Total and incurable blindness is the final prognosis for retinitis pigmentosa (RP) a type of progressive retinal dystrophy.   Abnormalities of the photoreceptors (rods and cones) or the retinal pigment epithelium (RPE) of the retina, a group of inherited disorders, leads to progressive visual loss, affecting about 1 in 4,000 people worldwide.

Progression of RP differs with each case, the worst being complete blindness as early as childhood, to being legally blind around age 40 or 50 with some retention of sight for life.  Those affected usually experience nyctalopia, (night blindness), followed by peripheral vision reduction (tunnel vision) and then loss of central vision over several years or decades.

Eberhart Zrenner, Chairman, University of Tuebingen Eye Hospital, Germany and Director of a small company called Retinal Implant AG is developing a sub-retinal impant which sits underneath the retina and works by directly replacing light receptors that are lost as a result of RP.  These light receptors allow the eye's natural image-processing functions to produce a stable visual image.

Developed by German scientists, the implant has had good results in a trial wherein three blind patients were able to see shapes and objects within days of treatment.  Describing the trial results as "phenomenal", experts believe the implanted device could change the lives of close to 200,000 people worldwide who suffer blindness due to RP.

Tiny in size, the device measures 3mm squared and 1/10mm thick with 1,500 light sensors connected to amplifiers and electrodes.

"We have shown that people can be provided with enough useful vision for daily life," Zrenner said in a telephone interview.

Published in the Proceedings of the Royal Society B journal, the study documents stunning results for one particular blind patient who was able to identify and find objects on a table in front of him after the sub-retinal implant procedure, and was able to walk around a room independently.  Tests conducted 7-9 days following the implant procedure were encouraging as researchers remarked that the patient could read a clock face and differentiate between seven shades of gray.

Zrenner said the trial results were a "proof of concept" and would progress into further trials in Europe of 25-50 patients.

Epiretinal implants, another type of retinal implant, sit outside the retina bypassing the intact light-sensitive structures in the eye requiring the patient to wear an external camera and processor unit.

Cautiously optimistic, Zrenner said if the device was developed further, it may be used in the future to help people with severe age-related macular degeneration which is the leading cause of blindness in older people.

Further trials of the implant should be completed in two to three years,  and if those proved successful Zrenner estimates the device could be on the market and available for thousands of patients in about five years' time.