Visual Impairment 1

sight loss that cannot be corrected using glasses/CL

• congenital/acquired

• reduced binocular VA

Low vision: VA less than 6/18 + better than 3/60 in better eye

Blindness: VA less than 3/60

• total blindness = no light perception

All definitions use BCVA + NVA & CS never considered

• 2.2billion people have VI ( 1 billion preventable)

• over 70% w/ sight loss = 65>

• 60% = women

Causes:

1. optom refers px to consultant opthalmologists ( only they may register px in England and Scotland)

   • in Wales, optom can register px if Certificate in Low Vision

2. Opthalmologist carry out tests:

   • px BCVA + VF + dilated fundus

3. May issue Certificate of Vision Impairment ( px can be severely sight impaired SSI or sight impaired SI)

SSI:

SI:

1. Blind Person's Allowance

1. 50% reduction on TV License Fee

2. automatic entitlement to Blue Badge parking

Access to Work scheme( gov initiative) = practical + financial support

Px has to inform DVLA

• RNIB

• Macular Society

• Glaucoma UK

• the Partially Sighted Society

• BlindAid

• Herts Vision Loss

1. closer WD for VA charts - adjust logMAR score

2. increase lighting with VA/subjective = increased contrast

3. Possible lens opacities - closer ret WD ( change compensation)

4. Use trial frame + halberg clips - allows for eccentric viewing + natural view

5. Px sees little change in subjective - use larger steps eg 1-2D

6. increase reliance on objective tasks

7. slower exam pace

8. use pinhole - VA will not improve much ( if does, due to uncorrected Rx)

9. use Berkeley Rudimentary Vision Test if px cant recognise letters or numbers

   • cards held at fixed distance with decreasing CS+ size

   • px asked to determine any stimulus

1. What caused your vision to deteriorate? When did you start noticing?

2. Vision stable/getting worse ( LVAs for mono only)

3. Any ongoing hospital appointments? Discharged?

4. Any tilting of head to see better? ( eccentric viewing)

5. Vision better indoors/outdoors?

6. Any glare?

7. Does px live alone? Spouse health? What home? Stairs?

8. What is px priority? Reading/signs

9. Quality of Life questionnaires

1. if VA<6/60, only significant Rx changes make a difference eg>2.00DC

2. if Rx makes small difference to VA, consider LVA to magnify image

**SHOW PX VA IN REAL WORLD

• use a word chart ( MNRead)

• record what type of illumination was preferred

• prescribe base in prism for each dioptre over +4.00D ( reduce diplopia & increases convergence)

at 25cm with +4.00D

1. 1. The faculty of Opthalmologists' near chart

   Ads:

   • 1 point = 1/72 inch

   • scale easy to use

   Disads:

   • inconsitent size ration with each line

   • ceiling affect with normal vision( N5=6/15@25cm)

   • poor replication of normal reading material

2. The Bailey-Lovie reading card

   Ads:

   • log scale ( N80 to N2)

   • random words ( reduce context effect)

   Disads:

   • limited words at larger sizes

   • poor replication of normal reading material

3. MNRead acuity chart

   Ads:

   • continuous text

   • log scale

   • comes in reverse contrast

2. Pelli-Robson

3. Mars- handheld version of pelli

4. Bailey Lovie

5. Vistech - px identifies orientation of gratings

1. estermann field- done binoculary

2. kinetic perimetry eg Goldmann

3. confrontation

high mag= lower FOV + closer WD

mag = F/4 where F is dioptric power given to px

normally 2:1

eg. If px's NVA = N6, rserve is N12 ( comfortable reading)