Letters: August 29

I write in response to Alan Gilbert who feels he has been hoodwinked by optometrists using Colourimetry, and equates that to behavioural optometry. However, Colourimetry is not behavioural optometry. Some behavioural OOs use a Colourimeter, as do some non-behavioural OOs, some orthoptists, and NHS eye departments.

The behavioural model is based on the neurology of the visual pathways - 80 per cent of the retinal fibres pass to the visual cortex giving sight, 18 per cent of the retinal fibres pass to the superior colliculus in the retino-tectal pathway, and the other 2 per cent pass to the hippocampus and amygdala giving visual input to spatial awareness, memory and emotion. At the superior colliculus the visual information is integrated with sensory information from the vestibular, proprioceptive, auditory and tactile systems. The brain uses all the sensory information together with previous experience, to create vision, which takes place in at least 36 areas of the brain.