Time and understanding are keys to reducing LASIK complications

With an increasing number of patients choosing LASIK, it is important to reduce complications by being wary prior to and after surgery.

NAGOYA, Japan — The keys to managing LASIK complications are preparation and knowledge, a refractive surgery expert told surgeons here. Richard Lindstrom, MD, told the audience at the Ocular Surgery News Symposium in Nagoya that the combination of preop prevention and postop early recognition of complications can lead to excellent visual outcomes.

“LASIK is on its way, at least in the United States, to becoming the most common operation performed. This year, U.S. surgeons will perform well over 1 million LASIK procedures. With a 1% complication rate and 1 million procedures, that is 10,000 individuals who will suffer from complications. And as any LASIK surgeon knows, the procedure has many possible complications,” said Richard Lindstrom, MD.

However, Dr. Lindstrom said the news isn’t bad, just that surgeons need to be aware. The good news is that surgeons have come very far, learned how to manage LASIK complications and can prevent significant loss of vision.

“The key is to recognize these complications early, know what they are, anticipate them and then treat them aggressively,” he said.

Dr. Lindstrom noted that intraoperative complications were in the 2% to 3% rate in early studies, but studies with newer keratomes have shown significantly reduced numbers of intraoperative complications.

Intraoperatively, most complications are related to the flap creation, according to Dr. Lindstrom. After changing to the Hansatome (Bausch & Lomb, Claremont, Calif.), a modern keratome, he said he has found that problems with insufficient sections, short passes, buttonholes, thin flaps, free caps and other problems all declined significantly, compared with earlier microkeratomes.

The learning curve

The U.S. Food and Drug Administration defines a significant loss of vision in their studies as loss of two lines or more of best corrected visual acuity (BCVA). The most common problems that cause people to lose vision after LASIK are flap dislocation, striae, folds or wrinkles, interface haze and epithelial ingrowth.

Compared with the early LASIK studies, Dr. Lindstrom said that more recently surgeons have been able to reduce this loss of BCVA to near zero, “not because we didn’t have the complications, but because we learned how to manage them.”

According to Dr. Lindstrom, LASIK surgeons have undergone a learning curve. In early LASIK studies, nearly 5% of patients lost two or more lines of BCVA. More recent studies have shown almost none. The difference is recognizing and aggressively treating the complications, he said.

The learning curve also applies to secondary treatments. Secondary treatments are used to treat complications and to correct residual refractive errors. In early studies, nearly 33% of LASIK patients required a second treatment. “Now we’re down to 15% in the modern studies. Ideally you’d like to get these secondary surgical interventions down to zero, but it is still part of the learning curve,” Dr. Lindstrom said.

DLK intervention

Diffuse lamellar keratitis (DLK) is a complication that every LASIK surgeon needs to learn to recognize, Dr. Lindstrom said. It presents as a white, granular appearance with glaze of increased density. Its exact cause has thus far remained somewhat of a mystery.

A host of potential sources have been implicated, including contaminants such as oil, metallic fragments, silicates, bacterial endotoxin, povidone-iodine prep and others. While efforts are being made to eliminate these potential etiologies, cases of DLK still will occur.

“I have a little different thought about the cause of DLK than some doctors,” Dr. Lindstrom said. “Some surgeons think this is an unusual reaction. I think some degree of DLK happens in everyone. I think it’s the same as flare and cell in cataract surgery. It’s usually very mild, with only a few cells in the interface.”

DLK can progress to higher stages, in which cells migrate centrally and become more prevalent. When there are more of these cells in the interface, they may start to aggregate. At this point, the patient begins to develop reduced vision, some photophobia and irritation of the eye. Dr. Lindstrom explained that if surgeons do not intervene at this point and irrigate the cells out of the interface, the patient can get corneal melting, interface haze and irregular astigmatism. “An end-stage case is very difficult to rehabilitate and often has permanent loss of vision,” he said.

Threefold management strategy

Dr. Lindstrom said his experience in a high-volume LASIK practice has provided his group with a strategy to successfully identify and manage the uncommon, yet potential sight-threatening, complication. His treatment strategy is threefold. It includes identifying cells in the lamellar interface, staging their location and severity and intervening at the appropriate point in time.

Careful inspection by slit-lamp examination on postoperative day 1 is crucial in identifying DLK, as the cellular reaction will almost always be present in the first 24 hours, he said. A fine, white, granular reaction in the lamellar interface, frequently more prominent in the flap periphery, will be seen on day 1.

“These cells should be carefully distinguished from epithelial surface abnormalities, such as punctate epithelial keratitis and tear film debris or meibomian gland debris that occasionally is trapped in the flap interface. Meibomium gland secretions have a glistening, oily appearance unlike the dull, white, and granular appearance of DLK,” Dr. Lindstrom said.

Once identified, a staging of severity and location can then be made. Dr. Lindstrom ranks DLK from stage 1 to 4.

Stage 1 is defined by the presence of white, granular cells in the periphery of the lamellar flap with sparing of the visual axis. This is the most common presentation of DLK at day 1.

Stage 2 is defined by the presence of white, granular cells in the center of the flap involving the visual axis. This appearance, occasionally present at day 1, is more frequently seen on day 2 or 3, the result of central migration of cells from stage 1 DLK.

Stage 3 DLK is the aggregation of more dense, white, clumped cells in the central visual axis, with relative clearing in the periphery. This is often associated with a subtle decline in visual acuity by one or two lines and a subjective description of haze by the patient. The cellular reaction collects in the center of the ablation and makes cells slightly inferior to the visual axis with gravity.

“Identification of this more intense central reaction of cells is paramount to preventing an unwanted outcome. If left untreated, a significant portion of these eyes will go on to develop permanent scarring. We have found that lifting the LASIK flap promptly following the appearance of stage 3 can prevent permanent scarring,” Dr. Lindstrom said.

Stage 4 DLK is the rare end result of a severe lamellar keratitis with stromal melting, permanent scarring and associated visual morbidity. The aggregation of inflammatory cells and release of collagenases results in central corneal edema, with overlying bulla formation and eventual stromal volume loss. A hyperopic shift may occur along with the appearance of corrugated mud cracks. Proper identification grading and appropriate intervention can prevent this from occurring.

Treatment

Dr. Lindstrom’s management of both stage 1 and stage 2 DLK consists of topical steroid drops administered every hour and steroid ointment administered at bedtime, although a more randomized study has conclusively demonstrated this to be of benefit.

Prompt follow-up in 24 to 48 hours will identify a minority of cases that will progress to stage 3. Once stage 3 DLK is identified, the management involves lifting the flap and debulking the inflammatory reaction by careful irrigation of the bed and undersurface of the cap. “This should be performed as soon as stage 3 is identified, usually at postop day 2 or 3, in order to block the inflammatory response and prevent permanent scarring,” Dr. Lindstrom said.

He also warned that lifting the flap at day 1 would miss the peak inflammatory reaction and result in unnecessary treatment of the majority of grade 1 and grade 2 cases which would be self-limited. However, waiting until day 5 or 6 will risk the development of permanent scarring. Instead, Dr. Lindstrom has found that lifting of grade 3 DLK, usually in 48 to 72 hours after the initial procedure, is effective.

“An example of grade 3 DLK intervention at postop day 3 where there’s a clumping of cells centrally is to take the flap back and lift it. The bed and undersurface of the cap are then rinsed with balanced salt solution and a sterile Merocel sponge. The flap is then floated back into position enough to dry in place. The patient is then maintained on intensive topical steroid treatment,” Dr. Lindstrom said.

Accuracy the first time

“It’s important for us to work to improve the accuracy of LASIK, to reduce the number of patients that require an enhancement. An accurate preoperative refraction, and perhaps wavefront analysis, will help. Also, accurate laser calibration is important. People continue to make errors in programming,” Dr. Lindstrom said.

He also said that personalized nomograms, careful control of intraoperative hydration and fast, reproducible operating times can all be very helpful in this regard.

“The nomograms we have for our lasers vary from laser to laser depending on the manufacturer. Each surgeon needs to personalize their nomogram in order to maximize their results,” he said.

The key to reducing LASIK complication is to make sure surgeons are as accurate as possible with their plan for LASIK and their plan to treat complications, according to Dr. Lindstrom.

“New technology has helped,” he said. “Modern keratomes prevent the flap complications. But through the surgeon’s skill and prompt recognition of complications followed by prompt treatment, a very minimum of our patients need suffer any loss of best-corrected acuity.”

For Your Information:

• Richard Lindstrom, MD, is head of Minnesota Eye Associates and chief medical editor of Ocular Surgery News. He can be reached at 710 E. 24th St. Ste. 106, Minneapolis. MN 55404; (612) 813-3633; fax: (612) 813-3660; e-mail: rllindstrom@worldnet.att.net.