Journal of Biomedical OpticsIn-the-spectacle-lens telescopic device
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Spectacle-mounted telescopic systems are prescribed for individuals with visual impairments. Bioptic telescopes are typically mounted toward the top of the spectacle lens (or above the frame) with the telescope eyepiece positioned above the wearer's pupil. This allows the wearer to use up and down head tilt movements to quickly alternate between the unmagnified wide view (through the carrier lens) and the magnified narrow field of view (available through the eyepiece). Rejection of this visual aid has been attributed mainly to its appearance and to the limited field of view through the smaller Galilean designs. We designed a wide-field Keplerian telescope that is built completely within the spectacle lens. The design uses embedded mirrors inside the carrier lens for optical pathway folding, and conventional lenses or curved mirrors for magnification power. The short height of the ocular, its position, and a small tilt of the ocular mirror enable the wearer to simultaneously view the magnified field above the unmagnified view of the uninterrupted horizontal field. These features improve the cosmetics and utility of the device. The in-the-lens design allows the telescope to be mass produced as a commodity ophthalmic lens blank that can be surfaced to include the wearer's spectacle prescription.