Influence of environment on visual performance
Download
1 / 64

OT 677 Environment l..> - PowerPoint PPT Presentation


  • 452 Views
  • Uploaded on

Describe the influence of the environment on occupational performance ... Required to match movement only to spatial features of environment ...

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'OT 677 Environment l..>' - Navneeth


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Learning objectives l.jpg
Learning Objectives

  • Identify factors affecting the visibility of environments

  • Describe the influence of the environment on occupational performance

  • Differentiate between visual factors that facilitate occupational performance and those that impede performance

  • Analyze environments in terms of their strengths and weaknesses in visibility

  • Select appropriate environmental modification to facilitate occupational performance


Vision is used primarily to gather information about the environment l.jpg
Vision is used primarily to gather information about the environment

  • Identify obstacles and threats to postural control and mobility

  • Identify the number and properties of objects to be manipulated and acted upon


Gathering of information is completed both focally and peripherally l.jpg
Gathering of information is completed both focally and peripherally

  • Focal perception

    • Conscious attention to specific visual information in the environment needed to complete a task

      • Example: selecting a place to sit in class

      • Vision is used deliberately and consciously for object identification and decision making

  • Peripheral perception

    • Unconscious attention to global composition of environment needed for orientation and safety

      • Example: CNS monitors verticality of walls, illumination, composition of support surface, number of obstacles

    • Information gathered allows one to remain upright in space during mobility, stay oriented and avoid collision


Slide5 l.jpg

Both types of perception are needed peripherally

to successfully adapt to the environment

  • Doesn’t do any good to be able to identify objects and establish a goal for movement if you can’t move toward your target without collisions

  • Ability to move and stay upright in the environment has no purpose if you don’t move in order to achieve a goal


All environments have specific features or qualities that dictate how we can interact with them l.jpg
All environments have specific features or qualities that dictate how we can interact with them

  • Environments can be

    • Static or dynamic

    • Novel or familiar

    • Simple or complex


Static or fixed environments l.jpg
Static or Fixed Environments dictate how we can interact with them

  • All objects in the environment are fixed in place

  • Required to match movement only to spatial features of environment

    • Can be completed visually or tactually

  • No temporal component

    • Timing is not important

  • Vision is nice but not necessary


Dynamic or moving environment l.jpg
Dynamic or Moving Environment dictate how we can interact with them

  • Objects are moving independent of performer

  • Required to match movement to spatial and temporal features

    • Timing of movement is determined by external factors

      • How fast the car is approaching/when will the elevator doors close

  • Performance is dependent on speed of information processing

  • Vision plays dynamic and critical role

    • Takes you farther into environment than any other system

    • Must be combined with cognition to be effective

      • Knowing where to look for crucial information


Familiar environments l.jpg
Familiar Environments dictate how we can interact with them

  • Have been in that environment before and know the layout

  • If the environment is also static, little vision is required if any

    • Navigate via kinesthetic awareness

      • Don’t have to think about the layout or where the table is-function on automatic pilot

  • Major argument for working with visually impaired older adults to “age in place”

    • Removing person from familiar environment often causes regression in performance


Novel environments l.jpg
Novel Environments dictate how we can interact with them

  • Unknown to the person

  • May also be dynamic and constantly changing

  • Requires increased use of vision and cognition

    • Most community environments fall into this category


Simple vs complex environments l.jpg
Simple vs. Complex Environments dictate how we can interact with them

  • Determined by

    • Number of objects

    • Visibility of objects

    • Placement of objects

    • Whether objects are in motion

  • Inter-plays with other qualities of environment and we often function in combinations

    • Static/simple or static/complex

    • Dynamic/simple or dynamic/complex

    • Familiar/complex or novel/complex

    • Familiar/static or novel/static


Most challenging environment l.jpg
Most Challenging Environment? dictate how we can interact with them


Most challenging environment13 l.jpg
Most Challenging Environment? dictate how we can interact with them

  • Novel

  • Dynamic

  • Complex


Least challenging environment l.jpg
Least Challenging Environment? dictate how we can interact with them


Least challenging environment15 l.jpg
Least Challenging Environment? dictate how we can interact with them

  • Familiar

  • Static

  • Simple


Movement is governed by regulatory conditions l.jpg
Movement is Governed by Regulatory Conditions dictate how we can interact with them

  • Objects and features of environments with which we interact

  • Include physical and sensory properties

  • Can be facilitatory or inhibitory to performance


Physical regulatory conditions l.jpg
Physical Regulatory Conditions dictate how we can interact with them

  • Nature of support surface

    • Uneven or even

    • Presence of steps, curbs, ramps etc

  • Number and nature of objects

    • Height and shape of furniture etc

    • Whether objects are in motion or static

  • Physical regulatory conditions can facilitate or inhibit travel performance

    • Well placed handrail can facilitate navigation

    • Broken pavement can increase risk of fall


Sensory regulatory conditions sound l.jpg
Sensory Regulatory Conditions dictate how we can interact with themSound

  • Sounds can facilitate or inhibit performance

    • Sound of traffic or footfalls can assist navigation

    • Loud or irritating noise can affect concentration

    • Background noise has been shown to have a detrimental effect on speech perception by older visually impaired adults

      • Moderately noisy environments can obscure weaker speech sounds

        • Normally sighted person pays more attention to the speaker’s facial expression, posture and gestures to acquire meaning when speech is difficult to hear

        • Person with visual impairment loses that advantage-doesn’t see well enough to compensate for effects of background noise


Sensory regulatory conditions temperature and tactual l.jpg
Sensory Regulatory Conditions dictate how we can interact with themTemperature and Tactual

  • Temperature

    • Extremes in either direction (too hot or too cold) limit endurance and concentration

    • Feeling the warmth of the sun on the face can facilitate orientation

  • Tactual

    • Texture and angle of support surfaces, objects

      • Change in tactile surface can indicate curb cut, grass etc

      • Rain slicked surface or plush carpet can cause fall

    • Wind coming from a certain direction can facilitate orientation


Sensory regulatory conditions olfactory l.jpg
Sensory Regulatory Conditions dictate how we can interact with themOlfactory

  • Olfactory senses are used to confirm

    other sensory input

    • Smell can assist in location of cafeteria

  • Olfaction can also inhibit performance

    • Noxious odors can be very distracting


Visual regulatory conditions l.jpg
Visual Regulatory Conditions dictate how we can interact with them

  • Luminance

    • Brightness

    • Reflectance

    • Quality of light source

    • Glare

    • Even-ness

  • Background contrast

  • Background pattern

    • Static

    • Moving


Visual regulatory conditions luminance l.jpg
Visual Regulatory Conditions dictate how we can interact with themLuminance

  • Two types of available light in environment

    • Direct

      • Windows and lights

    • Indirect

      • Reflected light off of surfaces

  • Components of illumination

    • Brightness

    • Quality of illumination

    • Presence of glare

    • Even-ness of illumination


Brightness l.jpg
Brightness dictate how we can interact with them

  • Measured from direct source or reflectance

  • Direct source (lamp)

    • Amount of light arriving on a surface

      • Measured in footcandles

    • Power of light is measured in lumens

      • 1 lumen is equal to 1 footcandle

  • Brightness is determined by dividing the candle power of the light source by the distance of the source to the surface squared


Slide24 l.jpg

Light source dictate how we can interact with them

surface

Distance of

source

to surface

Luminance of a surface is determined by

measuring the distance between the light

source and the surface and squaring it


Slide25 l.jpg

Distance of source to surface dictate how we can interact with them2

Then dividing it into the candle power

of the light source

Candle power of light source

Source to surface distance 2


Slide26 l.jpg

Footcandles can be determined using a light meter placed on the surface OR using the equation

1 lumen = 1 foot candle

**Light lumens are found on the package when you buy the

light bulb in the store

Power of light measured in lumens or

footcandles


Brightness of reading surface example l.jpg
Brightness of Reading Surface the surface Example

  • 75 watt bulb produces 1180 lumens

  • Distance to task is 3 feet

    1180 = 1180 = 131 footcandles

    32 9


Minimal task lighting recommendations l.jpg
Minimal Task Lighting Recommendations the surface

  • Absolute minimum lighting (in foot candles) for an individual aged 20-29 years with 20/30 vision

    • Reading: 70

      • Telephone directory: 200

    • Seeing black thread on black cloth: 1400

    • Grooming: 50

    • Dining area: 30


Reflectance l.jpg
Reflectance the surface

  • Another measure of brightness

  • Amount of illumination reflected back from the task surface to the eye

  • Measured in foot lamberts

    • Unit of brightness equal to the surface reflectance at a rate of 1 lumen per square foot


To measure reflectance l.jpg
To Measure Reflectance: the surface

  • Can only be measured with light meter

    • Which has foot lamberts measurement

  • Hold light meter at a constant distance above the surface

  • Take reading in foot lamberts

  • Divide foot lamberts by the footcandles of the power source to get approximate % of reflectance


Slide31 l.jpg

Foot lamberts the surface

Foot candles

reflectance

In foot lamberts


Slide32 l.jpg

2 feet the surface

1 foot

1180

12

1180

22

=

=

295 footcandles

1180 footcandles

Brightness can be increased two ways:

1. Move the light closer to the surface


Slide33 l.jpg

1180 the surface

22

1710

22

=

=

295 footcandles

428 footcandles

2. Get a stronger light

75 watt

100 watt

(1180 lumens)

(1710 lumens)

2 feet

2 feet


Quality of light source l.jpg
Quality of Light Source the surface

  • Different types of lights give off different color wavelengths

  • Incandescent

    • Favors red end of spectrum (yellow light)

      • Less easily absorbed by retina-more glare

  • Halogen

    • Favors blue end of spectrum

      • More easily absorbed by retina-less glare

  • Full spectrum

    • All colors-pure white light

      • More easily absorbed by retina-less glare


Presence of glare l.jpg
Presence of Glare the surface

  • Degrades the visibility of environment

  • Two sources

    • Direct

      • Light source

      • Incandescent glares more than halogen or full spectrum

    • Indirect

      • Reflected off of surfaces: tables, floors

      • Bright shiny surfaces reflect more glare


Even ness of illumination l.jpg
Even-ness of Illumination the surface

  • Areas of shadow

    • Degrade / obscure detail in environment

  • Moving between shadow and light

    • Difficult to adjust to

      • Cones take 7 minutes to replenish

      • Rods take 1 hour to replenish


Contrast l.jpg
Contrast the surface

  • Determines visibility of objects

    • Differentiation of object from background

  • Good contrast facilitates performance

  • Poor contrast diminishes performance


Slide38 l.jpg

Examples of Good Contrast in Environment the surface

Yellow lines indicate curb

Green grass line provides

shoreline border


Slide39 l.jpg

Examples of Inadequate Contrast the surface

Reduced contrast obscures depth of stairs both inside and

outside of the home


More examples of poor contrast l.jpg
More examples of poor contrast… the surface

Light switch blends into wall Handrail disappears


Background pattern l.jpg
Background Pattern the surface

  • Created by designs and objects in environment

  • Two types

    • Moving pattern

      • Created by people, cars etc.

    • Static pattern

      • Background pattern on support surfaces

      • Inlayed or overlayed


Moving pattern l.jpg
Moving Pattern the surface

  • Makes it more difficult to identify target

  • More difficult to move towards the target

    • Must monitor spatial and temporal features

  • Performance depends on speed of information processing

    • Increases demand for vision and cognition


Static pattern l.jpg
Static Pattern the surface

  • Types

    • Object clutter

    • Pattern inlayed in background surfaces

      • EX: Floral patterns woven into material

    • Pattern overlaying background surfaces

      • EX: shadows


Slide44 l.jpg

More static background pattern the surface

Over-layed as shadow

Inlayed as part of brick/stone pattern


Slide45 l.jpg

Greatest challenge is a combination of the surface

poor regulatory conditions

Example of pattern,low contrast, glare in entry way to outpatient clinic


Pattern and low contrast l.jpg
Pattern and Low Contrast the surface

Shadow overlaying steps with poor contrast

Along with low contrast hand rail


Analyzing environments l.jpg
Analyzing Environments the surface

  • Working with clients to function safely within the environment requires careful analysis of the environment

    • Reason for home visits and community outings

  • All environments have components which impede or facilitate occupational performance

    • OT job is to minimize or compensate for impediments while maximizing use of facilitators


Impediments to travel participation l.jpg
Impediments to Travel/Participation the surface

  • Travel hazards

  • Fluctuating environments

  • Complex environments

  • Monochromatic environments

  • Poor and uneven illumination

  • Insufficient/poor signage


Travel obstacle vs hazard l.jpg
Travel Obstacle vs. Hazard the surface

  • Obstacle

    • An architectural or environmental obstruction in the line of travel that is easily detected and negotiated

  • Hazard

    • An architectural or environmental obstruction in the line of travel that is not easily detected


Slide50 l.jpg

An obstacle can become a hazard because the surface

of poor design

Traffic lights are an obstacle

to the flow of traffic

Traffic lights are a hazard when

They can’t be easily seen


Slide51 l.jpg

Well marked curb cut the surface

Invisible curb cut


Fluctuating environments l.jpg
Fluctuating Environments the surface

  • Mostly occur with community/outdoor environments

    • Rain puddles, ice, snow, nighttime

    • Indoor environments used by multiple people are an exception

  • Can create false information

    • Looks like a puddle but is really ice

  • OR obscure information

    • Shadows, pile of leaves can hide surface


False obscure l.jpg
False Obscure the surface

Overlay of shadow

creates false impression

Shadow obscures surface

of sidewalk


Home messy home l.jpg
Home-Messy-Home the surface

Indoor environments can fluctuate too


Complex environments l.jpg
Complex Environments the surface

  • Significantly increase cognitive load

  • Complexity directly related to amount of

    • Visual clutter

    • Moving clutter

    • Variability

Grocery store is one of the most

complex environments



Even ness of illumination57 l.jpg
Even-ness of Illumination the surface

  • Areas of shadow

    • Degrade / obscure detail in environment

  • Persons with low vision report that adjusting to changing levels of illumination is the greatest challenge to mobility


Small obscure signage l.jpg
Small/Obscure Signage the surface

  • Significantly affects orientation

  • Creates stress and limits participation

  • in environment


Aides facilitators l.jpg
Aides/Facilitators the surface

  • Adequate/good quality illumination

  • Contrast in key structures

  • Visible safety features

  • Tactile guides to reinforce location

  • Properly placed and visible signage


Good quality illumination l.jpg
Good Quality Illumination the surface

  • Sufficient illumination

  • Non glaring illumination

  • Even illumination


Contrast in key structures l.jpg
Contrast in Key Structures the surface

Shadow obscures sidewalk but pavement

markings facilitate navigation through the pattern


Visible safety features l.jpg
Visible Safety Features the surface

Dark hand railing facilitates use of low contrast stairs


Tactual guides l.jpg
Tactual Guides the surface

Tactual input reinforces that support surface has changed and reinforces location


Visible signage l.jpg
Visible Signage the surface

Properly placed, large signage facilitates orientation


ad