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The symptoms and signs associated with convergence insufficiency are related to prolonged, visually demanding, near-centered tasks. They may include, but are not limited to, diplopia (double vision), asthenopia (eye strain), transient blurred vision, difficulty sustaining near-visual function, abnormal fatigue, headache, and abnormal postural adaptation, among others.
Light from a single point of a distant object and light from a single point of a near object being brought to a focus. 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.
The convergence will stretch the extraocular muscles – the receptors for this are muscle spindles. As happens with the monocular accommodation cue, kinesthetic sensations from these extraocular muscles also help in distance and depth perception. The angle of convergence is smaller when the eye is fixating on objects which are far away.
Accommodative insufficiency (AI) involves the inability of the eye to focus properly on an object. Accommodation is the adjustment of the curvature of the lens to focus on objects near and far. In this condition, amplitude of accommodation of a person is lesser compared to physiological limits for his age. [ 1 ]
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 an object can be seen, to the near point—the minimum distance for a ...
A random-dot stereogram (RDS) is stereo pair of images of random dots that, when viewed with the aid of a stereoscope, or with the eyes focused on a point in front of or behind the images, produces a sensation of depth due to stereopsis, with objects appearing to be in front of or behind the display level.
The type of changes from one eye to the other may differ depending on which level of stereoacuity is to be detected. A series of stereotests for selected levels thus constitutes a test of stereoacuity. There are two types of common clinical tests for stereopsis and stereoacuity: random dot stereotests and contour stereotests.
The two different types of near response are caused by different underlying disease processes. Adie's pupil is caused by damage to peripheral pathways to the pupil (parasympathetic neurons in the ciliary ganglion that cause pupillary constriction to bright light and with near vision).