There's more to implants than meets the eye

Apr 28, 2011

In this month's Physics World, Richard Taylor, professor of physics, psychology and art at the University of Oregon, warns that artificial retinal implants – a technology fast becoming a reality – must adapt to the unique features of the human eye in order to become an effective treatment.

The gap between digital and the is getting ever smaller, in terms of both the number of light-sensitive detectors and the space that they occupy. A human retina typically contains 127 million photoreceptors spread over an area of 1100 mm2. In comparison, today's state-of-the-art CMOS sensors feature 16.6 million photoreceptors over an area of 1600 mm2.

Despite the impressive progress of camera technology, several differences still remain, which is why, Taylor states, camera technology cannot simply be incorporated into the eye to restore the vision of patients with damaged rods and cones.

Taylor highlights that the eye tends to see what is directly in front of it – as the majority of its seven million cones are concentrated centrally – and less so on the periphery, whereas a camera captures everything in uniform detail with its pixels spread evenly across its entire field of view.

As such, the eye has to continually scan small areas to ensure that the image of interest falls mainly on the fovea – a pin-sized region positioned directly behind the lens that is crucial when visualizing detail. This is because the human eye exploits fractal patterns – geometric shapes that are present throughout nature and repeat themselves down to the smallest scale. If the eye employed the uniform distribution of photoreceptors found in cameras, there would simply be too much information for the brain to process in real time.

Furthermore, Taylor states how certain natural fractal patterns such as clouds, trees and rivers are more aesthetically pleasing and can greatly reduce stress. This stress-reduction process would not occur with a camera-based implant as movement in the eye would become unnecessary, eventually leading to the eye learning not to move and therefore not activating the relevant areas of the brain to relieve stress.

As Taylor writes, "Remarkably, implants based purely on camera designs might allow blind people to see, but they might only see a world devoid of stress-reducing beauty. This flaw emphasizes the subtleties of the human visual system and the potential downfalls of adopting, rather than adapting, camera technology for eye."

In addition to the problem of photoreceptor distribution, Taylor also highlights the problem of connecting an implant's electrodes to retinal neurons, which are fractal in structure and tend to stay intact even if the eye's rods and cones themselves are damaged by disease. A solution to this, developed by Taylor and his colleagues, is nanocluster deposition.

This involves the delivery, through an inert gas, of nanoclusters of materials onto the photodiodes of an implant. These clusters then self-assemble into the required fractal shape and enhance the connection between retinal implants and healthy neurons while at the same time allowing light to pass through onto the photodiode.

Explore further: Cadillac CT6 will get streaming video mirror

add to favorites email to friend print save as pdf

Related Stories

Retina implants: location is key

Mar 24, 2010

(PhysOrg.com) -- The first UK trial of a promising new retinal implant technique is to be led by Oxford University researchers.

Setting his sights on a cure

Jan 11, 2011

For poets and lovers, the eyes are windows to the soul. But for researchers like Dr. Henry Klassen, they provide unparalleled access to the central nervous system.

Australia reveals prototype 'bionic' eye

Mar 30, 2010

Bionic Vision Australia (BVA) today unveils their wide-view neurostimulator concept - a bionic eye that will be implanted into Australia's first recipient of the technology.

Recommended for you

Cadillac CT6 will get streaming video mirror

Dec 20, 2014

Cadillac said Thursday it will add high resolution streaming video to the function of a rearview mirror, so that the driver's vision and safety can be enhanced. The technology will debut on the 2016 Cadillac ...

Poll: Americans skeptical of commercial drones (Update)

Dec 19, 2014

Americans broadly back tight regulations on commercial drone operators, according to a new Associated Press-GfK poll, as concerns about privacy and safety override the potential benefits of the heralded drone ...

Cheaper, more powerful VR system for engineers

Dec 17, 2014

It's like a scene from a gamer's wildest dreams: 12 high-definition, 55-inch 3D televisions all connected to a computer capable of supporting high-end, graphics-intensive gaming.

Nokia HERE prepares maps for autonomous cars

Dec 17, 2014

Autonomous cars will need a new kind of map, a crucial element that until now has been given a back seat to the more popularly discussed issues of sensors and legal questions. Senior Writer Greg Miller in ...

Dutch launch 'intelligent bicycle' that warns of danger

Dec 15, 2014

The Netherlands on Monday launched its first-ever "intelligent bicycle", fitted with an array of electronic devices to help bring down the high accident rate among elderly cyclists in the bicycle-mad country.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.