Common conditions

How eye tests work

If you want to protect your eyesight, it’s a must to have an eye check regularly. But how do eye testing machines work and what can the eye tests reveal about your health? Here’s what you need to know about going in for an eye check-up.

Our eyes allow us to read a book, enjoy the beauty of a sunset and see the people we love, “so it’s important to have them checked regularly so that any issues can be detected and treated as early as possible”, says Whitney Lam, Managing Optometrist at HCF Eyecare Associated Optometrists.

So, what exactly happens when you visit an optometrist and how do eye tests work? Here’s a guide to understanding the eye check-up process, what optometrists look for and the eye tests performed.

Making your appointment

When you ring to book in for an eye exam, make sure you mention family history (of glaucoma, for example) or health conditions (such as diabetes) that may indicate you need a longer appointment. If you’re interested in being free of glasses and trying contacts for the first time, mention this too.

Pre-test consultation

If you’ve booked into one of HCF’s Eyecare Centres, you'll receive a pre-examination questionnaire, which gives you an opportunity to provide accurate information, like the list of medications you’re using and the details of your GP. On the day of your consultation, the optometrist asks additional questions to clarify the main reasons for your visit (such as if you’re experiencing headaches or blurred vision, or simply want an eye check-up).


When you go in for your eye check-up, your optometrist will conduct some or all of the following eye checks:

Visual acuity test
With one eye covered, you read letters of the alphabet from a chart, with the type getting smaller with each row. This measures your sharpness of vision.

Refraction test
If you need or use glasses your optometrist will ask you to look through a series of different lenses and pick which one looks clearer to determine the most appropriate lens power. The prescription is handed to an optical dispenser who helps you choose your glasses frames and arranges for them to be made up with the prescribed lenses. This may take a few days or weeks.

Eye function tests
The optometrist tests your muscle function, eye coordination and peripheral vision by getting you to visually track a moving object, look at a distant target and bringing objects or computer images into your line of vision. Colour vision and depth perception can also be tested by using special books and glasses.

Slit lamp check
A special microscope with a strong light illuminates the structures of your eye to allow assessment of your eyelids, lashes, irises, corneas and lenses. Here, an optometrist can pick up eye conditions like ocular dryness and cataract.

Glaucoma screening
Glaucoma is a condition which accelerates the natural deterioration of the optic nerve, causing side vision loss. Side vision is vital for essential day to day tasks like driving and navigation. Tests for the condition include an optic nerve examination and a visual field test. The optometrist uses a visual field test to analyse the extent of your side vision.

A tonometer measures the eye pressure by directing a small puff of air to the eye. “High eye pressure measurement may indicate a higher risk of glaucoma,” Lam says.

Dilation Test
The pupil controls the light travelling into your eye. When we shine light to the eye, it naturally constricts and becomes smaller. This can make it more difficult for the optometrist to assess the structures inside the eye, such as the macula and blood vessels, so they may use pupil dilating drops and a head-mounted instrument known as a Binocular Indirect Ophthalmoscope. It's also necessary to look at the structures further away from the centre of the back of the eye.

“As your vision may be affected for an hour or two after the test, we just recommend no driving for two hours and wear sunglasses to prevent glare,” Lam says.

Retinal & OCT imaging
A fundus camera allows the optometrist to take a photograph of the inside of the eye, or the retina. Here, the optometrist can show you the back of your own eye, and discuss what features they are looking out for, as well as conditions such as macular degeneration.

A high-tech scan, called an Optical Coherence Topographer, goes into further detail and looks at separate layers in the retina. This technology allows the optometrist to compare your eyes with age-related norms and track the progression of the retinal tissue over time. These tools offer excellent insight and allows the optometrist to intervene at earlier stages as soon as any signs of macular degeneration, glaucoma, or the impacts of stress and high blood pressure are detected.

What happens after your eye check-up

Did you know, there is more than just multifocal and single focus glasses?

With all the information gathered from the eye tests, the optometrist will make recommendations on solutions to suit your lifestyle. This can include contact lenses, prescription sunglasses, swimming goggles, cycling glasses, refractive surgery, as well as special lenses and lens coatings which are tailored to the level of your screen time, to name a few.

The optometrist also will advise you of when to have you next eye check-up and, if necessary, make recommendations on eye exercises, eyedrops, diet, lighting needs, or the need to see an eye specialist.

Words by HCF
Updated October 2021

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