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BARCELONA - Aggressive topical treatment may be adequate for eyes with post-LASIK diffuse lamellar keratitis (DLK) even when the condition has reached its most severe form, according to Matteo Piovella, MD, Centro Microchirurgia Ambulatoriale, Monza, Italy, who will be presenting his findings here at the 6th Winter Refractive Surgery Meeting of the ESCRS.

In a study involving eight eyes of five patients who developed advanced DLK after undergoing LASIK, the condition resolved in all cases and all were within about one dioptre of emmetropia at one year’s follow-up after an intensive course of topical therapy with antibiotics and steroids, Dr. Piovella told EuroTimes in an interview, adding:

“Diffuse lamellar keratitis, also known as “Sands of the Sahara,” is a condition of uncertain aetiology that occurs in one per 1000-2000 LASIK patients. It usually occurs within the first few days of a LASIK procedure. Many authors suggest that lifting the flap and irrigating the interface is necessary when the condition becomes more severe. However, in our study we were able to demonstrate that optimal results may be obtained with topical therapy alone even when corneal melting has begun to appear,” said Dr. Piovella.

The patients in the study had a mean age of 28.5 years and had all undergone primary LASIK to correct myopia with a mean spherical equivalent of -5.3 D Their mean pre-operative BSCVA was 20/21. The onset of DLK occurred within a mean of 2.6 days after surgery when their mean BSCVA fell to 20/37.5 ± 10.0. Seven of eight eyes already had dense cellular infiltrates with incipient corneal melting and had lost several lines of BSCVA (stage 3 Machat), while the remaining eye had PRK-like haze with some loss of vision (stage 2 Machat).

Intensive Topical Regimen
Following diagnosis of DLK, Dr. Piovella placed the patients on a regimen of topical therapy consisting of steroid (dexamethasone-heparin) and antibiotic (lomefloxacin) eyedrops applied every two hours during the day and applied as an ointment before going to bed. Patients continued their treatment for a mean of 27.8 ± 4.0 days. The mean follow-up was 12.6 ± 4.2 months. All were closely monitored throughout the treatment and follow-up periods.

At final follow-up, there was 0.5 haze, the mean BSCVA was 20/20 and the mean spherical equivalent was 0.3 + 1.3 D. The results were comparable to those achieved at other centres where lifting the flap and irrigating the interface would have been the preferred option, Dr. Piovella said, adding:

“In several cases DLK was diagnosed late because patients had not returned for the follow-up visits. As a result they already had a white spot in the middle of their cornea, which is the beginning of a corneal melt. The usual technique in such advanced cases is to lift the flap and irrigate the interface. However, had I done so more tissue would have been lost. In our study, topical therapy produced comparable one-year results to those achieved elsewhere by lifting the flap.

The distinguishing characteristic of DLK is the appearance of a dusting of creamy coloured leukocytes in the interface that is initially peripheral and later diffused and scattered through a large area. Infiltrates are confined to the flap/stromal interface and are more concentrated around surgical debris. In its later stages dense, white, clumped cells accumulate in the central visual axis, after which stromal melting and permanent scarring occur, he continued.

Several Theories as to Cause
The cause of DLK is unknown. Current theories suggest that it is an allergic or toxic reaction to chemotactic factors and the attraction of leukocytes from the limbal vasculature. The reaction may be due to a broad variety of foreign substances brought into the eye during surgery such as talc, oil, instrument milk, metallic fragments and bacterial endotoxins. Alternatively it may result from the introduction of endogenous substances not usually present within the layers of the cornea, such as meibomian secretions, red blood cells, and epithelial cells.

The microkeratome blade is one of the most likely means by which a causative agent becomes introduced into the intra-lamellar tissues. After several procedures on the same day, fluid may percolate from the engine of the device down to blade, which heats the stromal bed causing a chemical reaction and aseptic necrosis. There is hope that recent introduction of single-use microkeratomes may therefore reduce the incidence of the complication.

Another means of reducing the incidence of DLK may be to restrict the use of myopic LASIK to patients with a refractive error of less than 8.0 -9.0 D. While at present there is no evidence to directly link, the correction of higher degrees of myopia with the development of DLK, the 20-25% of patients who undergo such refractive corrections account for 80% of LASIK complications in general, he said, adding:

“LASIK patients need to be strictly monitored in the early post-operative period so that we can intervene at an early stage if DLK develops. However, our study has shown that even in cases which escaped early detection and severe DLK occurred a successful outcome was possible with intensive medical treatment and stringent follow-up. Flap-lifting and irrigation were not necessary and final patient satisfaction was remarkable.”

Dr. Piovella’s co-authors were Fabrizio I. Camesasca, MD,of the Instituto Clinico Humanitas, and Barbara Kusa, MD, also of the Centro Microchirurgia Ambulatoriale.