Module 1 Lesson 2 - 8 (Lab)
Completion requirements
Lesson 2 — Photoreception: The Eye
Lab - Vision Tests
Introduction
This lab involves measuring visual acuity using various methods.Procedure
Click the tabs to test your eyes.
Use the Snellen chart to determine your visual acuity for distance vision.
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Place yourself 1 metre from a standard-sized laptop screen (of about 15 inches) and cover one eye.
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Read the letters and continue until you can no longer visualize the letters clearly.
- Cover the other eye and do the same. Compare your results.
Snellen Chart. Public Domain.
Analysis
The eighth line on the Snellen chart is labelled 20/20, which indicates the visual acuity of an average individual standing 6 metres from the chart. If you were able to read only up to the fifth line (20/40 on the chart), you need to stand 6 metres away to read the fifth line but an average individual is able to see the fifth line clearly standing 12 metres from the chart.
Use the following Jaeger Chart to test your near vision acuity.
Analysis
The Jaeger chart often is used to determine the near vision acuity of individuals. This chart must be held at 14 inches from the reader; otherwise, it will modify the results significantly.
Look at the following image to test for astigmatism.
- Focus on the cross in the centre of the image.
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If any of the straight lines look darker or sharper than other lines, you may have astigmatism.
Astigmatism Test. Vision Correction. © Jan 16, 2020 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License 4.0 license. Download for free.
Analysis
Astigmatism is a common condition that results in blurred vision due to uneven cornea.
Observe the following Ishihara plate to test for colour blindness. Do you see number 74 or number 21 or no number?
Ishihara Plate. Public Domain.