Non optical devices and viewing strategies Flashcards
what is a non optical device
Any device other than a magnifier that enables VI individuals to function more easily
what is the most important non optical aid and how many % 0f LV patients only require this
- lighting
- 10-20% of low vision patients need only a GOOD REFRACTION and ADVICE ON LIGHTING’’
i.e. if a patient uses the right amount of lighting that may not need an LVA and may only need to use their glasses
what is the definition of Luminous Flux and what is it measured in
Amount of light emitted by a light source
Measured in Lumens
what is the definition of Luminous Efficacy
Ratio of the light output (lumens) to the energy input (watts)
what is the definition of Illuminance and what is it measured in
The quantity of light per unit area hitting the working surface or task.
Measured in Lumens per square metre (Lux)
what is the definition of the inverse square law
and what happens as the distance of the light source to the object doubles
Illuminance of an object is inversely proportional to the square of the distance of the light source from that object
As distance doubles area illuminated increases fourfold, but illuminance decreases by a factor of four
i.e. if the light is brought closer, the illuminance decreases in area, but the light hitting the surface increases/is more intense
what is the definition of luminance and what is it measured in
explain when this is used and what implications it can have
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
important when we look at computer screens as its reflecting light or in the clinic when are measuring va’s.
we may be using a computer screen or a custom made chart, so the luminance of the chart is very important because if its very low, the patient will struggle to read off the chart, given inaccurate va’s so the luminance of the chart should be at least 150 candelas per metre squared
what is colour appearance characterised by and what it is measured in
- characterised by colour temperature
- 7,500 kelvin colour temperature appears bluish (cold)
- 2,700 kelvin colour temperature appears yellow (warm)
what does colour rendering describe and what colour index value reveals a colour well
describes the affects of a light source on the colour appearance of objects as compared with their appearance under a natural light source
the colour rendering index is between 80 and 100 reveals a colour well
describe what general lighting is and what task lighting is
General lighting:
can be in a room e.g. a sitting/bedroom
lighting may be attached to a roof or walls or free standing
Task lighting:
near a telephone to help with dialling, lights in a cupboard, under the stairs
light will be strategically placed in different places
list the 5 different types of lamps
- Tungsten or GLS
- Fluorescent
- Compact fluorescent
- Halogen
- LED
how is light produced by a tungsten or GLS lamp and what is a advantages (2) and disadvantages (3) of this lamp
- light is produced by heating a tungsten filament
advantage:
- cheap and full light output when switched on
- can also dim/brighten the light using a dimmer switch
disadvantage:
- produces too much heat
- doesn’t last very long
- expensive to run and is energy inefficient
what is the advantages (4) and a disadvantage (1) of a fluorescent lamp
advantage:
- 5x more efficient than a tungsten bulb
- is cheaper to run
- does not get very hot
- lasts a long time, 8x more than tungsten
disadvantage:
- not easy to dim/brighten
what is a advantage and a disadvantage of a compact fluorescent lamp
advantage:
- can bend fluorescent tubes into different shapes = more compact
disadvantage:
- takes time for light to become brighter when switched on, no good for VI patient e.g. when using a staircase
what is the advantages (4) and disadvantages (2) of a halogen lamp
advantage:
- more efficient than tungsten
- comes on instantly when switched on
- reasonable price
- can attach a dimmer switch on them
disadvantage:
- less efficient than a fluorescent lamp
- produces lots of heat so uncomfortable when close
what is the advantage and disadvantage to LED lamps
advantage:
- cheap to run and lasts long
disadvantage:
- expensive to buy (but then lasts longer)
how does visual performance improve
how much light does a 60 year old retina receive compared to a 20 year old
- Performance increases with improvements in task illuminance
- 60-year-old retina receives one-third the amount of light that reaches the 20-year old retina (Weale,1961)
even if not visually impaired, need more light to see
list 5 things that can be done to optimise lighting for VI patients
- Increase general ambient level of illuminance
- Providing enhanced illumination for detailed tasks in a localised area (task lighting)
- Localised lighting not only while reading but also for other tasks such as over telephone, under wall mounted kitchen cabinets etc
- Carry torch when ambient lighting is poor
- Lighting for outdoor mobility
list 3 things that can be done to optimise light by Increasing general ambient level of illuminance
- Draw curtains well back, clean curtains regularly and avoid use of net curtains
- Paint house walls with light colours
- Use fluorescent fittings
list 3 things that can be used to optimise light by increasing lighting for outdoor mobility and which type of eye condition will this be beneficial for
- Mobility lights
- Wide-Angle Mobility Light (WAML)
- Night Vision Scopes
beneficial for retinitis pigmentosa
what is a disadvantage of Wide-Angle Mobility Light (WAML)
need to carry a battery pack to use them, which is heavy and impractical
how do Night Vision Scopes work
they work from IR radiation to help see in the dark
explain how ideal localised lighting should be used
- Place lamp in front of face, with shade arranged so that there is no light shining directly into the eyes
- Lamp should have flexible arm with heavy base
so can adjust the distance between the light source and e.g. the book - Light should NOT be at eye level, but should be placed BELOW eye level to avoid glare
- Do not recommend tungsten or halogen bulbs for this, it is better to use fluorescent bulbs
when does photophobia occur
when theres something wrong with the eyes e.g. uveitis and can’t look at bright light
which 2 classifications of glare is there and list the 3 types of glare and what causes them
which types of patients suffer from glare
- physiological/pathological
- Discomfort Glare: bright sunny day, VA is still the same
- Disability Glare: causes reduction in VA due to it being very bright, this tends to happen in VI people
- Reflection Glare
what can you use to quantify glare clinically and objectively
explain how to use this
- brightness acuity tester
Method:
- get px to read snellen chart
- then give them the brightness acuity tester
- the instrument produces different glare sources
- if the patient stars of to read 6/6 and then you give the BAT and dial a particular glare source
- then see what the px reads on the snellen chart
- if glare has no effect on px, then va will be the same
- if glare gives them a problem, then va will be reduced
- it is a good test for a cataract px
- can implicate surgery
list 7 things that can be done/used to decrease or eliminate glare
- Changes in the environment
E.g. Move child away from Blackboard
Use matt instead of gloss - Visors and shields
- Glasses with multiple pinholes
- Artificial Iris Contact Lenses (e.g. for albinism)
- Typoscopes (cut off glare from a page)
- Tints for discomfort glare
- Tints for disability glare
list 4 types of tints that can be used for disability glare
- Photo chromatic lenses
- UV and Noir shields-over spectacles
- Yellow and Amber tints: AMD
- Red Tints: Retinitis Pigmentosa
list 4 things that can be used to make reading/writing easier
- Reading stands
- Writing guide (to write in straight line)
- Typoscopes
- Signature Guide
how are typoscopes support to make reading/writing easier
it can highlight the sentence your reading. it is good for eccentric viewing and is supposed to reduce glare
list some large print items available to VI people
- Large button phones
- Large print books, address books, diaries, crosswords etc
- Large playing cards
- Big Print Newspaper
- Large number clocks/watches
list some talking devices
- Talking Watches, Talking Clocks
- Talking Microwave
- Talking Newspaper
- Talking Calculators
- Talking Blood Glucose meter
which talking device is available on the NHS
Talking Blood Glucose meter - for diabetic patients
what 2 things can be used for managing money
- Note Detector (detects some of note and vibrates e.g. once if £5 note)
- Coin Holder
list 11 Other useful gadgets/aids
- Audio described Videos: commentary in background describing scene of the movie)
- Pen Friend Voice labeller: you record your message and touch the black pen onto the white label when you want to know what something is)
- Pill Organisers
- Bump-ons: every social service will give this to their px. you can put it on a setting that the px always uses
- Liquid Level indicators: know when cup is full will beep/vibrate
- Special toys for children
- Recordable cards
- Chopping boards: different colours
- Rubber non slip Grips
- Felt Pens
- MP3 player
list 9 aids that can be used for orientation and mobility and who they are provided by
- White cane
- Symbol Cane
- Guide canes
- Long Cane
- Walking sticks
- GPS systems
- Guide Dogs, Guide Ponies
- Echolocation
- Mike May: Crashing Through
provided by social services
how is a guide cane used
helps to find obstacles infront of them and hold it diagonally across the body to find curbs or steps etc
what is used to symbolise that somebody is visually impaired
symbol cane
how is a long cane used for orientation and mobility
patient needs to be trained to use it
has a small ball at the end, use to sweep side to side and find obstacles in their path
required 100-200 hours training
what does a white and red cane stand for
visually and hearing impaired
what are walking sticks used for
for support in those who have difficult walking
how does echolocation work for orientation and mobility
it is the ability of an individual to be able to detect objects in their environment by sensing echoes from those objects and identifying where that object is
what 2 electronic visual enhancement systems are there
describe what each does
CCTV
introduced in the 1970’s
system where you have a screen and a camera and you put whatever you want to read under the camera and it magnifies it onto the screen
Head mounted devices
e.g. of the Jordy system:
a pair of glasses that you wear, if you have something in your hand you can e.g. put it over a book or a camera that you can adjust for distance, and whatever distance you adjust your camera for, the image appears on your glasses
list 9 advantages of a CCTV
- Large Range of Magnification:
- Variable Magnification: Deterioration of vision (dont always have to keep going back to LV clinic to get a stronger aid, can change from 2x-10x without having to change the aid)
- Good Contrast, Different Contrast Options, Contrast Reversal
- Good working distance (it is not determined by the optics of the aid)
- Good Field of View (depends of the size of the screen)
- Binocularity possible
- Minimal peripheral Aberration, less critical focus and reduced light loss
- Various option such as underlining text, splitting screen, cutting out unwanted text, scrolling of text
- Longer reading duration than optical aids
list 5 disadvantages of a CCTV
- More practice
- Bulky in many instances
- Expensive and requires regular maintenance
- Needs to be prescribed, not bought over the shelf (need training to use it)
- Can cause poor posture if bad position is adopted
what 3 types of CCTVs are there
- Mouse Style Devices
Need an ordinary TV or a computer
Cheapest Option - Portable devices
Also cheap - Desktop varieties
Expensive
But more options than mouse style devices or portable devices
how do you use a mouse style CCTV and what is the disadvantage to it
- mouse has a camera on it and you attach your tv to your computer, you place the mouse over the thing that needs magnifying
- you only get a fixed magnification = no flexibility
name 3 examples of a head mounted device
- Jordy
- Flipperport
- Maxport
name 2 advantages and 4 disadvantages to head mounted devices
Advantages:
- Can improve VA ten fold
- Can improve CS by up to 1.8 Log units
Disadvantages:
- Fitting Difficulties
- Claustrophobia and Motion Sickness
- Head and hand control
- Retinal stabilisation (as head shakes and moves the mouse)
for which 2 types of people should CCTVs be considered for
- Anyone who is in education or employment
- Anyone who has a progressive VF loss
how are mobile phone these days customised for VI people
- Talking Mobile phones
- Accessibility Options in many phones - i phone
- Lots of apps
Colour app
Dragon Dictation
what does a knfbReader Mobile allow a VIP px to do
- Read mail, receipts, handouts etc
- Scans documents and then reads out loud
- Can recognise US currency
In future
- Recognise products
- Indoor navigation
- Eventually people!!
list 4 other electronic devices/software
- E-books: E.g. Kindle
- i-pads
- Magnification software for PCs (may or may not include screen readers)
Windows
Dolphin
Supernova
Zoomtext - Screen readers (whatever comes out on the screen can be read to the px e.g. book scanned onto computer)
list 5 other PC options that can help a VI person
- Fresnel Lenses to magnify screen
- Large Print Keyboards
- Large Monitor
- Keyboard stickers (can make size of letters and numbers larger)
- Anti glare screens
name 2 tactile reading codes that enables VI people to access information by touch
Braille
Moon
how many VI people know braille and what is easier to learn that braille and why
- only 5% of VI people know braille
- Moon is easier to learn than braille - the code is simpler
name 4 braille gadgets
- Braille Note
- Braille Displays
- Braille Embossers and writers
- Tactile graphic maker
All of these gadgets come at a cost
how is braille made up
made up of a series of 6 dots, different sizes which make up the alphabet
who is eccentric viewing helpful for and why
how is it used
what 2 types is there
what can it be used with
- AMD and Stargardt’s
- because both have central vision loss
- Paracentral areas of the retina are used to fixate objects
- Preferred retinal locus (PRL) = learned on their own after manual loss, but as they’ve done it on their own = not necessarily using the best eccentric viewing area, may just choose something thats convenient for them
- Trained retinal locus (TRL) = uses area that is functioning well and with good retinal resolution and train person to use that area
- Can be used with LVAs
how does steady eye strategy work
Eyes are held in a steady position and text is moved from right to left
Used with eccentric viewing
which 2 ways can you learn to do eccentric viewing
- Macular society
- Do it yourself
what does evidence say about eccentric viewing and steady eye strategy used together
- Good evidence that EV training with SES or eye movement training improves reading ability
- No evidence regarding the effect of training on measures of distance visual acuity
- Good evidence that EV and SES/eye movement training improves the ability of participants with CVL to perform ADLs
- No evidence that there is an improvement in Quality of Life
name 2 technologies that can be introduced in the future for VI patients
- Retinal prosthesis
- Brain port devices
what is the aim of a Retinal/Visual Prosthesis and which VI patients is it best for
Device to amplify vision:
- Elicit sensation of light
- Detect motion
Good for px with RP, who has no perception of light or who can barely see hand movements, the device will never give 6/6 vision
how is a Retinal/Visual Prosthesis used and what does it do
- Externally-worn camera attached to a stimulator (electrode studded array) on the retina, optic nerve or visual cortex
The camera sees around you, sends a signal o the retina which then gets transferred to the brain and to the visual cortex as light and dark spots - Produces electrical impulses which are perceived by the visual cortex as patterns of light and dark spots
Brain learns to interpret these images through a period of time
what type of subjects is retinal/visual prosthesis best used for
Mainly for subjects with:
- Perception of light
- No Light Perception
- Degeneration of the retina E.g. RP with normally developed Optic Nerve (have to have intact optic nerve for this to work)
what is a brain port vision device and how does it work, what are patients able to see with this device
- Electro-tactile stimulation for sensory augmentation or substitution
- Visual information collected from avideo camera and translated into electrical stimulation patterns on surface of tongue (and learn to interpret these patterns)
- With training users may perceive: Shape Size Location Object Motion
what is the evidence that brain port devices work
- Not been approved by FDA
- No clinical Trials
what are assisted vision glasses and how do they work
- developed by oxford uni, built on an android platform
- uses system with a camera which projects the image in front of the patient’s eye
- by using this technology, it can either enhance the image onto the glasses, so you can customise these glasses depending on their visual impairment and depending on the image the patient perceives better e.g. if px sees black on white better, then glasses can do that
