Non-Optical aids Flashcards
What is the definition of a non-optical device?
Any device other then a magnifier that enables VI individuals to funciton more easily
What is one of the most important non-optical aid?
Lighting! 20% of px just need good refraction and advice on lighting
What is luminous flux?
Amount of light emitted by a light source ; lumens
What is luminous Efficacy?
the ratio of the light output to the energy input Watts
What is light colour temps
low number = yellow
high number = white light
what is illuminance?
the quanity og light per unit area hitting the wokring surface or task ; measured in lumens per square metre (lux)
what is illuminance ?
The intensity of light (brightness) emitted or reflected in a particular direction by an area which is either self luminous, or is reflecting incident light
Measured in Candelas per square metre
what is CFL light source?
5X more efficent then filament and takes time to reach full brightness. Only some of these are dimmable. It has a low cost
What is a halogen light source?
Instant output and dimmable
not as efficient as CFLs but more expensive then CFLs ; can get hot
what is LED light?
Expensive but getting cheaper, it is enegergy efficent
has a long life
provides an instant output
does not heat up
specical dimmer needed
currently provides low light output
How is visual performance effected by lighting?
performance increases with improvments in task illuminance
Older subjects will receieves less light to their retina compared to younger retina
How can be optimize lighting for VI px?
1.increase general ambient level of illuminance. draw the curtains well back
2.paint the house walls with light colours and use fluorescent fittings
3. Localised area lighting ; over the phone under kitchen cabinets
4. Carry torch when ambient lighting is poor
- Outside = night vision scopes, wide-angle mobility light and mobility lights
What are the 3 types of glare?
- Discomfort glare
- Disability glare
- Refleciton glare
How can quantify glare clinically?
Brightness acuity tester
How can we decrease glare?
changes in the environment ; move child away from blackboard
use matt instead of gloss
tinted visors and shields
pinholes
artificial iris CLs
typoscopes
what tint can we used if the px has AMD?
yellow and amber tint
Px has retinitis pigmentosa what colour?
Red