Prospective Study to Validate the Imaging Biomarker for NCP (R33)

Inclusion Criteria: All Subjects: 1. 18 years of age or older 2. Ability to consent 3. Best corrected visual acuity of 20/40 or better in each eye Dry Eye Disease Group: 1. Chief complaint is ocular surface discomfort or dry eye disease, but subject reports no ocular pain on OPAS questionnaire 2. Symptoms lasting at least 3 months 3. Presence of at least two of the following within the same eye: 1. Anesthetized Schirmer score =/\< 10mm 2. Corneal staining of \>3/15 based on NEI scale 3. Tear break up time \< 10 seconds Neuropathic Corneal Pain Group: 1. Chief complain is ocular surface discomfort or dry eye disease 2. Symptoms lasting at least 3 months 3. All of the following in both eyes: 1. Corneal staining of less than or equal to 3/15 based on NEI scale 2. Tear break up time =/\> 10 seconds 4. Must have at least 25% peripheral pain 5. Subject reported discomfort prior to drop response testing of at least 3 out of 10 Control Group: 1. No symptoms of ocular surface discomfort or dry eye disease 2. All of the following in both eyes 1. Anesthetized Schirmer score \> 10 mm 2. Corneal staining of less than or equal to 3/15 based on NEI scale 3. Tear break up time \> 10 seconds 3. The same sex and within 5 years of age of a patient within the NCP group. Exclusion Criteria: 1. Pregnant or nursing 2. Irregular corneal disease 3. Ocular surgery in the past 3 months 4. Ocular infection in the past 3 months 5. Active ocular allergies 6. Participation in a study that could potentially impact the IVCM in the opinion of the investigator 7. Current use of corneal nerve regeneration therapy that has been on-going for 3 months or more. 8. For NCP group only, patients for whom their pain and symptoms can be attributed to other causes in the opinion of the investigator