Glaucoma is a chronic, progressive condition that requires lifelong treatment. Multiple clinical trials have shown that sustained reduction of elevated intraocular pressure (IOP), regardless of glaucoma subtype, can prevent:

• Optic nerve damage
• Retinal ganglion cell death
• Vision loss
• Irreversible blindness

IOP is a balance between the production of aqueous humour (AH) and the drainage of this fluid through the trabecular meshwork. Most current treatment options focus either on limiting fluid production or increasing outflow. Each option, while somewhat effective, also poses challenges.

Medicated eye drops have side effects and are vulnerable to the vagaries of patient compliance. Laser therapy and surgery involve more risk, require close monitoring, and often need to be redone over time. 

Recently, however, an exciting development was found by a research team from the University of Bristol in England. In a Sept. 2020 study, this research team demonstrated the potential of using gene therapy to treat glaucoma with a one-time injection.* 

What they did

The goal of the study was to lower IOP with a single injection into the eye that would disrupt the production of aqueous humour. The team targeted the genomic sequence of the protein Aquaporin 1 (Aqp1) in the ciliary body (structure in the eye that generates AH). Aquaporins comprise a family of proteins that transport water across membranes, and they’re widely distributed throughout both the human body and animal bodies. 

The study consisted of several stages. The treatment was first used on normal human eye tissue. The experiment was then repeated in two mouse models. Lastly, it was used on human eye tissue in which the IOP was intentionally elevated.

What they found

The cumulative results of the four-part experiment showed:

• Significant, sustained reduction of IOP
• Significant, sustained prevention of ganglion cell loss
• No structural abnormalities in the ciliary body after 3 weeks
• No edema
• No significant corneal or retinal thickening 

What it means

The encouraging study results indicate that this therapy could greatly benefit glaucoma patients by lowering their IOP with one intravitreal (directly into the eye) injection, regardless of their glaucoma subtype. 

Advantages include:

• No customized medical approach would be required,
• It allows for local, instead of systemic, treatment. 
• The simplicity and safety of intravitreal injection enables delivery in a clinic setting.

Risks include:

• Heightened immune responses
• Ocular inflammation
• Possible vitreous infiltrates (passing of extraneous material through the membrane)

The research team is already looking forward to making some refinements that could further enhance the efficacy of the treatment, but human clinical trials are the next step toward getting the gene-editing treatment approved for initial widespread use. 

Dr. Colin Chu, a visiting senior research fellow at Bristol Medical School, said the team hoped to start clinical trials shortly. “If it’s successful,” Chu said, “it could allow a long-term treatment of glaucoma with a single eye injection, which would improve the quality of life for many patients.”

*Powell, S. (2020, Sep. 21). Gene Therapy as a Potential Treatment for Glaucoma. Optometry Today. https://www.aop.org.uk/ot/science-and-vision/research/2020/09/21/gene-therapy-as-a-potential-treatment-for-glaucoma

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