what are the guidelines of severely sight impaired according to the certificate of the visual impairment?
- visual acuity worst than 3/60
- visual acuity between 3/60 and 6/60 with a very contracted visual field unless long standing
- visual acuity better than 6/60 with a very constricted visual field especially if it involves the lower part of the field.
what are the terms referred to sight impaired and severely sight impaired before 2003?
sight impaired: partially sighted
severely sight impaired: blind
what are the guidleines of sight impaired according to certificate of visual impairment?
- visual acuity between 3/60 to 6/60 with full visual field
- visual acuity worst than 6/24 with a very contracted visual field, media opacities, or aphakia
- visual acuit with 6/18 or better with gross field defects and marked constriction of the visual field.
what are the types of visual impairment?
- poor light and dark adaptation
- central scotoma
- patchy field loss
- glare
- peripheral field loss
- reduced contrast sensitivity
- blur
- distortion
distribution in percentage of
cataract: 51%
unspecific: 21%
glaucoma: 8%
AMD : 5%
co : 4%
trachoma: 3%
RE: 3%
DR: 1%
severe impairment;
refractive error: 42%
cataract: 33%
undetermined: 18%
glaucoma: 2%
AMD CO Trachoma DR all of the above: 1% each
Number of people in the uk on 2011&2014 that classified under sight impaired or severely sight impaired?
2011:
sight impaired= 147,800
severely sight impaired= 151,000
2014:
sight impaired= 143,400
severely sight impaired=143,400
what are the main causes of blindness in UK for age group of 16-64?
*data obtained between 2009-2010
- hereditary retinal disorders 20.2%
- DR/maculopathy 14.4%
- optic atrophy 14.1%
what are the purpose of rehabilitation?
- will try to help people use their remaining vision effectively
- will try to promote independence
but,
will not help the eyes to see better.
what are the steps need to be taken when introducing magnifiers to patient?
- near VA with +4.00ADD
- estimate magnification required
- simple devices 1st
- realistic sized print
- correct working distance
- record VA and fluency for each LVA
what are the classification of low vision aids?
1) spectacle magnifiers:
- high reading adds
- hyperoculars
- clip on magnifier
2) hand magnifiers
- -fresnel sheet
3) stand magnifiers
- -flat field magnifiers
- -bar magnifiers
4) electronic LVAs
- CCTV
- head mounted CCTV
- computers and low vision
what are the advantages and the disadvantages of high reading add?
ADVANTAGES:
- binocular viewing is possible
- hands free
- cosmetically acceptable
- good field of view
- bifocals can go up to +16.00D
- ready readers/half eyes available
- can incorporate cyl
DISADVANTAGES:
- short working distances
- nead additional illumination
- often not tolerated by elderly people
what is hyperocular?
- very high plus aspheric lenses
- bi-convex, lenticular form
- no cyl incorporated
- monocular
- px choose to have occluder, frosted, clear lens on the fellow eye.
- x4 to x12
clip on magnifiers is one of the spectacle magnifiers beside the high reading adds and the hyperoculars, state whats the magnification of clip on magnifiers?
clip on magnifiers:
binocular up to x3
binocular up to x7
what are the advantages and disadvantages of hand magnifiers?
ADVANTAGES:
- illuminated hand magnifiers available
- wide range of powers
- socially acceptable
- simple to use
- inexpensive
- portable
- available up to x12.5
- useful out and about
DISADVANTAGES:
- need good dexterity
- magnification reduced if held closer to page than focal length of lens (within reason) although this does improve the field of view.
*commonly prescribe x3 to x7
what are the advantages and disadvantages of stand magnifiers?
ADVANTAGES:
- illuminated stand magnifiers available
- good range of powers
- fixed accurate working distance
- can use free hands in lower powers
- binocular viewing in lower powers
- up to x22
DISADVANTAGES:
- short working distance can reduce illumination
- USUALLY NEED READING PRESCRIPTION
- can be bulky/heavier
*commonly prescribe x3 to x7
what are the other type of stand magnifiers?
bright field/flat field magnifier:
- up to x2.2
- gathers light
bar magnifiers
- up to x2 in one direction
- gathers light
how do we describe magnifiers in clinic notes?
make
magnification
illumination
hand/stand magnifiers
coil x3 non-illum hand mag
what are the types of electronic LVAs?
CCTV:
- Tv screen mounted over X-Y table (up to x70 mag)
- television readers (up to x24 mag)
- head mounted
- portable
what are the advantages of CCTV compared with magnifiers?
Advantages:
- higher magnification possible up to x70
- better field of view
- binocular viewing
- longer working distance
- psychologically acceptable
CCTV disavantages:
- bulky
- difficult to use
- expensive
- not available on NHS
how to use LVAs? at initial LV assessment.
1) demonstrate eg. stand mag flat on page
2) anticipate difficulties
3) with or without specs? which eye?
4) confirm what LVA is for
5) lighthing,mclipboard,firm table, typoscope
6) encourage practice at home, few mons at a time
7) check patient understanding
8) give written instructions
compare between Galilean telescope and Keplerian telescope?
galilean telescope:
- smaller,lighter, and cheaper
- upright image
- poorer image quality
- magnification up to x4
keplirian telescope:
- bigger,heavier, and more expensive
- upright image but need roof prism
- a better quality of image
- magnification up to x12
what is exit pupil and why is it important?
exit pupil is image of the objective lens formed by the eyepiece.
exit pupil is important because when eye placed at exit pupil; eye receives all light entering the telescope, maximum lagiht, and maximum FOV (field of view).
*keplerian exit pupil outside telescope, and eye at close to exit pupil
what are the methods to differentiate between Galilean and Keplerian telescope?
1) looking trough exit pupil
- hold telescope 20cm from the eye, eyepiece towards you
- exit pupil is small bright of light
- move head side to side
- –with movement: galilean telescope
- –against movement: keplerian telescope (exit pupil much easier to see)
2)educated guess based on size / weight/ magnification
