A case report of central toxic keratopathy in a patient post TransPRK (followed by corneal collagen cross-linking)

Abstract

Purpose: The purpose of this article is to report a case of central toxic keratopathy in a patient post transepithelial photorefractive keratectomy (TransPRK), followed immediately by corneal collagen cross-linking.

Methods: This article describes the case of a 26-year-old male after bilateral aberration-free, TransPRK laser (Schwind Amaris 750S). The procedure was performed for compound myopic astigmatism in November 2015, followed immediately by accelerated corneal collagen cross-linking for early keratoconus.

Results: From day 3 post-op, tear film debris underneath both contact lenses with corneal haze and early, progressive central anterior stromal opacity formation only in the left eye were noted. At 2 weeks post-op, the left eye was noted to have a significant hyperopic shift with central corneal thinning in the anterior stroma. A central anterior stromal dense opacity had formed in the left eye with the surrounding superficial stromal haze. As of month 2, the opacity gradually started to improve in size and density. The hyperopic shift peaked at 2 months and continued to improve, largely due to epithelial compensation with a gradual recovery of stromal thickness.

Conclusion: The question remains as to what provokes the typical central corneal necrosis/thinning in central toxic keratopathy. We hypothesize that the space between the contact lens and the corneal surface post TransPRK is prone to a "pseudo-interface pathology" that could mimic diffuse lamellar keratitis-like pathology. Suboptimal lid hygiene, resulting in tear film combinations of bacteria, inflammatory cells, matrix metalloproteinases and other proteolytic enzymes, contributes to the degradation of vulnerable, exposed collagen stromal tissue post TransPRK or any surface corneal ablation. Refractive surgeons should maintain a healthy lid margin and tear film, especially in contact lens wearers, to prevent potential complications in refractive surgery procedures.

Keywords: PRK; TransPRK; central toxic keratopathy; complications; laser refractive surgery.

Figure 1

Pre-op Orbscan of the left and right eyes showing early ectasia. Abbreviations: OD, right eye; OS, left eye.

Figure 2

Left eye 3 weeks post-op.

Figure 3

(A and B) Left eye 4 months post-op showing central corneal opacity with dense central vertical striae.

Figure 4

Right eye 6 months post-op showing diffuse anterior stromal haze without the central dense opacity.

Figure 5

Early post-op (3 weeks) vs late post-op (6 months). Notes: (A) Corneal OCT of the left eye showing stromal thinning with the epithelium compensating for the thinning of the stroma with resulting improvement in the hyperopic refraction. (B) Pachymetry and epithelial maps of the left eye at 3 weeks and 6 months post-op. Notice the recovery of stromal thickness and epithelial compensation. Abbreviations: OCT, optical coherence tomography; SSI, scan score index; OS, left eye.

Figure 6

Post-op right eye (4 months) showing normalized postoperative stromal and epithelial thicknesses. Abbreviations: OD, right eye; SSI, scan score index.