Cheatography
https://cheatography.com
Basic information about vision
Anatomy of the Eye
Pupil- how much light enters the eye
Ciliary body- changes the shape of the lens (focusing)
Choroid- contains vessels that supply blood
Retina- contains the cells that are sensitive to light (rods and cones)
Lens- focuses light to the back of the eye
Sclera- the white part of the eye
Optic nerve- transmits visual information to the brain
Cornea- the transparent layer at the front of the eye
|
Components of Sight
Visual Acuity |
the level of detail a person sees |
Visual Field |
the total area one sees in a single view |
Contrast Sensation |
the ability to distinguish shades of light, dark, and similar colors |
Light Modulation |
the ability to adapt to changing light conditions |
Visual Perception & Interpretation |
the processing of information once it reaches the brain |
Macular Degeneration
a group of conditions that cause central vision loss |
Macular degeneration (AMD) is when the retinal pigment epithelium (RPE) layer begins to malfunction. |
Most AMD starts out as dry and some progress to wet |
Dry AMD is the build up of deposits called drusen, which causes macular scarring |
Wet AMD is the development of a cluster of blood vessels under the macula |
Cataracts
Cataract is the clouding of the crystalline lens in your eye |
Cataract surgery is one of the most common surgeries performed |
If left untreated, the cataract will dull color and blur vision |
Clients with cataracts will have decreased contrast sensitivity |
|
|
Hierarchy of Visual Perceptual Processing
Refractive Error
Myopia |
the problem with the lens ability to focus on the image with adequate power; the power is not strong enough resulting in undershooting the fovea/retina (focal length is too short) |
concave or negative (-) lens |
Hyperopia |
problem with the lens ability to focus on the image with adequate power; power is too strong and overshooting the fovea (focal length to too long) |
convex or positive (+) lens |
Astigmatism |
the shape of the cornea itself is misshaped impeding the ability to properly bend or refract light/image resulting in a distorted image |
misshaped cornea |
Refactive Error is due mishaped
What does 20/20 mean?
You can see at 20 feet as a person with standard vision can see at 20 feet |
Diabetic Rentiopathy
Diabetes causes damage to small blood vessels and the eye is not spared |
DR causes a number of different visual problems ranging from "floaters" to total blindness |
Background diabetic retinopathy is the early stage of DR |
Proliferative diabetic retinopathy is a more severe form of DR. |
|
|
What is low vision?
Low vision is defined as a visual impairment that cannot be corrected by medical or surgical intervention and is severe enough to interfere with the performance of activities of daily living but allows some usable |
Four Types of Vision Loss
Central Field Loss |
Age-related Macular Degeneration (AMD) or Stragardts Macular Degeneration (genetic) |
Peripheral Field Loss |
Glaucoma or retinitis pigmentosa |
Visual Field Cuts |
Neurological conditions stroke, brain injury, Parkinson's, and Multiple sclerosis |
Diffuse Vision Loss |
Usually caused by diabetic retinopathy |
Functional Implications of Central Field
Difficulty reading |
Decreased contrast sensitivity (e.g. poor detailed vision) |
Excessive head movement to search for items in their environment or during reading |
All things that require detailed vision will be affected (e.g. reading bills, text messages, following recipes, driving, etc) |
Self care is NOT affected |
Glaucoma
Glaucoma is caused by increased pressure in eye |
Glaucoma causes peripheral vision loss and will untreated can cause blindness |
Fortunately, glaucoma is very treatable with eye drops and surgery |
The key to treatment is catching it before it damages the optic nerve and cause vision loss |
How people see with glaucoma
Retinitis Pigmentosa (RP)
Retinitis pigmentoas is a progressive hereditary eye disease that causes deterioration of the retinal cells |
People usually start noticiting that they have night blindness, then they start losing their peripheral vision |
Central vision is spared in the beginning, but the visual flieds so small that they can only see small pinholes |
RP will eventually cause total blindness |
Retinitis pigmentosa image
|
Created By
Metadata
Comments
No comments yet. Add yours below!
Add a Comment
Related Cheat Sheets
More Cheat Sheets by prinsam98