Abstract
Purpose::
To determine the effect of two artificial tears, one more viscous than the other, in the relief of environmental dry eye induced by a novel ocular stress test (OST).
Methods::
Twelve healthy normal subjects were recruited in this crossover and single masked study. Ocular stress was induced by setting the inter-blink interval for each subject at 5 seconds more than the tear break up time over a 15 minute period. An auditory signal triggered the blink. The effect of stress on the tear film and the effectiveness of ‘symptom relief’ (drop instillation after OST), ‘immediate protection’ (drop instillation before OST) and ‘2 week prophylactic use’ (last drop instillation 1 hour before OST) was assessed for two artificial tears, Cellumed (Allergan Inc., CA) and Refresh Contacts (Allergan Inc., CA). Low contrast visual acuity (VA), symptoms with analogue scales (symptom scoring), non invasive tear breakup time (NITBUT) and tear evaporation were measured before and after the OST. One week of washout period was allowed between the assessments of the effect of different drops.
Results::
The induced stress on the tear film did not appear to have any effect on VA, tear evaporation and NITBUT. However, total symptoms score was found to be significantly higher post stress, than pre stress (p=0.002). No significant differences were seen between pre and post symptoms total scores in ‘symptom relief’ and ‘immediate protection’ visits of both Cellumed and Refresh Contacts. Post total symptoms score was seen to be significantly higher than pre stress score after two weeks of prophylactic use of both drops (p= 0.003 for both drops). Both drops were found to be equally effective in alleviating stress induced dry eye symptoms.
Conclusions::
There is an increase in dry eye symptoms after ocular stress. The use of artificial tears just before or after ocular stress is helpful in relieving the resultant symptoms of dry eye.
Keywords: cornea: tears/tear film/dry eye