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Duane syndrome is a congenital rare type of strabismus most commonly characterized by the inability of the eye to move outward. The syndrome was first described by ophthalmologists Jakob Stilling (1887) and Siegmund Türk (1896), and subsequently named after Alexander Duane, who discussed the disorder in more detail in 1905.
The earliest successful strabismus surgery intervention is known to have been performed on 26 October 1839 by Johann Friedrich Dieffenbach on a 7-year-old esotropic child; a few earlier attempts had been performed in 1818 by William Gibson of Baltimore, a general surgeon and professor at the University of Maryland. [2]
Porro prisms are most often used in pairs, forming a double Porro prism. A second prism rotated 90° with respect to the first, is placed such that light will traverse both prisms. The net effect of the prism system is a beam parallel to but displaced from its original direction, with the image rotated 180°.
Rollei was a German company that established a worldwide reputation with the Rolleiflex, a twin-lens reflex camera.. Rollei was founded in 1920 as the Werkstatt für Feinmechanik und Optik, Franke & Heidecke in order to make a twin-lens reflex camera.
Atmospheric refraction distorting the Sun’s disk into an uneven shape as it sets in the lower horizon. Astronomical refraction deals with the angular position of celestial bodies, their appearance as a point source, and through differential refraction, the shape of extended bodies such as the Sun and Moon.
A ray trace through a prism with apex angle α. Regions 0, 1, and 2 have indices of refraction, , and , and primed angles ′ indicate the ray's angle after refraction.. Ray angle deviation and dispersion through a prism can be determined by tracing a sample ray through the element and using Snell's law at each interface.
A Dove prism is a type of reflective prism which is used to invert an image. Dove prisms are shaped from a truncated right-angle prism. The Dove prism is named for its inventor, Heinrich Wilhelm Dove. Although the shape of this prism is similar to the shape described by a Dovetail joint, the etymology of the two is unrelated.
Finally there was the rarely seen 'F3AF', a model which included an autofocus (AF) pentaprism finder (DX-1) capable of autofocusing with two special AF Nikkor lenses—the first of their kind, which included focus motors in the lens bodies. Those lenses were the AF-80mm f/2.8 Nikkor and the AF-200mm f/3.5 Nikkor.