Low vision aids for peripheral vision Flashcards
list the 4 different effects of visual field loss
- Orientation and mobility (getting around) is difficult when:
VF less than 20 degrees
Hemianopia - Static and Dynamic VF
- Central VF loss - Aids to expand VF
- Peripheral VF loss - Aids to expand VF
which 2 types of visual field loss is orientation and mobility more difficult with and give a 2 examples of eye conditions that can cause problems
Types of visual field loss:
- VF less than 20 degrees
- Hemianopia
Eye conditions that can cause orientation and mobility problems:
- Glaucoma
- Retinitis pigmentosa
= more difficult for these patients to deal with
give 2 examples of eye conditions that do not have orientation and mobility problems and why
- AMD
- Diabetic macula oedema
They cause a central VF loss, so they still have peripheral VF which is still helpful in mobility
They can use a hand or stand magnifier which works well
which type of visual field happens more in real life and which one doesn’t and explain how
- Dynamic VF:
more realistic as we move our heads and eyes, which builds a picture around us
if on the henson/humphrey it shows the patient’s vf to be 5 deg but in real life it will be more as we move our heads and eyes
Static VF:
does not happen in real life as we don’t keep our head and eyes stationary which is tested in visual fields machines
which 3 things can be done to help with reduced peripheral vision
- Eye movement training
- Orientation and Mobility training
- Field Expansion
list 3 aids that can be used for field expansion to help with reduced peripheral vision
- Minus Lenses
- Reversed Telescopes
- Fresnel Prims
which 3 things can be done to help with a hemianopia
- Eye movement training
- Orientation and Mobility training
- Field Expansion
list 2 aids that can be used for field expansion to help with a hemianopia
- Mirrors - convex or plane
- Prisms
for reduced peripheral vision, which type of eye movement training is taught
give an example of which eye condition this is useful for and how they tend to do it
- Large eye movements into the non-seeing area
Usually develops spontaneously although training may help
- RP
it will be to both the right, left and inferiorly, as its a constricted vf
which type of patients may not need eye movement training for reduced peripheral vision and which type do
- patients who developed their eye condition at a younger age, as this will come to them naturally
- elderly px may need more training as they are not used to it
who is orientation and mobility training for reduced peripheral vision usually provided by
what are the 2 main aims for the methods of orientation and mobility training
give 4 examples for what techniques are taught for orientation and mobility
- provided by social services/charities through rehab officers and also RNIB
- Methods for gathering information from surroundings
- Methods for making home safe
- climbing stairs
- avoiding falls and injuries
- crossing streets
- how to use a white cane
which 2 types of reversed telescopes can be used for reduced peripheral vision
- Use a Galilean telescope the wrong way around
- Minifiers
explain how a galilean telescope is used the wrong way around (as a reversed telescope) and what results you get from this for a patient with reduced peripheral vf
what is the disadvantage to this
name a type of galilean telescope that can be bought for this
- +ve lens is towards the eye and the -ve lens is away from the eye, this increases and minifies the FOV
- but the optics is not so good as it is not specifically made for this purpose
- 4X12 Microlux
what is a better version of a reversed telescope than using the galilean telescope the wrong way around, for reduced peripheral vision
why is this reversed telescope better
name 2 types than can be bought
- Minifiers
- they are reversed telescopes that are manufactured for this purpose so the optics is clear and sharp and you get a good expansion in the FOV
- Ocutech
- Multilens (MLRP)
give 5 examples of minus lenses that can be used for field expansion to help with reduced peripheral vision
- Hand held minus lens
- Multilens RP Monocle
- Schweizer Minora
- Uncut minus lens blanks
- Amorphic Lenses
how should a hand help minus lens be used for field expansion to help with reduced peripheral vision
give an example of this type of lens and the available powers that it comes in
what result does it give
- it should be held 20-30cm from the eye and with any accommodation/addition required
- Multilens RP Monocle
- 7D (also available in 8D & 9D)
- everything is minified and the FOV is expanded
which type of minus lens is no longer available and which power was it available in, for field expansion to help with reduced peripheral vision
- Schweizer Minorka
- -6D
what result does Amorphic Lenses give for field expansion to help with reduced peripheral vision
things appear longer and squeezed together instead of minifying the object 360 deg
explain fully how prisms work for field expansion to help with reduced peripheral vision
- it will displace the image towards the apex
- so you must face the base towards the vf loss direction to shift the image of the object towards the seeing area from the non seeing area (i.e. the apex)
- a higher powered prism will shift more
- if is a smaller powered prism = shifts image into the side and can make small eye movements to see all of the image, so dont always have to look towards the image or make large eye movements
what is a fresnel prism
what is an advantage
what is a disadvantage
- Fresnel prisms: made up of tiny prisms: base to apex on a thin platform of plastic
- Thinner and lighter than conventional prisms
- Optical quality is not as good as conventional prisms (that are ground onto the lens)
explain how fresnel prisms are used as field expansion to help with reduced peripheral vision
what type of vf defects it is only useful for
what type of vf defect it is rarely used for
- Attached over part of the spectacle lens on the side of the field defect of the eye with the field defect with base towards the non-seeing area
- Only useful for overall field constriction and hemianopia
- Rarely used for overall field constriction
explain why fresnel prisms are not useful for overall field constriction and which eye condition this relates to
- as vf loss is 360 deg, so you need to attach a BU, BD, 2x BO = base towards the vf loss, this is too complicated in reality
- e.g. RP
give 2 reasons of choosing a reversed telescope over a minus lens as field expansion to help with reduced peripheral vision and one reason you will use a minus lens over a reversed telescope
- Reversed telescope
No accommodation needed
Hands free if required (can grind small hole in glasses superiorly and attach telescope, tilt head and look to expand vf)
whereas
- Negative Lens
Accommodation needed (no good for presbyope, unless attach a +ve lens to glasses, but is complicated)
Hand held - Reversed telescope
Expensive approx £200 - not available on NHS
whereas
- Negative Lens
Approx £70 (cheaper)
what does the aid needed depend on
and what should be done if nothing works
how much vf loss there is e.g. if 10 deg loss, a reversed telescope will be good for
if nothing works, then refer to social services
list 3 problems associated with a hemianopia
- Problems with orientation and mobility
- Increased incidence of falls
- Problems reading e.g. if R/L hemianopia, can’t find beginning or end of sentence as reading into the hemianopia
list 3 methods you can use to help people with a hemianopia
- Substitution: Use prisms or mirrors to optically expand the VF
- Restitution: Improve visual sensitivity in the blind VF by repeated stimulation to try to make the neurons active again e.g. flickering lights to make objects aware of in the non-seeing visual field
- Compensatory techniques: patients learn to direct their gaze towards the affected/non-seeing area
what can be used to help with eye movements in people with a hemianopia and name 3 examples
Computer based training
- Eye search (only free one)
- VISIOcoach
- NovaVision
how does the Eye search computer based training work for eye movement training in people with a hemianopa
it has different levels of video games to improve eye movements
how does the VISIOcoach computer based training work for eye movement training in people with a hemianopa
is a computer game which times how fast you can find something
as the px does these tasks, they get better and better at it
how does the NovaVision computer based training work for eye movement training in people with a hemianopa
shows flashing lights so stimulate the neurons in the lost vf area to find things = restitution method
name 2 aids that can be used as field expanders in people with a hemianopia
- mirrors
- prisms
describe how mirrors are placed to work as field expanders in people with a hemianopia
On the side of the lens away from the field defect
place the mirror on the side of the lens furthest away from field defect with reflecting surface towards the defect = the mirror reflects the object from the non-seeing area into the seeing area
so px sees what they can normally see, then something superimposed on that
can use a coloured side so the patient knows which side is the reflected side
what is the prism that is supposed to work as field expanders in people with a hemianopia called and what do they actually do to the field instead of expansion
name a disadvantage to this method
- Bilateral Sector prisms
Base right or left (BE) - Field relocation rather than expansion - shifts image from non seeing side to seeing side
- because it relocates the visual field instead of expand it, patients get a symptoms on a jack in he box effect, where the object suddenly appears in the vf from the non seeing to seeing field
name 2 types of prisms for field expansion that can be bought for people with a hemianopia
- Sector/Gottleib Visual field awareness system
- Peripheral prisms
Peli prisms
how do Sector/Gottleib Visual field awareness system, prisms work for field expansion in people with a hemianopia
instead of placing prisms on both lenses/each lens, you can just place a little round prism on one lens and that should expand the visual field
how are Peripheral prisms e.g. Peli prisms used/placed for field expansion in people with a hemianopia
who was it developed by
how much deg of expansion does it give
what powers is it available in for a left hemianopia and a right hemianopia
- fresnel prisms that you can cut into a round shape and attach on the eye which has the vf loss e.g. right homonymous hemianopia = attach prism to right eye and base of prism to always face the vf defect and attach to distance glasses
12 mm separation between prisms: Can be adjusted
Top prism: 6mm above pupil
Lower prism: 6mm below prism - Developed by Eli Peli
- 20/30◦ expansion
- 40∆ BO/57∆ BO (or oblique) LE- Left Hemianopia
- 40∆ /57 ∆ Base Out (or oblique) RE- Right Hemianopia
what is the aim of Peripheral prisms e.g. peli prisms in providing field expansion for someone with a hemianopia
- make you aware that something is in your peripheral vf
- a shadow makes the px aware = ghosting is in vf so will then head to see obstacles as your aware of it
- the reason you see half things is because the prisms are placed in the periphery i.e. above and below the pupil, so if you look through the actual prism, you will get diplopia
which type of patients are the Peripheral prisms e.g. deli prisms more successful in
what type of frame is needed
what must be explained to the px
after how long should you review your px
- younger patients
- large frame needed - 35mm height
- explain advantages and disadvantages
Mobility: Yes
Reading & Driving: No - review 4-6 weeks
what 2 things can be used to help with reading for people who have a hemianopia
- Typoscope
- Vertical Text - by training
instead of holding book horizontally, rotate it and hold it vertically so that the text does not fall into their visual field loss e.g. same as Japanese text
vertical reading speed will end up matching horizontal or even become faster
