Even if you miss one or two letters on the smallest line you can read, you are still considered to have vision equal to that line.

What is a Snellen chart? The so-called “Snellen chart” is an eye chart that is used to measure visual acuity, or how well somebody sees.

To determine the equivalent decimal acuity for the average we must use equation (2): fraction of the number of letters read correctly on a visual acuity line. 1.15 LogMar units, 0.141 – 11.5 lines in decimal units and 20/142 11.5 lines in Snellen units.

Snellen Test Chart

When using a mini-Snellen you must ask your patient to stand 3m from the chart and not 6….Assessing short distance vision:

1. Cover one eye and read from the set text for assessing acuity (N5 smaller than N8)
2. Read from largest to smallest.
3. Record smallest text size seen.
4. Do the same with other eye.

During a vision screening, you will typically be asked to sit or stand 20 feet away from the eye chart. In instances where the optometrist’s office is not 20 feet long, the chart may be located behind you and a mirror may be placed on the opposite wall to simulate a distance of 20 feet.

Does 20/20 mean perfect vision? No. 20/20 vision only indicates the sharpness or clarity of vision at a specific test distance. Other important vision skills, including peripheral awareness or side vision, eye coordination, depth perception, focusing ability and color vision, contribute to your overall vision ability.

Name 3 types of Snellen charts.

• Picture charts.
• Alphabet charts.
• E charts.

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1. Eat for your eyes. Eating carrots is good for your vision.
2. Exercise for your eyes. Since eyes have muscles, they could use some exercises to remain in good shape.
3. Full body exercise for vision.
4. Rest for your eyes.
5. Get enough sleep.
6. Create eye-friendly surroundings.
7. Avoid smoking.
8. Have regular eye exams.

You will be asked to remove your glasses or contact lenses and stand or sit 20 feet (6 meters) from the eye chart. You will keep both eyes open.

The third line is equivalent to 20/40, it is the driver’s test line.

5×5

Courier Bold

How to Do an At-Home Eye Test

1. Print or purchase a vision chart.
2. Tape the chart on a wall.
3. Place your child’s chair ten feet away from the chart.
4. Ask your child to cover one of his or her eyes.
5. Light the vision chart.
6. Have your child read each line of the chart.
7. Repeat the process with your child’s other eye covered.

The next time you are looking at an eye chart, you will notice that it does not contain every letter of the alphabet. The only letters used are C, D, E, F, L, N, O, P, T and Z. The reason for this is that some letters can be identified by the human brain even if they are too blurry to be seen clearly.

Distance visual acuity means, in these cases, the distance isn’t relevant, e.g. at 6m (6,000mm), the height of a 6/6 letter is 8.73mm; at 60m, it has to be 87.3mm and at 600m, 873mm etc. At 6m, the resolution is 1 minute of arc (letter height is 5 mins of arc), and thus 8.73/5=1.75mm is the gap size for a 6/6 letter.

If your number is between -0.25 and -2.00, you have mild nearsightedness. If your number is between -2.25 and -5.00, you have moderate nearsightedness. If your number is lower than -5.00, you have high nearsightedness.

6/6 vision describes being able to see at 6 metres what an average person can see at 6 metres. While 20/20 vision describes the same ability, but at 20 feet rather than 6 metres.

If you are able to read 6/6 without glasses clearly, then definitely there is no need to use glasses.

If you have a minus number, like -2.75, it means you’re short-sighted and find it more difficult to focus on distant objects. A plus number indicates long-sightedness, so objects up close appear more blurred or close vision is more tiring on the eyes.

This prescription is for the left eye, and -1.50 means that your nearsightedness is measured at 1 and 1/2 diopters. It’s considered a mild amount of nearsightedness.

Snellen recordings

There are three main points at which your eyesight will be tested for driving: when you take your driving test, a police roadside eye test, and at your optician visit.

If this is the smallest line a person can read, the person’s acuity is “6/12” (“20/40”), meaning that this person needs to approach to a distance of 6 metres (20 ft) to read letters that a person with normal acuity could read at 12 metres (39 ft).

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. If you notice any results that fall outside these standards, be sure to schedule an eye exam with your Vision Source doctor.

Having a 20/200 visual acuity means the smallest letters that you’ll identify from the chart by standing 20 feet away from it will be equal to the size of the smallest letters a person with “normal vision” would be able to identify at a distance of 200 feet from the chart.

If you can read the letters of the 8th line, your sight is optimal (visual acuity 20/20).

The bottom number indicates the distance at which a person with normal eyesight can read the same line. As an example, if the fifth row on the Snellen chart were the smallest row you could read, you would have 20/40 vision.