Understanding Visual Field Testing: Test Objects and Techniques
What Are Test Objects?
Eye doctors use special tools called test objects to check your visual field in front of a tangent screen. Moreover, these test objects help them map out how well you can see in different areas of your vision.
The Classic White Spot Test
The most common test object is a small white spot on a black wand. Furthermore, the doctor will move this spot around the tangent screen, which is a large black felt board with markings. You’ll sit about one meter away from the screen and focus on a central point. As the doctor moves the white spot, you’ll tell them when you can see it. This helps create a map of your visual field.
Size and Variety of Test Objects
Doctors use different sizes of test objects to get more detailed information. In fact, they might start with a larger spot and then use smaller ones to find the exact edges of your visual field. The size of the spot can range from 1mm to 10mm, depending on what the doctor wants to test.
Color and Complexity
Some doctors also use colored test objects. Additionally, they might use red, blue, or green spots to check for specific vision problems. For instance, red targets can help detect certain types of color blindness or eye diseases.
Advanced Testing Methods
Beyond simple spots, some doctors use more complex test objects. These can include small squares with patterns of lines or even tiny pictures. Consequently, these special objects help test for very specific vision issues.
Testing Each Eye Separately
The doctor will usually test each eye separately. They’ll have you cover one eye while they test the other. In this way, they can compare the visual fields of both eyes and spot any differences.
The Importance of Tangent Screen Testing
By using these various test objects, eye doctors can create a detailed map of your vision. Ultimately, this map helps them diagnose problems like glaucoma, eye-lid droop, or even some brain conditions that affect vision. The tangent screen test is a simple but powerful tool that gives doctors important information about your eye health.
The pictures show the test objects used with the tangent screen to check a person’s peripheral vision in diseases like glaucoma, brain tumors, and degenerative eye diseases. Probably from around 1900.
