• Chronic GVHD is diagnosed based on the history of allogeneic HSCT (Hematopoietic stem cell transplant) and the presence of systemic GVHD in organs other than the eye. In the ocular GVHD group, dry eye symptoms start after the development of systemic GVHD. If post-HSCT dry eye precedes GVHD clinical signs in other organs, the investigators will use the 2013 diagnostic criteria by International chronic ocular GVHD consensus group.

• The investigators will recruit patients for the study. The investigators plan to include ocular GVHD patients that are of age 18 years or older who have typical symptoms of dry eye with an Ocular Surface Disease Index (OSDI) score greater than 13 and corneal fluorescein staining (CFS) score of 3 or more (National Eye Institute \[NEI\] grading scale, 0-15). Normal age-matched volunteer group will include people whose OSDI less or equal to 13 and CFS score less than 3.

⁃ The patients will continue their current systemic and ocular medications, which may include one or combination of preservative free artificial tears, restasis or xiidra, serum tears, ointment, or scleral contact lens.