Interface Fluid Syndrome Masquerading as Diffuse Lamellar Keratitis After Small Incision Lenticule Extraction

Abstract

A 34-year-old male with no past medical or ocular history underwent bilateral uncomplicated small incision lenticule extraction (SMILE). On day 1, uncorrected distance visual acuity (UDVA) was 20/25 in the right eye (OD) and 20/20 in the left eye (OS). The intraocular pressure (IOP) was 12 mmHg in both eyes (OU). On day 17, UDVA was 20/70 OD and 20/30+2 OS. Slit-lamp examination (SLE) revealed diffuse 2+ haze at the interface suspicious for diffuse lamellar keratitis (DLK). Topical difluprednate was added twice a day (BID). Vision decreased by day 20 with a significant myopic shift and 3+ interface haze OU. A washout of the interface was performed. Topical steroids were increased with oral prednisone. One day after the washout, vision and interface haze improved. On day 3 status post washout, UDVA decreased to 20/70 OD and 20/50 OS. IOP was 42 mmHg OU. A diagnosis of interface fluid syndrome (IFS) was confirmed. All steroids were stopped while adding ocular hypotensive medication. One month later, visual acuity was 20/20 OU with a complete resolution of interface haze. Only a handful of IFS has been documented in SMILE, an incidence that may increase as SMILE becomes more common. Among all SMILE cases, IFS was most commonly associated with steroid-induced ocular hypertension and a myopic shift around 21 days postoperatively. A fluid cleft at the interface may not always be visible with SLE, masquerading as DLK. Scheimpflug densitometry and anterior segment optical coherence tomography (AS-OCT) may aid in quantifying interface edema needed to confirm a diagnosis when IOP is unclear. A corneal washout can immediately improve corneal edema, but the preferred treatment is discontinuing all steroid medication and starting glaucoma drops.

Keywords: diffuse lamellar keratitis (dlk); interface fluid syndrome (ifs); pressure-induced stromal keratopathy (pisk); small incision lenticule extraction (smile); steroid-induced ocular hypertension.

Figure 1. Normal Anterior Segment

Scheimpflug images of the anterior chamber, highlighting a clear cornea with no opacities of the (A) right eye and (B) left eye.

Figure 2. Corneal Tomography

Corneal tomography demonstrating normal levels of anterior and posterior corneal elevation in the OD and OS. No signs of underlying ectasia risks were observed in either eye. OD: right eye, OS: left eye

Figure 3. Automated Scheimpflug Densitometry

Automated Scheimpflug densitometry demonstrating a dense haze within the cap with corneal edema in the (A) right eye and (B) left eye. Central corneal thickness was (A) 488 μm and (B) 471 μm. OD: right eye, OS: left eye

Figure 4. Automated Scheimpflug Densitometry

Automated Scheimpflug densitometry demonstrating improvement in corneal haze and edema within the cap in the (A) right eye and (B) left eye. Central corneal thickness was (A) 447 μm and (B) 444 μm. OD: right eye, OS: left eye