Inclusion Criteria:

1. Military health care beneficiary between the ages of 21-55.
2. Male or female, of any race, and at least 21 years old and not older than 55 years old at the time of tear collection.
3. Appropriately aged individuals who report that their eyes are "normal" and who have no active eye illness as determined by principal investigator or sub-investigator.
4. Ability and willingness to understand and provide informed consent to participate in this study.

Exclusion Criteria:

1. Irritated eye reflected by patient statements or finding of "red" eye.
2. Individuals with any infections or inflammatory ocular condition (e.g. have "pink eye" or uveitis).
3. Individuals diagnosed with dry eye or other ocular surface condition, including but not restricted to neurotrophic keratitis, anterior basement membrane dystrophy, and recurrent corneal erosions.
4. Individuals who are on any topical eye medications.
5. Anyone who reports previous reaction or the possibility of an allergic reaction to 0.5% proparacaine.