Eye Health Facts
What is colour blindness?
The eye determines the colour of what we are looking at by how much response comes from each of three types of light receptors (red, green, or blue). The most common type of colour vision deficiency is where one type of light receptor, usually red or green, doesn't work as well.
This reduces the range and appearance of colours, with some colours that are clearly different to normal eyes appearing the same to a colour deficient people. What do they see? one demo, another.
True colour blindness - black and white only - is very rare. Colour vision deficiencies are usually inherited, and are more common in boys than girls.
Eye Health Facts
Ever wondered why cutting onions makes you cry?
As you slice an onion, the onion cells release a gas into the air. When this gas contacts the eye, it turns into weak sulphuric acid in the moist tear layer that coats the eye. Nerve endings in the cornea react to the acid, causing the sting, and trigger the lacrimal (tear) glands to produce lots of tears in an attempt to further dilute and flush away the acid.
If onions are in water, or near running water when cut, there will be much less gas in the air, and you are less likely to start crying.