If you use eyeglasses or contact lenses for driving or other distance vision tasks, wear them during the test. Cover one eye with your hand, a large spoon or some other item that completely blocks the vision of the coveredeye. Identify a line on the chart you can comfortably read. Read the letters on that line aloud. Have your assistant stand near the chart and record your accuracy. Have your assistant stop you when you fail to correctly identify at least 50 percent of the letters on a line.
Hemoglobin Level Chart. Sleep Duration Time Chart. Fever Temperature Chart. Height Weight Chart. Blood Cholesterol Level Chart. Blood Pressure Chart. Sometimes eye doctors can't use a standard Snellen eye chart. In these situations, the doctor might use a modification of the Snellen test called a "tumbling E" chart. A young child is having an eye test and either doesn't know the alphabet or is too shy to read letters aloud.
The patient has a handicap that makes it difficult or impossible to recognize letters or read them aloud. The tumbling E chart features the same scale as a standard Snellen eye chart, except all characters on the chart are a capital letter "E," rotated in different increments of 90 degrees. During a tumbling E test, the eye doctor will ask the person being tested to use either hand with their fingers extended to show which direction the "fingers" of the E are pointing: right, left, up or down.
Studies have shown that the measurements taken using a tumbling E chart are virtually the same as the measurements from a standard Snellen eye chart. Download a "tumbling E" eye chart. To evaluate your near vision , your eye doctor may use a small hand-held card called a Jaeger eye chart. The Jaeger chart consists of short blocks of text in various type sizes.
A Jaeger eye chart contains several blocks of gradually larger text and is used to test near vision. A Jaeger eye chart can be used in two different ways, depending on what your eye doctor is trying to measure:. The chart is held at a specific reading distance such as 14 inches and you are asked to read the passage with the smallest type you can see. There have been several modifications of the Jaeger chart or "Jaeger card" by different manufacturers since its invention in Modern Jaeger charts are not standardized, so the letter sizes on different Jaeger cards can vary slightly.
Download a Jaeger eye chart. It means that, while standing 20 feet away, you can read a letter that most human beings should be able to read from 20 feet. In the United States, the standard placement of the eye chart is on a wall that's 20 feet away from your eyes.
However, since many eye doctors have offices shorter than 20 feet long, the eye chart may hang behind the patient chair and reflect onto mirrors to simulate a distance of 20 feet. Eye charts can be configured in various ways. This means that your visual acuity is very poor. Since eye charts only measure visual sharpness, they can help your eye doctor figure out whether you need prescription eyeglasses or contact lenses. They can also help your local Department of Motor Vehicles determine who needs corrective lenses to drive and who shouldn't drive due to legal blindness.
But eye charts don't measure your peripheral vision , depth perception, color vision or ability to perceive contrast.
0コメント