Y2 OCaPE: NSB 4 Eye Chart Exam

SNELLEN Chart (1)

What does the SNELLEN chart test for?

Visual acuity (1)

Describe how this chart is used in the UK?

6 metres away

If patient wears glasses/lens, ask them to keep them on

Test one eye at a time, covering the other eye

Record scores (4)

PJ comes in for his routine check. He reads up to the 5th line, in which he makes two errors. 

What is his score?

• If you correctly identify five of the seven letters on the 20/32 line, your visual acuity for that eye is: 20/32–2/7

• If you correctly identify all seven letters on the 20/32 line and three of the eight letters on the 20/25 line, your visual acuity in that eye is: 20/32+3/8

So his in this is: 20/50 (-2/5)

(3 marks – no explanation is needed to get all three marks)

The patient is worried that his children may have red-green colour blindness. What is the mode of inheritance of this disease?

X-linked reccesive. (1)

What test is used to test colour vision and what are the typical results of someone with red-green colour blindness?

Isihara test – using coloured number plates.

 Red-green deficiency would mean seeing different numbers at some plates and no numbers at others.

They will see different numbers at 2-9

They will not see any numbers at plate 10-17 

(2)

As part of the exam, the GP also does a pupillary light reflex test 

When light is shined into the right eye, constriction takes place but there is no consensual constriction in the other eye. What is the issue?

Problem in the parasympathetic supply to the left eye. 

There could be a lesion anywhere from the E-W nuclei along the ciliary ganglion to the left oculomotor nerve. 

Tests should be done to assess whether the oculomotor nerve is damaged. 

If CNIII is damaged, you will also get a down and out gaze. (3)

You remember a patient yesterday who had a CNIII palsy. What other conditions may cause this?

Myasthenia gravies
MS
Head Trauma
Tumour compressions (2)