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Vergence movements are closely connected to accommodation of the eye. Under normal visual conditions, looking at an object at a different distance will automatically cause changes in both vergence and accommodation, sometimes known as the accommodation-convergence reflex.
The accommodation reflex (or accommodation-convergence reflex) is a reflex action of the eye, in response to focusing on a near object, then looking at a distant object (and vice versa), comprising coordinated changes in vergence, lens shape ( accommodation) and pupil size. It is dependent on cranial nerve II ( afferent limb of reflex ...
The 1 cm spaced grid indicates a near focus focal length of around 6cm. Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image or focus on an object as its distance varies. In this, distances vary for individuals from the far point —the maximum distance from the eye for which a clear image of ...
In visual perception, the near point is the closest point at which an object can be placed and still form a focused image on the retina, within the eye 's accommodation range. The other limit to the eye's accommodation range is the far point . A normal eye is considered to have a near point at about 11 cm (4.3 in) for a thirty year old. [1]
The maximum angular resolution of the human eye is 28 arc seconds or 0.47 arc minutes; this gives an angular resolution of 0.008 degrees, and at a distance of 1 km corresponds to 136 mm. This is equal to 0.94 arc minutes per line pair (one white and one black line), or 0.016 degrees.
Depth perception is the ability to perceive distance to objects in the world using the visual system and visual perception. It is a major factor in perceiving the world in three dimensions. Depth perception happens primarily due to stereopsis and accommodation of the eye .
In studies that used standardized definitions of convergence insufficiency, investigators have reported a prevalence of 4.2–6% in school and clinic settings. The standard definition of convergence insufficiency is exophoria greater at near than at distance, a receded near point of convergence, and reduced convergence amplitudes at near.
Amplitude of accommodation. The amplitude of accommodation is the maximum potential increase in optical power that an eye can achieve in adjusting its focus. It refers to a certain range of object distances for which the retinal image is as sharply focussed as possible. Amplitude of accommodation is measured during routine eye-examination.