What happens during an eye test? A step-by-step guide

Step 1: A few questions about you

The test starts with a conversation. Your optometrist will ask why you have come, whether you have noticed any changes in your sight, and what you use your eyes for most: driving, screen work, reading, sport. They will also ask about your general health, any medication you take, and whether eye conditions such as glaucoma run in your family. These answers shape the rest of the test, so mention anything that has been bothering you, even if it seems small.

Step 2: Reading the chart

Next comes the part everyone knows. You cover one eye at a time and read letters that get smaller line by line. This measures your visual acuity, which is how sharp your sight is at distance. Children and people who cannot read letters are shown shapes, pictures or letter E's pointing in different directions instead. Your near vision is checked with a small card held at reading distance. What 6/6 vision means explains how the result is written down.

Step 3: Finding your prescription

This step is called a refraction. The optometrist places different lenses in front of each eye and asks which looks clearer: "one, or two?" Each answer narrows down the lens power that gives you the sharpest and most comfortable vision.

People often worry about getting this part wrong. You cannot. If two options look the same, say that they look the same. It tells the optometrist they are close to the right answer. Before asking you anything, many optometrists also take an objective measurement by shining a light into the eye and watching how it reflects, which gives a good starting point and is especially useful for young children.

Step 4: Checking how your eyes work together

Clear sight in each eye is not the whole story. Your optometrist also checks:

• how your eyes move and whether they stay lined up
• how well they focus on near objects and change focus between distances
• your side (peripheral) vision
• how your pupils react to light

Problems here can cause headaches, tired eyes and double vision, even when the letters on the chart look sharp.

Step 5: Examining the health of your eyes

Using a bright light and magnifying lenses, the optometrist looks at the front of your eye (the lids, cornea and lens) and at the back (the retina, the blood vessels and the optic nerve). This is where early signs of cataracts, glaucoma and diabetic eye disease are picked up, often before you notice anything yourself.

Depending on your age and risk, further tests may be done or recommended, such as measuring the pressure inside your eyes or mapping your field of vision. Occasionally drops are used to widen the pupils for a better view. If so, your near vision will be blurry and lights will seem bright for a few hours, so you should not drive until it wears off.

Step 6: Your results

At the end the optometrist explains what they found. You will hear whether you need glasses, whether your prescription has changed, and whether anything about the health of your eyes needs watching or a referral to a specialist. If you need glasses, you get a written prescription. How to read your glasses prescription explains the numbers on it.

What to bring to an eye test

• your current glasses or contact lenses, and your last prescription if you have it
• a list of any medication you take
• your medical aid card and your ID
• sunglasses, in case drops are used
• your questions, written down if that helps

How a home eye test differs

The steps are the same. The difference is that the optometrist brings the testing equipment to you and sets up in your lounge, office or classroom. All you need is a reasonably quiet room and somewhere to sit. At See Better the visit is done by an HPCSA-registered optometrist, and an eye test at home costs R450. Read more in how an eye test at home works.