The Joy of LASIK

• Chapter 1
• Chapter 2
• Chapter 3
• Chapter 4
• Chapter 5
• Chapter 6
• Chapter 7
• Chapter 8
• Chapter 9
• Chapter 10
• Chapter 11

8. COMPLICATIONS OF LASIK

8-1. What sort of complications can occur after LASIK?

Complications with LASIK are rare, but unfortunately, they can occur. Now that LASIK has been widely performed for the past 15 years, and now that millions of procedures have been done, these complications have come to light. We can consider complications to be either temporary or permanent. They may resolve with time, or they may last as long as you live. We can also consider complications to be correctable, through medication or surgery, or uncorrectable. We will deal with each type of complication in this chapter.

8-2. What are the temporary complications of LASIK?

It is not unusual to have some side effects with any surgical procedure, and LASIK is no exception. There may, of course, be some pain after any type of surgery. With LASIK, the pain is usually mild, but occasionally, it can be moderate, or even severe. Pain may be scratchy in nature. Some people describe their pain as “stinging” or “burning.” Pain is thought to be caused by some aspect of the LASIK procedure. It may result from cutting the flap, laser treatment, a corneal scratch (or abrasion), excessive drying of the eye during surgery, pressure from the lid speculum or from the suction ring. Pain usually occurs in the first 12 hours after surgery, and is almost always gone the next day.

8-3. What if the pain lasts longer than 12 hours?

Occasionally, pain will last longer, perhaps 24 to 48 hours. This is unusual but not unheard of. Generally, the pain is not a cause for alarm. Since LASIK patients are seen by their doctor within 24 hours of surgery, the doctor can make sure the postoperative pain does not represent a serious complication.

8-4. What can I do for the pain?

It is best to close the eyes and try to rest. Closing the eyes avoids the kind of pain that is associated with blinking. Usually, if one can get to sleep, the pain will be gone upon awakening. Doctors will usually permit over-the-counter pain medication like aspirin, Tylenol, Advil, or Motrin. It is better not to remove the protective goggles, and better not to use any eye drops until the doctor says it is all right to do so.

8-5. What about the pain with PRK?

PRK is associated with more pain than LASIK, and it is not uncommon for PRK pain to last more than one day. PRK pain tends to be at its worst during the first 24 hours. It is controlled to some extent by applying a bandage contact lens immediately after laser treatment. In addition many doctors prescribe strong pain medication, and some even prescribe eye drops that numb the eye. PRK pain is worse than LASIK pain because PRK removes the surface layer of cells from the cornea and exposes the sensitive nerve endings beneath the surface. As the cornea heals, these nerve endings are covered with a new layer of cells.

8-6. What other temporary complications, besides pain, occur after LASIK?

There may be glare, halos around lights, fluctuating vision, and dry eyes.

8-7. Why does the corneal surface become disrupted during LASIK?

During LASIK, the eye is held open for several minutes by the lid speculum. The surface of the eye, especially the cornea, is normally covered by a thin layer of tears. This tear film is composed of water, oil, and mucin. The tear film protects the ocular surface and keeps it clear and lustrous. When the eye is held open, the tear film begins to evaporate. the coverage of the cornea becomes spotty, and the cornea starts to dry out. . It is a little like a windshield that is covered with rain. The windshield wipers normally spread the rain over the glass, keeping the moisture uniform. If the wipers are turned off, the film of water “breaks up,” allowing the windshield to dry out. The eye does not have windshield wipers, but it does have eyelids. If the eyelids are immobilized by the lid speculum, as they are during LASIK, the ocular surface will dry out and lose some of its smoothness.

8-8. What is an epithelial defect?

An epithelial defect is the result of a scratched cornea or a corneal abrasion. Most often, it is caused inadvertently by the LASIK surgeon. A scratched cornea can occur during the cutting of the LASIK flap with the microkeratome. Epithelial defects are usually small, but they can be painful. They produce a feeling of a foreign body in the eye. They can be treated with a bandage contact lens, or by just keeping the eyelids closed. Epithelial defects usually heal within 24 hours.

8-9. What is the reason for dry eyes after LASIK?

It is often said that the most common complication after LASIK is dry eyes, but the cause is not obvious. In fact, it is really unclear whether the post-LASIK dry eye is truly a dry eye at all. The patient often feels a sensation of dryness after LASIK. But when we measure the tear production, it is usually normal. In addition, the pattern of dry spots we see after LASIK is different than the pattern we see with true dry eyes caused by tear deficiency. .

8-10. What seems to be causing the dry eye?

The sensation of dryness seems to be caused by small surface defects concentrated in the center of the cornea. It is not entirely clear why they occur and they are not present in everyone who has LASIK. They may be the result of damaging some of the corneal nerves when making the LASIK flap. The corneal nerves carry some essential nutrients or tissue factors to the cornea. When the nerves are cut, the absence of these substances may lead to a breakdown of the corneal surface.

8-11. Is there a name for the condition caused by destruction of the corneal nerves?

It is referred to as post-LASIK neurotrophic epitheliopathy. This simply means a disturbance of the surface layer of the cornea (the epithelium), caused by loss of nerves, and occurring after LASIK.

8-12. How long does post-LASIK neurotrophic epitheliopathy last?

It can last as long as 1 year, but it usually resolves sooner. The average duration is anywhere from a few weeks to a few months. It may take more than 6 months for the corneal nerves to regenerate.

8-13. How long does it take for the dry eye sensation to go away?

Typically, the sensation of dryness lasts anywhere from a few weeks to a few months. Occasionally, the feeling of dryness persists for several months, but rarely, longer than 6 or 8 months. This is about the same time frame as post-LASIK neurotrophic epitheliopathy, so it adds weight to the idea that the two conditions are the same.

8-14. Is there a treatment for the sensation of dry eyes after LASIK?

Most doctors recommend artificial tears. These eye drops are available over-the-counter without a prescription. There are many good brands of artificial tears available. Some drugstores even have their own brand of artificial tears. Artificial tears rarely have any side effects, so they can be used as often as one wishes.

8-15. Is it better to use artificial tears with preservatives or without them?

Many artificial tears are available with or without preservatives. Some eye doctors recommend artificial tears without preservatives. They are a bit more expensive and it is a little harder to open the container. On the other hand, the preservatives found in today’s artificial tears are gentle on the eye and rarely cause problems, even when they are used many times during the day. Some thicker eyedrops, gels, and ointments are sometimes useful at night. They are less suitable for daytime use because they cause blurry vision.

8-16. Are there other treatments for dry eyes?

Punctal plugs, usually made of silicone, can be placed by the doctor into the tear drainage ducts, called “puncta.” There are four of these ducts, one at the inner edge of each eyelid. Putting a small plug in these ducts is like putting a stopper in a drain. The tears will be prevented from draining out, and the moisture of the eye will increase. The two lower ducts are the most important ones, since they carry away 90% of the tears.

8-17. Are there any oral medications for the treatment of dry eye?

There are some oral medications that can be used to increase tear production. Two examples are Salagen, and Evoxac. These medications may increase saliva production, as well as tears. They may also have unwanted side effects, such as nausea and sweating.

8-18. Is there a higher incidence of dry eye with a superior flap?

This has been suggested but there is little evidence to support it. The idea is that more nerves are cut with a superior hinge than a nasal hinge. Some of these nerves are important in tear production. Studies show, however, that tear production and dry eye symptoms are practically identical with nasal and superior hinges.

8-19. Can the cornea become too thin after LASIK?

Yes. We usually like to maintain a corneal thickness of at least 410 microns after LASIK. This means that for most corneas, 10 diopters of treatment is about the upper limit. If the cornea becomes too thin, it can bend too easily with blinking and eye pressure changes, and produce fluctuating vision. In addition, most LASIK surgeons like to have a corneal “bed” (the part of the cornea beneath the laser treatment) at least 250 microns thick in order to provide stability for the cornea.

8-20. Why do glare and halos occur?

We do not know for sure. Probably, it is due to mild disruption of the clear corneal surface caused by the LASIK procedure. When light strikes a clear cornea, it passes through without any “scatter.” When light strikes a cornea with a disrupted surface, it scatters and produces halos and glare.

8-21. Is there a treatment for post-LASIK neurotrophic epitheliopathy?

This condition resolves when the corneal nerves regenerate. Since the nerves regenerate slowly, the condition usually improves a little bit each week. There is usually no discomfort after the first month. Artificial tears, ointments, and gels may help relieve symptoms.

8-22. What other serious complications of LASIK can occur?

Complications can be divided into four categories: Those that get better without any treatment, those that require medication to get better, those that require an operation to get better, and those that cannot be fixed.

8-23. What are the complications that get better without treatment?

We have already discussed how halos, glare, and dryness of the eyes resolve over time. We should also include fluctuating vision. In the early weeks after LASIK, vision may vary from day to day, or even throughout the day. This is probably due to corneal healing, which may require weeks, or even months. The situation is similar to having plastic surgery on the skin. As the tissues mend, their strength and their shape change slightly from day to day. When corneal tissues change shape, vision can be affected. This process is sometimes referred to as “wound healing,” or tissue remodeling. Wound healing in the cornea can continue for weeks, months, or even years. Vision, however, usually stabilizes within a few weeks of the LASIK procedure.

8-24. What factors contribute to delayed wound healing?

Corneas that require a lot of laser treatment may take longer to heal than those that require only a little laser treatment. Therefore, fluctuating vision is more common among people with large amounts of nearsightedness or farsightedness.

8-25. What about difficulty with night driving, depth perception, and contrast sensitivity?

Most people have more difficulty driving at night than during the day whether or not they have had LASIK. This is particularly true of nearsighted people, probably due to the optical properties of the nearsighted eye. Generally, these problems are no worse after LASIK than before. However, these problems may be troublesome during the first few weeks after surgery, as the cornea heals.

8-26. What complications require correction by a surgical procedure?

The most common complications that require additional surgery are “undercorrection” and “overcorrection.” The surgeon uses the precise amount of laser treatment that is expected to produce a desired result. But some corneas “under-respond” to the laser treatment, and others “over-respond.”

8-27. Why do some people under-respond and others over-respond?

Corneal tissue varies slightly from one person to the next. This may be due to genetic factors. Some people are fast healers, while others are slow healers. Some people heal with noticeable scars, while others do not. These differences are probably programmed into a person’s genetic material. A person’s age may influence the healing response. Young people tend to under-respond to laser treatment of the cornea, while older people tend to over-respond. In other words, older people seem to require less laser treatment than younger people to achieve the same amount of correction. There may also be some differences related to the amount of myopia or hyperopia being treating. People with higher amounts of myopia require slightly less laser treatment per diopter than people with small amounts of myopia. Conversely, people with large amounts of farsightedness require more laser treatment per diopter than people with small amounts of hyperopia.

8-28. What is the effect of an under-response or an over-response?

If a person under-responds to laser treatment, they will fall short of achieving the desired correction. If a nearsighted person under-responds, they remain a bit nearsighted. If a farsighted person under-responds, they remain a bit farsighted. Conversely, if a nearsighted person over-responds, they become slightly farsighted, and if a farsighted person over-responds, they become slightly nearsighted.

8-29. How often do under-correction and over-correction occur?

It varies from one practice to the next. It has been reported to be anywhere from 1% to 35%. A good average would be about 10%. Most of these are under-corrections, since the surgeon would prefer to err on the side of under-correction rather than over-correction. These under-corrections and over-corrections are not serious. They can be treated with an enhancement. You will notice that 10% is about the same figure as the “enhancement rate.” This is understandable, since the surgeon and the patient will usually want an enhancement for any significant undercorrection or overcorrection.

8-30. What will my vision be like if I am a nearsighted person who is under-corrected or over-corrected?

Nearsighted people who are under-corrected, usually see much better without glasses or contact lenses than they did before LASIK. But, they may still need glasses to see well in the distance, and they may need glasses for driving. Reading vision is often very good if there is an undercorrection. If a nearsighted person is over-corrected, they may need glasses for distance, for reading, or possibly, for both. It depends on their age, the amount of overcorrection, and the type of work they do.

8-31. What will my vision be like if I am a farsighted person who is under-corrected or over-corrected?

Farsighted people who are under-corrected, usually see much better without glasses or contact lenses than they did before LASIK. They may still need glasses for distance, reading, or both. Farsighted people who are over-corrected, may need glasses for distance, particularly for driving. They may need reading glasses as well, but very often, reading vision is quite good.

8-32. How long do I have to wait after LASIK to have an enhancement?

Enhancements are usually performed at least 3 months after LASIK or PRK. Most are performed within the first year. The reason for waiting at least 3 months, is to make sure the vision, and the refractive error, have stabilized. If they have not stabilized, it is best to wait until they do. It is not unusual for enhancements to be performed several years after the original procedure. A LASIK flap can usually be “lifted” several years after the original procedure, and of course, PRK does not require lifting a flap. The surface of the cornea is simply re-treated.

8-33. Doesn’t the LASIK flap heal so well that it cannot be lifted for an enhancement?

The LASIK flap heals well, but adhesions of the flap to the underlying cornea can usually be broken by an experienced surgeon, even several years after LASIK.

8-34. Is the LASIK flap ever re-cut during an enhancement?

Some surgeons prefer to re-cut the LASIK flap rather than “lift” a flap that was previously created. Re-cutting is sometimes done if the flap cannot be lifted. Most surgeons prefer to lift rather than re-cut corneal flaps. They feel it may be better to have only one cut through the cornea rather than two. If the cuts overlap, pieces of the cornea could be “disconnected” from the flap. If re-cutting is necessary, a flap with a diameter different than the original cut is preferred.

8-35. How successful is an enhancement for under-corrections and overcorrections?

Enhancements are highly successful, both for under-corrections and over-corrections. The procedure is fairly simple. In LASIK, the edge of the flap is identified, usually at the slit lamp microscope. A drop of topical anesthetic is instilled, and the edge of the flap is marked and lifted slightly using a special instrument. The patient is brought to the laser and under the laser’s operating microscope, the flap is marked with ink, and then lifted completely. The corneal bed is dried, and a precise amount of laser treatment is applied to the bed. The laser treatment generally takes only a few seconds. The flap is replaced and smoothed into position. The ink marks help align the flap and return it to its original position. A bandage contact lens is then placed on the cornea. The contact lens improves comfort during the postoperative period and aids in the healing process. It is usually removed the day after the enhancement.

8-36. How are enhancements done for PRK?

Enhancements for PRK are even easier. Since there is no corneal flap, the entire enhancement is performed under the excimer laser. It consists of two parts. The surface layer of cells, the epithelium, is removed with the laser beam (laser scrape), with a scraping instrument, with a rapidly rotating brush (Amoils brush), or with alcohol, which loosens the epithelial attachments. Laser treatment is applied to the corneal bed, usually for only a few seconds. Antibiotic drops are instilled and a bandage contact lens is applied. The contact lens is left in place approximately 3 days.

8-37. Do enhancements ever need to be repeated?

Most LASIK and PRK patients do not require enhancements at all, but when they are required, one enhancement is usually all that is necessary. Occasionally, a second enhancement will be needed if the first enhancement does not achieve the desired effect. Very rarely, three or more enhancements will be needed. There is no absolute limitation to the number of enhancements that may be done. Each enhancement is associated with a very slight risk of infection or some other rare complication. From the patient’s and the surgeon’s point of view, enhancements are inconvenient, and the fewer the number of enhancements, the better.

8-38. What other complications require surgical corrections?

If a LASIK flap is cut irregularly, further corneal surgery may be required. Although extremely rare, corneal flaps can be cut too thick or too thin. They may be cut so thin that a hole develops in the center of the flap, a so-called “buttonhole.” Buttonholes can develop when the suction ring does not provide sufficient suction. The central part of the cornea can “bunch up” inside the ring and be removed during the passage of the microkeratome. If a buttonhole develops, the surgery should be stopped. Laser treatment should never be performed if a buttonhole develops. Buttonholes should be allowed to heal and the procedure can be performed later.

8-39. What are corneal striae?

Corneal striae are folds, or wrinkles, in the LASIK flap. They can interfere with the smoothness of the cornea, and lead to poor vision, and a poor LASIK outcome.

8-40. How do striae occur?

Corneal folds, or striae, are undesirable complications of LASIK. They occur when the corneal flap is not perfectly aligned with the surrounding tissues, or when the flap does not fit precisely in the corneal bed. A similar situation occurs when putting a soft contact lens on the eye. If the contact lens does not fit properly, or if it has the wrong shape, or curve, it may develop wrinkles.

8-41. Are there other reasons striae develop?

If the corneal bed is too dry when the flap is replaced, it may be difficult to “smooth out” the flap, and striae could develop. If a corneal flap is too thin, it may be so delicate that it does not smooth out properly. Likewise, if the corneal bed is too dry when the flap is replaced, it may be difficult to “smooth out” the flap, and striae may occur. Similarly, a LASIK flap can develop folds if it is too dry or not positioned properly.

8-42. How are striae treated?

It is important to correct striae as soon as they are detected. Otherwise, they can become permanent. If these wrinkles are not smoothed out, they can result in poor vision due to corneal irregularity. As soon as striae are recognized, the corneal flap must be lifted, or “re-floated,” on a layer of fluid, and smoothed down until the wrinkles disappear.

8-43. When do striae become permanent?

That depends on many factors, such as, how severe they are, how long they have been present, and how aggressive the surgeon tries to correct them. Striae are fairly easy to fix during the first few days after surgery. After a week they become more difficult to correct, and after a month, it may be very difficult to get rid of them.

8-44. What techniques are used to correct longstanding striae?

There are several. The flap can be lifted, “soaked” in a half and half mixture of sterile water and normal saline, then smoothed down in the proper position. Some authorities recommend suturing the flap in place with fine, tight nylon sutures. As many as 16 sutures may be used to stretch out the LASIK flap. Others have recommended heating the flap by bathing it with hot water and “ironing” out the wrinkles. This is similar to using a steam iron to remove wrinkles from a shirt. Still others, use the laser to chip away at the corneal surface and simply dissolve the wrinkles. Each of these techniques has its advocates. It is not entirely clear which technique is best for removing striae.

8-45. What if the striae do not resolve?

If striae do not resolve with one of these treatments, there are a few choices. If the vision is adequate, the eye can be left alone. Perhaps the vision will not be perfect, but it may be good enough. If vision is so poor that it interferes with routine activity, the flap can be removed. If there is some residual refractive error, PRK can be done. In extreme situations, a corneal transplant can be considered. The aim of a corneal transplant is to replace a distorted cornea with a new, clear cornea.

8-46. How is a corneal transplant performed?

Corneal transplants are one of the most common transplant procedures done today. About 40,000 are done in the United States every year. Corneas are obtained from eye banks. Every major city in the country has one or more eye banks. Eye banks receive donor corneas from people who donate their corneas after their death.

8-47. Do corneal transplants reject?

Corneal transplants can reject, but usually they do not. They are one of the most successful kinds of organ transplant. One of the reasons for success is the lack of blood vessels in the cornea. The cornea is relatively “avascular.” That is, it does not have much of a blood supply. Even though the transplanted cornea comes from an unrelated donor, the recipient’s immune system may not recognize the foreign tissue. Because the body’s white blood cells have minimal contact with the new cornea, it is protected from the rejection process.

8-48. Does a corneal transplant always solve the problem?

Corneal transplants are very effective in providing the eye with a new surface. It is a bit like changing the crystal of a watch. But, like most operations, there is no guarantee of success. There may, in fact, be distortions of the new cornea, which interfere with vision.

8-49. But isn’t the new cornea supposed to be perfectly clear?

Yes. It will be clear. But, the real problem could be astigmatism. This is the condition in which the curvature of the cornea is different in one direction than in another. In other words, after a corneal transplant, the curvature of the front part of the eye may not be a perfect sphere, like a baseball, having the same curve in each direction. It may be more like a football, in which there is a steep curve in one direction, and a flat curve in another direction. Astigmatism can usually be corrected with PRK.

8-50. Can infections occur after LASIK?

Infection is a serious complication of LASIK. Infections are rare, but they can have serious consequences. They can lead to scarring of the cornea and loss of vision. The loss can be mild or it can be severe.

8-51. Why do infections occur after LASIK?

Infections occur for at least three different reasons. First, if bacteria are accidentally introduced during the LASIK or PRK surgery, the tissues could become infected. Second, if a person’s hygiene is poor, they could accidentally infect their cornea after the surgery has been performed. Third, if a person has a deficiency in their immune system (such as cancer or AIDS), they could be more susceptible to infection.

8-52. How would bacteria be introduced at the time of surgery?

This could happen if the instruments are not properly sterilized. Since virtually all LASIK surgeons autoclave their instruments with high temperature sterilization, bacteria are not expected to survive. Bacteria could, however, be harbored in the eyelids and eyelashes. It is almost impossible to completely sterilize the eyelids or the skin. As a precaution, most surgeons cover the eyelids and lashes with sterile plastic drapes. Rarely, irrigating solutions used during surgery accidentally become contaminated. This could be caused by an error during the manufacturing process or poor sterile technique at the laser center. This type of contamination is rare, but it is not unknown.

8-53. How would poor hygiene cause an infection?

Most people touch their eyes or eyelids with their hands several times a day. We do this almost unconsciously. This is usually not a problem, as long as the hands are clean. But when we shake hands with people, pick up a newspaper, or turn a doorknob, we do not really know if we are touching a clean or contaminated object. When an eye has had LASIK, or any other kind of surgery, it is more susceptible to infection than usual. A good defense against eye infections is to do lots of handwashing, and try to remember not to touch the eyes. Needless to say, one must be careful with tissues and handkerchiefs. A separate tissue should be used for the nose and the eyes. Secretions from the nose or mouth should not be transferred to the eye.

8-54. What is the effect of an eye injury after LASIK?

Eye injuries are serious under any circumstances. But they can be even more damaging after LASIK surgery. This is because the eye has been slightly weakened by the LASIK cut.

8-55. What type of injuries can occur?

The most common injury is a finger in the eye, or some object thrown at the eye. This can happen when young children are being held or carried. Small children can quickly poke a finger into an eye before one has a chance to react. Objects that can injure the eye include sticks, plants, coat hangers, hairbrushes, mascara brushes, tennis balls, elbows, and hockey pucks. People who wear sunglasses or reading glasses after LASIK must use care when putting on their glasses. A good habit is to hold both stems near the “free” end, rather than near the lenses, and slip the glasses on carefully.

8-56. What about airbag injuries?

At least 500 eye injuries have been caused by activation of airbags. These safety devices inflate in a fraction of a second, and there may not be enough time to get out of the way or even close the eyes. Occasionally, LASIK flaps have been displaced by these injuries.

8-57. Can a LASIK flap be repaired after an airbag injury?

In general, the answer is yes. It helps to see the doctor as soon as possible. Displaced flaps should be repositioned within a few hours of the injury if possible. The surgeon “refloats” the flap. This is done by gently “irrigating” beneath the LASIK flap with sterile saline. A blunt tipped cannula is used to deliver the saline beneath the flap. This refloating technique allows the flap to be repositioned in its proper location, and then smoothed into place with the cannula or moist sponges.

8-58. Can infections occur when the LASIK flap has been displaced?

Yes. Anytime there is a disturbance of a surgical wound, a potential infection must be considered. This is particularly true if the object causing the trauma was contaminated with bacteria or fungi. For example a tree branch would be more likely to cause an infection than a clean finger. For all cases of displaced LASIK flaps, broad-spectrum antibiotics should be used to guard against any possibility of infection.

8-59. How are LASIK infections treated?

LASIK infections are treated using the same principles for treating infections elsewhere in the body. Antibiotics are used as soon as an infection is suspected. These are usually in the form of an eyedrop. Occasionally, an injection of antibiotic will be given in the tissues around the eye. This creates a deposit of antibiotic, which is slowly released over hours or days to the infected tissue. Antibiotics are usually not given by mouth or by intramuscular or intravenous injection. Eyedrops or subconjunctival injection deliver a much higher concentration to the cornea.

8-60. What kind of antibiotics are used?

Broad-spectrum antibiotics are used initially. Most ophthalmologists use fluoroquinolone antibiotic eye drops as their first choice. Examples would be ciprofloxacin, ofloxacin, levofloxacin, gatifloxacin and moxifloxacin. If an infection does not respond quickly, a different antibiotic can be used. The choice of a more specific antibiotic is usually guided by cultures and bacteriologic sensitivity testing. That is why it is important to culture all serious eye infections.

8-61. How are LASIK infections cultured?

LASIK infections are usually near the corneal surface. A sterile swab is used to take a sample from the infected tissue. The sample is transferred to culture plates, which are sent to a microbiology laboratory and examined daily for bacterial or fungal growth. Infections may be located beneath the LASIK flap. In these cases, the flap must be lifted gently with a pair of surgical forceps so the infected tissue can be cultured.

8-62. What are the most common types of bacteria that cause infections after LASIK?

Staphylococcus and streptococcus are the most common. They are among the so-called “Gram-positive bacteria,” because they stain blue with a dye known as “Gram stain.” “Gram-negative bacteria,” which stain red with Gram stain, can also cause infections after LASIK. One of the most common Gram-negative infections is caused by the bacterium, pseudomonas. Many other bacteria have been reported to cause infection after LASIK. These include mycobacteria (a relative of the bacteria that causes tuberculosis), actinomyces, nocardia, and klebsiella.

8-63. Can organisms beside bacteria, cause infection after LASIK?

Fungi, viruses, and parasites can cause infection after LASIK. These, of course, do not respond to routine antibiotics, which are specific for bacteria. There are antifungal and antiprotozoal medications, but none are specifically made for the eye. Since these infections are very rare, most ophthalmologists will use antimicrobial agents from whatever sources they can find. Sometimes a “compounding” pharmacy can make up a preparation that may not be commercially available.

8-64. Are fortified antibiotics ever used?

Yes. Fortified antibiotics are highly concentrated antibiotics which are made up by compounding pharmacies. Many ophthalmologists prescribe highly concentrated antibiotics, which are not commercially available, when there is a sight threatening infection.

8-65. What is the outcome of a LASIK infection?

Infections can range from mild to severe. The outcome of an infection depends on the organism that caused the infection, the organism’s susceptibility to treatment, and how long it took for treatment to be started. Mild infections may clear up with no residual scarring, or loss of vision. Severe infections can lead to scarring and significant visual loss. Fortunately, infections are rare. When they occur, they must be treated promptly and vigorously.

8-66. What is DLK?

DLK stands for diffuse lamellar keratitis. It is sometimes called “Sands of the Sahara,” because at the slit lamp microscope, it looks like waves of sand. It appears as an infiltrate beneath the LASIK flap. It does not seem to be an infection. Rather, it is a type of inflammation.

8-67. What causes DLK?

DLK seems to have multiple causes. It appears to be an inflammatory response to foreign material that gets underneath the LASIK flap at the time of surgery. This foreign material stimulates an inflammatory response beneath the LASIK flap, and white blood cells are drawn to the area. Presumably, the white cells are there to rid the eye of the foreign material.

8-68. What kind of foreign material causes DLK?

No one is completely sure, but there are several suspected candidates. Some come from the patient. These include oil from the meibomian glands along the rim of the eyelids. Dead bacteria from the eyelids, or blood seeping beneath the LASIK flap can cause DLK.

8-69. What other sources are there for the foreign material that causes DLK?

Some toxic material may be introduced accidentally at the time of surgery. This includes iodine used to prepare clear the skin of the eyelids before surgery, lubricant from the microkeratome, rust from the microkeratome or its blade, rust, particulate matter, such as powder from the drape or surgical gloves, and detergent used to wash the hands or instruments.

8-70. What is the most likely cause of DLK?

Some studies have narrowed down the cause to endotoxin, a product of Gram-negative bacteria. Endotoxin is a component of the bacterial cell wall. It is highly toxic and can cause fever and inflammation when it gets into the body. It is the most likely culprit in toxic shock syndrome.

8-71. How does endotoxin get under the LASIK flap?

Studies have shown that endotoxin accumulates in sterilizers, especially those which are not completely drained of water each day after their use. Endotoxin is a stable substance, and is not easily destroyed. If traces remain in the sterilizer, they may coat the instruments when they are sterilized for LASIK surgery.

8-72. How often does DLK occur?

DLK is rare, but there have been “epidemics” in which many cases are reported at the same laser center. Presumably, this is because the surgical instruments repeatedly get coated with endotoxin. When the sterilizer is thoroughly cleaned and the water is completely drained, these epidemics seem to clear up. So some laser centers have had many cases, while others have had none. Those centers which are meticulous about cleaning their equipment have a lower incidence of DLK than those which are not.

8-73. What is epithelial ingrowth?

Epithelial ingrowth is an unwanted complication of LASIK in which the top layer of corneal cells grow underneath the LASIK flap.

8-74. Why does epithelial ingrowth occur?

We do not always know exactly why epithelial ingrowth occurs. We do, however, know some of the factors which contribute to this undesirable condition. The epithelium is a rapidly growing sheet of cells which migrates wherever there is an opening in the cornea. If the LASIK flap does not fit tightly on the corneal bed, the epithelium “finds” a space through which to grow.

8-75. Why would there be a space between the LASIK flap and the corneal bed?

If the LASIK flap is damaged when it is being created, it may have an irregular edge that does not fit snugly over the corneal bed. Damage to the LASIK flap may be caused by a dull or damaged microkeratome blade, by inadequate suction of the microkeratome’s suction ring, or by some other malfunction of the microkeratome. Similarly, poor surgical technique or excessive movement of the patient during the creation of the LASIK flap can lead to an irregular edge of the flap.

8-76. If the LASIK flap is well made, can epithelial ingrowth still occur?

Yes. Even if the LASIK flap is made correctly, there may be some circumstances which lead to epithelial ingrowth.

8-77. What postoperative factors might lead to epithelial ingrowth?

Any condition which “lifts” the edge of the LASIK flap can open a space between the flap and the corneal bed leading to epithelial ingrowth. This includes eye rubbing, inflammation, infection and swelling.

8-78. Are there other reasons for epithelial ingrowth?

Yes. Anything that causes a less than perfect LASIK flap during surgery and anything that prevents the LASIK flap from fitting over the corneal bed in a smooth, precise, wrinkle-free way can potentially lead to epithelial ingrowth. For example, very thin LASIK flaps may not smooth down over the corneal bed precisely. Just as a bed sheet may wrinkle and not fit exactly over the surface of the bed, an extremely thin LASIK flap may not fit exactly over the corneal bed.

8-79. Can epithelial cells be “seeded” beneath the LASIK flap?

Yes. Epithelial cells can become trapped beneath the LASIK flap. This can happen inadvertently if epithelial cells attach to the microkeratome blade. As the blade makes its way through the cornea, cells can be deposited beneath the LASIK flap. These cells can multiply and spread. Epithelial cells can also be swept under the LASIK flap accidentally with a surgical instrument.

8-80. What is the effect of epithelial ingrowth?

If epithelial ingrowth is mild, there may be no effect on the outcome of the LASIK procedure. If epithelial ingrowth is severe, the result could be a poor visual outcome.

8-81. What determines if epithelial ingrowth is mild or severe?

If a few epithelial cells grow beneath the edge of the LASIK flap and then stop growing, this would be considered “mild” epithelial ingrowth. If epithelial ingrowth is mild, there would, most likely, be no important consequence of epithelial ingrowth. It, however, epithelial cells spread to the center of the cornea, epithelial ingrowth would be considered “severe.” Severe epithelial ingrowth would, most likely, interfere with vision.

8-82. Is there a way to prevent epithelial ingrowth?

The best way to prevent epithelial ingrowth is with meticulous surgical technique. The surgeon must be careful that epithelium is not deposited under the LASIK flap, and the corneal bed must be thoroughly irrigated during LASIK surgery.

8-83. What is “stromal melting?”

Stromal melting is a term used to describe the progressive thinning of the cornea which occurs in certain pathologic conditions of the eye. One of these conditions is epithelial ingrowth. “Stromal” refers to the corneal stroma, the bulk of the corneal tissue beneath the epithelium. With severe epithelial ingrowth, the stromal tissue can become thinner and thinner, as if it were “melting” away. If the melting continues, it can lead to a corneal perforation, that is, a through and through opening in the front part of the eye. This could, in turn, lead to infection or other disastrous consequences.

8-84. Why does stromal melting occur?

We don’t know for sure, but it seems to occur after cutting off oxygen and nutrition to the cornea and activation of certain enzymes. The cornea receives most of its oxygen and nutrients by diffusion from surrounding fluids. If there is interference with the flow of these fluids, melting can occur. The main enzyme which is activated is known as “collagenase.” This enzyme dissolves collagen, a major component of the cornea.

8-85. What is the treatment for stromal melting?

The most direct treatment is to remove the epithelial ingrowth. This can be done by lifting the LASIK flap and thoroughly scraping away the unwanted epithelium. Sometimes the LASIK bed and the underside of the LASIK flap are treated with the laser or with chemicals to make sure that all the epithelial cells are removed. Some of the chemicals that have been tried are alcohol, cocaine, and an anticancer drug called mitomycin.

8-86. What happens if stromal melting cannot be stopped?

If melting cannot be stopped, and the cornea becomes extremely thin, or perforates, a corneal transplant must be done to restore the integrity of the eye. A corneal transplant is a bit like replacing the crystal of a watch. The damaged tissue is replaced with a donor human cornea obtained from an eye bank.

8-87. What is “corneal ectasia?”

Corneal ectasia refers to progressive thinning of the cornea. The term implies a destabilization of the normal cornea. The destabilization occurs because an abnormally thin cornea cannot maintain its shape when a person blinks. A very thin cornea may also change shape throughout the day as the pressure within the eye fluctuates. The end result of an unstable corneal structure is fluctuating vision throughout the day, especially during a blink.

8-88. Why does corneal ectasia occur?

There are three reasons. Corneal ectasia can occur if too much corneal tissue is removed by the laser during LASIK surgery; it can be the result of corneal melting caused by epithelial ingrowth; or it can be caused by medical conditions unrelated to LASIK, such as keratoconus, or pellucid marginal degeneration.

8-89. How is ectasia prevented during LASIK surgery?

Ectasia is prevented by making careful measurements before performing LASIK. People who might develop ectasia should not have LASIK. During LASIK, it is important to avoid removing too much tissue and making the cornea too thin. The excimer laser removes about 12 microns of tissue for every diopter of correction. By measuring the thickness of the cornea before LASIK, one can determine how thick the cornea will be after LASIK. If the calculations show that the cornea will be too thin after LASIK, it may be better to perform a different operation, such as PRK, or perhaps, to avoid laser vision correction all together.

8-90. What happens if LASIK or PRK are performed in people with keratoconus?

Keratoconus, a cone-shaped thinning, or ectasia, of the cornea, is one condition in which laser vision correction should not be performed. But, keratoconus is not always easy to diagnose. It may be rather subtle and difficult for the ophthalmologist to recognize with the slit lamp microscope. Corneal topography can help, and so can a keratometer, a machine that measures the steepness of the cornea using reflected images. No doubt, many eyes with keratoconus have unintentionally had LASIK or PRK. Retrospective studies show that these eyes are more likely to develop ectasia. These eyes may become progressively more nearsighted with time, and vision may become more distorted because of increasing astigmatism.

8-91. How can I be certain I don’t have keratoconus?

Keratoconus is rare and difficult to diagnose, but it does have some warning signs. Since keratoconus is inherited, it sometimes, but not always, runs in families. People with keratoconus usually have steep corneas which are thinner than normal and have a lot of astigmatism. Usually the astigmatism is irregular. For example, the lower part of a keratoconus cornea may be thinner, and have a steeper curve, than the upper part of the cornea. Astigmatism in keratoconus is often diagonal, rather than the more typical horizontal or vertical astigmatism. The overall cornea has more of a cone shape than a normal cornea. Most often the cone is not exactly in the center of the cornea, but rather, slightly below center. With careful examination, and modern methods of corneal imaging, ophthalmologists can usually detect even subtle keratoconus.

8-92. If LASIK or PRK are inadvertently performed in keratoconus, what happens to the vision?

If laser vision correction is inadvertently performed for keratoconus, the visual outcome is hard to predict. There may be excessive corneal thinning or an unexpected amount of nearsightedness, farsightedness, or astigmatism. In keratoconus, the vision can sometimes be corrected to a satisfactory level with contact lenses, instead of the laser. Occasionally, a corneal transplant might have to be performed to restore good vision.

8-93. What is scleritis and how does it affect LASIK and PRK?

Scleritis is an inflammation of the wall of the eye. It occurs most commonly with rheumatoid arthritis, but may also occur with lupus, fibromyalgia, polymyalgia rheumatica, or other, related conditions. When the white part of eye, the sclera, is inflamed, it may begin to dissolve and become dangerously thin. Often the cornea adjacent to an area of scleritis will become inflamed too, and undergo thinning. If this happens after LASIK is performed, the success of the operation could be threatened. For this reason, most ophthalmologists will not perform LASIK in people who have had scleritis.

8-94. Can the LASEK epithelial flap develop striae or other problems?

There may be some temporary folding of the LASEK flap, but probably no long term or permanent complications. The cells of the epithelium are replaced within a matter of a few days with new epithelial cells. Defects in the flap are quickly repaired as new cells are produced and smoothed over by the eyelids.

8-95. Are there any complications of LASEK?

There are not many complications of LASEK. Although there is a corneal flap, the flap is composed only of epithelium, the superficial layers of the cornea. The epithelial cells are constantly being shed and replaced, much like the superficial cells of the skin. So, even if a LASEK flap is not perfect, it will be replaced with a perfect layer of cells within a few days.

8-96. Are lawsuits common after LASIK?

Lawsuits are uncommon after LASIK. However, with nearly 2 million LASIK procedures being performed in the United States each year, even a small percentage that results in a lawsuit seem like a lot. The exact percentage is unknown, but it is far less than 1%.

8-97. What are the reasons for malpractice lawsuits after LASIK?

There are many reasons for lawsuits after LASIK, but many are related to poor communication between the doctor and patient before or after surgery. Poor communication can lead to a misunderstanding about what LASIK can and cannot accomplish. If a patient does not have a thorough understanding of all the possible outcomes of LASIK surgery, there may be unrealistic expectations for LASIK. If the outcome is something other than the patient anticipates, there may be disappointment and consequent legal action.

8-98. Aren’t some of the complications of LASIK the fault of the surgeon?

Yes. Surgeons sometimes make mistakes. But they routinely use their best judgment. Surgeons must make hundreds of decisions during the course of one case, and thousands of decisions during a day of surgery. Occasionally, one or more of these decisions is wrong. The surgeon hopes, as much as the patient, that the mistake will not lead to a poor visual outcome. If the mistake leads to a poor outcome, the surgeon uses whatever resources are available to correct the problem.

8-99. What should I do if I have a complication with LASIK surgery?

If you have a complication of LASIK surgery, first of all, do not panic. The surgeon should discuss the complication openly and honestly with you and your family members. Listen to what the surgeon has to say about correcting the problem. Ask about the “prognosis,” the expectation for good vision. Stay in close communication with the surgeon. Discuss any concerns you may have. If you would like a second, or even a third opinion, ask your surgeon about this. The surgeon may want you to see a consultant who is an expert in offering second opinions about LASIK. The surgeon may not want you to see a LASIK surgeon who cannot offer an expert opinion.

8-100. Is there a way to avoid complications of LASIK surgery?

There is no surefire way to avoid complications of LASIK. But remember, complications are rare. Even the best LASIK surgeon can experience occasional complications. It is sometimes said, “The only surgeons who do not have complications are the ones who do not operate.” If you educate yourself about LASIK, have realistic expectations, and select an experienced LASIK surgeon, the possibility of a complication is extremely low.

8-101. Should I hire a lawyer if I have a complication with LASIK?

The decision to hire a lawyer depends on the circumstances. The vast majority of problems that occur after LASIK can be corrected. Many resolve spontaneously. Others require additional surgery. If a lawyer is brought in, the surgeon may feel threatened, and may be unwilling or unable to work with the patient to resolve the problem.

8-102. Are there any guidelines to follow in choosing an attorney for a LASIK case?

Naturally, it is preferable to choose an attorney who has experience with LASIK cases. An experienced lawyer is likely to be realistic about the possibility of a successful lawsuit. Keep in mind that some attorneys will take on cases that have little or no merit, simply in order to generate legal fees. You should also remember that if a surgeon used reasonable medical judgment, an unexpected complication would not be grounds for a successful lawsuit.

8-103. Is there any way to identify a LASIK surgeon who has been sued or is more likely to be sued?

Surgeons will sometimes respond frankly to a question about previous lawsuits. Some information about lawsuits is available through the state board of medical examiners. These boards, which are responsible for licensing physicians in each state, will answer questions about individual doctors. They often have web sites that answer these questions. These agencies are also interested in keeping track of complaints about physicians. For what it is worth, lawsuits are more common among “high profile,” high volume, LASIK surgeons who advertise. On the other hand, high volume LASIK surgeons are often among the most skilled practitioners because of their vast experience.

8-104. What is PISK?

PISK is an acronym for pressure-induced stromal keratitis. It is caused by swelling, or edema, or the cornea after LASIK. The cause of this corneal edema after LASIK is an increased pressure within the eye. Increased pressure is often due to the use of steroid eye drops after surgery. A small percentage of the population “responds” to steroid eye drops with an increase in eye pressure. These individuals are referred to as “steroid responders. If they receive steroid eye drops after LASIK, their eye pressure may increase, forcing fluid into the cornea, and leading to blurred vision.

8-105. Is PISK temporary or permanent?

PISK is temporary, but it may take several weeks, or even months for the corneal edema to clear. With patience, and conservative management, the ultimate visual outcome is usually excellent.

8-106. How do I know if I could develop PISK after LASIK?

It may not be possible to predict whether or not a person will develop PISK after LASIK. However, PISK is probably more likely to develop in someone who has glaucoma, or a family history of glaucoma. People who are known “steroid responders,” that is, those who have increased eye pressure after using steroids, must be considered at risk for PISK.

8-107. How is PISK treated?

PISK is treated by conservative methods. This means watching and waiting. It is important to give the cornea enough time to recover. Gradually, the swelling will decrease because of evaporation, and fluid balance within the cornea will reach an equilibrium. The physician should reassure the patient that visual recovery will take anywhere from a few weeks to a few months. They must be patient and confident that vision will be fine.

8-108. Are there any eye drops that will speed up the recovery from PISK?

PISK is rare, and there are no proven methods to speed up the recovery. Artificial tear eyedrops can be used, and the doctor may even suggest “hyperosmotic” eyedrops. These drops are essentially a 5% solution of sodium chloride, or table salt. They are thought to “draw out” fluid from the cornea through a “hyperosmotic effect.” It is not clear how well they work, or whether they really do speed up the resolution of corneal edema.

8-109. Is there any surgical procedure that will speed up the recovery from PISK?

When visual recovery is delayed after LASIK, there is often a temptation to do further surgery to try to fix the problem quickly. Sometimes, it is better to wait. PISK seems to be one of those situations in which watching and waiting is preferable to additional surgery. It may be difficult for the patient and the surgeon to do, essentially, nothing. Sometimes, a second opinion from a LASIK surgeon who specializes in treating complications, will reassure the doctor and the patient.


8-110. Can vitamin C prevent corneal haze from occurring after PRK?

It has been suggested that vitamin C, 500 mg twice a day for one week preoperatively, and two weeks postoperatively, will help prevent corneal haze after PRK. Human corneas have relatively low levels of vitamin C. Diurnal animals have higher levels than nocturnal animals, and the reindeer has the highest concentration of any animal studied. It is possible that vitamin C confers some protective effect against haze after LASIK, but there is no proof of this concept at the present time.

8-111. What is epitheliopathy?

Epitheliopathy is a general term for diseases of the epithelium, the surface layer of cells on any tissue, but for our purposes, the cornea. Epitheliopathy is important in LASIK, because it can occur as a postoperative complication. The original name given to this condition was “laser in situ keratomileusis-induced neurotrophic epitheliopathy.” You can see why it has been shortened! It appears for unknown reasons after a small percentage of LASIKs. To the eye doctor, epitheliopathy looks like pitting of the central corneal surface. From the patient’s perspective, it causes blurred vision. While epitheliopathy may be disturbing to the patient, and the physician, it almost always goes away, and rarely does it cause any permanent change in the vision. It can, however, take up to six months to resolve. During this time, the patient may experience scratchiness, light sensitivity, and blurred vision. The most likely explanation for epitheliopathy is interruption of the sensory corneal nerves when the flap is made. This reduction of the nerve impulses to the corneal surfaces causes small defects in the cornea. Sometimes, epitheliopathy can be confused with dry eye, since the appearance is similar. However, the pattern of the defects is somewhat different. In dry eye, the defects are mostly in the lower cornea, and in epitheliopathy, they are in the center of the cornea.