What does the first number in the Snellen eye chart represent?

What does the first number in the Snellen eye chart represent?

The first number in the term is the distance a person with normal visual acuity stands from the eye chart, measured in feet. The second number is the distance the tested person stands while reading the same line on the eye chart, measured in feet.

How do you read Snellen eye chart results?

Recording Snellen Results Top number equates to the distance (in metres) at which the test chart was presented (usually 6m), Bottom number identifies the position on the chart of the smallest line read by the ‘patient’. Eg; 6/60 means the subject can only see the top letter when viewed at 6m.

What is the top letter on an eye chart?

The most common eye charts used in America today are called Snellen charts, named after Hermann Snellen, a Dutch ophthalmologist in the 1800s. They start with a single, large letter E at the top of the chart.

What do the distance numbers on a Snellen eye chart mean?

The top number refers to the distance you stand from the chart. This is often 20 feet (6 meters). The bottom number indicates the distance at which a person with normal eyesight could read the same line you correctly read.

What does plus and minus mean in eyesight?

In general, the further away from zero the number on your prescription, the worse your eyesight and the more vision correction (stronger prescription) you need. A “plus” (+) sign in front of the number means you are farsighted, and a “minus” (-) sign means you are nearsighted.

What does 6/24 mean in an eye test?

Perfect vision in a Snellen test would equal 6/6, which means the person can see at 6 metres what they ‘should be’ able to see at 6 metres. 6/24 for example, means the person can see at 6 metres what a normally sighted person could see much further away, that is at 24 metres.

What line should you be able to read on an eye chart?

A 3- to 4-year-old should be able to read the 20/40 line, and a 5-year-old the 20/30 line. Older children and adults should be able to read the majority of letters on the 20/20 line.

What is the meaning of 6 6?

Many people refer to ‘perfect’ vision as ‘6/6′ or ’20/20’ (US notation measured in feet), but this is not strictly true – these terms refer to ‘average’ vision. If you achieve a vision measurement of 6/6, this means that you can see at a distance of 6m what an average person also sees at the same distance.

When reading a Snellen eye chart What does 20/20 mean?

20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/100 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 100 feet.

How far away should a Snellen chart be?

20 feet
How is visual acuity measured with the Snellen chart? A Snellen chart is placed at a standard distance of 20 feet away in the US (or 6 meters in the rest of the world).

What does minus 4 mean in eyesight?

A visual acuity of -4.00 is roughly equivalent to 20/400 vision. A person with 20/400 eyesight needs to be within 20 feet of an object to see it clearly. However, a person with normal vision can see the object clearly from 400 feet away.

How many lines are in a Snellen eye chart?

The chart consists of 11 lines of block letters, beginning with a large single letter on the top row. The number of letters on each row increases moving from top to bottom.

What does 20 / 10 mean on a Snellen chart?

In the rare instances where vision may test better than normal on a Snellen chart, a value of 20/10 vision means that you can see clearly from a distance of 20 feet, what a person with normal vision sees well at a distance of 10 feet.

What do the numbers mean on an eye chart?

The Snellen chart (see image) is the most commonly used eye chart by health care professionals. There are two sets of numbers in a Snellen chart value: the numerator, the number above, and the denominator, the number below. The numerator stands for the distance between the patient and the chart, which is ideally 20 feet away.

What does the Big E in Snellen mean?

The “Big E” chart – or Snellen eye chart – is the most familiar type of visual acuity test. Hopefully by now, we’ve all seen one. The projected or wall-mounted Snellen eye chart, usually topped by the big letter “E”, is a common visual acuity test used to measure your sharpness of vision at multiple distances.