Background: Increased UV radiation and ozone exposure may cause "dry eyes of environmental origin", if the normal anti-oxidative capacity of the tear film can no longer cope with the oxidative stress. The use of artificial tears with an adequate anti-oxidative effect may be beneficial in the treatment of dry eyes caused by environmental factors.
Methods: The anti-oxidative capacity of various commercial artificial tear preparations was determined with a modified TRAP procedure. The two preparations with the strongest anti-oxidative effect were then examined for their protective effects against UV or ozone exposure in a hyaluronate model.
Results: Of 19 artificial tear preparations tested, only 6 showed strong to moderate anti-oxidative effects. All others were at best weakly anti-oxidative or had no anti-oxidative effect at all. Some of them even acted as oxidants. Although the two most strongly anti-oxidative preparations performed somewhat differently on UV and ozone exposure, they were both found to be highly protective against these important oxidative stress factors.
Conclusions: The anti-oxidative capacity of artificial tear preparations varies widely. While some are strong anti-oxidants, others are less active or even act as oxidants. If the carefully elicited history of patients with dry eyes suggests that noxious environmental factors may be causally involved, artificial tears which are not just lubricants or contain wetting agents, but act as anti-oxidants, should be chosen for treatment from the many commercially available preparations. Such an etiology-oriented concept would probably improve the success rate of treatment for dry eyes.