The prosthetic visual system built by Second Sight Medical Products Inc. is now covered by Medicare in Alabama, Georgia and Tennessee, bringing the total number of states where the product and related surgical procedure are covered by the government-subsidized health insurance program to 31.

The Sylmar-based biotechnology firm announced Tuesday that a Medicare contractor in the three southeastern states had agreed to provide coverage for Second Sight’s Argus II, an implanted device that restores eyesight in patients with a disease called retinitis pigmentosa. The product works by electrically stimulating cells in the retina, thereby allowing patients to experience a functional equivalent of vision.

Five of the seven national Medicare administrative contractors – private health insurance companies that process Medicare claims – now cover the Argus II, according to Second Sight. The firm is working on obtaining coverage with the remaining three, it said in a statement.

Shares of Second Sight (EYES) fell 1 cent, or about half a percent, on Tuesday to close at $1.80 on the Nasdaq.