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Introduction to Vision Cheat Sheet by

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

Elements of Vision

1. sight
2. eye movement

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

Visual Pathway Overview

Macular Degene­ration

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

How People see with AMD

Cataracts image

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 Retino­pathy

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.

How people see with 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

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

   
 

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