Visually Impaired may Drive Using Glasses Embedded With a Telescope

by Rajashri on Jul 25 2008 4:08 PM

Using glasses embedded with a telescope may help visually impaired people to drive or perform other activities requiring sharper distance vision, say experts.

Scientists at Schepens Eye Research Institute, an affiliate of Harvard Medical School, say that they have already made a pair of spectacles that may serve as a model for future designs.

"This new design has several advantages. One major advantage is the appearance of the glasses. Because they look almost like normal everyday spectacles, it is more likely that visually impaired people will use them," says Dr. Eli Peli, the inventor of the glasses.

He says that the glasses are easier to use than existing telescope models because of a wider magnified view and easier access to that view.

He adds that shifting the magnified view up leaves the unmagnified view of the road unobstructed, which is important for safety and facilitates navigation.

The existing designs have the telescopic eyepiece above the wearer's pupil, and thus require the driver to tilt his/her head up and down rapidly to view alternatively the magnified and unmagnified scenes.

Furthermore, many potential users have resisted such bioptic telescopes due to their strange appearance, and because the magnified view through the telescope is narrow.

Dr. Peli and his colleagues have addressed these problems by designing a wide-field telescope made of straight and curved mirrors built completely within the spectacle lens.

To embed the whole telescope inside the spectacle lens, the researchers had to obtain the magnifying power from curved mirrors instead of lenses because mirrors maintain their power when embedded inside the spectacle lens, while the lenses lose their power when not in the air.

Their design is based on spherical and flat mirrors with the flat mirrors implemented as tilted beam splitters that use polarization to reduce light loss.

"The short height of the actual magnifier, its position, and inclusion of a small tilt of the last flat mirror (the one closest to the user's eye), enables the wearer to simultaneously view the magnified field above the unmagnified view of the uninterrupted horizontal field," says Dr. Peli.

A research article in the Journal of Biomedical Optics says that not only will the new glasses improve the cosmetics and usefulness of this type of device, the in-the-lens design will make it possible to mass-produce the telescopic magnifier as a standard spectacle lens blank and allow an individual's prescription to be added using the standard procedure for grinding regular spectacle lenses.

This process should also reduce the price of bioptic telescopes, the article adds.

The next step for the research team is to find a corporate partner to manufacture the lens blanks, and distribute them to the public.