X-ray radiation that targets only the eye may provide lifelong protection from the development of glaucoma, according to a study in the April 2 issue of the Journal of Clinical Investigation.1
Cells, shown here by arrows, enter untreated eyes through the bloodstream but rarely enter radiation-treated eyes. Image: Jackson Laboratory
Using glaucoma-prone mice, researchers at the Jackson Laboratory in Bar Harbor, Maine, demonstrated that localized irradiation of just the eye protects against the disease—at lower doses than previously published.
They found that a single X-ray treatment to an individual eye prevented detectable neuronal damage and dysfunction in the targeted eye, but offered no protective effect in the untreated eye.
This discovery supports previous research, which indicated that whole-body irradiation along with bone marrow transfer in mice provided protection against glaucomatous damage (96% of treated eyes exhibited no signs of glaucoma at one-year follow-up vs. just 20% of untreated eyes).2
Senior staff scientist Simon John, Ph.D., and associates explained that a class of immune cells known as monocytes enter the optic nerve and retina in response to early tissue damage secondary to glaucoma development.
The monocytes then express destructive molecules that are widely responsible for optic nerve damage and subsequent vision loss in glaucoma patients. However, radiation treatment appears to affect the entry of the monocytes into the optic nerve and retina.
“While more work is needed to fully understand how the radiation confers long-term protection, radiation appears to hinder the adhesion and migration of monocytes into the areas of the eye prone to nerve damage,” says study co-author Gareth Howell, Ph.D., research scientist at the Jackson Laboratory.
This finding suggests vision may be maintained in eyes with high intraocular pressure using treatments that block the entry of monocytes into the eye.
Before attempting localized radiation of the eye to prevent glaucoma in humans, the authors suggest it will be necessary to conduct additional research in other animal models to further assess the safety and efficacy of targeted X-ray therapy.
1. Howell GR, Soto I, Zhu X, et al. Radiation treatment inhibits monocyte entry into the optic nerve head and prevents neuronal damage in a mouse model of glaucoma. J Clin Invest. 2012 Apr 2;122(4):1246-61.
2. Anderson MG, Libby RT, Gould DB, et al. High-dose radiation with bone marrow transfer prevents neurodegeneration in an inherited glaucoma. Proc Natl Acad Sci U S A. 2005 Mar 22;102(12):4566-71.
