vision Flashcards
The eye is protected by
Bones of the skull that make up the orbit (eye socket)
2. Eyelids and Eyelashes – keep debris out of the eye
3. Tears – secreted from the lacrimal gland
- Cleanse the surface of the eye
- Prevent the surface of the eye from drying out
- Have antibacterial properties
outer layer: sclera
Sclera = connective tissue surrounding the eye. Forms
the whites of the eye
middle layer: Choroid
Choroid = pigmented layer between sclera and retina that contains blood vessels (provide nutrients/O2 to retinal cells). Is continuous with the…
middle layer: Ciliary body
Ciliary body = connects choroid to iris. Has suspensory ligaments
and smooth muscle that control the shape of the lens.
middle layer: iris
Iris = visible pigmented portion of the eye (eye colour). Contains smooth muscles for pupil constriction and dilation. These muscles are controlled by the autonomic nervous system.
outer layer: Cornea
Cornea = most anterior part of the eye. Clear transparent layer that light can pass through. If you wear contact lenses, they sit on the cornea.
inner layer: retina
Outer pigment cell layer – dark green colour. Absorbs excess light so that it does not reflect back into eye
Photoreceptor layer – 2 types of photoreceptors that transduce light energy into electrical and chemical
signals
inner layer: rods
More abundant photoreceptor type
- grey scale/night vision
-Low acuity (detects sizes, shapes, brightness) more convergence
located: peripheral retina
inner layer: cones
less abundant
colour/day vision- less convergence
located: fovea
Anterior compartment
between cornea and lens
- filled with aqueous humor (has similar composition to extracellular fluids)
Posterior compartment
between lens and retina
- filled with vitreous humor (gelatinous substance
produced by the ciliary body)
Choroid
lens, pupil and fovea
bends light to focus it on the retina
opening in the iris that allow light to enter the posterior compartment of the eye.
area of the retina onto which most light entering the eye is focused
Myopia
near sightedness
(Difficulty seeing distant objects, but near objects are clear).
Focal point falls in front of the retina instead of directly on the retina
because eye is longer than normal or the cornea is curved too much.
Hyperopia
far sightedness
(Difficulty seeing near objects, but distant objects are clear).
Focal point falls in behind the retina instead of directly on the retina
because eye is shorter than normal or cornea is curved too little
Astigmatism
flaws in curvature of cornea or lens causes some rays of light to scatter and not hit the fovea , resulting in blurred vision.
