Visual field
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This document defines the visual field and describes how it is examined. The visual field refers to the area that can be seen and has normal limits of 60 degrees superiorly, 60 degrees nasally, 75 degrees inferiorly, and 100 degrees temporally. The visual pathway involves the optic nerves transmitting signals from the retina to the brain. Visual field examinations assess central and peripheral vision using techniques like confrontation testing, Amsler grids, and perimetry. Common visual field defects include scotomas and hemianopias, which can be caused by conditions like glaucoma and optic neuropathies.
Visual field
- 2. contents Definition , normal limits . Visual (optic nerve) pathway. Examination of visual field . Visual field defect . References .
- 3. Definition The visual field refers to the total area in which objects can be seen in the side (peripheral) vision while you focus your eyes on a central point . or it is the portion of the subject's surroundings that can be seen at one time.
- 4. Normal limits 60°superiorly . 60°nasally . 75°inferiorly . 100° temporally * The macula corresponds to the central 13 degrees of the visual field; the fovea to the central 3 degrees. ** the visual field is limited by size of retina and margins of the orbit .
- 6. Visual (optic nerve) pathway. The neurons from each eye form the two optic nerves that transmit visual information to the brain.after leaving the back of the eye it travels to the optic chiasm, located just below and in front of the pituitary gland. In the optic chiasm, the optic nerve fibers emanating from the nasal half of each retina cross over to the other side; but the nerve fibers originating in the temporal retina do not cross over. From there, the nerve fibers become the optic tract which continues to the lateral geniculate nucleus . from the lateral geniculate body, fibers of the optic radiation pass to the visual cortex in the occipital lobe of the brain . The visual cortex ultimately interprets the electrical signals produced by light stimulation of the retina, via the optic nerve, as visual images .
- 9. Examination of the visual field A visual field examination can detect dysfunction in central and peripheral vision which may be caused by various medical conditions such as glaucoma, stroke, brain tumours or other neurological defects. Confrontation visual field testing * Sit or stand about 50 cms away from the patient ask the patient to cover or close one eye and you close the one opposite ask the subject to stare at your eye or nose and you do the same .
- 10. (Confrontation visual field testing (continued * Starting at the top outer quadrant, move your fingers (or the pin( in from the side, wiggling them as they go, and ask the patient to tell you when he first see your fingers and, as you move towards the centre, whether they disappear. * Repeat the process in each quadrant and for each eye separately.If you detect a defect, reexamine that area and define it further. * This technique compares the patient's visual field with yours, so it does assume normal examiner visual fields!
- 12. Amsler grid testing * This assesses the central 10° the visual field. It detects central and paracentral scotomas. * In the test, the person looks with each eye separately at the small dot in the center of the grid. Patients with macular disease may see wavy lines or some lines may be missing.
- 14. Perimetry ( Static and kinetic( * Static Perimetry :- points of light are flashed onto a white screen and the observer is asked to press a button if he or she sees it. The most common perimeter used is the automated Humphrey Field Analyzer. This can assess various amounts of the visual field (10° to full field(.
- 16. (Perimetry ( Static and kinetic * Kinetic perimetry :- Here the patient is asked to sit 1 meter from a screen with a target on the center. The eye that isn't tested is covered during the exam. While the patient stares at the target the examiner will move an object toward the patient's visual field. The patient signals the examiner when the object comes into view. This exam allows the patient's visual field to be mapped. • The most commonly used kinetic test is Goldmann perimetry.
- 20. Visual field defects * Visual field defect :- a portion of visual field missing. This may be central or peripheral . There are many causes of visual field loss : Central field loss occurs with: Optic neuropathy Macular degeneration Macular holes Cone dystrophies Peripheral field loss occurs with: Retinitis pigmentosa Chorioretinitis Glaucoma Retinal detachment Lead poisining
- 21. Visual field defect types of visual field defects:- • Scotoma :- It is a blind spots surrounded by normal visual field. Types : Central scotoma :- Visual field loss appears in the central vision . Peripheral scotoma :- Visual field loss appears in the peripheral region.
- 26. Visual field defect • Hemianopia :- binocular visual defect in each eye's hemifield. Bitemporal hemianopia :- the two halves lost are on the outside of each eye's peripheral vision, effectively creating a central visual tunnel. Homonymous hemianopia :- the two halves lost are on the corresponding area of visual field in both eyes, i.e. either the left or the right half of the visual field. Altitudinal hemianopia :- upper or lower halves of visual field are lost; may be unilateral or bilateral. Quadrantanopia :- ( incomplete hemianopia) Visual field loss in a quarter of the visual field of the eye. The defect is usually bilateral.
- 30. References www.medlineplus .com Smythies J (1996). "A note on the concept of the visual field in neurology, psychology, and visual neuroscience". Jay WM (1981). "Visual field defects". American Family Physician 24 (2): 138–42. PMID 7258077.
- 31. Names • علي صل ح مهدي • عبد ا حاكم مرزوك • رند هادي كريم
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