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Ophthalmology. In ophthalmology, horror fusionis is a condition in which the eyes have an unsteady deviation, with the extraocular muscles performing spasm-like movements that continuously shift the eyes away from the position in which they would be directed to the same point in space, giving rise to diplopia. Even when the double vision images ...
Binoculars may have eye relief ranging from a few millimeters to 25 mm or more. Eye relief can be particularly important for eyeglasses wearers. The eye of an eyeglasses wearer is typically farther from the eye piece which necessitates a longer eye relief in order to avoid vignetting and, in the extreme cases, to conserve the entire field of view.
Thus an eye care professional, having determined that a myopic (nearsighted) person requires a basic correction of, say, −2 dioptres to restore normal distance vision, might then make a further prescription of 'add 1' for reading, to make up for lack of accommodation (ability to alter focus). This is the same as saying that −1 dioptre ...
Sixth nerve palsy, or abducens nerve palsy, is a disorder associated with dysfunction of cranial nerve VI (the abducens nerve ), which is responsible for causing contraction of the lateral rectus muscle to abduct (i.e., turn out) the eye. [1] The inability of an eye to turn outward, results in a convergent strabismus or esotropia of which the ...
By measuring this zone, the autorefractor can determine when a patient's eye properly focuses an image. The instrument changes its magnification until the image comes into focus. The process is repeated in at least three meridians of the eye and the autorefractor calculates the refraction of the eye, sphere, cylinder and axis.
ophthalmic trial frame is used to hold lenses and other accessories during correction of refractive errors. Test of. Visual acuity. A trial frame is a tool used by ophthalmic professionals like ophthalmologists and optometrists. It is basically an adjustable spectacle frame with multiple cells, used to hold corrective lenses, and other ...
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°. A double Porro system provides four ...
A twisted prism is a nonconvex polyhedron constructed from a uniform n-prism with each side face bisected on the square diagonal, by twisting the top, usually by π / n radians (180 / n degrees) in the same direction, causing sides to be concave.