Abstract
Purpose::
Dry eye is frequently encountered and often treated with artificial tears (AT). The administration of an AT can disrupt the tear layer resulting in an immediate decrease in contrast sensitivity (CS) and visual acuity. While this immediate effect was shown to be dependent on viscosity of the AT, the longer-term effect of continuous use of ATs has not been investigated. The purpose of this study was to determine if long-term use of ATs altered the immediate effect of AT administration on CS.
Methods::
Thirty two subjects (10 normal, 13 mild and 9 moderate/severe dry eye) used either Refresh Plus (Allergan) or Optive (Allergan) on a daily basis for two weeks. The subjects were examined before and at 1 and 2 weeks after daily AT use. At each visit, the subjects answered a Schein dry eye questionnaire, underwent a slit lamp evaluation, and had CS measured. CS to a 14 cpd sine wave grating was continually tracked (using a 2 AFC technique) before and after (minimum of 35 minutes) a drop of the AT was instilled in the test eye.
Results::
The Schein questionnaire indicated subjective improvement in dry eye symptoms with both ATs (all p values < 0.05), whereas, the slip lamp findings did not change (p > 0.05). There was no significant change in CS with Refresh Plus for the normal or dry eye subjects across visits (ANOVA, all p values > 0.05). Optive did not produce a change in CS over time for the normal (p = 0.38) but it did for the dry eye subjects (p = 0.03). Dry eye subjects using Optive showed a significant decrease in CS at pretreatment and week one (p < 0.05) not seen after two weeks of treatment.
Conclusions::
These results confirm that the viscosity of an AT has a significant effect on CS. Refresh Plus (3 cps, no effect on CS) and Optive (15 cps) have low viscosity and Optive may marginally alter CS. The long term use of Optive by dry eye subjects altered the immediate effect of AT administration on CS. The loss in CS with Optive instillation decreased after 2 weeks of treatment. This suggests that continued use of Optive may normalize the tear layer.
Clinical Trial::
www.clinicaltrials.gov NCT00395759
Keywords: cornea: tears/tear film/dry eye • contrast sensitivity