Human eye - Responding to the environment

Accommodation

The ability to change the focal length of the object by changing the convex shape of the lens to assist with focussing on a near or distant object

Astigmatism

Uneven curvature of the lens or cornea resulting in distorted images

Astigmatism Treatment

Glasses or contacts

Aqueous humour

Watery liquid that protects the lens of the eye and supplies the cornea with nutrients

Long-sightedness

An eye condition in which close objects appear blurred. this is caused by a lens that cannot become rounded enough to refract light, so the image falls behind the retina

Long-sightedness treatment

convex lens or laser surgery

Short-sightedness (myopia)

The ability to see close objects clearly; distant objects appear blurry, this is caused by a lens that is too rounded, so the image falls short of the retina
​

short-sightedness treatment

concave lens or laser surgery

catatract and treatment

cloudiness of the lens and can be treated through surgery

Optic nerve

The nerve that carries impulses from the retina to the brain

Photoreceptors

Specialized receptors to receive the stimulus of light and convert it to an impulse.

Refraction

To bend light-refraction takes place when light passes through a lens that is bent by a convex [()] shape or a concave [)(] shape

Binocular vision

The ability to focus the two eyes in a coordinated manner in order to see one image

Importance of binocular vision

allows for 3D dimensional vision

Sclera

outer white protective layer of the eye

sclera function

helps to maintain the shape of the eyeball and where eye muscles attach

cornea (function and location)

Clear layer on the front of the eye that helps focus light onto the retina

choroid

middle, vascular layer of the eye, between the retina and the sclera

choroid function

the blood vessels nourish the other layers of the eye, and the melanin helps to absorb excess light

iris function

controls how much light enters the eye

pupil

The opening through which light enters the eye

Retina

Light sensitive layer of the eye; contains rods and cones

retina function

receive light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition

Cilairy Body

secretes aqueous humour

ciliary muscle

controls the shape of the lens for near or far vision

Photoreceptors function

convert light into nerve impulses

Rods

Sensory cells in the retina that are activated in dim light and allow us to see black and white

Cones

sensory cells in the retina that are sensitive to bright light and provide color vision.

Lens

the transparent structure behind the pupil that changes shape to help focus images on the retina

suspensory ligaments function

hold the lens in place

yellow spot function and location

small area on retina that contains only cones and responsible for sharp central vision

Blind spot

the point at which the optic nerve leaves the eye, creating a "blind" spot because no receptor cells are located there

Pathway of light in the eye

cornea, aqueous humor, pupil, lens, vitreous humor, retina, optic nerve

Accommodation for near vision

ciliary muscles CONTRACT > ciliary body moves INWARDS > suspensory ligaments SLACKEN > elastic lens become more CONVEX/ROUNDED > clear image on retina

Accommodation for distance vision

ciliary muscles RELAX > ciliary body moves OUTWARDS > suspensory ligaments become TIGHT > elastic lens become more leas CONVEX/FLATTER > clear image on retina

pupillary light reflex

Contraction of pupils in response to light.

Pupils to Bright Light

RADIAL muscles RELAX
CIRCULAR muscles CONTRACT
pupils CONSTRICT
LESS light enters eye

Pupils to Dim light

RADIAL muscles CONTRACT
CIRCULAR muscles RELAX
pupils DILATE
MORE light can enter the eye