HEAD-BORNE BINOCULAR INDIRECT OPHTHALMOSCOPE WITH INTEGRATED TELESCOPE

摘要

abstract There is presented an improved head-borne binocular indirect ophthalmoscope for viewing the aerial image of the fundus of the eye, having the unique feature that it incorporates within each of its two observing portions a two-lens telescope of low magnifying power which magnifies said aerial image of the fundus. The telescope incorporated into the ophthalmoscope differs from the usual coaxial type in that the optical axis of the high powered objective lens and that of the high powered ocular lens of said telescope are caused to intersecteach other at an angle of about 94.degree. at the surface of a laterally positioned oblique front surface mirror, said lenses and said mirror being in a fixed relationship to each other within a transversely movable mounting as a fixed telescope unit such that the reflected secondary focus of the objective lens falls at the primary focus of the ocular lens, said unit being attached to a slide which is transversely movable along ways toward and away from a medially positioned oblique front surface mirror whereby adjustments can be made within the ophthal moscope to accommodate the interpupillary distance of the observer without affecting the relative position of the elements of said telescope unit. A single lowpowered columnating lens whose primary focus is at the aerial image of the fundus when said image is at the usual working distance in performing indirect ophthalmoscopy, is fixed in position in front of both of the medially positioned oblique mirrors. Since the telescope and mirror unit is a fixed unit and since the light reflected from said medially positioned oblique mirror and incident upon said telescope objective lens of said unit is columnated, movement of said unit toward and away from said medially positioned oblique mirror along the direction of the incident columnated light rays requires no relative adjustment of said telescope when it is moved transversely to accommodate the observer's interpupillary distance. The incorporation of aberration correcting aspherical objective and ocular lenses within said unit of the indirect ophthalmoscope of this invention and the use of the columnating lens provides to the observer viewing the aerial image of the fundus binocularly a magnified, stereoscopic clear image of the aerial image of the fundus of the eye. Two types of telescopes are used in this invention: a Galilean telescope wherein the objective lens is of strong positive power and wherein the ocular lens is of strong negative power and the image is seen as clear, enlarged, and inverted, and, an astronomical telescope wherein the objective lens is of strong positive power and the ocular lens is of strong positive power and the image is reinverted and is seen as clear, enlarged, and upright.