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Friday, February 14, 2014

Children who are born blind can develop sight years later

Being born with cataracts in both eyes (bilateral cataracts) is a common cause of blindness in newborns. Ideally, children with this condition are operated on very soon after birth, restoring normal vision. However, in poor regions of the world, families can’t afford the treatment until much later, if ever. This is especially problematic because it had been thought that after a few short years, blind children would lose the ability of ever being able to process sight. Even if their vision were corrected, they would never be able to interpret the visual inputs.

However, the conventional wisdom on curing blindness in children is changing. In some cases, children who were as old as fifteen years when they underwent treatment were able to learn how to see at least to some extent.

Five out of eleven children who had been born with cataracts and not treated until they were at least eight years old showed remarkable improvement in seeing contrast six months after their surgery. While, this may sound like a modest improvement, discriminating between shades of gray is critical for many visual activities, like reading.

Some of the shapes used for testing sensitivity to contrast.
Image courtesy of Luis Lesmes and Michael Dorr
Nature doi:10.1038/nature.2014.14592

Perhaps more significant, some children even learned to recognize objects by sight, though it didn’t happen immediately. When they first gained the ability to see, the kids couldn’t recognize an object without feeling it.

These results show doctors that it is worthwhile to restore sight to children, even if they are fifteen years old when they are first given the opportunity to undergo treatment. Contrary to prior thought, the window on developing normal vision does not close very early in childhood.

Kalia A, Lesmes LA, Dorr M, Gandhi T, Chatterjee G, Ganesh S, Bex PJ, & Sinha P (2014). Development of pattern vision following early and extended blindness. Proceedings of the National Academy of Sciences of the United States of America PMID: 24449865.  

Sinha P, Chatterjee G, Gandhi T, & Kalia A (2013). Restoring vision through "Project Prakash": the opportunities for merging science and service. PLoS biology, 11 (12) PMID: 24358024.