Deep corneal calcification associated with preservative-free eyedrops and persistent epithelial defects

To describe the formation of deep calcareous degeneration of the cornea associated with the use of preservative-free eyedrops in patients with a persistent epithelial defect and active ocular surface inflammation.

A case series of 6 patients with persistent epithelial defects (1 with diabetes, 3 with penetrating keratoplasty, and 2 with herpes zoster) treated with preservative-free medications was reviewed over 18 months. Each patient subsequently developed deep calcareous corneal degeneration. Data regarding underlying etiology, diagnosis, clinical findings, and medications used were recorded. Each medication used was analyzed for phosphate levels by using a Roche 917 analyzer.

All 6 cases of calcareous degeneration of the cornea had persistent epithelial defects, treated with preservative-free medications (timolol, dexamethasone, and prednisolone), in the presence of active inflammation on the ocular surface. The mean levels of phosphate were 130, 42.9, and 22.9 mM in timolol, dexamethasone, and prednisolone, respectively. All 6 patients had some degree of corneal opacification and reduced visual acuity.

A contributory factor in our case series seems to be the use of preservative-free medications in persistent epithelial defects. The preservative-free medications we measured had high levels of phosphate, which may not be common knowledge.