In this study the investigators aim to examine the effects of Transcranial Direct Current Stimulation (tDCS) on pain levels as well as the changes in cognitive (thought) processing in individuals with chronic pain of the cornea -- and also compared with healthy controls.

Inclusion Criteria (for all subjects):

1. Provide informed consent to participate in the study;
2. 18 to 65 years old;

Additional Inclusion Criteria for Subjects with Chronic Corneal Pain:

1. Corneal pain for six months or more;
2. Referral from a corneal specialist (Dr. Perry Rosenthal) with refractoriness to conventional ophthalmologic treatments for corneal pain such as local topical medications and soft bandage contact lenses;
3. Report a Visual Analogue Scale (VAS) for pain of 4 or greater in the previous 3 weeks;

Exclusion Criteria (for all subjects):

1. History of alcohol or substance abuse within the last 6 months as self-reported;

2. Diagnosis of any neurological diseases (such as epilepsy);

3. Episodes of seizures within the last 6 months;

4. Unexplained loss of consciousness

5. Use of carbamazepine or neuropsychotropic drugs

6. Contraindications to tDCS

   • Metal in the head
   • Implanted brain medical devices

7. Pregnant at time of enrollment