Visual Fields Test
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Related to Visual Fields Test: perimetry
Visual Fields Test
Synonym/acronym: Perimetry, VF.
To assess visual field function related to the retina, optic nerve, and optic pathways to assist in diagnosing visual loss disorders such as brain tumors, macular degeneration, and diabetes.
Area of applicationEyes.
The visual field (VF) is the area within which objects can be seen by the eye as it fixes on a central point. The central field is an area extending 25° surrounding the fixation point. The peripheral field is the remainder of the area within which objects can be viewed. This test evaluates the central VF, except within the physiological blind spot, through systematic movement of the test object across a tangent screen. It tests the function of the retina, optic nerve, and optic pathways. VF testing may be performed manually by the examiner (confrontation VF examination) or by using partially or fully automated equipment (tangent screen, Goldman, Humphrey VF examination). In the manual VF test, the patient is asked to cover one eye and fix his or her gaze on the examiner. The examiner moves his or her hand out of the patient’s VF and then gradually brings it back into the patient’s VF. The patient signals the examiner when the hand comes back into view. The test is repeated on the other eye. The manual test is frequently used for screening because it is quick and simple. Tangent screen or Goldman testing is an automated method commonly used to create a map of the patient’s VF.
This procedure is contraindicated for
- Detect field vision loss and evaluate its progression or regression
- Normal central vision field extends in a circle approximately 25–30° on all sides of central fixation and out 60° superiorly (upward), 60° nasally (medially), 75° inferiorly (downward), and 90° temporally (laterally). There is a normal physiological blind spot, 12° to 15° temporal to the central fixation point and approximately 1.5° below the horizontal meridian which is approximately 7.5° high and 5.5° wide. The patient should be able to see the test object throughout the entire central vision field except within the physiological blind spot.
Abnormal findings related to
- Blurred vision
- Brain injury
- Brain tumors
- Cerebrovascular accidents
- Choroidal nevus
- Diabetes with ophthalmic manifestations
- Macular degeneration
- Macular drusen
- Optic neuritis or neuropathy
- Ptosis of eyelid
- Retinal detachment, hole, or tear
- Retinal exudates or hemorrhage
- Retinal occlusion of the artery or vein
- Retinitis pigmentosa
- Rheumatoid arthritis
- Subjective visual disturbance
- Use of high-risk medications
- VF defect
- Vitreous traction syndrome
Factors that may impair clear imaging
- An uncooperative patient or a patient with severe vision loss who has difficulty seeing even a large vision screen may have test results that are invalid.
- Assess and make note of the patient’s cooperation and reliability as good, fair, or poor, because it is difficult to evaluate factors such as general health, fatigue, or reaction time that affect test performance.
Nursing Implications and Procedure
- Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
- Patient Teaching: Inform the patient this procedure assesses visual field function and vision loss.
- Obtain a history of the patient’s complaints, including a list of known allergens.
- Obtain a history of the patient’s known or suspected vision loss; changes in visual acuity, including type and cause; use of glasses or contact lenses; eye conditions with treatment regimens; eye surgery; and other tests and procedures to assess and diagnose visual deficit.
- Obtain a history of symptoms and results of previously performed laboratory tests and diagnostic and surgical procedures.
- Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
- Measure visual acuity with and without corrective lenses prior to testing. Instruct the patient to wear corrective lenses if appropriate and if worn to correct for distance vision. Instruct the patient regarding the importance of keeping the eyes open for the test.
- Review the procedure with the patient. Address concerns about pain and explain that no discomfort will be experienced during the test. Inform the patient that a health-care provider (HCP) performs the test in a quiet, darkened room and that to evaluate both eyes, the test can take up 30 min.
- Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
- Note that there are no food, fluid, or medication restrictions unless by medical direction.
- Potential complications: N/A
- Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient.
- Instruct the patient to cooperate fully and to follow directions. Ask the patient to remain still during the procedure because movement produces unreliable results.
- Seat the patient 3 ft away from the tangent screen with the eye being tested directly in line with the central fixation tangent, usually a white disk, on the screen. Cover the eye that is not being tested. Ask the patient to place the chin in the chin rest and gently press the forehead against the support bar. Reposition the patient as appropriate to ensure the eye(s) to be tested are properly aligned in front of the VF testing equipment. While the patient stares at the disk on the screen, the examiner moves an object toward the patient’s visual field. The patient signals the examiner when the object enters his or her visual field. The patient’s responses are recorded, and a map of the patient’s VF, including areas of visual defect, can be drawn on paper manually or by a computer.
- Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
- Recognize anxiety related to test results, and be supportive of impaired activity related to vision loss, perceived loss of driving privileges, or the possibility of requiring corrective lenses (self-image). Discuss the implications of the test results on the patient’s lifestyle. Provide contact information, if desired, for a general patient education Web site on the topic of eye care (e.g., www.allaboutvision.com). Provide contact information regarding vision aids, if desired, for ABLEDATA (sponsored by the National Institute on Disability and Rehabilitation Research [NIDRR], available at www.abledata.com). Information can also be obtained from the American Macular Degeneration Foundation (www.macular.org), the Glaucoma Research Foundation (www.glaucoma.org), and the American Diabetes Association (www.diabetes.org).
- Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
- Instruct the patient in the use of any ordered medications. Explain the importance of adhering to the therapy regimen. As appropriate, instruct the patient in significant side effects and systemic reactions associated with the prescribed medication. Encourage him or her to review corresponding literature provided by a pharmacist.
- Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.
- Related tests include CT brain, EEG, evoked brain potentials, fluorescein angiography, fructosamine, fundus photography, glucagon, glucose, glycated hemoglobin, gonioscopy, insulin, intraocular pressure, microalbumin, plethysmography, PET brain, and slit-lamp biomicroscopy.
- Refer to the Ocular System table at the end of the book for related tests by body system.