Sankhajyoti Saha, M.Optometry
Assistant Professor, NSHM Knowledge Campus-Kolkata
In the world of Brainless Jellyfish, a small sensory structure like an eye, called rhopalium detects light level around the environment which helps them to avoid objects, while moving. (1) Similarly in the world of vision science, Visual Prosthesis is something which provides functional vision to low vision or visually impaired people, mostly for visual navigation.
How the bionic eye works:
Phosphene vision, a weak visual stimulus, is an Entoptic phenomenon of experiencing seeing various light patterns without light entering the eye. (2) This phenomenon is something which bionic eyes provide to the visually impaired person who previously could see.
Figure 1: Device diagram
- The glass-mounted small camera converts the visual inputs into visual stimulations in two ways. Distance sensor cameras highlight objectives or obstacles, and thermal sensor cameras highlight human shapes.
- Stimulus forwarded to handheld devices via external wire.
- Stimulus is processed and sent back to glass in the form of digital data.
- Data sent wirelessly to electrodes which aim to replicate the function of missing or damaged light sensitive cells (Photoreceptors).
- Implants stimulate the retina to send data to the brain (visual cortex) via visual pathway.
The visual scene experienced by a bionic eye is light fringes of various shapes and intensity, within 30° span at arm’s length. Three commercially available bionic eyes are Argus II, Alpha-AMS and the IRIS V2, that have allowed the people to scan and detect objects, avoiding obstacles of an unfamiliar environment. (2)
Figure 2: Visual scene perception diagram
Recipients of Bionic Eye:
The retina contains millions of photoreceptors (Rods and Cones), which connect different types of nerve in the retina and transmit visual information from the eye to the brain. Most of the bionic eye requires a healthy optic nerve and a developed visual cortex, which enumerates patients who could see in the past.
Implants can be planned based upon the type and roots of blindness. Retinal based implants are suitable for the patients with hereditary blindness, which causes loss of vision by destroying the photoreceptors, with intact optic nerve status. Other types of blindness such as traumatic eye injury or glaucoma causes permanent damage to the optic nerve and visual pathway, making them a good candidate for cortical band implants, with a technology bypassing the optic nerve. (3)
That is why to treat different cases of blindness; researchers are working on different levels of bionic implants.
Coming down the pick:
Hitherto, evolution is at its infancy. The further modification demands a bionic eye with a greater number of electrodes and to figure out how to array visual information to correctly stimulate those electrodes. Since the time researchers are working on more modern ways to understand and mimic the neural code retina uses to communicate with the brain, so that the resulting vision would become significantly more natural.
In the offing, technology with the most scientific discovery someone can see their loved ones’ smile again, after years of darkness.
1. Wikipedia contributors. (2018, April 16). Rhopalium. In Wikipedia, The Free Encyclopedia. Retrieved from https://en.wikipedia.org/w/index.php?title=Rhopalium&oldid=836720068 (Last accessed: March 23, 2021, 19:00 IST)
2. Petoe , M., Ayton , L., & Shivdasani , M. (2020, November 20). Artificial vision: what people with bionic eyes seeM. The Conversation. . Retrieved from https://theconversation.com/artificial-vision-what-people-with-bionic-eyes-see-79758. (Last accessed: March 30, 2021, 22:30 IST)
3. Mischa. (2017, September 26). Seeing the future: the bionic eye. Curious. Retrieved from https://www.science.org.au/curious/people-medicine/bionic-eye(Last accessed: March 30, 2021, 23:00 IST)
Figure 1& 2: Picture is digitally modified and created for representational purpose by the author.