Electrical stimulation treatment gives new hope to patients with retinitis pigmentosa

The treatment stimulates release of growth factors, restoring damaged cell function and visual field area.

Issue: June 2012

Electrical stimulation might help to slow disease progression and restore visual field in patients with retinitis pigmentosa.In the first prospective sham-controlled clinical trial with 24 patients at the University of Tübingen [Germany], we have demonstrated that electrical stimulation therapy (EST) is safe and effective in the early stages of the disease,” Florian Gekeler, MD, said. “Other studies are under way. One of them is a large cohort clinical trial and is evaluating stimulation parameters and their efficiency, while a second one is a multicenter open-label safety study, where patients with different stages of the disease are enrolled, sponsored by Okuvision GmbH.

Retinitis pigmentosa is an inherited form of retinal degeneration, occurring in one in every 3,000 to 4,000 people. Visual field loss, typically starting in early adulthood, progressively leads to blindness.

“In those affected, photoreceptor cells are genetically programmed to gradually deteriorate, slowly at first and then very rapidly,” Eberhart Zrenner, MD, said. “No effective treatment for this condition has been so far available, but several studies are presently being performed.”

EST device

Electrical stimulation is aimed at promoting photoreceptor cell regeneration by release of endogenous growth factors as proven in several animal studies. It also has been demonstrated that growth factors introduced into the eye have the ability to improve damaged cell function.

Eberhart Zrenner

Rather than injecting growth factors, we can induce the body to produce them. The positive effects of electrical stimulation in this respect have also been shown in studies of several centers in the past few years,” Prof. Zrenner said.

The new EST device OkuStim (Okuvision) has a CE mark and is currently available on the European market under prescription. Potentially, it can be bought and used by the patient at home. However, Prof. Zrenner and Prof. Gekeler recommended caution.

“Results have been observed so far only in small studies, and the treatment should at this stage be done only under medical supervision, within large open-label clinical trials to ensure an absolute safe application,” Prof. Zrenner said.

Encouraging results

The OkuStim EST device delivers small amounts of current to the retina through a thread electrode. The device comprises a spectacle-like frame for application of the thread electrode and a hand-held stimulation controller. A wire, as thin as a strand of hair, is passed across the lower edge of the conjunctiva and cornea, and a low amount of energy is continuously delivered for 30 minutes.

“The patient only experiences a slight tickling sensation, but no pain or discomfort,” Prof. Gekeler said. “In our first study, we administered the treatment weekly for a period of 6 weeks, with follow-up visits every 3 months.”

Florian Gekeler

The study included 24 patients with retinitis pigmentosa, subdivided in three groups: a group receiving a lower degree of electrical stimulation, a group receiving a higher degree of electrical stimulation in relation to patients’ individual phosphene threshold and a control group with sham stimulation.

“In the group receiving a higher stimulation, a 20% improvement in the visual field was obtained. There was also a general trend toward visual acuity gain. Most patients were happy and wished to have the treatment repeated,” Prof. Gekeler said.

Because retinitis pigmentosa is a heterogeneous disease in terms of both pathophysiology and progress, the response of patients is variable. Further study is necessary to establish prognostic parameters for the various groups and the optimal amount of current delivery, Prof. Zrenner said.

“What’s important for now is that we have been able to prove that the treatment has a positive effect on retinal function and is easy to apply, noninvasive and safe within the schedule and parameters used in the study,” he said.

The only side effect reported so far is a transient dry eye sensation immediately after the treatment, which can be treated with artificial tears. However, long-term safety in relation to the stimulation of growth factor production will have to be tested.

“Retinitis pigmentosa is a progressive disease, and knowing the mechanism of the treatment, an indefinitely repeated stimulation is probably the way to go,” Prof. Gekeler said. – by Michela Cimberle

For more information:

Florian Gekeler, MD, can be reached at Department für Augenheilkunde, Universitäts-Augenklinik, Schleichstraße 12, D-72076 Tübingen, Germany; +49-7071-2984761; fax: +49-7071-294763; email: florian.gekeler@uni-tuebingen.de.
Eberhart Zrenner, MD, can be reached at Department für Augenheilkunde, Universitäts-Augenklinik, Schleichstraße 12, D-72076 Tübingen, Germany; +49-7071-2984786 or 2987311; fax: +49-7071-295038; email: ezrenner@uni-tuebingen.de.
Disclosures: Prof. Gekeler is principal investigator in studies on EST. He has no financial interest in the product. Prof. Zrenner is on Okuvision’s advisory board.