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Eye - Acuity

Eye - Acuity: Encyclopedia II - Eye - Acuity

Visual acuity can be measured with several different metrics. Cycles per degree (CPD) measures how much an eye can differentiate one object from another in terms of degree angles. It is essentially no different from angular resolution. To measure CPD, first draw a series of black and white lines of equal width on a grid (similar to a bar code). Next, place the observer at a distance such that the sides of the grid appear one degree apart. If the grid is 1 meter away, then the grid should be about 8.7 millimeters wide. Finally, increas ...

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Eye, Eye - Accommodation, Eye - Acuity, Eye - Adnexa and related parts, Eye - Anatomy, Eye - Cytology, Eye - Diseases disorders and age-related changes, Eye - Dynamic range, Eye - Evolution of eyes, Eye - Eye movement, Eye - Eyebrows, Eye - Eyelashes, Eye - Eyelids, Eye - Microsaccades, Eye - Optokinetic reflex, Eye - Rapid eye movement, Eye - Saccades, Eye - Smooth pursuit movement, Eye - The orbit, Eye - Varieties of eyes, Eye - Vergence movement, Eye - Vestibulo-ocular reflex, WikiSaurus:eye — the WikiSaurus list of synonyms and slang words for eyes in many languages, Adaptation, Binocular vision, Corrective lens, Crystallin, Evil eye, Eye color, Eye contact, Eye tracking, Eyeglass prescription, Macropsia, Micropsia, Nictitating membrane, Ocular tremor, Ophthalmology, Optician, Optometry, Persistence of vision, Phosphenes, Snellen chart, Staring contest, Tears, Visual perception

Eye: Encyclopedia II - Eye - Acuity

Eye - Acuity

Main article: Visual acuity

Visual acuity can be measured with several different metrics.

Cycles per degree (CPD) measures how much an eye can differentiate one object from another in terms of degree angles. It is essentially no different from angular resolution. To measure CPD, first draw a series of black and white lines of equal width on a grid (similar to a bar code). Next, place the observer at a distance such that the sides of the grid appear one degree apart. If the grid is 1 meter away, then the grid should be about 8.7 millimeters wide. Finally, increase the number of lines and decrease the width of each line until the grid appears as a solid grey block. In one degree, a human would not be able to distinguish more than about 12 lines without the lines blurring together. So a human can resolve distances of about 0.73 millimeters at a distance of one meter. A horse can resolve about 14 CPD (0.62 mm at 1 m) and a rat can resolve about 1 CPD (8.7 mm at 1 m).

A diopter is the unit of measure of focus.