When light energy enters the eye it passes through the Cornea – the tough protective lining of the eye, and then through the Lens which together focus the incoming rays against the Retina – the back of the eye.
If the light energy is strong enough it will cause a light chemical reaction within the Retina generating a nerve signal that passes from the Retina to the Vision centre located at the back of the brain.
The eyes are able to function at very bright levels of light and can also detect very low levels of light – made possible by the Pupil – the variable hole at the front of the eye. There are 2 different types of light receptor within the Retina.
After diving the increased nitrogen solution may have been insufficient to cause decompression sickness, but if further decompression occurs associated with a flight at altitude then decompression sickness may be triggered
This blood vessel blockage causes pain and various other symptoms, for example, sometimes similar to those of a stroke (such as sudden weakness on one side of the body, difficulty speaking, or dizziness), or even flu-like symptoms. Nitrogen bubbles also cause inflammation, causing swelling and pain in muscles, joints, and tendons.
Any reduction in pressure / increase in altitude causes nitrogen to come out of solution and form nitrogen gas bubbles
These gas bubbles move about the body and can become lodged in the joints, brain, spinal cord and under the skin
As outside pressure decreases during a climb, the accumulated nitrogen that cannot be exhaled immediately forms bubbles in the blood and tissues. These bubbles may expand and injure tissue, or they may block blood vessels in many organs—either directly or by triggering small blood clots.
Decompression sickness, sometimes called the bends, occurs due to nitrogen in the bloodstream turning into gas bubbles – causing joint and muscle pains
It is usually as a result of a diver ascending too quickly
