Uncommon Corneal Finding Following Phototherapeutic Keratectomy For Bullous Keratopathy

To report a case of late onset chronic indirect fistula in a decompensated cornea after multiple ocular surgeries including a recent phototherapeutic keratectomy (PTK). Our observations provide a mechanistic explanation of the possible etiopathogenesis behind this presentation and highlights the essential role of AS-OCT for assessing the findings.

The reported case presented to King Khaled Eye Specialist Hsopital after undergoing multiple palliative procedures for a pseudophakic bullous keratopathy (PBK)  in the left eye, including a PTK, with a late onset corneal leak on routine clinical examination. Serial Anterior Segment Opitcal Coherence Tomogoraphy (AS-OCT) sections were obtained which revealed distinctive multilayer corneal changes during the healing process. 

A 73-y/o female presented for a routine follow up to our institiute as a case of bilateral chronic angle closure glaucoma and a PBK in the left eye. Given the advanced stage of glaucoma with guarded visual potential in the diseased eye, she underwent multiple palliative procedures including a deep PTK (ablation depth: 200 μm) in 2019.

Three years later, the patient was at a regular follow up when a pinpoint corneal leak was noted on fluorescein staining of the left cornea. Her best corrected visual acuity was hand motion and intraocular pressure (IOP) was 40 mmHg. Examination  showed a diffusely scarred cornea, with a paracentral area of slowly appearing, spontaneous, pinpoint corneal leak with an underlying intrastromal fluid pocket. The anterior chamber was formed and there was no corneal thinning or epithelial defect. AS-OCT of the left eye, showed a diffuse anterior stromal hyper-reflectivity corresponding to the induced scarring post-PTK, in addition to an area of intrastromal hypo-reflectivity at the inferior paracentral cornea (lacunae) and an irregular Descemet membrane with areas of discontinuity.

A thin layer of glue was applied over the leaking area followed by bandage contact lens placement. The patient was started on a topical antibiotic, and three topical anti-glaucoma drops. Postoperatively, clinical exam showed a well apposed layer of glue with no evidence of leak. The previously noted intrastromal fluid collection was resolved and the IOP was well controlled.

This report presents a rare finding of an indirect corneal fistula during the healing process of a decompensated cornea. With the help of AS-OCT, an indirect communication between the AC and the exterior of the cornea was observed, where the stromal lamellae acted like a valve, slowing the leak of aqueous and maintaining a formed AC.  Similar subtle leaks in the setting of a formed anterior chamber, can often be missed and carry a risk of infection. Keen observation and a habitual check for leakage using fluorescein stain should be practiced over the long term of compromised corneas during their healing process.