P3D Re: Exotropia and stereo

[gandalf@xxxxxxxxxxxxxxxx (Eric J Fleischer, MD)]

On Thu, 8 Jan 1998 12:28:34 -0700, Jim Crowell
<crowell@xxxxxxxxxxxxxxx> wrote:

>At 10:48 PM -0800 1/7/98, Andrew Woods wrote:
>>
>>I've read that if Stabismus isn't corrected in a child by a certain
>>age that the brain pathways which process stereoscopic information
>>may not be formed.
>
>That's right.  I'm afraid I don't remember when the sensitive period ends
>exactly--maybe age 7 or 8?  Anyone know?

  The pathways for very high levels of stereopsis  (40 seconds of arc)
form well before two years of age, according to Dr M. M. Parks, one of
the world leaders in strabismology. After that, gross stereopsis can
still form, even without perfect ocular alignment. In the previously
discussed Titmus Fly Stereo Test, the people with gross stereopsis can
see the fly's wings above the page (3000 seconds of arc), but have
trouble with the other part of the test (800 down to 40 seconds). Mark
probably has this gross stereopsis, so is able to perceive depth on
stereograms with fairly wide angular separations.

   The age of 7 or 8 is when the visual pathways are fully formed
("visual maturity"). It is after this age that amblyopia cannot be
improved, nor can it be induced.


<ELF> - Dr Gandalf - Eric J Fleischer, MD
AlfHeim Imaging
gandalf@xxxxxxxxxxxxxxxx


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