FAQ

  1. Definition

  2. How the test is performed

  3. How to prepare for the test

  4. What the risks are

  5. How the test will feel

  6. What abnormal results mean

  7. Why the test is performed

  8. Display calibration

  9. Defects

 

Definition    

The field of vision represents the relative ability to detect visual stimuli at different points. The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments", while field of view "refers to the physical objects and light sources in the external world that impinge the retina". In other words, field of view is everything that (at a given time) causes light to fall onto the retina. This input is processed by the visual system, which computes the visual field as the output. It can be tested most simply by confrontation, comparing the examiner's field of vision to the patients; with a grid pattern, like the Amsler grid; with a tangent screen, a flat screen positioned 1 m from the patient; with manual perimetry, the Goldmann perimeter (a bowel with the target 1/3 m from the patient's eye) or automatic perimetry.The visual field is the total area in which objects can be seen while the eye is focused on a central point. A visual field test measures how much 'side' vision you have.A perimetry test (visual field test) measures all areas of your eyesight, including your side, or peripheral, vision.             Return to top

How the test is performed     

The visual field is measured by perimetry. Essentially lights are flashed on, and you have to press a button whenever you see the light. You press a mouse button or use other means to indicate your response when you perceive the computer-generated light suddenly appearing in your field of view. If you are unable to see objects in an appropriate portion of your field of view, then you may have a blind spot indicating vision loss.

PC automated perimetry: The patient sits comfortably in front of a monitor/projector screen and asked to stare/focus on the target at the center of the screen. The eye that is not being tested is covered. Each eye is tested separately. Both eyes are refracted to the best corrected vision. Pupils are not usually dilated.. The proper focusing lens (eyeglass) for your eye is placed in front of your eye for the best vision. You may wear your own glasses if the correction is correct.  A computer-driven program flashes small lights at different locations within the screen's surface. The lights are bright or dim at different stages of the test. Some of the flashes are purely to check you are concentrating. A mouse is given to the patient to be used during the exam. The patient clicks the left mouse button whenever a light is seen. (You press the right mouse button to pause the exam. The responses are used to determine the presence of defects within the visual field.  A computer records the spot of each flash and if you pressed the button when the light flashed in that spot. Each eye is tested separately, and you should allow 15-30 minutes to have the whole test.

The software then automatically maps and calculates the patient's visual field. Plotting of the visual field is important for many disorders, particularly disorders of the optic nerve and brain.

VERY important: during the examination the patient should focus on the target at the center of the screen at all times. It is VERY important that you keep your eye focused on the central target throughout this examination. Your head should be still  To get the best results, you must be alert and concentrate on the central target. Some patients find it difficult to maintain their focus on the central target during field testing. Here are a few tips.You may pause the test for a short break, if necessary. Try to book the test during the hours when you feel most alert during the day. The results are affected by your level of vision and attentiveness.              Return to top

How to prepare for the test     

No special preparation is necessary for the test. You need to bring your reading. as well as your distance glasses with you.              Return to top

What the risks are     

There are not risks associated with this test, if you can use a computer then you can perform this test.             Return to top

How the test will feel     

There is no discomfort with this test. Occasionally a test might take a long time and may be tiring. It is a straightforward test, painless, and does not involve eye drops.             Return to top

What abnormal results mean     

Visual field tests assess the potential presence of blind spots (scotomas), which could indicate eye diseases. This would include glaucoma (an optic nerve disorder), strokes, brain tumors. etc. Patients often incorrectly assume that because they can see their hand waving off in the periphery, their peripheral vision is fine. However, testing peripheral vision with such a gross test as a waving hand is likely only to be useful for the most severe losses of peripheral vision, as sometimes occurs in stroke. The much more common and subtle peripheral vision deficits may only be detected by the sophisticated methodology of a computerized visual field analyzer. Once the results from this test are printed out by the computer, your eye doctor can easily detect blind spots in your visual field. The printout shows if there are areas of your vision where you did not see the flashes of light. These are areas of vision loss. Loss of peripheral vision is often an early sign of glaucoma. A perimetry test makes a detailed record of your visual fields. A blind spot in the field of vision can be linked to a variety of specific eye diseases, depending on the size and shape of the scotoma. A perimetry test can help find certain patterns of vision loss. This may mean a certain type of eye disease is present. It is the single best test to check for glaucoma. It is very useful in finding early changes in vision caused by nerve damage from glaucoma. Regular perimetry tests can be used to see if treatment for glaucoma is preventing further vision loss.             Return to top

Why the test is performed    

The test is performed to detect any loss of peripheral vision and provide a map of that loss which will be helpful in diagnosing the cause. The visual field test is used to determine whether the visual field is affected by diseases that cause local scotoma or a more extensive loss of vision. Visual field loss may occur due to disease or disorders of the eye, optic nerve, or brain.              Return to top

Display calibration

Any display with resolution: 1024x768 or higher, brightness: 300 cd/m2 or higher, contrast: 255/1 or higher should do.             Return to top

Color temperature:
The background of this form should be a neutral gray. If your background appears to have a color (red green or blue), your display is probably setup wrong. On most displays you can adjust the 'color' of the screen. Check your manual to see how to adjust this. Adjust the red, green and blue intensities, if necessary, so that the background of this form is a neutral gray. Most displays are aldready preset to this color temperature.             Return to top

Color depth:
Set your color depth to High Color (16 bit) or higher. 1) Click on the Windows "Start" button, 2) select "Settings", then 3) "Control Panel." 4) find the "Display" icon and click on it, 5) Click on "Settings" and  you should see the "Colors" box. 6) set it at "High Color (16 bit) or higher 7) Click on "Apply" - your computer may have to reboot in order for the new  settings to be used. If the "High Color (16 bit)" choice isn't available, you may need to change to a better video card. Most graphics cards are aldready preset to this color depth.

Set Brightness-Contrast:
Brightness sets the black point, determines the low light output level (black level) of the display. Contrast sets the white point and defines the range between black and white.  
Look carefully at the grey stepwedge target at the Display Calibration Form. You should be able to see 25, more or less distinct, shades of grey in the "steps" below the numbers. The lightest step is labeled "25" the darkest "1". The difference between steps 1 and 2 and the difference between 24 and 25 are usually the most difficult to see.If you see fewer than 25 steps you'll need to adjust your display. If your video card/display combination can't be adjusted to separate steps 1 & 2  and 24 & 25 or you can't see see 25 steps after adjustment you may need to replace your display and/or video card for optimum performance.  To adjust the display first set BRIGHTNESS to obtain a true black that will maximize contrast, then adjust CONTRAST for the appropriate brightness:  1) turn the CONTRAST control to minimum, 2) adjust the BRIGHTNESS control to reproduce black "1" correctly, 3) adjust the CONTRAST control to the  higher possible brightness level that displays step "24" and "25" correctly. When you adjust contrast it affects brightness and brightness affects contrast. You'll have to go back and forth between the two and tweak until both seem right.


visual field test calibrate screen stepwedge

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VISUAL FIELD DEFECTS

UNIOCULAR VISUAL FIELD DEFECTS

Temporal                          Nasal
normal visual field test

Normal

Temporal                         Nasal
visual field test Horizontal arcuate fiber defect

Horizontal arcuate fiber defect
Associated with Anterior ischemic neuropathy
and Giant cell arteritis

Temporal                         Nasal
visual field test Ceco Central scotoma

Ceco-Central scotoma
Visual loss pattern: Involves macula & enlarged blind spot
Associated with: Tobacco-Alcohol amblyopia; Leber's optic neuropathy

Temporal                         Nasal
visual field test Central scotoma

Central scotoma
Optic nerve lesion
(Sharp borders)

Temporal                         Nasal
visual field test Central scotoma escaping to periphery

Central scotoma
escaping to periphery


May suggest optic nerve neoplasm

Temporal                         Nasal
visual field test Central scotoma retinal damage

Central scotoma
Retinal lesion
(Distorted borders)

 

Temporal                         Nasal
visual field test Superior nasal quadrantanopia

 

Superior nasal quadrantanopia
Associated with Glaucoma

Visual field defects in glaucoma
may be unilateral or bilateral

Temporal                         Nasal
visual field test Central altitudinal sparing

Central altitudinal sparing
Associated with Visual loss in severe glaucoma

Temporal                         Nasal
visual field test Enlarged blind spot

Enlarged blind spot & narrowed visual field
Associated with papilledema

Temporal                         Nasal
visual field test Pie in the sky field defect

Pie in the sky field defect
Visual loss involves upper temporal field
Anterior temporal lesion

Temporal                         Nasal
visual field test Ring scotoma

Ring scotoma
Retinal lesion
Associated with retinitis pigmentosa

 

BINOCULAR VISUAL FIELD DEFECTS             Return to top

 

visual field test Non congruent superior binocular defects

Non-congruent superior binocular field defects
Associated with Temporal lobe lesion

visual field test Wedge shaped homonymous hemianopia

Wedge-shaped homonymous hemianopia (Left)
Associated with right
Lateral choroid artery (PCA) lesion;
Lateral geniculate ischemia

visual field test 1/2 field defect

1½ field defect
Associated with Anterior lateral chiasm defect

visual field test Bilateral noncongruous central scotoma

Bilateral, noncongruous central scotoma
breaking through to upper periphery

Associated with
Leber's hereditary optic atrophy

visual field test Binasal hemifield defects

Binasal hemifield defects 1

Anatomic: Lesion lateral to chiasm (Aneurysm)
Other: Glaucoma; Optic disc drusen;
    Chronic raised intracranial pressure; Syphilis (Tabes)

 

visual field test Altitudinal hemianopia

Altitudinal hemianopia
Associated with Occipital cortex ischemia
(Posterior circulation)

visual field test Bitemporal hemianopia

Bitemporal hemianopia

Anatomy: Lesions of the optic chiasm
Lesion types
    Pituitary adenoma
    Sellar meningioma
Partial defects may require red object to detect

 

visual field test Bitemporal central scotomas

Bitemporal central scotomas

Anatomy: Posterior chiasm lesion

Lesion types
    Hydrocephalus
    Craniopharyngioma
    Pinealoma

 

visual field test Bilateral central scotomas

Bilateral central scotomas
Associated with
Toxic disorders (Lead, CS2)
& Multiple sclerosis

visual field test congruent partial hemianopia

Congruent partial hemianopia
Associated with Occipital lobe lesion

visual field test Preserved temporal crescent

Preserved temporal crescent: With Homonymous Hemianopsia 1

  • Localizing Sign: Intracranial disease

  • Etiologies: Cerebrovascular disease (Most common), Birth injury, Trauma, Aneurysm, Migraine.

  • Anatomy

    • Sparing of most rostral portion of calcarine cortex

    • Occipital lobe more common than optic radiations

     

  • Visual pathways: Right and left monocular fields

    • Partially overlapping regions: Binocular field extends 120°

    • Monocular temporal crescents: Extend an additional 45° on each side

  • Clinical associations

    • Dyslexia: With preserved crescent in Right eye

    • Hallucinations: 44%

 

visual field test Homonymous hemianopia

Homonymous hemianopia
Associated with severe contralateral
Optic tract or Hemisphere lesion

visual field test Spared binocular macular vision

Spared binocular macular vision
Associated with
Posterior cortical watershed infarction;
Psychogenic tunnel vision

visual field test Quadruple sectoranopia

Quadruple sectoranopia (Left)
Associated with right
Distal anterior choroid artery (ICA) occlusion;
Lateral geniculate ischemia

The information provided 'as is' and should not be used during any medical emergency or for the diagnosis nor for the treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Visual-Field.com makes no representation or warranty regarding the accuracy, reliability, completeness of the content, text or graphics. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites.             Return to top

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