Artificial means for restoring vision

Introduction

Degeneration of the retina occurs in age related macular degeneration and retinitis pigmentosa, resulting in loss of vision. Age related macular degeneration is a major cause of visual impairment among people over 65 in Western countries1; in the United Kingdom its incidence has increased by 30-40% over the past 40 years.2 Retinitis pigmentosa generally occurs in a younger age group (incidence 1 per 4000 live births) and affects 1.5 million people worldwide.3

In both conditions patients are visually impaired due to loss of photoreceptors. At present few treatments can remedy this and lead to recovery of vision.4 5 Photodynamic laser therapy has been beneficial in some patients with age related macular degeneration, but this therapy does not address photoreceptor loss. Different gene and drug therapies have been tried,4 5 but their ability to replace lost photosensitive tissue is limited. Researchers are therefore investigating the possibility of using prostheses to restore vision.

Advances in microtechnology have facilitated the development of a variety of prostheses that can be connected to the brain or implanted in the eye. Some of these approaches have improved the eyesight of patients with visual impairment. This article gives an overview of the methods that are being assessed to restore vision in patients with severe sight loss.

Methods

We carried out a comprehensive search through Medline and PubMed using the terms “age related maculopathy”, “visual prosthesis”, “retinitis pigmentosa”, “retina”, and “eye”. We also searched for the latest developments in artificial vision through the website of the Association for Research in Vision and Ophthalmology.

A brief history of visual prostheses

Efforts to develop visual prostheses are not new. Attempts at artificial vision began in the 18th century with direct electrical stimulation of blind eyes.6 In the 1920s, the German neurosurgeon Otfrid Foerster developed this approach further by investigating direct …