Abstract: A refractometer for measuring spherical refractive errors of an eye is shown. The refractometer includes an objective first lens system adapted to be moved along a predetermined path between a first position and a second position. A linear diopter scale measuring means is responsive to the movement of the objective first lens system for providing spherical refractive diopter measurements. A fixed second lens system is positioned at a selected location from the first position and is in alignment with the objective first lens system. A Pechan inverting prism system is located in the focal plane or the fixed second lens system and the first position. An adjustment means is operatively coupled to the objective first lens system for moving the same between said first position and said second position. A method for self-testing for spherical refractive errors of an eye using a refractometer of the present invention is shown.

Abstract: A two lens stand magnifier having variable degrees of magnification of an object at a constant distance from an observer is disclosed. A permanently mounted plus lens and a movably mounted minus lens are arranged on a stand such that the plus lens is a constant distance away from the object to be magnified. As the minus lens is moved relative to the positive lens, magnification of an object located on the opposite side of the plus lens from the minus lens varies while the image stays substantially in focus at the constant distance from the observer. Defocus of the image during movement is avoided by the choice of the lens powers as well as the spacing of the range of movement of the minus lens relative to the plus lens.

Abstract: A wafer thin reading telescope utilizing a unique parallelogram shaped prism, together with plus and minus lenses comprises a Galilean reading telescope. The telescope is mounted in the bifocal region of an eyeglasses lens at an approximately 221/2 degree downward angle relative to the straight ahead gaze. The reading telescope is sufficiently small and light weight in nature so as to be mountable to the back surface of the carrier lens by the use of adhesive. The eyepiece and objective lenses are truncated vertically to provide a wide horizontal field of view relative to the vertical field of view. The telescope is capable of magnifying objects to a power of about 2.5.times. to about 4.times. and is focusable by moving the image or alternatively by reciprocating the eyepiece lens within a threaded collar. The telescope can be enclosed within a housing.

Abstract: A magnifying apparatus comprising a prism, a magnifying lens, and a housing for spacing the prism apart from the lens. The prism converts a horizontal image into an image at an angle from the horizontal, and the magnifying lens then magnifies the image for viewing. A method of using the magnifying apparatus for viewing the image of an object on a relatively horizontal surface at an angle from the horizontal is also provided.

Abstract: An apparatus for increasing visual acuity while viewing an image comprising a roof prism having an apex with apex faces adjacent thereto, an eye piece lens mounted to a first apex face of the roof prism, and an objective lens mounted to a second apex face of the roof prism and to the lens of a pair of eyeglasses. The objective lens is mounted to the eyeglasses lens at a point such that the eye of a patient wearing the eyeglasses must be rotated at a angle of from about 25.degree. to about 50.degree. relative to the visual axis of the patient's eye when looking straight ahead to view an image through the apparatus.

Abstract: A device for automatically measuring the spherical power, cylindrical axis and power and prism of an ophthalmic lense, with each determined independently of each other without a servo system. At least two LEDs act as point-sources of light, as Scheiner apertures. The light from the LEDs pass through an objective lense, thence through a selectively translatable aperture target, and then pass through a collimating lense. The LED rays then pass through the lens under study, and the target images are focused by a telescope objective lens onto a light sensitive detector. The detector which is selectively rotatable in concert with the LEDs is partitioned into Cartesian quadrants. Rotation of the detector and LEDs until the target images fall on the major detector axis discloses the axis of the cylinder of the lens being measured independent of lens power. Translation of the target until the target images maximally coincide reveals the power of the lens in its principal meridian.