Patients suffering from retinal disorders have their visual fields shrinking from the outside – like looking through a cardboard tube, before the tube itself goes black. It can be a highly distressing situation. Now, however, a new retinal transplant technique gives them a fighting chance to see well.
The retina is part of the eye that lets you read this page, or appreciate the burnt orange color of autumn leaves. It is a layer at the back of the eyeball and comprises light-sensing rods that translate all light passing through the lens and the iris.
When the retina is damaged or degenerated, its owner goes through a slow downward spiral to blindness. This happens via either retinitis pigmentosa or macular degeneration.
Unlike in the Simon and Garfunkel song, nobody wants to call darkness their old friend. It is for that reason that researchers have continuously tried to find a solution to address those retinal disorders. They tried implantable bionic retinas. Then they thought of transplanting new photoreceptor cells into the retina, and reaped some success, only to learn later that transplanted cells do not integrate well into a patient’s existing retina, ultimately preventing the restoration of sight.
Exciting Research on Mice
Three years ago, an ophthalmologist from Japan’s RIKEN Center for Developmental Biology, Michiko Mandai, sought to push the envelope further in the search for a cure. Instead of transplanting just photoreceptor cells, she thought – why not transplant an actual piece of retinal tissue?
The tissue was grown from stem cells and 21 mice were bred to develop degenerating retinas, to which the tissues were transplanted. The initial results were positive, with the transplanted tissue developing into the ideal photoreceptor layer, with the perfect structure.
Mandai, however, wanted to be certain if the stem-cell-grown grafted tissue actually restored a mouse’s vision. Hence, this new study revealed that the mice with the transplanted tissue appeared to have improved by 50 percent in recognizing light signals before an electric shock.
The brain signals of those mice confirmed that their grafted retinas did make them aware of the light signals. The study was recently published in the Stem Cell Reports journal.
The Light at the End of the Tunnel
The next big step is to see if tissue developed from human stem cells can also be grafted successfully to damaged or degenerated human retinas. Mandai is hopeful that clinical trials can start in about two years.
In the meantime, she cautions people from having big expectations. The likelihood is that blindness will only be alleviated small steps at a time – like with a pinprick of light at first. Nonetheless, the research and processes for total sight restoration are ongoing. Yet for blind people who have grown used to calling darkness their old friend, that small light sparks enormous hope at the end of a dark, woeful tunnel.