Viola Palmer, of Waikanae, asks :-

The human retina receives a view of the world that is upside down and the brain learns to re-interpret this. I read recently of a man who wore spectacles which provided the upside down image. It took only 8 days for his brain to get the image the correct way up. How long does it take for a baby's brain to learn to see the world the right way up?

Gordon Sanderson, an opthalmologist at the University of Otago's School of Medicine, responded.

You have asked a question which has been pondered over for a long time. The person you are referring to who first made what are called “inverting glasses”, was George Stratton and he did this in 1896. By wearing a tube containing two lenses in front of one eye, with the other eye covered, he was able to turn the world as he saw it, upside down. He wore this device for a few days. taking it off at night and covering that eye before going to bed. After a while he began to realize that he was not so disorientated as he had been when first putting on this device. However, when he finally took it off he noticed that the visual world became normal again quite quickly. He attributed this to an effect called neural adaptation.

The fascination with image inversion seems to stem from the fact that the image in our eye just like that in a camera, is inverted. Of course since we have never known anything different, we interpret the world that we see as the ‘right way round’. The reason for this is that we are actually born ‘blind’. And if a baby were kept in a black box from the day they were born, they would never learn to see anything. Of course as soon as we are born we start to assemble a picture of the world around us. I liken it to programming that computer in our heads called the brain. This process takes a considerable time, generally vision is not very sharp until we reach about 2 years of age; it keeps improving until we are about 7. After that time, it is pretty much fully developed.

Curiously, one of the first parts of our brain to develop is the region that enables us to recognize faces, this is why babies often smile when we play peek-a-boo with them. It also explains why some children are given a patch to wear over one eye. This is because for some reason, the brain has ignored the information from one eye during this crucial development phase. If we cover the other (good) eye for a few weeks, the brain is forced to recognize the vision from the poorer eye and it doesn’t remain a “lazy eye”.

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