“It ain’t what you don’t know that gets youinto trouble. It's what you know for sure that just ain't so that is theproblem.”
Mark Twain, the famous American author, issaying there are many things that are thought to be true that simply are not.This is certainly true in the area of the treating amblyopia and strabismus.The sad fact is that many traditional ophthalmologists and optometrists stillcling to outdated beliefs that recent scientific research has clearly shown tobe untrue. The even sadder fact is that many people are still subjected to old,invasive, and even damaging treatment while they could be helped but are notreceiving the necessary treatment.
DEMYSTIFYINGTHE “CRITICAL PERIOD” |解读“关键期”
There is no age limit totreat amblyopia and strabismus! So, why has it taken so long for the scientificcommunity to accept neural plasticity?
In 1981, Drs. TorstenHubel and David Wiesel won the Nobel Prize in Physiology and Medicine fortheir experiments on the visual cortex of cats and monkeys.
In their studies, the Nobel Prize winnersdemonstrated that cats and monkeys deprived of vision in one eye could regainvisual function in that eye but only during a specified period in early lifeknown as the critical period. After this time, it was felt that recovery wasnot possible. The results of these experiments, conducted on animals, were thenextrapolated to humans, and it was said that the critical period for vision inhumans lasted only until 7 or 8 years of age. After that, nothing could be doneto improve vision because neural plasticity was lost.
It is very important to bear in mind thatcats and monkeys are not humans, and were not treated with any form of visiontherapy. It is also important to understand that the conclusions drawn from theexperiments equated critical period of development with critical period inrehabilitation. This is an incorrect assumption and one which was never made byHubel and Wiesel. This incorrect assumption has hurt many patients and shouldhave never been made! In fact, subsequent scientific experiments on cats byDuffy, Snodgrass, et al. as well as by Kratz and Spear clearly demonstratedthat vision can be regained, sometimes very rapidly, even after the criticalperiod.
Another important point concerning theconcept of critical periods is explained by Dr. Susan Barry in the a blog onPsycology Today called, Eyes on the Brain. Dr. Barry pointed out that in Hubeland Wiesel’s experiments, the animals’ eyelids were sewn closed, so they didnot receive any form of vision through the closed eye. While this manipulationsimulates form deprivation amblyopia caused by a congenital cataract orcomplete ptosis (droopy eyelid completely covering the eye), it does notsimulate functional amblyopia. Only about1% of all the people with amblyopiasuffer from deprivation amblyopia. The critical period experiment does notapply to 99% of those with amblyopia.
（文章摘自: CROSSED & LAZY EYES MYTHS,MISCONCEPTIONS AND TRUTHS）
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