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Esophoria is an eye condition involving inward deviation of the eye, usually due to extra-ocular muscle imbalance. It is a type of heterophoria. Cause. Causes include: Refractive errors; Divergence insufficiency; Convergence excess; this can be due to nerve, muscle, congenital or mechanical anomalies.
Prentice's rule, named so after the optician Charles F. Prentice, is a formula used to determine the amount of induced prism in a lens: = where: P is the amount of prism correction (in prism dioptres) c is decentration (the distance between the pupil centre and the lens's optical centre, in millimetres)
Efforts must first be made to identify and treat the underlying cause of the problem. Treatment options include eye exercises, wearing an eye patch on alternative eyes, prism correction, and in more extreme situations, surgery or botulinum toxin.
Convergence Insufficiency. Other names. Convergence disorder. Specialty. Ophthalmology, optometry. Convergence insufficiency is a sensory and neuromuscular anomaly of the binocular vision system, characterized by a reduced ability of the eyes to turn towards each other, or sustain convergence .
In this example the first eye, with a −1.00 diopter prescription, is the stronger eye, needing only slight correction to sharpen the image formed, and hence a thin spectacle lens. The second eye, with a −4.00 diopter prescription, is the weaker eye, needing moderate correction to sharpen the image formed, and hence a moderately thick ...
The majority of esotropias are concomitant and begin early in childhood, typically between the ages of 2 and 4 years. Incomitant esotropias occur both in childhood and adulthood as a result of neurological, mechanical or myogenic problems affecting the muscles controlling eye movements.
It was first introduced by Hermann von Helmholtz in late 19th-century Germany as supportive evidence for his perceptual learning theory (Helmholtz, 1909/1962). [1] Since its discovery, prism adaptation has been suggested to improve spatial deficits in patients with unilateral neglect .
Importantly, the formula can be re-written as a linear equation in terms of f: P = ( 5 10 q − 5 90 ( 1 − q ) ) f + 5 90 ( 1 − q ) . {\displaystyle P=\left({\frac {5}{10}}q-{\frac {5}{90}}(1-q)\right)f+{\frac {5}{90}}(1-q).}
For a given genetic covariance between two traits, one with genetic variance and the other with genetic variance , the genetic correlation is computed in the same way as the correlation coefficient .
Microscopy. Scanning electron microscope image of pollen (false colors) Microscopic examination in a biochemical laboratory. Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). [1]