amblyopia Flashcards
define amblyopia
reduced acuity in one or both eyes with no pathological cause for the reduced VA
How is amblyopia caused?
Caused by abnormal visual development during the critical period or visual development
How many people affected?
affects 1% - 4% of the population
What type of amblyopias are there
Refractive
Stimulus deprivation
Strabismic
What is refractive type of amblyopia
Results from uncorrected refractive error in one or both eye usually anisometropia
e.g R eye only 4 accommodation and L eye no accommodation so the eye becomes lazy for length period of time results into amblyopic eye
what is the Importance of good refractive technique?
sloppy refractive techniques you can get away with non amblyopic px but amblyopic patient can give you grieve if the refraction technique is not right.
what aspects of refraction technique is important for amblyopes?
- Choice of dioptric interval
- Crossed cyl target
- Crossed cyl power
- Fan and block
- Pinhole disc
- BB ( Binocular Balancing )
- Retinoscopy in strabismic amblyopia
what if you give small choice of dioptric interval?
small D intervals such as 0.25D steps will lead to wrong results and waste time. px will see things same not better.
What powers DS should amblyopes be givemn
Amblyope patient to be given high powered sphere to begin with depending on patients acuity and then refine results with small powers
what is the large then small powered dioptric interval technique called?
Bracketing technique
What cross cyl targets used for amblyopes
if px vision in better that 6/12 use concentric rings for x cyls
what VA do the concentric rings represent?
Inner ring approx equivalent to 6/6 snellen chart
outer ring approx equivalent to 6/15 snellen chart
what can xcyl do with vision?
crossed cylinders can reduce the vision in one or both positions
if patienty has VA worse than 6/12 ?
Do not use concentric rings for cross cylinders
what cross cylinder powers should you use in amblyopic eye?
use bracket approach
begin with high powered cyl +/- 0.50 and use +/-n 0.25DC only if changes produced are appreciated by the px
when do you use more that +/- 0.50DC cylinders?
Use +/- 0.75 or +/- 1.00DC if the vision is severely impaired. refine with small powers if px appreciates it.
What Vision is Fan and block equivalent to?
Fan and block is quivalent to 6/15 snellen chart
when should you not use fan and block?
do not use fan and block if px vision is worse that 6/12
when can you use fan and block?
use fan and block is vision is better that 6/12
How does pinhole work in Amblyopes?
Distinguish between poor acuity/vision due to bad refraction or poor acuity/vision due to amblyopia ( or eye disease)
what if acuity improves with pinhole?
errors in refraction
what if acuity does not improve with pinhole?
unlikely to improve acuity with refraction and has underlying pathology
what does pinhole do?
pinhole cuts out parallel rays smaller apeture and makes image clearer and acuity is improved.
Which patient can you Balance?
Any patient with good binocular sincle vision and good acuity in each eye
