low vision aids for peripheral loss Flashcards
what are the effects of visual field loss?
orientation and mobility
static and dynamic VF
central VF loss
Peripheral VF loss
how can you help someone with reduced peripheral vision\?
- eye movement training
- orientation and mobility training
- field expansion ( minus lenses, reverse telescope, fresnel prisms)
- OXSIGHT glasses
how can you help someone with hemianopia?
- eye movement training
- orientation and mobility training
- peli lenses
- oxford glasses
how does eye movement training work?
large eye movements into the non-seeing area - usually occurs without training but training may help
who provides orientation and mobility training?
social services
charities through rehab officers
how does orientation and mobility training work?
methods for gathering info from surroundings, making home safe
techniques for climbing stairs, avoiding falls/injuries, crossing roads etc
often involves using long cane or sunu band
what are the 2 types of reversed telescope?
- galilean telescope the wrong way around
- minifiers
what is the disadvantage of reversed telescopes?
increase in field = reduced VA
what are 2 examples of minifiers?
ocutech
multilens (MLRP)
how is a minus lens used as a field expander?
held 20-30 cm from eye
what is a disadvantage of using minus lenses as a field expansion?
need accommodation or a reading addition
what are some other examples of minus lenses and their strengths?
multilens RP monocle (-7D, -8D and -9D)
schweizer minora (no longer available)
uncut minus lens blanks
amorphic lenses
what are fresnel prisms?
made up of tiny prisms - base to apex - on a thin platform of plastic
advantage of fresnel prisms?
thinner and lighter than conventional prisms
disadvantage of fresnel prisms?
optical quality is not as good as conventional prisms
how do fresnel prisms work for field expansion?
attached to a part of the glasses lens on the SAME side as the field defect with base towars the non-seeing area
what would you give someone with a hemianopia?
fresnel prism/peli prism
what are oxford glasses?
assistive technology - form of electrical aid
camera streaming a live feed into 2 HD video displays, placed in front of the patients area of useable vision
what are the 2 types of oxford glasses?
prism and crystal
oxford glasses increase FoV by how many degrees?
68 horizontally
how much is a reversed telescope ?
~£200
how much is a negative lens?
~£70
how much are oxford glasses?
~£3000 - £4000
what are the 3 types of aids for hemianopias?
substitution
restitution
compensatory techniques
how do substitution aids work and what are they?
PRISMS - optically expand the VF
how do restitution aids work?
improve visual sensitivity in the blind VF by repeated stimulation
how do compensatory techniques work?
patients learn to direct their gaze towards the affected area
what are 3 examples of computer based training for eye movement training?
eye search
VISIOcoach
Durham Reading & exploration (DREX) training
what are 4 forms of field expanders?
mirrors
bilateral sector prisms
peripheral prisms (PELI PRISMS)
sector/gottleib visual field awareness system
how do bilateral sector prisms work?
base right or left BE
field relocation rather than expansion
which glasses are Peli prisms attached to?
attached to DISTANT glasses
how do peli prisms work?
40/57 BO prism on left eye for left hemianopia
and RE for right hemianopia
what is the sepeeration distance on peli prisms?
12 mm
how much do peli prisms expand the VF by?
20-30 degrees
can be 30 degrees if you use 50 D
which patients are more likely to be successful when using peli prisms?
young patients
what height do you need on glasses for a peli prism?
35mm
what activities can you NOT do when wearing a peli prism?
reading and driving
when should you review a patient after prescribing peli prisms?
4-6 weeks
how much do peli prisms cost?
~£500-600
what are the options for those who struggle when reading?
typoscope
vertical text
read-right
DREX
