Norm of Tangent Screen Test
Normal, no loss of visual field.
Usage of Tangent Screen Test
Detection and monitoring of central visual field loss.
Description of Tangent Screen Test
A screening test that measures central vision. It is often used in the diagnosis of optic neuritis. The test involves having the client indicate when an object moving across a visual field of concentric circles is seen. The tangent screen consists of circular stitching every 5 degrees and radial stitching every 22.5 degrees on a black felt background. The test indicates field defects, or “scotomas,” based on client responses to moving or covering and exposing different portions of the target.
Professional Considerations of Tangent Screen Test
Consent form NOT required.
- The client should wear corrective lenses during the test.
- Have the client sit 1 meter from the target screen.
- Occlude one eye and perform the tangent screen test.
- Repeat the procedure with the other eye occluded.
- If the test is positive, the client should be referred to a neuro-ophthalmologist.
Client and Family Teaching
- The client should fixate on a central target.
- The examiner will move an object into the client's visual field at 30-degree intervals while he or she remains fixated on a central target.
- The client will signal when he or she sees the object come into view.
Factors That Affect Results
- The client must be able to cooperate with signaling when the object enters his or her visual field.
- Central visual boundaries vary with object size, brightness, contrast background, pupil size, and the client's age.
- The test is more sensitive the darker the illumination and the smaller the screen.
- Abnormal results warrant further examination with a perimeter to measure peripheral visual fields.