Overview of Laser In Situ Keratomileusis (LASIK)
LASIK, or Laser-Assisted in Situ Keratomileusis, is a common eye surgery used to fix vision problems. It was first patented by Dr. Gholam Peyman in 1989 and started being used on patients by Dr. Ioannis Pallikaris in the early 1990s. The operation quickly became popular because it had fewer complications, worked well, and had a quicker recovery time. It’s now one of the most researched and inspected surgical procedures for FDA approval. With improvements over the last 30 years, LASIK continues to work well and safely, with most patients happy with the results compared to wearing glasses or contact lenses.
Lasik was a big advance in how to correct vision problems. To understand its impact, we need to look at its history. Before LASIK, in the 1930s, radial keratotomy was the main method to correct vision issues. This was created by Dr. Tsutomu Sato in Japan. This procedure involved making cuts deep into a layer of the eye known as Descemet’s membrane, which flattened the cornea (the clear front part of the eye) and corrected nearsightedness. But there were a lot of complications that came from making these deep cuts. Doctors then tried to find other methods like the hexagonal keratectomy by Dr. Antonio Méndez in Mexico, though it was still hard to correct patients with astigmatism or those with an asymmetrical shape of the cornea.
In the 1950s and ’60s, Spanish eye doctor José Barraquer brought about a new idea: reshaping the cornea, called keratomileusis. He used a tool called a microkeratome, which cut away the top layer of the cornea to expose the layer under it, made another cut, and then sutured the top layer back into place. This was known as anterior lamellar keratoplasty (ALK). But his microkeratome wasn’t perfect and led to treatments that weren’t exact. The microkeratome was improved in the 1980s by Barraquer’s student, Dr. Luis Ruiz.
In the 1970s and early ’80s, Dr. Stephen Trokel and Dr. Rangaswamy Srinivasan discovered the excimer laser which made a major contribution to the development of a procedure called photorefractive keratectomy (PRK), first performed in the late 1980s by Dr. Marguerite McDonald. This technique uses a special type of laser to reshape the superficial layers of the cornea, allowing for a much more precise correction of vision issues.
LASIK is a mix of ALK and PRK, and it was first used in the early 1990s. Improvements were made to the lenticule flap (the part of the cornea that is cut and lifted during the procedure) so that it could be put back without needing stitches. In the 1990s, the femtosecond laser – developed by Dr. Imola Ratkay-Traub, Dr. Tibor Juhasz, and Dr. Ron Kurtz – allowed doctors to create a corneal flap without a mechanical blade.
Anatomy and Physiology of Laser In Situ Keratomileusis (LASIK)
The cornea, which is the front surface of the eye, contributes significantly to the eye’s ability to focus, accounting for about two-thirds of its ability. LASIK eye surgery is used to modify the focusing power of the cornea to improve vision in people who are nearsighted, farsighted, or have astigmatism.
The cornea is a thin tissue layer on the front of the eye, half a millimeter thick. It is composed of five layers, starting from the front and going deep into the eye: a layer of squamous epithelium, Bowman’s membrane (the front basement membrane), a stroma layer filled with keratocytes and collagen fibers, Descemet’s membrane (the back basement membrane), and a single layer of endothelium (cells that line the inner part of the cornea) which separates the cornea from the front chamber of the eye.
LASIK surgery modifies the focusing power of the cornea by initially creating a small flap from the front layers of the cornea. This process exposes the more back layers for treatment. In nearsighted people, the curvature of the center of the cornea is reduced, resulting in a decrease in the eye’s overall focusing power to reach normal vision. In farsighted individuals, the non-central area is flattened through the procedure, making the central cornea steeper, thus increasing the focusing power of the eye. After the precise laser treatment, the flap is laid back down where new cells will grow on the flap edge. The process does not require any stitching.
Why do People Need Laser In Situ Keratomileusis (LASIK)
LASIK (Laser-Assisted In Situ Keratomileusis) surgery is a procedure that uses a laser to correct vision problems, like shortsightedness (myopia), long-sightedness (hyperopia), and astigmatism (which makes objects appear blurry). It’s been found that LASIK can improve shortsightedness in people with a wide range of vision impairment. However, it’s mainly used for patients with mild to moderate short-sightedness as these patients have the best chance of achieving perfect or near-perfect vision (emmetropia).
LASIK surgery has also proved to be safe and effective in patients with hyperopia and astigmatism. Although LASIK can successfully treat long-sightedness up until a certain point, it’s recommended for such patients whose vision impairment is only up to a certain limit. Similarly, it can only effectively treat a certain range of astigmatism.
An eye surgeon will choose LASIK or another treatment based on a number of factors. These include the type of vision problem, how severe it is, the patient’s age, the thickness of the cornea (the clear, outer surface of your eye), changes in the crystalline lens (which helps focus light onto your retina), the shape of the cornea, and mapping of the cornea’s surface.
At present, LASIK is the most popular laser treatment to correct vision. Not only can it treat a variety of vision problems, but people who undergo LASIK also experience less pain compared to other procedures. The recovery to normal eyesight usually takes just a few days. But it’s important to discuss and understand what you can realistically expect from LASIK with your doctor. Keep in mind that LASIK procedures are not cheap and they are typically not covered by insurance because they are considered cosmetic, rather than medically necessary. This is because the procedure normally uses two types of lasers, which can cost between $1,500 to $2,500 per eye.
Furthermore, it’s also important to know that LASIK doesn’t correct presbyopia (an age-related condition where your eyes gradually lose the ability to see things clearly close up). Therefore, even after LASIK, some people may still need reading glasses. Also, as you age, you may still develop a cataract or a shift in vision towards short-sightedness.
When a Person Should Avoid Laser In Situ Keratomileusis (LASIK)
There are certain conditions that might stop someone from getting LASIK eye surgery, either permanently or until they’re resolved:
Firstly, your eyesight needs to be stable. If your eyeglass prescription has changed a lot (more than 0.5 D) in the past year, surgery could be risky. The procedure can’t be reversed, so if your eyesight is changing rapidly, complications like corneal ectasia might occur after the operation. This instability can occur for a number of reasons, like if you are pregnant, breastfeeding, or have uncontrolled diabetes.
Secondly, your corneas (the front part of your eyes) need to be thick enough. Normally, these are around 540-550 microns thick. If they’re less than 500 microns thick before surgery, or if they end up less than 250 microns thick after surgery, the risk of developing keratectasia (the warping or distortion of the cornea) is increased by 5%.
Thirdly, keratoconus, which is a condition where the cornea shapes into a cone, stops you from having LASIK as it increases the chance of corneal ectasia. Even a ‘hidden’ form of keratoconus that doesn’t show up on tests needs to be considered.
Fourthly, diseases like lupus, Sjögren syndrome, rheumatoid arthritis, Graves’ disease, Crohn’s disease, and others can cause dry eyes or other eye problems. If these are uncontrolled, it can be dangerous to proceed with LASIK surgery.
Lastly, any active eye infections, such as bacterial blepharitis and keratitis, need to be treated before considering LASIK surgery. If not, they can increase the risk of spreading infection and inflammation into the eyes.
Some other factors might affect the decision to get LASIK, but don’t completely stop you:
Your age is taken into account. While children generally don’t get LASIK because their vision is still developing, it has been done successfully in some cases of severe eye problems.
Herpes in the eye should be treated before LASIK. If you’ve had it before, it’s best to wait a year for it to be dormant before having surgery.
Mild cataracts (clouding of the eye lenses) don’t stop you from having LASIK, but when they advance later on, they might impair your vision again.
People with glaucoma (a condition causing high eye pressure) can still have LASIK but have to accept the risks of pressure inaccuracies after surgery and possibility of optic nerve damage during the procedure.
Corneal dystrophy (genetically inherited eye disorders that cause a buildup of material on the cornea) can be accelerated by surgeries like LASIK, but it’s been done successfully in some cases.
If you’ve a history of developing keloids (scars that grow outside the boundaries of the original wound), it could affect surgical results. But many patients with keloids also have reported good surgery results.
Having larger than average pupil size used to be a risk factor for post-surgery complications, like seeing haloes or star-bursting with light and experiencing glare. Although, this risk has reduced with the use of new laser technology.
Equipment used for Laser In Situ Keratomileusis (LASIK)
The Excimer Laser is a tool approved by the US Food and Drug Administration (US FDA) for certain eye surgeries. It’s essentially a kind of laser that has specific features that doctors can choose from to match each patient’s needs. These features include the size of the laser beam, its speed, and certain advantages like eye-tracking, which helps the laser follow the motion of the eye.
A common technique used today is called custom-LASIK. This procedure uses either topography-guided or wavefront-guided approaches. In simpler terms, the topography-guided approach uses measurements of the eye’s surface to program the laser. On the other hand, the wavefront-guided approach uses the way light is deflected off the cornea to adjust the laser accordingly. Customised lasers like these can be used along with spot or slit-scanning lasers to shape the cornea with great accuracy, which often leads to lesser issues after the surgery.
The Femtosecond Laser is another tool used in LASIK surgeries, typically to create the flap, which is the thin layer of tissue that doctors cut and fold back to reshape the cornea beneath. This laser is preferred over traditional, mechanical techniques because it can create a thinner, more precise flap. This can lead to better results and less chance of complications related to the flap after surgery.
Preparing for Laser In Situ Keratomileusis (LASIK)
Before a visit for eye checks, it’s generally wise to stop wearing contact lenses about one to two weeks beforehand. This helps your eyes regain their normal surface and gives the doctor a more precise view. A doctor also needs to get some background information and do a physical exam before recommending a specific eye surgery called LASIK. This eye check involves testing how well you see, making sure all eye parts are healthy and working properly, checking for dry eyes, and measuring eye pressure.
A doctor will also evaluate the front surface of your eye (the cornea), using tools called keratometry and pachymetry. People with corneas of a normal thickness, around 550 microns, are usually good candidates for LASIK. There are also two other tests called topography and tomography that help screen for eye conditions that might affect your suitability for surgery, such as keratoconus.
To get a better idea if you’re a good candidate for LASIK, a doctor might use something called the Randleman criteria. This helps identify patients who might be at higher risk for an eye abnormality that can appear after surgery called corneal ectasia. The criteria use information from all the eye tests, and factors like your age and eye prescription. A score of 4 or more indicates a higher risk for developing this condition after LASIK.
Once the doctor determines you’re a suitable candidate for LASIK, they use a formula called the Munnerlyn formula to plan the surgery. This includes calculating how much eye tissue to remove, the size of the area to be treated, and the power of your eye prescription change. Measuring the proportion of tissue altered (PTA), which considers corneal thickness and the depth and thickness of the cut, is also useful in estimating the risk of corneal ectasia after LASIK. It has been found that a PTA of 40% or more is linked with the development of corneal ectasia.
How is Laser In Situ Keratomileusis (LASIK) performed
Before The Surgery
Safety checks are done on all the equipment to ensure they are in good condition. The important data is transferred into a type of laser, called an excimer laser, a tool which plays a key part in the surgery. You will also be given details about what will happen during the procedure and asked to sign a document to show that you understand what will happen, and that you agree to the surgery.
How The Surgery Works
In general, LASIK (laser-assisted in situ keratomileusis) eye surgery is done like this: You’ll lay on a table and get comfortable. One of your eyes will be covered, while the other is kept open with a tool called a speculum. To numb any pain, you’ll get eye drops. Then a suction ring is put on the outer part of your eye, the cornea. A part of the cornea is marked for a flap to be made, using a tool or a certain kind of laser known as a femtosecond laser that uses light and energy to make microscopic changes to your tissues. The flap that is created has a specific size and position, like a small custom door on your eye.
After this flap is made, the surgeon will carefully open it up to get to the stroma, the layer beneath it. The excimer laser is used to reshape the stroma so that light entering your eye can be properly focused. This is what will fix your vision. Once this step is done, the little flap is put back where it was. You can get LASIK on both eyes on the same day, if needed.
After The Surgery
It is common for your eyes to feel dry after the surgery. To help with this, you will be asked to use preservative-free artificial tears. You may need to use them often, but if your eyes still feel dry after this, you might need additional treatment like punctal plugs, a small device inserted into your tear duct to block it from draining tears. You will also be given antibiotic and steroid eye drops to use for 5 to 14 days after the surgery. You will have follow-up appointments with your surgeon as needed, and may need to have minor touch-ups to your eyes if they are needed to perfect your vision.
Other Options
There are other laser-assisted eye surgeries that you might consider, besides LASIK:
PRK
Some studies have shown that while LASIK might fix your vision faster, PRK (photorefractive keratectomy) might give you better long-term results. Some studies have shown better outcomes with PRK in patients with specific vision problems, like nearsightedness, with fewer complications compared to LASIK. Your doctor will help you figure out what’s best for you. While PRK was traditionally more painful than LASIK, new techniques and pain management methods have made recovery smoother and less painful.
Femtosecond Lenticule Extraction (FLEx) or Small Incision Lenticule Extraction (SMILE)
In these procedures, the femtosecond laser is used to remove a thin layer of your cornea without creating a flap. It can be a good option for people with severe nearsightedness. Studies have shown that these procedures have similar results to LASIK, but fewer people reported dry eyes afterwards.
Laser Epithelial Keratomileusis (LASEK)
In the LASEK method, an alcohol solution is used to assist in the removal of the superficial corneal layer. Epi-LASEK is a similar procedure where a special knife is used to remove the layer. Both of these are types of PRK and can be considered as an alternative if you’re not a good candidate for other procedures.
Possible Complications of Laser In Situ Keratomileusis (LASIK)
One of the temporary side effects after LASIK eye surgery is dry eyes due to less tear production. This happens because some nerves are cut during the surgery, affecting the eyes’ natural way of making tears. Studies show that dry eyes occur in 85% to 98% of people one week after the surgery. However, this reduces to about 60% after one month. To help with the dryness, artificial tears or small medical devices called punctal plugs are used until the nerves recover.
Some people, about 20%, report changes to their vision after surgery. These changes can include glare, seeing halo or star-shaped patterns around lights, hazy vision, and decreased ability to see contrasts. The FDA says that these visual disturbances typically stabilize three to six months post-surgery.
Some patients might feel like there’s something in their eye or their vision is blurry due to a condition known as diffuse lamellar keratitis, also referred to as “sands of Sahara” syndrome. This is a non-infectious inflammation condition where inflammatory cells accumulate under the flap of the cornea. This scenario may occur in about one of 50 cases of LASIK, typically appearing one to two days after surgery but getting resolved within a week with appropriate treatment.
There are a few complications related to the flap of the cornea used in the surgery, such as wrinkling, incomplete formation, or dislodging of the flap. But they’re rare, with 0.1-4% of patients experiencing some form of complication. Some of these complications could lead to loss of sharpness in vision.
If the cornea is thin before surgery, there’s a risk of developing ectasia or further thinning of the cornea. This is a rare occurrence and ranges from 0.04% to 0.6% of cases. A type of LASIK surgery that uses a laser to create a thinner flap can help prevent this problem. Specific criteria are used to screen for patients who are at high risk of developing ectasia before the surgery.
Less than 0.1% of patients might develop an infection after LASIK surgery. The primary sources of infection are certain types of bacteria, especially if the infection starts one to two weeks after surgery.
Very rare but possible complications of LASIK, occurring in less than 0.1% of patients, include ischemic optic neuropathy (damage to the blood supply of the optic nerve), retinal detachment (separation of the retina from the supportive tissue), vitreous hemorrhage (bleeding into the clear, jelly-like substance in the back of the eye), and posterior vitreous detachment (pulling away of the vitreous from the retina).
What Else Should I Know About Laser In Situ Keratomileusis (LASIK)?
LASIK, a type of laser eye surgery, can be used to correct vision problems like nearsightedness (myopia) and astigmatism – a condition that blurs vision due to an irregularly shaped cornea. This procedure is particularly effective for individuals with a myopia of -6.0 D (dioptres) or less, and astigmatism of less than 2.0 D.
Recent studies suggest that LASIK procedure produces similar improvements in vision and poses similar safety caution as other vision correction procedures. One of the major benefits of LASIK is its quick recovery time and the less severe pain felt after operation compared to other eye surgeries.
Furthermore, LASIK tends to yield high satisfaction rates. In numerous studies, about 92% to 95% of patients who have undergone LASIK were happy with their results.
