Retinoscopy Technique

Question 1

What are the steps of the technique?

Answer 1

1) Determine Principal meridia
2) Interpret the reflex
3) Add correcting lenses
4) Record results

Question 2

Determining the principal meridia

Answer 2

• begin with beam at 90, then rotate to 180, 45 and to 135

Question 3

Interpret the Reflex

Answer 3

• as each principal meridian has a diff power, the reflex seen in each meridian will be of a diff speed and shape
• if the astigmatism is high the reflex will tend to be a more distinct shape, better defined than a low astigmatism

Question 4

Add correcting lenses

Answer 4

• begin with sphere
• correct the meridian with the slowest with or fastest against movement (highest positive power; lowest negative)
• keep sphere in and move onto the other meridian
• use a minus cylinder to correct the against movement
• the cyl lens has a marked axis and perpendicular to this is the power
• means we need to place the axis perpendicular to the meridian in which we found the against movement

Question 5

‘With’ movement seen in both meridians?

Answer 5

Neutralise the slowest with movement first with sph lenses

Question 6

‘With’ movement seen in one meridian and ‘against’ in the other?

Answer 6

-Neutralise the with movement first with sph lenses

Question 7

‘Against’ movement seen in both meridians?

Answer 7

Neutralise the fastest against movement first with sph lenses

Question 8

No movement seen in one direction and ‘with’ in the other?

Answer 8

-neutralise ‘with’ movement first with sph lenses

Question 9

No movement seen in one direction and ‘against’ in the other?

Answer 9

No sph lenses needed, add -ve cyl in against meridian

Question 10

Common errors during ret?

Answer 10

• high powers (dull/no movement) confused for reversal
• neutralised incorrect meridian first resulting in +ve cyl
• low cyl powers confused for reversal therefore not corrected
• cyl axis off - recheck constantly esp in high powers/ changes