1. We do not see with the eyes alone
The retina converts light into nerve signals, but the brain organises them into shape, movement, depth and meaning. Vision is therefore the work of the complete visual system.
2. The pupil adapts to light
It becomes smaller in bright conditions and larger in darkness. However, adaptation also involves rods and cones changing their sensitivity.
3. Dark adaptation takes time
When moving from a bright to a dark place, full adaptation is not immediate. Cones dominate first; then the more light-sensitive rods increasingly support vision.
4. Blinking protects the eye surface
Blinking spreads the tear film, removes small particles and keeps the cornea moist. Blink rate can fall during concentrated screen use, contributing to dryness and discomfort.
5. Each eye has a natural blind spot
Where the optic nerve leaves the retina, there are no photoreceptors. We usually do not notice this because the brain fills in the scene and the visual fields overlap.
6. Depth perception uses many clues
Binocular cooperation is important, but the brain also uses perspective, size, shadow and movement. This helps us judge distance even when some binocular information is limited.
7. Colour is a neurological interpretation
Three main cone types respond to different parts of the visible spectrum. The brain compares their signals to create colour perception. Inherited colour-vision deficiencies do not normally mean seeing only in black and white.
