convergence

1. The tending of two or more objects toward a common point. 2. The direction of the visual lines to a near point. [L. con-vergere, to incline together]

- accommodative c. the meter angle of c. expressed in diopters; equal to the product of the meter angles of c. times the interpupillary distance measured in centimeters.

- amplitude of c. the distance between the near point and far point of c.. SYN: range of c..

- angle of c. the angle that the visual axis makes with the median line when a near object is viewed.

- far point of c. the point to which the visual lines are directed when c. is at rest.

- near point of c. the point to which the visual lines are directed when c. is at its maximum.

- negative c. the slight divergence of the visual axes when c. is at rest, as when observing the far point or during sleep.

- positive c. inward deviation of the visual axes even when c. is at rest, as in cases of convergent squint.

- range of c. SYN: amplitude of c..

- unit of c. meter angle.

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con·ver·gence kən-'vər-jən(t)s n

1) an embryonic movement that involves streaming of material from the dorsal and lateral surfaces of the gastrula toward the blastopore and concurrent shifting of lateral materials toward the middorsal line and that is a process fundamental to the establishment of the germ layers

2) independent development of similar characters (as of body structure in whales and fishes) by animals or plants of different groups that is often associated with similarity of habits or environment

3) movement of the two eyes so coordinated that the images of a single point fall on corresponding points of the two retinas

4) overlapping synaptic innervation of a single cell by more than one nerve fiber compare DIVERGENCE (2)

con·verge -'vərj vb, con·verged; con·verg·ing

con·ver·gent -'vər-jənt adj

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n.

1. (in neurology) the formation of nerve tracts by fibres coming together into one pathway from different regions of the brain.

2. (in ophthalmology) the ability of the eyes to turn inwards and focus on a near point so that a single image is formed on both retinas. The closer the object, the greater the degree of convergence.

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con·ver·gence (kən-vurґjəns) [L. convergere to lean together] 1. in evolution, the development of similar structures or organisms in unrelated taxa. 2. in embryology, the movement of cells from the periphery toward the midline during gastrulation. 3. in ophthalmic physiology, the coordinated inclination of the two lines of sight toward their common point of fixation, or the point of fixation itself. 4. in neurology, the exciting of a single sensory neuron by incoming impulses from multiple other neurons, particularly in the central nervous system.