It is generally thought that most visual abilities develop in the first years of life, and if they do not get a chance to develop (usually through eye problems), they cannot be gained later.
For example, people who have had severe congenital cateracts from birth that prevent light from entering the eye, often have trouble making sense of objects if this condition is cured later in life, because the brain has not developed the necessary functions to make sense of objects.
Sacks and Siegel’s letter follows a previous report in Nature that reported on the development of useful vision after 30 years of blindness.
Both of these reports suggest that the brain is more ‘plastic’ (able to reorganise) than was previously thought. This is contrast to ten years ago, when it was largely accepted that the brain developed few new functions after early adulthood.
Link to letter ‘Seeing is believing as brain reveals its adaptability’.