Lacan's notion of the mirror stage seems to rely directly on the ability of the child to see. Some are born blind, so they do not have the opportunity to "see" their self-image in a mirror.
A similar case could be made for children in an Amazonian tribe. They wouldn't have access to mirrors, nor to other reflecting surfaces (rivers are pretty muddy).
The British philosopher Raymond Tallis, in his book Not Saussure: A Critique of Post-Saussurean Literary Theory, makes a similar argument, pointing out the apparent absurdity of any theory that proposes an accidental basis for a fundamental aspect of human development:
One measure of the value, truth or explanatory power of a theory is its ability to predict novel facts or at least to accommodate facts that were not taken into account when the theory was originally formulated. If epistemological maturation and the formation of a world picture were dependent upon catching sight of oneself in a mirror, then the theory would predict that congenitally blind individuals would lack selfhood and be unable to enter language, society or the world at large. There is no evidence whatsoever that this implausible consequence of the theory is borne out in practice.
— Raymond Tallis, Not Saussure: A Critique of Post-Saussurean Literary Theory, Macmillan, 1988, p. 153
How does Lacan get around this? What relevance (if any) does this theory hold for the developmental process of children who are unable to see?