Letter: More to seeing

I was pleasantly surprised to read Bill Harvey’s column in Optician. He explains that he has always been concerned that we (optometrists) tend to focus too much on Snellen acuity as a gauge of vision quality when much of what we see, indeed perhaps most, is down to higher processing by the brain.

This is exactly what behavioural optometrists have been explaining for at least 50 years.

Sight cannot be regarded on its own. In order to read one needs to see the letters, but also to maintain exact focus without tiring, to point both eyes exactly to the letter being viewed and then follow along the line of print accurately. To do this the cortex has to send signals to all 12 extra ocular muscles plus the focusing muscles – quite a complex task.