Accommodation is one of the mechanisms that allow us to see up close. It is the focusing of the lenses in each eye. This action, combined with the convergence, allows for us to see clearly up close.
Accommodation is the result of the contraction of the ciliary bodies in the eye which allows for the lens to get thicker, focusing the image better on the fovea. This action also includes the constriction of the pupil which more precisely focuses the light on fovea making the image sharper. Here is a video of this in action
“It’s blurry up close”
When accommodation does not work, one may see blurry up close, get headaches or rub the eyes due to eye strain. The ciliary muscles attempting to make the image clear causes this discomfort. Accommodation can be exercised to strengthen it, to improve near vision. This is generally performed in conjunction with convergence exercises to improve near vision when one treats convergence insufficiency.
The Hart Chart
A simple way to improve accommodation is by using a Hart chart. With this activity, a grid of letters is placed at a distance and another, small version, is held by the patient, near. The patient then reads a line close (or letter) then a line at distance. This is done with one eye occluded so the accommodative action is exercised as the eye focuses near than far. In my clinic, this is performed while standing on a balance board to further challenge the patient. This simple activity is quite effective at strengthening accommodation. A Hart chart can be purchased from Bernell or found on the internet. Heres a video.
The Hart chart is one-way accommodation can be strengthened. In optometric vision therapy, lenses can be used to strengthen accommodation using an activity called Accommodative Rock.
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A complete binocular vision assessment should be conducted before performing these tasks to make sure that they are appropriate. Only an ophthalmologist or optometrist can accurately diagnose an accommodative problem.