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Phosphate buffers may cause severe corneal calcification
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Sodium hyaluronate artificial tears may cause deep calcium deposits in patients’ corneas if used frequently, according to a small case series in Switzerland.
Wolfgang Bernauer, MD, and colleagues at the University of Zurich examined patients who used phosphate-buffered hyaluronic acid artificial tears. Patients used the drops often, sometimes as frequently as every 10 minutes, or 100 drops in one day.
Patients were being treated for several different conditions, including severe conjunctivitis, Sjogren’s syndrome, complications from surgery and keratitis. The researchers found that the concentration of phosphate in the eye drop was 50 times higher than that of the normal serum. The calcium deposits developed rapidly and required corneal graft surgery to restore vision, they said.
“In our series, the phosphate buffers had the crucial role in the calcification process,” they said.
They suggested that manufacturers declare the amount of phosphate buffers on drop bottles and inserted leaflets.
The study was published in the March issue of the British Journal of Ophthalmology.