The eye is our organ of vision#
Its complicated design means that an image can pass through its many layers and end up crisply focused on the back of the eye, called the retina. The retina is covered with light sensitive cells, called rods and cones. Information on shape, color and pattern is picked up by the retina and carried to the brain via the optic nerve.
Starting from the front of the eye, the various parts include:
- the curved back layer of the eye covered in light sensitive cells
- called rods cones
- that can ‘see’ shape color pattern – sends information from the retina to the brain
Humans have binocular vision#
The right and left eye each see a slightly different view. The brain combines the two views and the result is a three-dimensional image.
The cornea has a fixed focus#
Adjustments in focus are made by the lens that sits just behind the iris. It has tiny muscles that change its shape according to how far or near the eye needs to focus. The colored part of the eye, the iris, is a muscular ring or sphincter which controls the amount of light entering the eye.
It causes the pupil to dilate (get bigger) in darkness so as to let in more light.
In bright light, the iris causes the pupil to constrict (get smaller)#
Where the optic nerve enters the back of the retina, there are no rods or cones.
This tiny patch of blindness in both eyes is compensated for by the brain. It processes the image surrounding the blind spot then fills in the blanks accordingly. You can ‘see’ your blind spot by drawing two dots on a piece of paper, around 10 centimetres apart.
Close your right eye and look at the dot on the right. Move the paper back and forth until the dot on the left seems to disappear. Tears lubricate the eye and stop the surface from drying out. A thin film of tears is swept over the eye surface every time you blink.
Stray eyelashes and particles of dust are also collected by the tears and flushed out of the eyes. Some common complaints of the eye include:
- jelly-like fluid that fills the eyeball
- Ear Hospital
Key Points#
- It causes the pupil to dilate (get bigger) in darkness so as to let in more light
- In bright light, the iris causes the pupil to constrict (get smaller)
- Some common complaints of the eye include:
Sources & further reading
For evidence-based global guidance on this topic, consult authoritative public-health bodies such as the World Health Organization (WHO), CDC, NHS, and ECDC.