Refractor heads/phoropters

Question 1

what is a phoropter

Answer 1

a contained unit allowing rapid lens presentation before each and both eyes by mechanical or electronic measurements

Question 2

list all the mechanical features of a phoropter

Answer 2

• sphere/cyl lens tracks
• cross cyl twirl
• occluder
• pinhole
• polaroid filters
• maddox rod
• rotary prisms
• vertex distance gauge
• near target
• convergence for near

Question 3

what do electronic features of a phoropter include

Answer 3

all those of mechanical plus:
- input from auto refractor: electronically transferred to phoropter lens put infront of px eye

• input from foci meter
• immediate correction comparison: can compare your findings with old rx
• automatic PD adjustment
• link with projection chart: but better we do subjective refraction ourselves
• data storage
• data print out

Question 4

how would you refract using a mechanical refractor head

Answer 4

• set PD
• set vertex distance
• refract as normal (change lenses etc)

Question 5

how would you refract using a electronic refractor head

Answer 5

• set patient up on instrument
• programmed refraction or manual
• comparison check (to old rx)
• print out for records

Question 6

what two ways may you control a electronic refractor head

Answer 6

• hand set controller
  or
• controller pad

Question 7

list 6 advantages of refractor heads/phoropters

Answer 7

• speed: helps stabilise accommodation and keep attention
• quick and easy to compare VA with two different lens powers
• accuracy of cyl axis (which can move in trial frame)
• rotary prisms for fusional reserves
• patient comfort (nose, ears)
• lens cleanliness

Question 8

list 3 additional advantages or electronic refractors

Answer 8

• comparison check: compare px current rx with what you find
• date transfer and storage
• practitioner comfort: remote and less physically demanding

Question 9

list 4 disadvantages of refractor heads/phoropters

Answer 9

• the glass protecting the lens sometimes steams up unless a large vertex distance is used
• not always ideal for:
  
  • very young (esp behavioural probs) or old patients
  • presbyopic contact lenses (performance is pupil dependent)
  • patients with visual imparement (ambient light can significantly affect patient performance)
• barrier to communication
  
  • particularly with anxious patients
• can’t create an artificial visual environment for near vision testing
  
  • so good for distance but bad for near

Question 10

list 4 disadvantages of refractor heads/phoropters

Answer 10

• the glass protecting the lens sometimes steams up unless a large vertex distance is used
• not always ideal for:
  
  • very young (esp behavioural probs) or old patients
  • presbyopic contact lenses (performance is pupil dependent)
  • patients with visual impairment (ambient light can significantly affect patient performance)
• barrier to communication
  
  • particularly with anxious patients
• can’t create an artificial visual environment for near vision testing
  
  • so good for distance but bad for near

Question 11

list 4 disadvantages of refractor heads/phoropters

Answer 11

1. the glass protecting the lens sometimes steams up unless a large vertex distance is used
2. not always ideal for:
   
   • very young (esp behavioural probs) or old patients
   • presbyopic contact lenses (performance is pupil dependent)
   • patients with visual impairment (ambient light can significantly affect patient performance)
3. barrier to communication
   
   • particularly with anxious patients
4. can’t create an artificial visual environment for near vision testing
   
   • so good for distance but bad for near