Practical Opthal Skills for OSCE

Question 1

Outline how you would record a patient’s visual acuity using a Snellen chart

Answer 1

The Snellen chart is held 6m away (test distance)

Numerator is the test distance, e.g. 6m.

Denominator is the distance at which someone with ‘normal’ vision would be able to see the letter e.g. 60m for A

If patient does not get all of the letters of a line correct expressed as + and – letters.

For example obtaining: A, DF, HZP, TXU = 6/18-1

Obtaining: A, DF, HZP, TXUD, Z = 6/18+1

Question 2

How could you modify a Snellen test for someone with significantly reduced vision?

Answer 2

Conduct at 3m test distance

Top letter would have a 3/60 score

Question 3

If the patient correctly identified the letters highlighted in green, what is their VA?

Answer 3

6/12 -2

Question 4

The LogMAR chart is another simple chart that can be used to assess visual acuity.

What are it’s advantages over the Snellen chart?

Answer 4

Uniform reduction of letter size
Crowding effect on each line

Question 5

Outline how visual acuity can be scored using a LogMAR chart

Answer 5

Each line from top to bottom has a score of 0.1

Each letter has a score of 0.02 (as five letters per line)

Question 6

If the patient correctly identified the letters highlighted in green on this LogMAR chart, what is their VA?

Answer 6

0.64 logMAR

Question 7

How can you roughly assess visual acuity in children too young to verbally communicate what they can see?

Answer 7

8 weeks - 12 months : Keeler Preferential Looking Cards
3-18 months: Cardiff Acuity Cards
2-4 years: Kay Pictures

Question 8

If visual acuity is too low to perform any of the normal tests, what options remain?

Answer 8

Counting Fingers (CF)
Hand Movements (HM)
Perception of Light (PL)
No Perception of Light (NPL)

Question 9

What initial ocular observations or additional observations can you make about this child?

Answer 9

Anisocoria (different pupil sizes), Right miotic pupil and Right sided ptosis

Question 10

What initial ocular observations or additional observations can you make about this child?

Answer 10

Significant R Esotropia

Question 11

What is manifest squint?

Answer 11

a squint (strabismus) that is present at rest

Question 12

On this diagram, A shows a normal eye position.

How would you describe the types of strabismus shown in B, C and D?

Answer 12

B = Left Convergent Squint or Esotropia
C = Left Divergent Squint or Exotropia
D = Left Hypertropia (as opposed to turned down which is Hypotropia)

Question 13

What feature can help you to detect subtle squints?

Answer 13

looking for the symmetry of the corneal reflections

Question 14

What is this child exhibiting?

Answer 14

Fully Accomodative Esotropia (can be fixed by correcting refractive errors)

Question 15

The top image shows the child fixating on a near target. The bottom image shows the child focusing on a distant target.

What is this called?

Answer 15

Intermittent Distance Exotropia

Question 16

What are the different types of diplopia that patients may experience?

Answer 16

Question 17

How can you differentiate between monocular and binocular diplopia?

Answer 17

Monocular diplopia = present in both eyes independently, e.g. when you cover the L eye they will still see double through the R eye and vice versa

Binocular diplopia = present when both eyes used together, will not be present when one eye is covered