TUTORIAL 1

Question 1

What sort of patient might retinoscopy be useful for?

Answer 1

-Children
-babies
patients with problems with mobility/unable to sit still for long periods
-patients -subjective response
-patients with suspect cataract, keratoconus, tear film issue
-When we want to know about a patients accommodation
-Malingerers/suspect malingeres

Question 2

What do you think would happen if you did not remove the working distance allowance at the end of retinoscopy?

Answer 2

• Final estimate too positive by +1.50DS*** (assuming WD is 2/3m)
• Patient’s vision will be blurred by this amount
• Remember this is done because you’re working close to patient instead of at infinity (which would be impossible!) – make sure to keep your WD constant

Question 3

Using the table below, think about what happens to the light from
your retinoscope when your viewing distance or the lens changes? (IN CS BOOK AS EX 2)

Answer 3

• When working distance is 0.66m (2/3) and lens in front of eye is +1.50DS the reflex movement is Neutral- (causes light to converge and focus on back on retina) (3/2= +1.50DS- so we know it will focus on retina hence neutral as know eye is calibrated/emetropic)
• If your WD is 0.66m, and lens in front of eye is +2.00DS the reflex movement is against movement (light focuses in front of retina) - makes eye more myopic than it actually is
• If your WD is 0.3m (1/3) and lens is +2.00DS- as 0.3m is 1/3 which the reciprocal is 3/1= +3.00DS. So we know a +3.00D lens infront of the eye allows light to focus on the retina. A +2.00D lens in front of eye won’t converge light enough to focus on retina instead focuses behind retina. Appears as though eye is hyperopic

Question 4

What happens if a with movement is seen in one meridian and against in the other ?

Answer 4

• You should neutralise the with movement with a positive Sphere lens
• then neutralise against with a minus cyl lens

Question 5

What happens if a with movement is seen in both meridians?

Answer 5

You should neutralise the slowest movement first with a sphere lens and against with a minus cyl lens

Question 6

What happens if no movement is seen in one direction and with in the other?

Answer 6

• Neutralise with movement first with a sph lens and then neutralise against with a minus cyl lens.
• Always neutralise slowest with movement first and that leaves you with an against movement which you then have to neutralise after.

Question 7

What happens if “against” movement seen in both meridians?

Answer 7

Neutralise the fastest “against” movement first with sph lens

Question 8

What happens if No movement seen in one direction and “against” in the other?

Answer 8

No sphere lens needed, add –ve cylinder in against meridian

Question 9

Why do we correct with movement first?

Answer 9

want to correct the most positive meridian first

or if 2 against moments correct the least. negative one.

Question 10

How to neutralise astigmatic lenses?

Answer 10

-Need to neutralise a with movement first
-then move ret beam to perpendicular axis and neutralise the against
-Add the negative cyl lens on top of spherical lens on dummy lens
-Check for reversal: putting a +/- 0.25 lens to check if changes the movement from with to against and vice versa
-And change the WD. a little bit to see reversal
-Correct WD allowance- remove +1.50 as at 2/3m= 1.50D
so take away 1.50.

Question 11

What would be the final Rx if we were working at 1/2 metre from the patient? for e.g

Answer 11

• do reciprocal= 2/1= +2.00D

- TAKE AWAY -2.00D from the Sphere lens

Question 12

What are the common powers?

Answer 12

High powers (dull/no movement) confused with reversal
• Neutralised incorrect meridian first resulting in +ve cyl
• Low cyl powers confused for reversal therefore not corrected
• Cylinder axis off – recheck constantly especially in high powers/changes