Colour vision

Colour Vision Assessment – OSCE Guide

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Assessment of colour vision using Ishihara plates can sometimes appear in OSCEs. This guide provides a brief step-by-step guide to using Ishihara plates to assess colour vision, with an included video demonstration.


Introduction

Wash your hands and don PPE if appropriate.

Introduce yourself to the patient including your name and role.

Confirm the patient’s name and date of birth.

Briefly explain what the examination will involve using patient-friendly language.

Gain consent to proceed with the examination.

Position the patient sitting on a chair.

Ask if the patient has any pain before proceeding.


Colour vision assessment

Colour vision can be assessed using Ishihara plates, each of which contains a coloured circle of dots. Within the pattern of each circle are dots which form a number or shape that is clearly visible to those with normal colour vision and difficult or impossible to see for those with a red-green colour vision defect.

How to use Ishihara plates

If the patient normally wears glasses for reading, ensure these are worn for the assessment.

1. Ask the patient to cover one of their eyes.

2. Then ask the patient to read the numbers on the Ishihara plates. The first page is usually the ‘test plate’ which does not test colour vision and instead assesses contrast sensitivity. If the patient is unable to read the test plate, you should document this.

3. If the patient is able to read the test plate, you should move through all of the Ishihara plates, asking the patient to identify the number on each. Once the test is complete, you should document the number of plates the patient identified correctly, including the test plate (e.g. 13/13).

4. Repeat the assessment on the other eye.

  • Assess colour vision using an Ishihara chart at arms length
    Assess colour vision using an Ishihara chart at arms length

To complete the examination

Explain to the patient that the examination is now finished.

Thank the patient for their time.

If mydriatic drops were instilled, remind the patient they cannot drive for the next 3-4 hours until their vision has returned to normal.

Dispose of PPE appropriately and wash your hands.

Summarise your findings

Suggest further assessment and investigations

All of the following further assessments and investigations are dependent on the patient’s presenting complaint and in most cases, none of them would need to be performed:

  • Amsler chart: to assess for central visual loss and distortion which is commonly associated with macular degeneration.
  • Complete visual assessment: including visual acuity, visual fields and fundoscopy.
  • Cranial nerve examination: to further assess for evidence of cranial nerve pathology (e.g oculomotor nerve).
  • Retinal photography: to better visualise any abnormalities noted on fundoscopy.

 

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