Eyeworld

52 PISK discoverer and recent researcher elucidate these kissing cousins W hat looks like diffuse lamellar keratitis (DLK) appears shortly after LASIK, but is there a significantly different pathology? It's called pressure-induced in- terlamellar stromal keratitis (PISK), and case reports have been sporadic since its discovery in 2002. "PISK is a poorly documented phenomenon," wrote Theofilos Tourtas, M.D., resident, Department of Ophthalmology, University of Erlangen-Nuremberg, Germany, in a study on PISK published in Cornea. "Whereas DLK has been well de- scribed in the literature, there have been only a few reports of PISK." In interviews with EyeWorld, both Dr. Tourtas and the first oph- thalmologist to report PISK in 2002, Michael Belin, M.D., professor, ophthalmology and vision science, University of Arizona College of Medicine, Tucson, suggested that it's critical to distinguish PISK from DLK for treatment purposes. Stumbling upon PISK Dr. Belin explained that in his initial report on PISK, a series of patients presented with classic-appearing DLK, but were not responsive to steroids or anti-inflammatory agents. In one patient, Dr. Belin no- ticed the pressure was fairly high, and treated him both with continu- ous steroids and pressure medica- tions, after which the patient improved. "Literally a week after that case, I was a visiting professor in Taiwan and one of the leading refractive sur- geons presented an unknown case of DLK," Dr. Belin said. "The first thing out of my mouth was, 'What was his pressure?' He looked at me like, 'Why are you asking that?'" The patient's pressure was in- deed high and documented another case of PISK. Since then, there have been others—but relatively few re- ported in medical literature. Dr. Tourtas' case involved a 42- year-old man who experienced blurred vision in both eyes, seeking treatment for the problem 3 months after LASIK. DLK was diagnosed and topical steroids were increased. There was no improvement, but IOP markedly increased to 48 mm Hg. The patient was then diagnosed in- stead with PISK, and pressure-reduc- ing drops were added. One week later, the patient's visual acuity im- proved while interface haze de- creased. Dr. Tourtas distinguishes DLK from PISK in his report as follows: DLK is an idiopathic interface inflammation that typically occurs within the first postoperative week, with clinical features ranging from asymptomatic infiltrate confined to the interface to stromal necrosis. PISK is a condition with DLK-like in- terface haze caused by steroid-in- duced ocular hypertension after LASIK. The clinical findings are not associated with an accumulation of inflammatory cells but caused by edema. Inflammatory mononuclear cells and granulocytes, typically seen in patients with DLK, are absent in patients with PISK. "You don't hear or see much about [PISK]," Dr. Belin added. Part of the reason is that ophthalmolo- gists are more cognizant of checking IOP after LASIK now. "You are going to treat IOP ele- vation if it's clinically significant re- gardless of what the situation is," Dr. Belin said. "We're not seeing the cases because we're catching and treating pressure elevation before it gets the chance to cause a problem." Identifying and treating PISK It's still very important to be able to distinguish PISK from DLK since treatments are different, and time is of the essence. Be mindful of the following in confronting a potential PISK prob- lem, Dr. Belin said: • Anytime you see what looks like DLK, check the patient's IOP; • Note that sometimes you can get a falsely low pressure reading with fluid accumulation; • If there is any suspicion of PISK, treat the patient with anti-glau- coma medications, and to be safe, use prudent anti-inflammatory medications that will cause few if any steroid responses; • DLK tends to be more focal. It's diffuse but has focal areas. PISK tends to be more evenly distrib- uted. "The last thing you want to do in classic DLK is to stop anti-inflam- matory drugs," Dr. Belin said. "If I was presented with a nuance that appeared to be DLK and the pressure also was elevated, I would not ini- tially suggest discontinuing anti-in- flammatories until I had a clear pic- ture of what was going on." Further, if a patient's pressure is 50, Dr. Belin would be more com- fortable diagnosing PISK. Alterna- tively, if pressure is in the 20s, he would not stop anti-inflammatories. "If the pressure is moderately el- evated, it behooves the surgeon to treat the pressure in addition to the anti-inflammatory treatment for pre- sumed DLK," Dr. Belin said. There also are greater conse- quences to getting DLK wrong, Dr. Belin said. "DLK can progress to stromal necrosis and flap melt," Dr. Belin said. "The consequence of [PISK] would only be long-term if pressure was high enough to induce nerve damage, which can happen. But acutely, untreated DLK risk is much more substantial." Dr. Tourtas added a few more points about PISK, which differ from Dr. Belin's somewhat. "DLK is dif- fuse lamellar keratitis that appears in the first few days after LASIK," Dr. Tourtas said. "PISK appears after the first post-operative week." But Dr. Belin said, "I wouldn't want to keyhole this [difference] into a time period." Dr. Tourtas also emphasized the consequence of PISK leading to glau- coma. "If it is not diagnosed, then the patient develops glaucoma with an optic nerve atrophy," Dr. Tourtas said. He added that PISK can be a symptom of glaucoma. In his patient, he reported, "Funduscopic examination revealed an incipient glaucomatous optic at- rophy with diffuse visual field sensi- tivity loss." Finally, Dr. Tourtas found SL- OCT to be useful in diagnosing PISK. "The first step is to measure IOP," he said. "If it's normal, then we can do an SL-OCT to rule out fluid accumulation that would lead to a falsely normal IOP." EW Editors' note: Drs. Belin and Tourtas have no financial interests related to this article. Contact information Belin: 520-321-3677, mwbelin@aol.com Tourtas: theofilos.tourtas@uk-erlangen.de EW REFRACTIVE SURGERY 52 December 2011 by Matt Young EyeWorld Contributing Editor A fine line of difference between PISK and DLK PISK appears similar to DLK. This patient experienced haze grade +1/+2 in a pattern suggestive of DLK Source: Michael Belin, M.D.

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