Low tear flow rate may reduce antioxidant supply to cornea in older patients

Optom Vis Sci. 2011;88(4):507-511.

Older patients may experience more corneal stress and dry eye syndrome due to low tear flow rates, a study found.

A low flow rate decreases the level of antioxidants in tears, making the eye more susceptible to photo-oxidative and other oxidative processes, according to the study authors.

One hundred twenty Chinese subjects were divided by age: 58 were aged 19 to 29 years and 62 patients were aged 50 to 75 years. Minimally stimulated tears were obtained from the subjects. All were reported in good health, did not wear contact lens, had no symptoms of dry eye and had normal external ocular health without any pathological changes in eyelids, meibomian glands, conjunctivae or cornea.

The antioxidant content of the tears from the younger and older subjects showed no significant differences. Tear flow rates were significantly lower (P < .0001) in the older subjects: 43% of the older subjects had a flow rate of less than 2 µL/min, whereas 36% of the younger subjects had a flow rate greater than 24 µL/min.

"The effect of low flow rate on the dynamic antioxidant supply to the corneal surface indicates that older subjects have poorer overall defense against photo-oxidative and other oxidative processes," the study authors said.