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Distance PD is the separation between the visual axes of the eyes in their primary position, as the subject fixates on an infinitely distant object. [ 2] Near PD is the separation between the visual axes of the eyes, at the plane of the spectacle lenses, as the subject fixates on a near object at the intended working distance. [ 3]
Myopia. Myopia, also known as near-sightedness and short-sightedness, [ 5] is an eye disease [ 6][ 7][ 8] where light from distant objects focuses in front of, instead of on, the retina. [ 1][ 2][ 7] As a result, distant objects appear blurry while close objects appear normal. [ 1]
In the most familiar acuity test, a Snellen chart is placed at a standard distance: 6 metres. At this distance, the symbols on the line representing "normal" acuity subtend an angle of five minutes of arc, and the thickness of the lines and of the spaces between the lines subtends one minute of arc. This line, designated 6/6 (or 20/20), is the ...
An inferiority complex occurs when the feelings of inferiority are intensified in the individual through discouragement or failure. Those who are at risk for developing a complex include people who: show signs of low self-esteem or self-worth or have low status in their peer group. They may also display symptoms similar to depression.
Dyslexia. Dyslexia, previously known as word blindness, is a learning disability ('learning difficulty' in the UK [ 6]) that affects either reading or writing. [ 1][ 7] Different people are affected to different degrees. [ 3] Problems may include difficulties in spelling words, reading quickly, writing words, "sounding out" words in the head ...
Amblyopia, also called lazy eye, is a disorder of sight in which the brain fails to fully process input from one eye and over time favors the other eye. [ 1] It results in decreased vision in an eye that typically appears normal in other aspects. [ 1] Amblyopia is the most common cause of decreased vision in a single eye among children and ...
The human eye is a sensory organ in the visual system that reacts to visible light allowing eyesight. Other functions include maintaining the circadian rhythm, and keeping balance . Arizona Eye Model. "A" is accommodation in diopters. The eye can be considered as a living optical device. It is approximately spherical in shape, with its outer ...
An eye chart is a chart used to measure visual acuity comprising lines of optotypes in ranges of sizes. Optotypes are the letters or symbols shown on an eye chart. [ 1 ] Eye charts are often used by health care professionals, such as optometrists , physicians and nurses , to screen persons for vision impairment .