What you need to know about supercharging your vision

If you take your vision for granted, you could be doing yourself a disservice. See what you could be doing to improve your eyesight.

• Have you ever wondered why some people have much sharper vision than others? It's because the number, type and distribution of cones in the retina vary between people.
• The more densely packed your cones are within the macula, the more acute your vision will be, because more cones react to incoming light and more signals are sent to the brain, giving more information about the scene viewed and consequently better-than-normal eyesight.
• But — unless colour-blind — everyone perceives colour in the same way; while the eyes have colour-sensitive receptors, colour interpretation is a function of the brain.

• The devilish red gleam in photographs is due to light reflected back from the blood vessels supplying the retina. It occurs when the pupil cannot contract quickly enough to stop the light bouncing back into the camera lens.
• The cure is to position the flash to the side or above the camera, or to bounce light off a nearby white surface, as professional photographers do. If you have a built-in flash, try asking your subjects to look over your shoulder.
• Most new cameras include a red-eye reduction setting, which fires a series of pre-flashes, causing the pupils to contract before the final flash.

• Rods — the photoreceptor cells in the retina responsible for night vision — are concentrated around the periphery of the retina.
• Over the course of a lifetime, most cone cells remain intact, but we lose around a third of our rods — which is why it gets harder to see in the dark as we get older.
• Our rods also take longer to adjust when moving from bright to dimmer light and we become less good at spotting movements out of the corners of our eyes — the periphery of our visual field.

• Just like a camera aperture setting, your eye can alter the diameter of the pupil to control the amount of light it lets in.
• In dim light, the pupil gets wider to let in more light. The area of your pupil more than doubles in size in near darkness, and shrinks in very bright light to around half the size it is under normal room lighting.
• In young eyes, this adjustment happens almost instantaneously; it's a little slower and less efficient in older eyes.
• Changes in pupil size are due to contraction and expansion of the iris, the coloured part of the eye surrounding the pupil, which is actually a ring of muscle.
• In common with other muscles, it weakens with age, making pupils less responsive to sudden changes in light level.