Subjects participating in the Sponsor's natural history study (protocol NHS) for at least 12 weeks and that meet all other eligibility criteria will be randomized 1:1 to receive ophthalmic administration of B-VEC three times a week or placebo three times a week for the first 12 week intervention period. During the second 12-week intervention period subjects will be crossed-over to receive the alternative Investigational Product (IP) for an additional 12 weeks. IP will be administered in the home setting by a trained designee. The Investigator (or designee) will contact subjects (or their parent/legal guardian) to assess for any adverse events or changes in medications, treatments, or procedures. Subjects (or their parent/legal guardian) will complete weekly symptom diaries and monthly questionnaires to document corneal abrasion symptoms and frequency and gauge overall subject (or parent/legal guardian) impressions of disease severity and disease/symptom changes during the study.
