Visual Impairment

Question 1

What is visual impairment?

Answer 1

• being unable to see or unable to see very clearly
• how much one sees depends on a number of factors, not just the level of sight
• the external environment may play a role

Question 2

What is visual acuity?

How is it measured?

Answer 2

The ability of the eye to see in detail
Distance acuity
- each eye is tested separately using a Snellen chart
- tested at distance of 6m - normal is 6/6 or 20/20 in USA as feet used
- if cannot see the top letter at 6 metres then test nearer the chart
- snellen comprises rows of letters of decreasing size
- normal distance acuity = 6/6
- the row of letters with the number 6 underneath can be read at a distance of 6m

Question 3

What the levels of decreasing visual acuity?

Answer 3

counting fingers CF
hand movements HM
perception of light PL
no perception of light NPL

Question 4

If visual acuity is not at least 6/9 then use ………. test
Why?

Answer 4

pinhole test

to reduce peripheral vision and solely assess vision with one ray of light

Question 5

What is the WHO definition of blind

Answer 5

between 3/60 and 1/60

more than this is severe visual impairment

Question 6

is there a register for blind and partial sight in the UK?

Answer 6

registration takes place on the recommendation of an ophthalmologist

Question 7

What are the risk factors for sight loss?

Answer 7

2/3 women
black and minority ethnic communities are at greater risk of some of the leading causes of sight loss
3/4 of people with learning disabilities are estimated to have either refractive error or to be blind or partially sighted

Question 8

What are the main causes of blindness in adults in the UK?

Answer 8

• age-related macular degeneration
• glaucoma
• cataract
• diabetic retinopathy

Question 9

What is the difference between dry and wet age-related macular degeneration?

Answer 9

Dry - non treatment

Wet - abnormal blood vessels that pierce retina and bleed

Question 10

What is refractive error?

Answer 10

eye cannot clearly focus the images from the outside world, resulting in blurred vision, that is sometimes so severe that is causes visual impairment

Question 11

What are the three most refractive errors?

Answer 11

• myopia - difficulty in seeing distant objects clearly
• hypermetropia
• astigmatism - distorted vision resulting from irregularly curved cornea

Question 12

What are the causes of worldwide blindness?

Answer 12

cataracts
uncorrected refractive errors
glaucoma
age related macular degeneration 
corneal opacities
diabetic retinopathy
childhood blindness
trachoma
onchocerciasis

Question 13

What is trachoma?

Answer 13

eye disease caused by infection with the bacterium Chlamydia Trachomatis

• leading cause of infectious blindness globally
• endemic in 55 countries including Africa and Asia

Question 14

What does a guide dog do?

Answer 14

• walks in a straight line in the centre of the pavement unless there is an obstacle
• not to turn corners unless told to do so
• stops at kerbs and waits for the command to cross the road, or to turn left or right
• to judge heigh and width so that its owner does not bump their head or shoulder
• how to deal with traffic

Question 15

What help is available to blind people?

Answer 15

• government benefits, but less if registered sight imparied
• eye clinic liaison officer
• social worker, mobility officer, technical officer, rehabilitation worker
• voluntary organisations e.g. RNIB, guide got for the blind
• low vision aids e.g. magnifier