The objective of the study is to demonstrate a change in osmolarity over time when moderate to severe dry eye subjects are treated with TheraTears lubricating drops.

Symptomatic dry eye subjects exhibited a significantly higher tear osmolarity than observed in normal subjects, this is thought to relate to the inherent tear film instability of dry eye disease. Lubricating eye drops are frequently prescribed to relieve the symptoms of dry eye.

Inclusion Criteria:

1. Is at least 21 years of age and has full legal capacity to volunteer;
2. Has read and signed the information consent letter;
3. Is willing and able to follow instructions and maintain the appointment schedule;
4. Is diagnosed with dry eye syndrome (in at least one eye), indicated by current ocular examination, prior history (self-reported history of dry eye is acceptable) and current use of treatments for dry eye;
5. Has a minimum osmolarity reading of 316 mosm/kg at the baseline visit in at least one eye or a osmolarity reading of at least 308 (in worse eye) and at least an 8 point difference between the two eyes.

Exclusion Criteria:

1. Has taken part in another research study within the last 30 days;

2. Planned contact lens wear during the course of the study;

3. Staff at the investigational site or family member of site staff or family member of currently enrolled participant;

4. Any subject that violates the washout period by using eye drops during the 72hrs washout period;

5. Has any known ocular disease* including active ocular infection, inflammation or allergy, especially Salzmann's nodular degeneration, symptomatic conjunctivochalasis, and fixation disparity syndrome;

6. Restasis use can be included if they have been on it for at least 3 months and are stable.Used Restasis (or similar topical medication) within the last 6 months;

7. Has a systemic condition that in the opinion of the investigator may affect the dry eye status of the subject, especially those newly diagnosed, newly prescribed and/or unstable;

8. Is pregnant, lactating or planning a pregnancy at the time of enrolment (verbal confirmation necessary);

9. Use of systemic anti-histamines, as long as they have been on them continuously for at least 1 month. Use of medications such as: Systemic Antihistamine (e.g., Allegra®, Benadryl®, Claritin®, Dimetapp®, Unisom®, Zyrtec®, etc.), Isotretinoin (e.g., Accutane®, Roaccutane®, Amnesteem®, Claravis®, Isotroin®, Sotret®) or similar medications;

10. Has known sensitivity to the diagnostic pharmaceuticals to be used in the study;

11. Has undergone ocular surgery(LASIK, Cataract, etc)within the last year;

    • For purposes of this study, ocular conditions that are typically associated with dry eye status, such as meibomian gland dysfunction, mild (i.e. not considered clinically relevant) blepharitis, corneal and conjunctival staining are not considered an exclusion.