Visual Acuity Tests: What 6/6 and 20/20 Mean
A visual acuity test measures how clearly you can see details at a set distance. It is the familiar part of an eye examination in which you read letters, numbers or symbols from a chart, usually one line at a time. The result gives an objective description of sharpness for distance vision, near vision or both.
The figures can look confusing because Australia commonly uses the metric 6/6 format, while clinics in the United States often record 20/20. These results describe the same standard of clarity, expressed using different distances. A result that seems “normal” still does not rule out every eye problem, so visual acuity is only one part of a comprehensive examination.
| Result or test | What it generally indicates | What it does not establish |
|---|---|---|
| 6/6 or 20/20 | Standard distance visual acuity | Healthy eyes in every respect |
| 6/12 or 20/40 | You see at six metres what standard vision sees at twelve metres | The exact cause of blur |
| Near acuity | Clarity for reading and close work | Whether distance vision is clear |
| Pinhole acuity | Whether blur may improve when stray light is reduced | A final glasses or contact lens prescription |
| Contrast sensitivity | Ability to distinguish subtle differences in light and shade | Performance on a standard letter chart |
How Visual Acuity Is Measured
During a distance test, you usually sit or stand at a fixed point facing a chart. One eye is covered while the other eye reads the smallest line possible, then the process is repeated with both eyes together. The clinician may use an illuminated wall chart, a projected display or a digital screen. Children may identify matching shapes or picture symbols rather than letters.
The first number in a result is the testing distance. In Australia, 6/6 means the chart was read from six metres and the line is designed to be read at that distance by standard eyesight. In the United States, 20/20 describes the same concept at twenty feet. Since twenty feet is approximately six metres, 6/6 and 20/20 are equivalent standards rather than different levels of vision.
A person who records 6/12 can read at six metres what a person with standard acuity can read from twelve metres. A result of 6/60 indicates considerably blurrier distance vision. The figures are fractions, but they are not school grades: 6/12 is not “half as good” in every practical situation, and the result does not directly measure how healthy the eyes are.
Reading the Numbers and Letters
A visual acuity result may be written separately for each eye. “OD” refers to the right eye and “OS” to the left eye, while “OU” means both eyes together. Some records use plain language instead, such as right eye 6/9, left eye 6/6, and both eyes 6/6. A small difference between eyes can be harmless, but a new or pronounced difference deserves assessment.
The test may include a pinhole occluder, a small device with a single opening. If vision improves through the pinhole, refractive error such as short-sightedness, long-sightedness or astigmatism may be contributing to the blur. Glasses or contact lenses can often improve this type of vision. If acuity remains reduced, the cause may involve the cornea, lens, retina, optic nerve or another part of the visual system.
Visual acuity also appears in driver licensing requirements. In Australia, the Austroads standards guide assessments for private and commercial driving, with requirements covering visual acuity, visual fields and other factors. A person applying for or renewing a licence in Sydney, Brisbane, Perth or a regional area should check the relevant state or territory transport authority rather than assuming that 6/6 is the only requirement.
What the Test Can and Cannot Show
A clear result means that you can resolve a particular level of detail under the test conditions. It does not measure colour vision, peripheral awareness, eye pressure, focusing stamina, depth perception or the health of the retina. Someone with 6/6 vision can still have glaucoma, early retinal disease, dry eye or difficulty changing focus between a phone and a distant road sign.
The testing environment also affects performance. Glare, tiredness, an unfamiliar chart, poorly fitting spectacles or a dry ocular surface can make letters appear less distinct. Older adults may have fluctuating clarity from dry eye or cataract, while children may perform inconsistently if they are anxious or do not understand the instructions. The clinician interprets the result alongside symptoms, eye history and examination findings.
For people who spend long periods on screens, clarity at six metres does not guarantee comfortable computer vision. Australians commonly move between bright outdoor light and air-conditioned offices, classrooms or shops, and long periods of close work can expose focusing or surface-eye problems. Regular blinking, sensible screen breaks and appropriate lighting may help, but persistent headaches, burning or fluctuating blur should be assessed.
When Results Need Follow-Up
A sudden drop in vision, a dark curtain or shadow, new flashing lights, a shower of floaters, severe eye pain or marked redness requires prompt medical attention. These symptoms are more urgent than an isolated chart result because they can signal retinal problems, infection, acute pressure changes or injury. Delaying care while waiting for a routine eye test is unwise when vision changes rapidly.
A scratched cornea can make the chart look worse because the clear front surface of the eye becomes painful and irregular. It may follow contact with dust, a fingernail, a tree branch or a contact lens. Guidance on corneal abrasion care can help explain home-care principles, but significant pain, light sensitivity, discharge or reduced vision calls for professional review.
Routine follow-up is also important when the result is stable but risk factors are present. Diabetes, a family history of glaucoma, previous eye surgery, high short-sightedness and long-term medication use can alter recommended examination intervals. In Australia, Medicare-subsidised optometry visits depend on eligibility and timing rules, and fees or bulk-billing policies vary between practices. Checking the clinic’s current policy before booking avoids unexpected costs.
Practical Details Before Your Eye Test
Preparing carefully can make the measurement more representative of everyday vision. Bring current glasses, contact lens details and a list of medicines, including eye drops. Tell the optometrist about headaches, eye strain, night-driving difficulty, previous injuries and any change in one eye. A complete history gives meaning to the number on the chart.
Two short checklists can help organise the appointment:
Bring or record:
- Current glasses and contact lens information
- Previous prescriptions or eye examination results
- Medical conditions, medicines and family eye history
- Examples of situations that cause blur or discomfort
Mention before testing:
- Recent flashes, floaters, pain or sudden vision loss
- Trouble reading road signs, menus or subtitles
- Dryness after screen use or in air conditioning
- Difficulty adapting between bright sun and indoor light
Contact lens wearers may need to remove lenses before some measurements, particularly when the clinician is checking the corneal surface or refining a prescription. The timing varies with lens type and the purpose of the visit, so follow the practice’s instructions. Do not drive if dilating drops have been used and your vision feels blurred or light-sensitive; arrange transport or allow time for the effects to settle.
Families in Australia may choose between independent optometry practices, corporate optical stores and ophthalmology clinics. The choice can depend on location, appointment availability, lens range, fees and access to additional testing. A practice with retinal imaging and an on-site optical laboratory, such as Kramer Family Eyecare in Columbia, Missouri, can combine clinical assessment with frame and lens services, although local Australian availability differs by city and region.
Turning a Result Into Everyday Vision
A visual acuity measurement is most useful when it is compared with your previous results and your real-world needs. A person with 6/9 vision who functions comfortably may need a different plan from someone with 6/6 vision who struggles with night glare, reading or contact lens discomfort. Prescription lenses can sharpen images, while dry eye treatment, cataract care, glaucoma monitoring or retinal assessment may address other causes of visual difficulty.
Near vision is especially relevant as people move through middle age and begin experiencing presbyopia, the gradual loss of focusing ability at close range. Reading glasses, multifocal lenses or occupational lenses may improve comfort, but the correct option depends on work distance, hobbies and how often a person moves between near and far tasks. A standard distance result cannot predict which option will feel most natural.
Children should have age-appropriate vision checks because they may not recognise that one eye is weaker. Adults should arrange assessment when glasses no longer seem effective, when one eye appears different from the other, or when ordinary tasks become harder. Keep the practical meaning in view: the number tells you how sharply you read the chart, while the full examination explains why and what can help.