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The individual would experience difficulty in near vision, often relieved by reading glasses, bifocal, or progressive lenses. [15] Astigmatism is when the refractive power of the eye is not uniform across the surface of the cornea because of asymmetry. In other words, the eye focuses light more strongly in one direction than another, leading to ...
Negative Hirschberg sign: the reflections form congruent points on both corneas. It is performed by shining a light in the person's eyes and observing where the light reflects off the corneas. In a person with normal ocular alignment the light reflex lies slightly nasal from the center of the cornea (approximately 11 prism diopters—or 0.5mm ...
Paper flashcards have been used since at least the 19th century. Reading Disentangled (1834), a set of phonics flashcards by English educator Favell Lee Mortimer, is believed by some to be the first known usage of flashcards. [5] A single-sided hornbook was also known to have been used for early literacy education.
Software Microsoft Windows. macOS. ChromeOS. Linux. Android. iOS (iPhone, iPod Touch, iPad) . BlackBerry. Windows Mobile, Pocket PC Maemo. Web browser J2ME. Palm OS ...
The flashcards and learning progress can be synchronized both ways with Anki using AnkiWeb. With AnkiDroid it is possible to have the flashcards read in several languages using text-to-speech (TTS). If a language does not exist in the Android TTS engine (e.g. Russian in the Android version Ice Cream Sandwich), a different TTS engine such as ...
Adaptation to the small field of view offered by the reading segment of bifocals can take some time, as the user learns to move either the head or the reading material rather than the eyes. Computer monitors are generally placed directly in front of users and can lead to muscle fatigue due to the unusual straight and constant movement of the ...
One type of optical coating is an anti-reflective coating, which reduces unwanted reflections from surfaces, and is commonly used on spectacle and camera lenses. Another type is the high-reflector coating , which can be used to produce mirrors that reflect greater than 99.99% of the light that falls on them.
Other additives used in crown glasses include zinc oxide, phosphorus pentoxide, barium oxide, fluorite and lanthanum oxide. The crown/flint distinction is so important to optical glass technology that many glass names, notably Schott glasses, incorporate it. A K in a Schott name indicates a crown glass (Krone in German).