Restoring vision to blind mice

December 1, 2006

Retinal cell transplants have successfully restored sight to blind mice, according to research published in a recent edition of Nature magazine.

Retinal cell transplants have successfully restored sight to blind mice, according to research published in a recent edition of Nature magazine.

Scientists from the University College London Institutes of Ophthalmology and Child Health and Moorfields Eye hospital in the UK took early stage retinal cells from newborn mice and transplanted them into the retinas of mice, which had been genetically designed to gradually lose their sight - mimicking retinitis pigmentosa (RP) or age-related macular degeneration (AMD).

The transplants succeeded; the photoreceptors made electrical connections to the animal's existing retinal nerve cells. Tests showed that the mice's pupils responded to light and activity was observed in the optical nerve, demonstrating that signals were being sent to the brain.

Nanotechnology delivers the goods

Nanotechnology is being developed that could improve drug delivery to the eye to treat diseases such as glaucoma, according to a report in a recent issue of the Journal of Materials Chemistry.

John Tsibouklis and colleagues from the University of Portsmouth, UK, have developed biodegradable polymer nanoparticles that can be combined with drugs to allow controlled release. Once in the eye, the nanomaterials swell to form an aqueous material that sticks to the eye. As more moisture is absorbed, the drug is slowly released. Traditional methods, such as eye drops, are easily washed out of the eye and generally only 5% of the active ingredient remains.

Polymer nanomaterials are already approved for pharmaceutical use, however, new quality control methods are needed before the technology could go into commercial production.

Laser therapy ineffective in AMD

According to a report in the November issue of Ophthalmology, low intensity laser treatments are less effective in preventing vision loss or slowing the progression of age-related macular degeneration (AMD) in eyes with large drusen.

The Complications of Age Related Macular Degeneration Prevention Trial (CAPT), sponsored by the US National Eye Institution enrolled 1,052 subjects at 22 clinical centres to examine the efficacy of low intensity laser treatments. All subjects had bilateral large drusen, defined as greater than 125 μm in diameter, and visual acuity (VA) better than 20/40 in both eyes.

One eye was treated with a laser, 514 μm argon green, while the other acted as an untreated control. The initial laser protocol specified 60 barely visible burns (15 burns per quadrant), applied in a grid pattern within an annulus between 1,500 μm and ,2000 μm from the foveal centre. Twelve months from baseline, any eye with a significant amount of remaining drusen was retreated with 30 burns.

At five years follow-up, 188 (20.5%) of treated eyes and 188 (20.5%) of untreated eyes had lost three or more lines of vision (p=1.0). This change in VA, according to the researchers, was associated with the development of late stage AMD but not with the treatment group. The cumulative incidence of late AMD was 19.7% for treated eyes and 20.4% for untreated eyes. Incidence of choroidal neovascularization was 13.3% for both treated and untreated eyes (p=0.95) and the incidence of geographic atrophy was 7.4% and 7.8%, respectively (p=0.64).

The authors concluded that low intensity laser treatment is not successful in preventing vision loss resulting from AMD and suggested that the only way for subjects with large drusen to decrease the risk of vision loss is for them to take daily high dose antioxidant vitamins and minerals.

Light sensitive switches could restore sight