Incredible Human Machine Page #2

to a very different sensory organ.

Blue or brown,

green or hazel,

they are the most vital sensory organ

that the incredible machine has.

Our day hasjust begun,

and the magnificent miracle of sight

leads the way.

Navigating the morning rush hour is something

most human machines do on autopilot,

oblivious to the staggering task

we leave to two gelatinous orbs.

Eyes sit squarely on the front of our faces

for a reason.

Peering forward, and set apartjust enough

to let us gauge distance,

they let us spot and track whatever we desire.

ln microseconds, our eyes sight, follow,

focus and process images

fractions of an inch long

or moving at hundreds of miles per hour

enabling us to assess and appreciate

the world around us more than any other sense.

They may be the windows to our souls,

but on a less poetic level,

eyes are just hungry harvesters of light,

trapping and translating it into

electrical impulses the brain can understand.

Light hits the cornea first.

This transparent layer, cleansed and lubricated

about 1 0 times a minute with every blink,

admits and directs incoming light rays.

From there, they pass through

the dark opening of the pupil,

then a transparent protein lens.

Gatekeepers of light, the muscles of

the colourful iris squeeze the pupil closed

against too much light.

Not enough, the iris relaxes

and the pupil opens.

And in just a fraction of a second,

it can slide back and forth between the two.

Focused by cornea and lens,

light then flies through the jelly-like bulk

of the eye and onto its rear wall.

Just about a hundredth of an inch thick,

this is the retina,

where more than 1 20 million photoreceptors

convert light into electrical impulses,

before processing

and shipping them off to the brain.

ln a mind-boggling feat that soaks up

about a third of our brain power,

our brains continually compare new data with

information processed a split second before.

Combine that with

what they already expect to be there

and vision is born.

At least, that's how it's supposed to work.

When it doesn't,

the world can look more like this.

62-year-old Linda Morfoot has a genetic disease

called retinitis pigmentosa.

which has been gradually degrading her

eyes'photoreceptors for the past 40 years.

They haven't turned light into sight

for the last ten.

lt's frustrating to lose your sight

because you run into things,

you run into people.

And it can be depressing.

Just open up real wide.

Very good.

Now, thanks to Dr Mark Humayun

of the University of Southern California,

she may see again.

All along we've been told it's impossible,

it's science fiction, it can't happen.

Look up.

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