A sight test can involve letters on a chart, several different instruments and a page of figures that seems designed for an optician rather than a patient. This eye test results guide translates the common terms into plain English, so you can leave knowing what your results mean for everyday life – from driving and screen work to reading, hobbies and choosing new glasses.
At Mark Darling Eyecare & Opticians, we take the time to discuss your results as an individual. Your prescription is only one part of the picture. How your eyes feel, what you need them to do and the health of your eyes all matter too.
Your eye test results guide: the prescription
Your prescription describes how lenses can focus light more accurately on your retina, the light-sensitive layer at the back of the eye. It is not a score for how good or bad your eyes are, and a stronger prescription does not automatically mean poorer eye health.
Most prescriptions are laid out with separate figures for the right eye and left eye. You may see R and L, or OD and OS, which are clinical abbreviations for right and left eye. The figures can look technical, but each one has a practical purpose.
SPH: short-sight or long-sight
SPH, or sphere, is the main lens power. A number with a minus sign, such as -2.00, usually indicates short-sightedness. Distance objects may be blurred without glasses or contact lenses, while closer work is often clearer.
A plus sign, such as +1.50, indicates long-sightedness. This can affect close work, although some people also notice distance blur or tired eyes, particularly when the prescription is higher. Children can sometimes compensate for a degree of long-sightedness by focusing very hard, which is one reason a thorough children’s eye examination is so valuable.
The larger the number, the greater the lens power required. However, two people with the same figure can have very different visual needs and experiences.
CYL and AXIS: astigmatism explained
CYL, or cylinder, measures astigmatism. This is extremely common and simply means that the front surface of the eye, or sometimes the lens inside it, is shaped more like a rugby ball than a perfectly round football. It can cause blur or distortion at both distance and near.
AXIS is a number between 1 and 180. It tells the laboratory the orientation in which the astigmatism correction needs to sit. It is not a measure of severity, and a change in axis is not necessarily a cause for concern.
Astigmatism may make road signs look slightly shadowed, lines of text appear less crisp, or night driving feel more uncomfortable because lights can flare. The right lenses often make a noticeable difference, especially if you have previously been wearing an older prescription.
ADD: extra help for close work
ADD means addition. It is an additional magnifying power for close tasks, usually needed from the mid-forties onwards when the eye’s natural focusing flexibility begins to reduce. This normal age-related change is called presbyopia.
An addition may be used in reading glasses, bifocals, varifocals or occupational lenses designed for desk and screen distance. The best choice depends on your day. Someone who moves between meetings, a computer and driving may benefit from a different solution to someone who mainly reads, sews or uses a tablet at home.
Prism: helping the eyes work together
Occasionally, a prescription includes prism. This helps align the images seen by each eye when the eyes do not work together as comfortably as they could. It may be prescribed for symptoms such as double vision, headaches or strain, but it is always considered alongside the wider findings from your examination.
Prism lenses require careful measurements and fitting. If your new glasses include prism, let your optician know if anything does not feel right during the adjustment period.
What 6/6 vision means – and what it does not
You may hear your vision described as 6/6, 6/9 or 6/12. These figures are measurements of visual acuity: how clearly you can see detail at a set distance.
In simple terms, 6/6 is commonly considered standard distance vision. If you see 6/12, you need to be six metres away to see what a person with 6/6 vision could see from 12 metres away. Your optometrist will assess each eye separately and usually both eyes together, with and without correction where appropriate.
Visual acuity is useful, but it does not tell the whole story. You can have 6/6 vision and still experience dry, uncomfortable eyes, glare from headlights, difficulties with contrast or problems maintaining focus at a screen. Equally, someone whose chart result is not perfect may function very well with the right correction and support.
For driving, the legal requirement is based on being able to read a number plate from 20 metres in good daylight, as well as meeting the required visual-field standard. If you are unsure whether your current glasses meet your driving needs, ask during your appointment rather than relying on an old prescription.
Eye health results are just as significant
A comprehensive eye examination checks much more than whether you need new glasses. Your optometrist examines the front of the eye, the lens, the retina, optic nerve and blood vessels, using clinical observations and imaging where appropriate.
You may be told that your eyes are healthy, which is reassuring. You may also hear terms such as dry eye, early cataract changes, blepharitis, retinal changes or optic nerve appearance. These findings vary greatly in significance. Some simply need practical management or monitoring; others may need a shorter review interval or a referral for further assessment.
Eye pressure may be measured as part of your examination. Raised pressure can be one risk factor for glaucoma, but a single pressure reading alone does not diagnose glaucoma. Your optometrist considers it alongside your optic nerves, visual fields, family history, corneal thickness and previous results. This is why regular care with a practice that knows your history can be so helpful.
Retinal photographs and scans can provide a valuable baseline for comparison over time. A small change is not always harmful, but spotting change early gives us the best opportunity to decide what should happen next.
Why your prescription can change
A change in prescription is not automatically a sign that something is wrong. Eyes change throughout life. For many adults, minor changes occur gradually. Hormonal changes, prolonged close work, certain medicines, diabetes and cataract development can all affect vision or cause prescriptions to fluctuate.
Children and teenagers may experience more noticeable changes as their eyes develop. Regular examinations help ensure they can see clearly enough for learning, sport and everyday confidence. If a child squints, sits close to screens, complains of headaches or avoids reading, an eye examination is sensible even if they have not said that things look blurred.
It is also worth remembering that your written prescription has an expiry date because it reflects your eyes at one point in time. Wearing an older pair of glasses is not always a problem, but do not assume an old prescription remains suitable for driving, detailed work or contact lens wear.
When to ask more questions about your eye test results
You should feel comfortable asking what any result means for you. Useful questions include whether your prescription is needed all the time or for specific tasks, whether lens options could improve comfort, and when your next examination should be. If dry eye is affecting your vision, ask about a plan that addresses the cause rather than simply masking the symptoms.
Some symptoms should not wait for a routine appointment. Seek urgent advice if you develop sudden loss or marked reduction of vision, a curtain or shadow in your vision, new flashes with a sudden shower of floaters, severe eye pain, or a painful red eye. These symptoms do not always indicate a serious problem, but they need prompt assessment.
A good eye test result is not just a line of numbers to file away. It is a chance to understand how your eyes are working now, protect their health for the future and make everyday vision feel easier. Bring your questions with you, and give yourself permission to ask for an explanation that makes sense.