What is a normal result on the Snellen visual acuity test?

What is a normal result on the Snellen visual acuity test?

For example, 20/20 (6/6) is considered normal. 20/40 (6/12) indicates that the line you correctly read at 20 feet (6 meters) away can be read by a person with normal vision from 40 feet (12 meters) away.

How is the visual acuity test scored?

Visual acuity is expressed as a fraction, such as 20/20. Having 20/20 vision means that your visual acuity at 20 feet away from an object is normal. If you have 20/40 vision, for example, that means you need to be 20 feet away to see an object that people can normally see from 40 feet away.

How many types of Snellen charts are there?

These include Snellen Chart, LogMAR Chart, Jaeger Chart, E Chart, and Landolt C Chart. These charts are described thoroughly below. It was developed by Dutch ophthalmologist Herman Snellen in 1862 and thus is named after him. Snellen used symbols based on a 5×5 unit grid while developing the charts.

What is a good visual acuity score?

What does 20/20 vision mean? 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.

How do you calculate Snellen letter size?

Optotype size calculation is same as Snellen’s optotypes. Usually, 14 lines are taken. Letter separation (space between letters on each line) = letter width on that line. Row separation (space between the rows of adjacent lines) = height of letters in a smaller row.

How is Snellen chart used?

Snellen chart, also called Snellen eye chart, chart used to measure visual acuity by determining the level of visual detail that a person can discriminate.

What does 6/24 mean in an eye test?

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. The American still use feet and “20 /20 vision” means the person can see at 20 feet what they should be able to see at 20 feet.

What is the meaning of 6 6 and 6 9 vision?

The ability for a person to read or see the last line on the visual chart is recorded (at a test distance of 20 feet or 6 metres) and defined by terminology 6/6 vision (normal), 6/9 (one line less than 6/6), 6/12 (2 lines less than 6/6) etc. as the Snellen fraction. Distance vision impairment is considered.

What size is the Snellen chart?

5×5
Snellen designed his optotypes on a 5×5 grid, on which the line thickness is one unit and the letter width and height are five units. This system is followed for most letter and number charts.