Why is close monitoring required with frequent or prolonged Opatanol (olopatadine hydrochloride) use in patients with dry eyes or damaged corneas?

Close monitoring is required with frequent or prolonged Opatanol (olopatadine hydrochloride) use in patients with dry eyes or damaged corneas because its benzalkonium chloride has been reported to cause punctate keratopathy and/or toxic ulcerative keratopathy.