An electrode developed in Brazil reduces the costs of retinal exams

A device developed by researchers in São Paulo is approximately four times less expensive than imported equipment and can make electroretinography more accessible

By Karina Toledo

Agência FAPESP – Researchers at the Universidade Federal de São Paulo (UNIFESP) developed a Brazilian version of an electrode used in electroretinograms (ERGs), an exam that evaluates the retina’s electrical responses to light stimuli and helps diagnose retinal diseases.

The results of this work were presented during the 27th Annual Meeting of the Federation of Experimental Biology Societies (FdSBE) held in Águas de Lindoia from August 22-25.

“Brazil currently imports these electrodes, which are disposable and cost from US$ 30-40 each. We developed a similar product at one quarter of the price,” said Adriana Berezovsky, the coordinator of the study, which was financed by FAPESP under its Regular Research Program.

The electrode is approximately 3 centimeters long and, like the imported version, is made of fabric with a silver filament. During the exam, it is placed in the conjunctival sac of the lower eyelid and captures the electrical signals emitted by retinal cells in response to light stimuli emitted by the ERG equipment.

“There is no need for anesthesia. The patient feels only a slight discomfort while it is being inserted,” said Berezovsky.

The human retina has two types of photoreceptors, which are the cells responsible for capturing light and retransmitting the electrical impulse to other cells and the optic nerve.

“The rods are responsible for night vision, and the cones are responsible for day vision. However, some illnesses cause these cells to die. This can lead, for example, to night blindness or the loss of peripheral vision,” she explained.

An ERG makes it possible to evaluate rod and cone function and, according to Berezovsky, can help ophthalmologists identify problems before an exam reveals perceptible changes in the back of the eye, during which the doctor can see the structures that form the retina.

Validation

The researchers tested the Brazilian-made electrode on a group of 50 healthy volunteers and compared the results with those of exams performed with the equivalent imported version. The performance of the two electrodes was similar. The data were published in Arquivos Brasileiros de Oftalmologia in 2008.

The following year, with support from FAPESP through its Intellectual Property Support Program (PAPI/Nuplitec), the team applied for a patent on the electrode, which has yet to be granted.

Since then, the researchers have compared the performances of their electrode and the imported device in volunteers suffering from retinal diseases. “We have tested it on approximately 50 patients and had good results. However, we still need to increase our sample size,” explained Berezovsky.

The studies have been performed in patients with hereditary diseases such as retinitis pigmentosa, cone dystrophy and Stargardt disease. The preliminary results were presented at the Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO), the field’s most prominent conference.

The electrode has also been tested for veterinary use. The performance of the Brazilian version was compared to that of the imported version in ten healthy Yorkshire terriers, with similar results.

“The data have been submitted for publication in an international journal. We now plan to test the electrode in dogs with retinal disease,” said Berezovsky.

The team also intends to improve the model developed in Brazil. “We are studying the size and material to better adapt the electrode to the needs of Brazilian patients and doctors,” she said.