Tear Osmolarity Changes After Instilling Isotonic Hyaluronate Artificial Tears
Condition: Dry Eye
MeSH terms: Dry Eye Syndromes
Study type: Interventional
Phase: Phase 4

Summary: 
      Background:

      Osmolarity is defined as the concentration of particles dissolved in a solution. Normal tears
      contain various dissolved particles including proteins, salts and other electrolytes. The
      investigators plan to investigate how osmolarity of the tear film changes over time after
      instillation of artificial tears containing hyaluronate. This is one kind of artificial tear
      that is used to treat dry eye.

      Dry eye and tear osmolarity:

      Dry eye is a significant health problem, but diagnosis and treatment are often ambiguous and
      ineffective. There has been a resurgence of interest and research in dry eye in the past 5
      years, and tear osmolarity has emerged as perhaps, one of the most effective ways to evaluate
      tear quality and dry eye status. Dry eye is usually treated with artificial tears, and many
      formulations are available. The investigators will test an isotonic solution that contains
      hyaluronate. Hyaluronate binds water and should help to maintain water on the eye.

      Objective:

      We plan to study the time course of possible changes in tear film osmolarity following
      instillation of an isotonic artificial tear containing hyaluronate. The investigators will
      use the TearLab, a new clinical instrument that has been developed to quickly and easily
      measure tear film osmolarity. Understanding how artificial tears affect tear film osmolarity
      over time can help doctors determine efficacy and dosing schedules. The investigators will
      test the isotonic hyaluronate (Blink Contacts) artificial tears relative to normal saline
      solution.

      Hypothesis:

      The investigators should be able to measure a decrease in tear osmolarity over time following
      instillation due to the water-binding effect of hyaluronate artificial tears relative to a
      control (normal saline solution).
    

Detailed description: 
      ABSTRACT:

      Introduction: Tear hyper-osmolarity may be a fundamental cause of dry eye in many cases.
      Hyaluronate is an agent used in some artificial tears, which binds water and can protect
      against evaporation. It may therefore be an effective treatment for tear hyper-osmolarity.

      Purpose: Our purpose was to measure changes in tear osmolarity over time following
      instillation of Blink Contacts, an isotonic ocular lubricant containing hyaluronate. We
      hypothesized that even in isotonic solution, the water-binding properties of hyaluronate
      would reduce tear osmolarity. This will help us better understand efficacy of this treatment
      and develop a rational basis for dosing schedules.

      Methods: After baseline osmolarity measurements, eight subjects received either Blink
      Contacts or normal saline drops in both eyes. We re-measured osmolarity five minutes later,
      and then at 15-minute intervals up to 95 minutes. Subjects also rated comfort at each time.
      The next day, the experiment was repeated with the alternate drops for each subject.
    

Intervention name(s): Artificial tears
Intervention type(s): Drug
Intervention description(s): At random, subjects will receive isotonic artificial tear or a control (normal saline).
Intervention MeSH terms: Lubricant Eye Drops
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Treatment
Keywords: dry eye; artificial tears; tear osmolarity; residence time