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While moving the streak or spot of light through the pupil across the retina, the examiner observes the relative movement of the reflex or manually places lenses over the eye (using a phoropter or trial frame and trial lenses) to "neutralize" the reflex. [2] Static retinoscopy is a type of retinoscopy used in determining a patient's refractive ...
Humphrey field analyser ( HFA) is a tool for measuring the human visual field that is commonly used by optometrists, orthoptists and ophthalmologists, particularly for detecting monocular visual field. [ 1] The results of the analyser identify the type of vision defect. Therefore, it provides information regarding the location of any disease ...
Cataract surgery is the most common application of lens removal surgery, and is usually associated with lens replacement. It is used to remove the natural lens of the eye when it has developed a cataract, a cloudy area in the lens that causes visual impairment. [ 4][ 10] Cataracts usually develop slowly and can affect one or both eyes. [ 4]
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A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glasses or "spectacles" are worn on the face a short distance in front of the eye. Contact lenses are worn directly on the surface of the eye.
Optometer (ophthalmic instrument) The optometer was a device used for measuring the necessary spherical and/or cylindrical corrections to be prescribed for eyeglasses, from the middle of the 18th century until around 1922, when modern instruments were developed. [1] [2] [3] The term, coined in 1738 by W. Porterfield to describe his Scheiner ...
Prism dioptres. Prism correction is commonly specified in prism dioptres, a unit of angular measurement that is loosely related to the dioptre. Prism dioptres are represented by the Greek symbol delta (Δ) in superscript. A prism of power 1 Δ would produce 1 unit of displacement for an object held 100 units from the prism. [ 2]
A photograph showing two Fulton MX-991/U Flashlights, next to an unofficial reproduction and a standard angle-head flashlight. The MX-991/U Flashlight (aka GI Flashlight, Army flashlight, or Moonbeam[ 1]) from the TL-122 military flashlight series of 1937-1944 and is a development of the MX-99/U flashlight issued in 1963 [clarification needed].