Pressure-Induced Interlamellar Stromal Keratitis (Pisk) After Femtosecond-Assisted Superficial Anterior Lamellar Keratoplasty (Salk)

To report a case of pressure-induced interlamellar stromal keratitis (PISK) after Superficial Anterior Lamellar Keratoplasty (SALK) to manage anterior stromal scarring in a patient with aniridia and limbal stem cell deficiency (LSCD)

Corneoplastic Unit, Queen Victoria Hospital, East Grinstead, UK

We report the case of a 58 year old female patient with a history of aniridia, LSCD, glaucoma and pseudophakia. The patient underwent a right eye (RE) limbal stem cell transplant with COMET first, to improve and stabilize the ocular surface. Six months later a RE femto-second assisted SALK was performed to address the anterior corneal stromal scarring. The femto-SALK surgery was performed uneventfully with a 8mm diameter graft of 200microns thickness, along with amniotic membrane transplant was performed at the same time. The initial post-operative course was uncomplicated, with the patient receiving prednisolone 0.5% four times a day, Alphagan and brinzolamide/timolol drops twice a day. At 4 weeks post-operative she presented with visual acuity of CF (counting fingers) and IOP of 4mmHg on GAT, while central corneal haze was noted. Initially considered a potential graft rejection, the frequency of topical steroids was increased to every two hours. Subsequent evaluation one week later using AS-OCT revealed the accumulation of fluid at the interface between the SALK graft and recipient stroma leading to diagnosis of PISK/ IFS. Given the inaccurately low GAT IOP reading and the pre-existing regimen of IOP-lowering medications, the patient was commenced on oral acetazolamide 250mg three times daily. Remarkable resolution of the interface fluid was observed within two weeks, resulting in a smooth integration between the SALK graft and the recipient corneal bed.

This is the first case of PISK/IFS following SALK, diverging from the traditional association with LASIK and, more recently, SMILE surgery. PISK or IFS has been typically linked with LASIK surgery and more recently after SMILE surgery. Unlike prior reports of PISK/IFS post-corneal transplant, which involved patients with a history of LASIK surgery and fluid accumulation beneath the LASIK flap, our case demonstrates PISK/IFS occurrence directly between the SALK graft and the recipient cornea. The utilization of femtosecond laser in SALK to excise diseased anterior corneal stroma introduces a similar risk for creating a low-pressure interface conducive to fluid accumulation, thereby precipitating PISK.