Understanding time course of DLK can help eliminate visual loss

Proper identification, staging and intervention is crucial.

---DLK also is known as shifting sands phenomenon or Sands of the Sahara Syndrome. (Figure 1)

---A striking characteristic of DLK is a white, granular appearance. (Figure 2)

With the volume of laser in situ keratomileusis (LASIK) procedures growing exponentially, there is an expanding role for ophthalmologists and other eye care providers to be aware of an uncommon post operative condition known as diffuse lamellar keratitis (DLK), which has the potential to derail an otherwise ideal outcome.

Understanding the time course of the disease, along with proper identification, staging and intervention, can help eliminate visual loss associated with this condition.

Background

Stage 1 DLK is defined by the presence of white, granular cells in the periphery of the lamellar flap, with sparing of the visual axis. (Figures 3A and 3B)

The first anecdotal reports of a mysterious post-LASIK inflammatory syndrome began to surface only a few years ago, which is when LASIK began to rise in popularity and acceptance among patients and physicians. Maloney and Smith were one of the first to report on this unusual syndrome at the 1997 American Academy of Ophthalmology meeting in Chicago.

The condition would eventually come to be known by a variety of names, including shifting sands phenomenon or sands of the Sahara syndrome, alluding to the white, granular appearance with waves of increased density (Figure 1).

Since then considerable amount of speculation has been focused on possible etiologies (Table). Anecdotal reports of case clusters seem to point the finger toward a contaminant in the lamellar interface introduced at the time of surgery.

Still more cases appear to be associated with epithelial defects at the time of surgery or even delayed epithelial abrasions occurring weeks or months later. This cumulative evidence suggests that no one agent is completely responsible for the syndrome, and that a multifactorial etiology is likely.

Despite efforts to eliminate potential causes of DLK, an increasing number of cases are being reported as the volume of LASIK procedures performed worldwide continues to grow. Although difficult to accurately document, the authors’ own experience suggests that the incidence of severe vision-threatening DLK cases may be in the range of 1 in 5,000, while very mild cases may be as frequent as 1 in 50.

The authors’ experience in a high-volume LASIK practice has provided significant insight into this elusive condition, along with a strategy to successfully identify and manage this uncommon yet potentially sight-threatening complication.

Our treatment strategy is threefold, and includes identifying cells in the lamellar interface, staging their location and severity, and intervening at the appropriate time.

Identification

Stage 2 is defined by the presence of white, granular cells in the center of the flap, involving the visual axis, and/or in the flap periphery. (Figures 4A and 4B)

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. A fine, white, granular re action in the lamellar interface, frequently more prominent in the flap periphery, will be seen on day 1 (Figure 2). These cells should be carefully distinguished from epithelial surface abnormalities, such as punctate epithelial keratitis, epithelial edema and tear film debris.

These cells also should be distinguished from meibomian gland debris that occasionally finds its way into the lamellar interface. Meibomian gland secretions will have a glistening, oily appearance, unlike the flat, white and granular appearance of DLK.

Once identified, a staging of severity and location can then be made.

Staging

Stage 3 DLK is the aggregation of more dense, white and clumped cells in the central visual axis, with relative clearing in the periphery. (Figures 5A and 5B)

Stage 1. Stage 1 is defined by the presence of white, granular cells in the periphery of the lamellar flap, with sparing of the visual axis (Figures 3A and 3B).

This is the most common presentation of DLK at day 1 and, with careful inspection, may be present in as many as 1 in 25 to 50 cases.

Stage 2. Stage 2 is defined by the presence of white, granular cells in the center of the flap, involving the visual axis, and/or in the flap periphery (Figures 4A and 4B).

This appearance, occasionally present at day 1, is more frequently seen on day 2 or 3, the result of central migration of cells in stage 1 DLK, giving it the so-called “shifting sands” appearance. This occurs in approximately 1 in 200 cases.

Stage 3. Stage 3 DLK is the aggregation of more dense, white and clumped cells in the central visual axis, with relative clearing in the periphery (Figures 5A and 5B). This is often, but not always, 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 may settle slightly inferior to the visual axis with gravity. The frequency of stage 3 DLK may be as high as 1 in 500 cases.

Identification of this more intense, central reaction of cells is paramount to preventing an unwanted outcome, because if it is 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, or threshold DLK, can effectively blunt the inflammatory response and prevent permanent scarring from occurring. No eyes in our series of more than 12,000 patients have had any loss of best corrected visual acuity when the interface is irrigated promptly at the identification of stage 3.

Stage 4. Stage 4 DLK is the rare end result of a severe lamellar keratitis with stromal melting, permanent scarring and associated visual morbidity (Figures 6A, 6B and 6C). The aggregation of inflammatory cells and release of collagenases result in fluid collection in the central lamellae, with overlying bullae formation and stromal volume loss. A hyperopic shift because of central tissue loss, along with the appearance of corrugated “mud cracks,” are an ominous sign.

Lifting and irrigation at this point is of little benefit and may actually result in additional stromal volume loss if aggressive tissue manipulation is performed. Proper identification, grading and appropriate intervention can prevent this from occurring. The incidence of a severe stage 4 DLK is approximately 1 in 5,000.

Intervention

Stage 4 DLK is the rare end result of a severe lamellar keratitis with stromal melting, permanent scarring and associated visual morbidity. (Figures 6A and 6B)

A brief look at the time course of DLK will guide you to the most appropriate time to intervene in the process (Figure 7). While the severity or stage of the inflammation may differ from case to case, the time course of the disease is fairly consistent. Our experience has shown that the cellular reaction is nearly always present at postop day 1 and peaks at approximately postop day 5. DLK can be best thought of as a threshold disease, where after a certain level of inflammation is reached, permanent scarring is likely to occur.

Stage 1 DLK will follow a self-limited course, resolving in a week to 10 days, as will stage 2 DLK. Our management of both stage 1 and stage 2 DLK consists of topical steroid drops (fluoromethalone 1%) administered every hour, and steroid ointment administered at bedtime, although no randomized study has conclusively demonstrated this to be of benefit. Prompt follow-up in 24 to 48 hours will identify the 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 blunt the inflammatory response and prevent permanent scarring. As seen in Figure 7, lifting all flaps at day 1 would miss the peak inflammatory reaction and result in unnecessary treatment of the majority of grade 1 and grade 2 cases that would be self limited.

However, waiting until day 5 or 6 will risk the development of stage 4 DLK, with permanent scarring. Thus, we have found that lifting of grade 3 DLK, usually at 48 to 72 hours after the initial procedure, is effective.

The lifting procedure comprises delineating the edges of the flap with a blunt spatula and lifting and retracting the flap peripherally to its hinge (Figure 8). This can be accomplished with relative ease in the first 72 hours after surgery. Once the flap is retracted, the bed and undersurface of the cap are gently but thoroughly rinsed with balanced salt solution on a blunt-tipped cannula. The bed and cap are gently cleansed with a lightly moistened Merocel sponge. Bladed instruments and aggressive debriding are to be avoided. The flap then is carefully reflected, floated back in to position and allowed to dry in place. The patient then is maintained on continued intensive topical steroid administration for the next several days. This is then tapered along with clearing and resolution of the cellular reaction.

Proper identification, staging and intervention can help eliminate visual loss from this mysterious condition.

---Time course of DLK, with stage 1 (blue), stage 2 (green), stage 3 (orange) and stage 4 (red), with ideal time for lifting and irrigation of stage 3 DLK on days 2 to 3. (Figure 7)

---The lifting procedure comprises delineating the edges of the flap with a blunt spatula and lifting and retracting the flap peripherally to its hinge. (Figure 8)

For Your Information:

• Eric J. Linebarger, MD, is an assistant professor of ophthalmology at the University of California-San Diego, Shiley Eye Center, La Jolla, Calif. He can be reached at 9500 Gilman Drive, Mail code 0946, La Jolla, CA 92093-0946; (619) 534-6290; e-mail: linebarger@eyecenter.ucsd.edu.