Published in:
01-08-2006 | Laboratory Investigation
Phosphate concentration in artificial tears
Published in: Graefe's Archive for Clinical and Experimental Ophthalmology | Issue 8/2006
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Background
Irrigating solutions and eye drops may contain phosphates as part of their buffer system. In the presence of epithelial keratopathy, a high concentration of phosphate favours corneal calcification. Knowledge of the phosphate concentration in artificial tear products helps to prevent this sight-threatening complication. This study gives an overview on the amount of phosphate contained in artificial tears.
Methods
Fifty-nine samples of commercially available artificial tear preparations were tested. The quantification of phosphate was performed using the molybdate method on a Modular P autoanalyzer.
Results
Twenty-six of 59 (44%) artificial tear products had a phosphate concentration above physiological levels (>1.45 mmol/l). A phosphate concentration above 25 mmol/l was found in nine products (15%), a concentration higher than 50 mmol/l in three (5%).
Conclusions
Many artificial tear formulations contain unphysiological levels of phosphate, but very high concentrations are found only in a few products. These preparations have the potential to favour the formation of insoluble crystalline calcium phosphate deposits when used on a damaged corneal surface, and should therefore be used cautiously.