usually become very uncomfortable and the vision will become markedly worse. When attended to promptly, the flap can be repositioned with a full recovery of vision. If a displaced or wrinkled flap is not treated promptly, it can become very difficult to get it back into the correct position. 

It is important to avoid rubbing the eye or exposing it to trauma after having LASIK surgery. This is especially true in the first few months after surgery. In the past flap wrinkling and displacement was more common. That was when LASIK flaps were cut using a mechanical cutter called a microkeratome, rather than the more modern technique of using lasers to create the flaps.

Epithelial Ingrowth

Occasionally, skin cells from the surface of the eye can grow underneath the flap – a condition called epithelial ingrowth. This is relatively uncommon after a first LASIK procedure but occurs more commonly after retreatments. In many cases, these skin cells that have grown under the flap will resolve, with no issues. If the area of skin cells under the flap is large or increasing in size, or if the cells are affecting vision, comfort or the health of the surface of the eye, removal is recommended. Removal can involve lifting the LASIK flap.

Vision loss or changes

Rarely, you may experience a loss in quality of vision due to surgical complications. Some people may not see as sharply or as clearly as they did with glasses or contacts prior to having laser eye surgery. This can occur if the reshaping of the cornea to correct vision, or the healing of the corneal surface, has resulted in a complication. If this occurs, it may be possible to improve vision with further laser surgery, or it may be necessary to wear glasses or contacts to achieve satisfactory vision.

Ectasia

Ectasia is a condition in which the cornea develops progressive bulging and distortion, and results in deterioration in vision. This condition is a serious complication of laser eye surgery, but it is rare.

Laser eye surgery involves removing small amounts of corneal tissue to reshape the cornea, and this causes a slight weakening of the cornea. Most corneas are strong enough to not be adversely affected by this reduction in thickness. But some corneas have an underlying weakness, predisposing them to develop ectasia. These “weaker” corneas can usually be detected by testing carried out during the laser assessment. If a cornea is found to be too weak, laser eye surgery is avoided. 

If ectasia develops after laser eye surgery, a procedure called corneal collagen cross linking will usually be carried out. Cross linking strengthens the cornea and will stop further distortion of the cornea. Vision may still be poor and it may be necessary to wear glasses or contacts to get good vision.

How can you avoid complications from laser eye surgery?

To reduce the risk of complications we recommend:

• Having a comprehensive examination with an experienced laser eye surgeon. This is your best chance at ensuring your suitability for surgery. This should include looking at the thickness and shape of your cornea as well as your overall eye health. Our surgeon Dr Andrew Logan has been performing laser eye surgery for over 20 years.
• Follow all post procedure instructions – this will include actions to reduce the chance of infection, flap displacement and dry eyes.
• Drops! Make sure you use all eye drops as directed.

At the Wellington Eye Centre, we understand that the list of complications can be quite daunting. However, the vast majority of people having laser eye surgery obtain excellent postoperative vision without significant complications. The overall safety and effectiveness of laser eye surgery has improved enormously in the past thirty years. Our team takes every possible precaution to keep your eyes safe. Going the extra mile to ensure you are well-informed.

Feel free to get in touch with the team at Wellington Eye Centre if you have any other questions or wish to book a consultation with Dr Logan. You can call us on 0800 733 327 or complete the contact form below.

SMILE® is a registered trademark of Carl Zeiss Meditec.

References

1. Risk of LASIK surgery vs contact lenses. Mathers, W.D, Fraunfelder, F.W and Rich, L.F. Archives of Ophthalmology, 2006, Vol. 124(10), pp. 1510-1511.

2. Infectious keratitis in 266,191 laser in situ keratomileusis. Llovet-Osuna, F., et al. Archives of the Spanish Society of Ophthalmology, 2010, Vol. 85(11), pp. 355-359.

3. Modern laser in situ keratomileusis outcomes. Sandoval, HP., et al. Journal of Cataract & Refractive Surgery, 2016, Vol. 42(8), pp. 1224-1234.