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Hope for restoring optic nerve damage from glaucoma

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A potential scientific breakthrough holds the possibility of being able to restore some visual function in people blinded by glaucoma. Mice with similar optic nerve damage to that caused by glaucoma were able to regenerate nerves that conduct impulses from the eye to the brain that enable sight.

Two factors were involved in the breakthrough: gene therapy to get the nerves to regenerate and, most vitally, a channel-blocking drug cocktail to help the nerve transmit the impulses.

It has to be stressed that no human trials have been conducted and the results may not translate from mice to people. What is creating most optimism, though, is that gene therapy – which has been successful in sight-restoration previously – can only be done in a laboratory whereas drugs can be administered elsewhere. The researchers are hopeful that, eventually, drugs alone can be used to achieve similar results.

The technique of genetic modification carries the risk of causing cancer because it deletes or blocks tumour-suppression genes to stimulate nerve regeneration. The drug approach does not interfere with the tumour-suppression genes.

The breakthrough of this research was getting regenerated nerve fibres (axons) to not only form working connections with brain cells but to also carry impulses (action potentials) all the way from the eye to the brain. Previous experiments have achieved nerve regrowth but the fibres grew without the insulating sheath known as myelin which helps propagate nerve signals over comparatively long distances.

Earlier efforts were unable to achieve the necessary speed for nerve signals to reach the brain quickly enough to enable vision. But a review of medical literature revealed a potassium channel-blocker, 4-aminopyridine, that strengthens nerves signals when myelin is absent. This blocker is used to treat multiple sclerosis which also involves a loss of myelin.

The scientists – from Boston Children’s Hospital – believe suitable drugs can be identified to achieve further advances, even if they have to be teamed with visual training to facilitate recovery. Relief for glaucoma patients is not close but this new discovery does offer some hope.

Source: Boston Children’s Hospital

Last updated: November 29, 2018

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