Second Sight: Argus II Retinal Prosthesis

1. What is it?

Built on the work contributed by Kwabena Boahen at Stanford University, a ASR is a retinal prostheses able to improve impaired vision. It is a silicon chip with 4 ganglion cell types which relay signals to the optic nerve. Their activity allows us to accommodate our vision in both dim and bright light.

The Argus II Retinal Implant is FDA and CE Mark approved.

Figure 1: An image of the fundus in retinitis pigmentosa (WESTERN OPHTHALMIC HOSPITAL/SCIENCE PHOTO LIBRARY)

2. Why is it important?

Retinitis Pigmentosa (RP) affects 1 in 4, 000 people in the UK (Hartong et al, 2006). Usually presenting with impaired night vision and peripheral vision, many experience a loss of sight as a result. RP is diagnosed by fundoscopy and electroretinopathy and due to inheritance patterns, patients may receive genetic counselling for family planning. There is no way to reverse the damage caused by RP which is why the Argus II retinal implant could provide a significant treatment of choice which may restore some visual loss.

Visual impairment can have many affects on the social and financial aspects of an individual whereby this treatment could help alleviate the long term costs of its implications. Currently, the cost is higher for the retinal implant in comparison to gene therapy which many would like to see come down over time in order to benefit more patients (Farvadin, 2018).

3. How does it work?

  • The device requires a surgical procedure under general anaesthesia
  • Implantation occurs in the sub retinal space where the Argus II Retinal Implant sits flat against the retina
  • 4 weeks post surgery, the device is activated in clinic and adjusted to the needs of the patient
  • A pair of glasses incorporated with a video camera is provided to the patient which sends wireless signals to the retinal implant of the visual field
  • The signals picked up by the retinal implant are interpreted by the occipital cortex to relay the messages as images to the visually impaired user

Additional Information

  • The chip can help stimulate the growth of new ganglion cells to improve vision of the patient
  • The chip holds 3, 500 photoreceptor diodes
  • Dimensions: 2 mm in diameter, 1/1000 inch in thickness
  • The device battery is powered by light but requires additional source of energy under dim light conditions
  • Please note: this device does not restore vision loss since birth and there is no perfect replacement of natural vision

Figure 2: Diagram of the Argus II retinal prothesis sytem, the artificial retina and its imaging (Chandrabharti, 2013)

Second Sight are now working on the cortex’s visual perception in silicon as a project for the future of ophthalmology.


1.Hartong, D., Berson, E. and Dryja, T., 2006. Retinitis pigmentosa. The Lancet, 368(9549), pp.1795-1809.

2. Farvardin, M., Afarid, M., Attarzadeh, A., Johari, M., Mehryar, M., Nowroozzadeh, M., Rahat, F., Peyvandi, H., Farvardin, R. and Nami, M., 2018. The Argus-II Retinal Prosthesis Implantation; From the Global to Local Successful Experience. Frontiers in Neuroscience, 12.

3.  Chandrabharti, P., Ashutosh, A. and Gupta, R., 2013. The Bionic Eye – &quotRay of Hope&quot A Review. International Journal of Computer Applications, 69(18), pp.7-11.

80+ Publications by Kwabena Boahen:

TED Talk: A computer that works like the brain

Second Sight

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