Bitesize Breakthroughs

Ancient Roots

• Researchers at Johns Hopkins University School of Medicine appear to have uncovered an “ancient” light-sensing mechanism in modern mice (1) – and it is likely found in human retinas too. The team was researching the biochemical pathways of “non-image forming” photoreceptors (intrinsically photosensitive retinal ganglion cells or ipRGCs), when they discovered that one subtype (M4) didn’t use the previously discovered phospholipase C pathway but something novel: HCN-channel-mediated phototransduction. And, perhaps more surprisingly, subtype (M2) appears to use both mechanisms. “Some evolutionary biologists have proposed that […], through evolution, these two mechanisms separated into different cell types. Our research seems to provide evidence that photoreceptors containing both light-sensing mechanisms may still exist in modern mammals,” said King-Wai Yau, a professor of neuroscience, who led the study.

High and Dry

• Does dry eye affect visual function? According to a team at Wilmer Eye Institute, the answer is yes. In a study of 186 participants, those with clinically significant dry eye read fewer words per minute than those with dry eye symptoms only. It was found that chronic dry eye slowed reading rate by as much as 10 percent, making it difficult for participants to concentrate for longer than half an hour. Researchers collected small vials of tears from each participant for future studies in the hope of understanding the exact mechanisms behind the condition (2). 

End to AMD injections?

• A Phase II clinical study has trialed an implantable, refillable drug delivery system for wet AMD. The device – no bigger than a grain of rice – contains a refillable reservoir of Lucentis and is implanted under the eyelid. In the study, led by Wills Eye Hospital in Philadelphia, some patients were able to go 15 months between treatments. Researchers hope the device will provide an alternative to the current standard of care for AMD – monthly injections – and result in better visual outcomes. “Fewer injections and office visits is exciting,” said Carl Regillo, Chief of Retina Service and Professor of Ophthalmology. “If you’re a week or two late for a visit from time to time, you may have a decline in vision, and you can’t always recover from that. It’s a relentlessly progressive disease (3).”

Picture Perfect

• For the first time, researchers have been able to view the retina in unprecedented detail by combining two imaging modalities – adaptive optics and angiography. The project, led by a team at the National Eye Institute, used deformable mirrors and computer-driven algorithms to compensate for light distortions, allowing researchers to see live neurons, epithelial cells and blood vessels in the outermost region of the retina. The team hope the multimodal approach will help in the development of targeted treatments for diseases like AMD and Alzheimer’s (4).