Convergence, accomodation and pupils

Question 1

Tests

Answer 1

-Accommodative Facility with Flipper Lenses
-Accommodative Lag/Lead with Nott Dynamic Retinoscopy
-Pupil Assessment – Near reflex
-Pupil Assessment – Light reflex
-Swinging light test to test for an RAPD

Question 2

Accommodative Facility with Flipper Lenses

Answer 2

Perform with glasses on
Ask patient to hold Snellen stick at 1/3m and fixate on this (can also test in the distance)
Select appropriate strength flipper lenses e.g. +/-2DS
It is ideal to let the patient have a quick practice before you begin the test.
Place one set of lenses over the patients (e.g. +2DS) eyes and ask them to inform you when the image is clear.
When clear, flip the lenses over (now -2DS) and ask them to inform you when the image is clear.
Clearing both sets of lenses = 1 cycle
Reduce the strength of the flippers if the patient cannot see clearly through them. This is important to know they are relaxing and inducing accommodation appropriately.
Once the patient has had a practice of 1 cycle you can begin the test and count how many cycles they can achieve in 1 minute.
The test can also be performed monoculary.

https://www.youtube.com/watch?v=EMEQunRC3B8

Question 3

Recording results in accomodative facility test

Answer 3

Record the result. E.g.:
Accommodative facility with +/- 2DS at Near BEO: 12 cpm

Question 4

Accommodative Lag/Lead with Nott Dynamic Retinoscopy

Answer 4

Perform with glasses on
Ask patient to hold and fixate target at near at their preferred reading distance
Hold the retinoscope at the same distance as the target and observe the reflex in one eye.
If there is a ‘with’ movement = accommodative lag = move back until neutral.
If there is an ‘against’ movement = accommodative lead = move forward until neutral

Calculate the lag or lead of accommodation as per the following example:
Measure the distance from eyes to target e.g. 35cm
Convert this distance (in m) into D: 1/0.35m = 2.86D
This is the amount of accommodation that should be exerted.
Measure the distance from the eyes to the retinoscope e.g. 45cm
Convert this distance (in m): 1/0.45m = 2.22D
This is the amount of accommodation actually exerted.
Calculate the difference between the two: 2.86D – 2.22D = 0.64D lag of accommodation
This is within normal limits.

Question 5

Note for Accommodative Lag/Lead with Nott Dynamic Retinoscopy

Answer 5

NOTE that many students try to calculate the lead/lag of accommodaytion by subtracting the 2 distances and then converting into dioptres. This is incorrect and would give an abnormal value. For the example above you would get 45cm – 35cm = 10cm; 1/0.1m = 10D.

Watch the following video for more information. They use the Cardiff Cube which is a target on a ruler, making it easier to read off measurements and interpret the results. We don’t have this available but it is the same concept
https://www.youtube.com/watch?v=oAtonBZ5YI8

Question 6

Pupil Assessment – Light reflex

Answer 6

Direct and Consensual response
Note any anisocoria
Introduce a pen torch in front of one eye.
The pupil of that eye should constrict = direct response
Re-introduce the pen torch to the same eye but now observe the response in the other eye. The other pupil should also constrict = consensual response
Repeat the direct and consensual assessment for the other eye.
Can perform multiple times if needed to check the responses.
If the responses are as expected the findings can be reported as PEARL = pupils equal and reactive to light.

Question 6

Pupil assessment- Near reflex

Answer 6

Hold an accommodative target, such as a Snellen stick, at near.
Push the target towards the patient’s eyes.
Observe the pupils – you should see pupil miosis in both eyes

Question 7

Pupil assessment- Light reflex recording

Answer 7

Can also be recorded as PERRLA =
PE: pupils equal
R: round
RL: reactive to light (direct and consensual)
A: responsive to accommodation (near target)
If there is any abnormality this should be described. E.g. anisocoria, oval or abnormal shape pupil, sluggish or no reaction to light.

Question 8

Swinging light test to test for an RAPD

Answer 8

Introduce a pen torch in front of one eye. The pupil of that eye should constrict followed by slight dilation.
Swing the pen torch to the other eye. The pupil of that eye should constrict followed by slight dilation.
Can repeat multiple times to check the responses.
If normal, record as no RAPD.
If there is an RAPD present, there will be pupil dilation instead of constriction when moving the light from the unaffected to the affected side

https://www.youtube.com/watch?v=HSYo7LhfV3A&feature=youtu.be