Epidemiology and demographic of visual impairment: Flashcards
What is visual impairment
*Reduced binocular visual acuity, which cannot be improved even with best optical correction provided by conventional lenses
*Conventional lenses include the required distance correction and near vision additions up to +4DS
What are conventional lenses
The required distance correction and near vision additions up to +4DS
Example of someone who doesn’t have reduced VI
*If 6/6 in RE and 3/60 in LE with a binocular visual acuity of 6/6
*Then this individual would not be classified as having a visual impairment?
*Cause their binocular visual acuity is 6/6, which would not be classified as a visual impairment.
Why is it important to define a visual impairment:
*It’s important to define a visual impairment because there are certain benefits associated with being visually impaired
*Best corrected VA i.e with glasses
*For example:
oFinancial help
oSocial help
*Because someone with a visual impairment might have difficulties with their activities of daily living e.g. reading, and might have a decline in quality of life.
*It’s also important in terms of epidemiological studies to understand what visual impairment is.
oSo when doing a large-scale study and want to know how many people don’t see particularly well in your area or in your country.
What are the benefits associated with VI
*Financial help
*Social help
What are difficulties of someone with VI
*Activities of daily living e.g. reading
*A decline in quality of life.
How many definitions are there of VI
65
What are the different terms used for vi
- Blind
- Partial sight
- Low vision
- Subnormal vision
- Visual impairment
WHO vi
Presenting VA in better eye cause hard to get glasses so cause don’t have glasses, they might be visual impaired cause of that
Mild VI
- 6 / 12 – 6/18
Moderate VI
- 6/18 – 6/60
Severe VI
- 6/60 – 3/60
Blindness
> 3/60 E.G. if someone had VA of 2/60 and presenting VA in better eye was 2/60 then theyd be blind
Near VI
Near vision worse than N6 or N8 at 40cm and best corrected VA better than 6/12
What are the 2 categories of vi registration
*Severely sight impaired / blind
*Sight impaired / partially sighted
Severely sight impaired / blind
- Blinds person act 1920 and National Assistance Act 1948
- Blind as unable to perform any work for which eyesight is essential
- There is no reference to near vision, occupation or any particular occupation or disability
Severely sight impaired / blind guidelines
- 1.Acuity in better eye was below 3/60
- Above 3/60 but below 6/60 with significantly contracted field ( cause can cause difficulties with activities of daily living )
- Acuity better then 6/60 but with substantially contracted fields especially inferior
- Note blind category was changed to severely sight impaired 2003
Sight impaired / partially sighted guidelines
- There is no legal definition.
- Substantially and permanently handicapped by defective vision caused by congenital defect, illness or injury.
- NOTE: Partial sight category was changed to sight impaired in 2003
- 3/60 to 6/60 with a full field
- Up to 6/24 with moderate restriction of the field, opacities or aphakia
*If have corneal opacities, hard to correct with glasses so might need cl’s but these opacities can cause abrasions and VA not good
- Up to 6/24 with moderate restriction of the field, opacities or aphakia
- 6/18 or better with a gross field defect i.e stroke or hemianopia or glaucoma or retinitis pigmentosa
What is aphakia
- Cataract done and intraocular lens implanted in eye
- If emmetrope before cataract surgery, you end up with high plus glasses so become hyperopic = magnified = not good depth perception and poor va and hard judging distances
Guidelines for children
- Children can be born with a visual impairment, or can develop it later on in their childhood.
- Children, unless they’re obviously blind, should always be classified as being sight impaired.
- At the age of 4 and over, its better to use binocular visual acuity when making a decision as to which category the child should be placed under.
- Children with visual acuity of 6/24 or better, as long as all that’s wrong with them is that they’ve got a visual impairment should be considered candidates for mainstream schooling.