The purpose of this study is to evaluate the clinical efficacy and safety of ISV-502 compared to AzaSite® alone, Dexamethasone alone, and vehicle in the treatment of subjects with Non-bacterial Blepharitis.

Inclusion Criteria:

• Are at least 18 years of age at Visit 1 (Day 1, Baseline) of either sex and any race.
• Signature of the subject or legally authorized representative on the Informed Consent Form.
• Are willing and able to follow all instructions and attend all study visits.
• Are willing to avoid disallowed medication for the duration of the study.
• If female is of childbearing potential, agree to and submit a urine sample for pregnancy testing. Post menopausal is defined as having no menses for at least 12 consecutive months.
• Additional inclusion criteria also apply.

Exclusion Criteria:

• Have known sensitivity or poor tolerance to any component of the Investigational Drug.
• Have an acute ocular infection (bacterial, viral or fungal) or active ocular inflammation other than Blepharitis in the study eye.
• Have used topical corticosteroid medications or topical ophthalmic solutions that the investigator feels may interfere with the study parameters.
• Have used any non-diagnostic topical ophthalmic solutions in the study eye.
• Be currently pregnant, nursing, or planning a pregnancy; or be a woman that has a positive urine pregnancy test.
• Currently suffer from alcohol and/or drug abuse.
• Have prior (within 30 days of beginning dosing) or anticipated concurrent use of an investigational drug or device.
• Have a condition or a situation which, in the Investigator's opinion, may put the subject at increased risk, confound study data, or interfere significantly with the subject's study participation.
• Additional exclusion criteria also apply.