Polyquaternium-1-Associated Dendritiform Keratopathy.

Purpose: To report a case of polyquaternium-1 (Polyquad, PQ-1) associated dendritiform keratopathy that developed after exposure to the tear substitute Systane (Alcon Laboratories, Inc, Fort Worth, TX). Methods: A retrospective review of the case was performed. Results: Dendritiform keratopathy developed in the patient after an increase in the use of topical Systane from 4 times per day to every hour. Keratopathy resolved with discontinuation of Systane. Conclusions: Polyquaternium-l associated dendritiform keratopathy can occur in patients who have previously tolerated the preservative. Because keratopathy seems to have developed and improved because of dose-dependent factors, the mechanism is more likely toxicity than hypersensitivity.