How mice are giving new hope to patients fighting blindness

A landmark study using mice has taken a major step towards treating blindness Photo:

Here's a story that definitely falls into the category "It's early days but..."

Let's start with Rachael Stevens. When Rachael walks down the High Street, its as if she's looking through a porthole - she has no peripheral vision. She has a disease called Retinitis Pigmentosa that's damaged the nerve cells in her eyes and it could get worse. But now research in mice is pointing to treatments that could one day help tens of thousands of patients like Rachael.

Rachael Stevens has a disease called Retinitis Pigmentosa that's damaged the nerve cells in her eyes

Scientists have done a clever bit of research that proves in principle that it's possible to reverse that process. Professor Robin Ali and his colleagues at the Institute of Opthalmology in London took mice that were night blind - they had no nerve cells called rods in their retinas - these are the nerve cells used in night vision. When they put these rats in a water maze in a dimly-lit room, they couldn't swim to a platform indicated by a visual cue - they just couldn't see the cue.

But when they injected immature rods from very young mice into the adult mice, they grew into new rods and made connections with the brain that restored some sight to the mice - enough to enable them to complete the maze.

Their video of the experiment is here:

In short, they have proved in principle that transplanted photoreceptors can restore sight. Their next step is to repeat the transplant with other photoreceptors called cones, that are responsible for fine vision and colour vision. And then to use not immature photoreceptors but special cells taken from embryos - called embryonic stem cells. These are cells that can grow into any tissue - and the scientists know they can grow them into photoreceptors.

The aim is to be able to inject embryonic stem cells into patients, in one form or another, that grow and restore their sight.

But, don't hold your breath - the first human trials are, Professor Ali told me, at least five years away. But at least they now know they're going in the right direction.

Science and Medical Editor Lawrence McGinty has the full report: