Once the test is complete, you should document the number of plates the patient identified correctly, including the test plate (e.g. 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. If the patient is unable to read the test plate, you should document this.ģ. The first page is usually the ‘test plate’ which does not test colour vision and instead assesses contrast sensitivity. Then ask the patient to read the numbers on the Ishihara plates. Ask the patient to cover one of their eyes.Ģ. If the patient normally wears glasses for reading, ensure these are worn for the assessment.ġ. 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. In comparison, papilloedema (optic disc swelling from raised intracranial pressure), does not usually affect visual acuity until it is at a late stage.Ĭolour vision can be assessed using Ishihara plates, each of which contains a coloured circle of dots. Optic nerve (CN II) pathology usually causes a decrease in acuity in the affected eye. Optic nerve (CN II) pathology such as optic neuritis.Retinal diseases such as age-related macular degeneration.Ocular media opacities such as cataract or corneal scarring.
Assess if they can detect light from a pen torch shone into each eye (“Perception of Light”/”PL” or “No Perception of Light”/”NPL”).ĭecreased visual acuity has many potential causes including: Assess if they can see gross hand movements (recorded as “Hand Movements” or “HM”).ĥ. Assess if they can count the number of fingers you’re holding up (recorded as “Counting Fingers” or “CF”).Ĥ. Reduce the distance to 1 metre from the Snellen chart (1/denominator).ģ. Reduce the distance to 3 metres from the Snellen chart (the acuity would then be recorded as 3/denominator).Ģ. If the patient is unable to read the top line of the Snellen chart at 6 metres (even with pinhole) move through the following steps as necessary:ġ. When recording the vision it should state whether this vision was unaided (UA), with glasses or with a pinhole (PH).įurther steps for patients with poor vision.If the patient gets more than 2 letters wrong, then the previous line should be recorded as their acuity.If the patient reads the 6/6 line but gets 2 letters incorrect, you would record this as 6/6 (-2).Visual acuity is recorded as chart distance (numerator) over the number of the lowest line read (denominator): Repeat the above steps with the other eye. You can have the patient read through a pinhole to see if this improves vision (if vision is improved with a pinhole, it suggests there is a refractive component to the patient’s poor vision).ĥ. Record the lowest line the patient was able to read (e.g. Ask the patient to cover one eye and read the lowest line they are able to.ģ. Stand the patient at 6 metres from the Snellen chart.Ģ. If the patient normally uses distance glasses, ensure these are worn for the assessment.ġ. Visual acuity Assessment of visual acuity (distance)īegin by assessing the patient’s visual acuity using a Snellen chart. You might also be interested in our OSCE Flashcard Collection which contains over 2000 flashcards that cover clinical examination, procedures, communication skills and data interpretation.
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