PATIENTS SEE THE BENEFITS

An increasing amount of clinical data support the use of electronic subretinal implants for the restoration of some useful, functional vision in patients blinded by retinitis pigmentosa, according to Dr Eberhart Zrenner MD, of the University of Tübingen in Germany.

“Patients described being able to see things like their granddaughter in a little white dress, the silhouette of Tübingen town-hall, fireworks, blooming flowers in the garden, a goose swimming in a pond, and being able to differentiate between red and white wine,” Dr Zrenner told the 14th EURETINA Congress in London.

Dr Zrenner presented the 12-month visual and safety outcomes of a prospective, multi-centre clinical trial on the safety and efficacy of subretinal implants for partial restoration of vision in 29 patients who had lost all vision due to retinitis pigmentosa. Research teams from Germany, England, Singapore, Hungary and Hong Kong participated in the study.

“Electronic implants are presently the only possibility for these patients to regain some vision, which can currently reach 20/550,” he said.

The Alpha IMS subretinal implants (Retina Implant AG, Reutlingen, Germany) were positioned beneath the foveal region. Each of the 1,500 photodiodes, which represent one pixel each, controls an amplifier that, depending on the strength of the light, emits currents to stimulate overlying bipolar cells. Power and control signals are supplied inductively via a subdermal, retroauricular coil from which a subdermal cable leads to the eye.

Detection, localisation and recognition of shapes and objects in activities of daily life were significantly better with implant power switched on than off during the first three months.

The patients, who were on average 53 years old, had on average lost the ability to read 17 years ago. However, after implantation, four patients (14 per cent) could read letters 4-8cm in size. Thirteen patients (45 per cent) reported useful visual experiences, including recognition of shapes or details in daily life and eight patients (28 per cent) could localise objects in daily life. Four patients gained no light perception.

The presentation was highlighted by several videos of patients using their devices. One video showed a patient identifying and accurately grasping tableware objects.

“Psychophysical testing and self-reported outcomes show restoration of useful vision in a majority of patients,” said Dr Zrenner. Of the 29 patients, six reported “very good visual experiences”, seven reported “useful visual experiences” and eight described being able to localise light sources, albeit without shape or details. Eight patients reported no useful visual experiences in daily life.

Technically, there is room for improvement for use in daily life, said Dr Zrenner, referring to improvements in visual resolution, visual field and practicability. Besides two serious but treatable adverse events there were no safety concerns.

Eberhart Zrenner: ezrenner@uni-tuebingen.de