For Physicians

Who to contact

If your ophthalmology practice treats many patients with HZO and is interested in becoming a Participating Clinical Center, please email the ZEDS Coordinating Center at NYU Langone Medical Center at

Rationale for the ZEDS Trial

The need for a large-scale trial is supported by extensive published evidence of chronic active Varicella Zoster Virus (VZV) infection contributing to complications of Herpes Zoster (HZ), and the efficacy of suppressive antiviral treatment in reducing recurrent Herpes Simplex Virus (HSV) in the eye.

The landmark study of long-term use of oral acyclovir for the prevention of recurrent Herpes Simplex Virus (HSV) ocular disease, the Herpetic Eye Disease Study (HEDS) Acyclovir Prevention Trial (APT), demonstrated a 45% reduction in recurrent ocular disease over one year, and was most beneficial for patients with a past history of HSV stromal keratitis.

In addition, a recent retrospective study reported a 35% reduction of recurrent disease in HZO patients on relatively low-dose suppressive antiviral treatment, which was comparable to the benefit for HSV eye patients in the same study.

Given the similarities between HSV and HZO keratitis, suppressive antiviral treatment in HZO may reduce stromal keratitis and other disease manifestations thought to be predominantly immune-mediated, as well as dendriform keratitis and iritis.

For more information, see the ZEDS Background and Rationale slides.

ZEDS Trial Design

Approximately 60 clinical sites in the U.S will be enrolling 1,050 patients with a history of episode(s) of certain types of eye disease due to HZ0 within the past year.

The study is a double-masked, placebo-controlled multi-center, randomized clinical trial (RCT) that will enroll immunocompetent study participants age 18 years and older who have HZO diagnosed at variable times in the past, with an episode of dendriform keratitis, stromal keratitis, endothelial keratitis, and/or iritis within one year prior to enrollment. Eligible study participants will be randomized in a 1:1 ratio to long-term suppressive treatment with oral valacyclovir 1000 mg daily or placebo for one year. They will be followed every 3 months for a total of 18 months, to determine outcomes of new or worsening dendriform keratitis, stromal keratitis, endothelial keratitis, and/or iritis during 12 months of treatment and for 6 months following treatment discontinuation among study participants randomized to valacyclovir compared to placebo. In addition, the incidence, severity and duration of postherpetic neuralgia will be evaluated in study participants randomized to valacyclovir compared to placebo, as a secondary outcome.

For more information, contact