Kolkata, June 2 (IANS) It's time to rephrase the idiom 'as blind as a bat' as two American sight therapists teach blind students in the city to 'see' using echolocation - the technique used by bats to fly.

Brian Bushway and Daniel Kish of the US-based organisation World Access for the Blind, both of whom are blind, are trying to give a new vision to 133 blind children here.

'Echolocation is the technique used by bats to move about. They make a ticking sound while flying. This sound on hitting an object in front bounces back. Every object reflects sound differently. Hence bats know what kind of object lies in front of them - its height, width, and density - and can easily bypass it,' Kish told IANS.

Bushway and Kish held a week-long workshop for the blind students of Divine Fellowship Blind School run by Mercy Hospital here to teach the children the technique of echolocation.

Talking about his early days when he learnt echolocation, Kish said: 'From early childhood I had this tendency to make a sound in my mouth while moving about. Using this process I could know about what lay ahead of me and I could even climb up and down the fence like my sighted friends. Gradually, practice made the technique more accurate and advantageous.'

But is echolocation more beneficial for blind children than walking sticks?

'Echolocation helps in detecting the location, dimension and density of the object. A walking stick is just like spectacles that are a tool to vision but echolocation literally optimises the senses other than vision,' said Kish.

'After learning this technique a blind child will be able to analyse the exact scene or location that he is in. Besides he will be able to detect the height, breadth, contour and solidness of nearby objects,' he added.

The workshop is being held in three phases.

Initially, students will be taught to conceptualise images. They will be introduced to familiar objects like trees, walls, fences and bushes to make them understand the difference between the sounds reflected by each of them. This sharpens the imaging system of their brains.

In the next step, the students learn the difference in dimension of the given stimuli. For example, they will be taught to detect the difference between the thickness between a plant and a bush by sound reflections.

'The final stage is the most crucial where the brain learns the most. It is called self-directed discovery stage. Here the students are taken to an unfamiliar environment and left to test how much they learnt from the earlier steps. They learn by themselves to familiarise with the unknown situation,' Kish explained.

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