What is the normal acuity of vision?
20/20 vision is normal vision acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at a distance.
What does a visual acuity of 6 7.5 mean?
For the Snellen chart, when assigning vision as the lowest line on which all letters were read correctly, all participants with vision of 6/7.5 or better could read a number-plate at 20 m, and no participant with worse than 6/36 was able to successfully read a number-plate (figure 1).
What do visual acuity numbers mean?
An eye chart measures visual acuity, which is the clearness or sharpness of vision. The top number is your distance in feet from the chart. The bottom number is the distance at which a person with normal eyesight can read the same line. For example, if you have 20/30 vision, it means your vision is worse than average.
What does 6 60 mean in an eye test?
On the Snellen scale, normal visual acuity is called 6 / 6, which corresponds to the bottom or second bottom line of the chart. If you can only read the top line of the chart then this would be written as 6 / 60. This means you can see at 6 metres what someone with standard vision could see from 60 metres away.
What is the meaning of 6 6 and 6 9 vision?
A:This means that the letters on the chart which should be read at 9 feet, you are only able to see at 6 feet. In other words you are only short of one line on the chart. We all have slight astigmatism and you should not worry about this at all.
What is the meaning of 6 18 eyesight?
The larger the second number, the worse the vision. If vision is 20/40 (6/12), the person can read at 20 ft (6 m) what people with normal vision can read at 40 ft (12 m). If vision is 20/60 (6/18), the person can read at 20 ft (6 m) what people with normal vision can read at 60 ft (18 m).
What does a visual acuity of 3 60 mean?
This means you can see at 6 metres what someone with standard vision could see from 60 metres away. The figures 6 / 60 or 3 / 60 are how the result of a Snellen test are written. The first number given is the distance in metres from the chart you sit when you read it.
What does visual acuity 6 9 mean?
6/9 and 6/12 means you have poor vision in both your eyes and you are rightly using glasses. As mentioned by Dr Seema it is a way to measure eyesight, and the technique used is known as Snellen’s chart, just as most other things like milk, sugar, gas etc are measured.
What is the optic acuity of a human eye?
Between these extremes is the pupil diameter that is generally best for visual acuity in normal, healthy eyes; this tends to be around 3 or 4 mm. If the optics of the eye were otherwise perfect, theoretically, acuity would be limited by pupil diffraction, which would be a diffraction-limited acuity of 0.4 minutes of arc (minarc) or 6/2.6 acuity.
What are the other measures of visual acuity?
Other measures. Normally, visual acuity refers to the ability to resolve two separated points or lines, but there are other measures of the ability of the visual system to discern spatial differences. Vernier acuity measures the ability to align two line segments. Humans can do this with remarkable accuracy.
What is a 6/6 visual acuity?
A visual acuity of 6/6 is frequently described as meaning that a person can see detail from 6 metres (20 ft) away the same as a person with “normal” eyesight would see from 6 metres.
What is the normal range of visual acuity?
In England, for example, doctors of optometry express visual acuity in meters (6/6 is considered normal). Why do some people have less than 20/20 vision? Many factors affect visual acuity.