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Examination of the visual field, whether on a hemispheric surface (in which case one is doing perimetry) or on a flat surface (where one is doing campimetry) is perhaps the single most important diagnostic test in neuro-ophthalmology.
By visual field we mean the sum total of all visual sensation experienced by on observer with a fixed head and torso position, with eyes steadily gazing at a stationary object. It is useful to ask patients specifically whether they have been aware of visual field defects (called positive scotomas) or changes in their field of view, such as metamorphopsia. Temporary blurring of vision or passing bouts of darkening can be manifestations of the obscurations of vision associated with papilledema, or may suggest a problem with intermittent optic nerve compression.
As an initial step in the examination, the hands or fingers of the examiner can be held (under steady control of fixation) in either or both halves of the visual field, but moved in only one hemifield at a time (¦ Fig. Alternatively, when there is a suspicion of a hemianopic loss of field, the examiner can present both hands - held motionless - to either side of the vertical meridian, and ask the patient to report the total number of fingers being held out. When examining small children, the examiner can maintain control of fixation while an assistant positioned behind the child introduces objects of visual interest into the various quadrants of the peripheral visual field. Confrontation testing should be used routinely, when examining small children or uncooperative patients, whenever there is a suspicion of an advanced degree of visual loss. A very effective modification of confrontation testing, useful in cases of homonymous visual field loss, has the examiner face the patient at a distance of about 30 in., while the patient fixes on the center of the examiner's face. The Amsler grid is a visual field test that encompasses the central visual field to an eccentricity of 10°.
The Amsler grid test is particularly useful when evaluating subjective symptoms of distorted images, reading problems, or signs of abnormal fundus appearance in the macular region.
Tests of reading ability, with an age-appropriate correction for near, are an effective method for examining a portion of the central visual field. Testing of the symmetry of color saturation is best done with a brightly colored (red is usually best) object, such as the top of a mydriatic bottle. In cases where optic atrophy is seen or an optic neuropathy is likely (as in patients with relative afferent pupillary defects), testing of color saturation by these simple methods is often very helpful (see Chap. When correlating visual field defects with lesions in the afferent visual pathway, it is helpful to keep in mind that the optical inversion of images in the eye causes an inversion of the visual field with respect to the afferent pathway.
The currently accepted definition of the differential luminance sensitivity is related to the perimeter-specific maximum stimulus luminance capacity, complicating any comparison of results between differing instruments (¦ Fig. Multiple presentations with a constant stimulus value detect contours of isosensitivity, comparable to the isobars of meteorological maps, and are called isopters (¦ Fig. The dimensions of the test objects in the Goldmann perimeter are listed in ¦ Table 4.1, and their luminance levels are given in ¦ Fig.
For static profile perimetry, test objects are held in stationary positions, and their luminance levels are varied.
This is in contradistinction to field of view and oculomotor fields, in which it is understood that the head and eyes are allowed all freedom of movement.
One should also briefly inquire whether there have been episodic periods of visual loss that might indicate a problem with transient ischemic episodes (see Chap.
Not uncommonly, such symptoms begin as monocular, affecting one eye more heavily than the other, can be provoked with only minimal head movements, and indicate a disturbance of axoplasmic flow (see Chap. 2) is not a visual field test in the narrower sense, it should be used routinely as a quick and simple means of detecting afferent visual problems prior to a more thorough examination of the visual field.

The child's head movements on detection of these stimuli allow a judgment of the intactness of the visual field.
This preliminary method can also be put to use when circumstances do not allow use of conventional perimetric testing, such as at bedside consultations or in intensive care units. It allows for the subjective detection and ongoing monitoring of retinal, primarily macular, diseases.
A small, printed figure of the grid can be given to a patient for self-monitoring of visual changes at home.
Fluency of reading requires the normal function of a region at least 2° to the left and right and 1° above and below the point of central fixation (see Chap. The object should be shown to one eye and then the other by slowly alternating monocular occlusion.
Thus, objects in the superior visual field are imaged in the inferior half of the retina, and the encoded data for that image remain in the fibers of the inferior half the pathway, at least for the optic nerves, the chiasm, and the retrogeniculate path.
In kinetic perimetry, moving test objects are presented, while in static perimetry test objects are held in stationary positions when presented (¦ Fig. The stimulus is projected onto a matte surface of uniform light intensity that serves as an adapting background. This stimulus should be used in all kinetic perimetric tests so that the results of the various examinations can be more easily compared to one another. For diagnostic testing, the most discriminating (and therefore most significant) test objects are those of low luminance and small size. The various locations are arrayed along straight lines that pass through the field center, and the choices of lines are determined by the regions of interest in the central and paracentral parts of the visual field (usually within 30° of eccentricity). The visual field examination, in contradistinction to testing the pupils with the swinging flashlight test (see Chaps. Correlation between type of scotoma and location of disease in the visual pathway: If the defect lies in the superior half of the field, the causative lesion lies in the lower half of the retina or the lower half of the retrobulbar visual pathway, up to and including the primary visual cortex and vice versa.
It can detect monocular or significantly asymmetric, bilateral disturbances of vision in the prege-niculate (anterior) portions of the afferent pathway, and is an objective method that does not depend on the patient's cooperation.
The patient views an orthogonal grid of vertical and horizontal straight lines at a reading distance of about 17 in (40 cm). Looking at and describing the examiner's face in the case of a homonymous visual field defect (the corresponding values for eccentricity at a distance of 75 cm [approximately 30 in.] are shown). It made more sense to adopt a standard of reference in which the adapting background (surround) luminance level was agreed upon and held constant for all instruments.
The test objects (the projected light stimuli) are moved from nonseeing to seeing areas of the visual field, as perpendicular as is possible to the expected peripheral boundaries of perception (¦ Fig. Each isopter is tested within at least eight evenly spaced meridians, with stimuli moving from the periphery toward the center of the visual field. These are best suited to the detection of subtle, relative central and paracentral scoto-mas. 2 and 5), is not an objective test, but rather depends on the cooperation of the patient being examined.
Visual field defects have been divided into seven primary types (left side of diagram); in the right half of the diagram are commonly occurring subtypes.

The swinging flashlight test is indicated by any unexplained disturbance of vision, as well as by any suspicion of a lesion in the afferent visual pathway. The closer a defect is to the vertical meridian, and the smaller is the remaining, congruous portion of the paracentral visual field (¦ Fig.
If the patient with a hemianopic defect while fixing attention on the bridge of the examiner's nose can describe details only as far as the inner canthus of the examiner's eye, and all details peripheral to this locus are not seen, the visual field defect extends up to a point within 1° or less of fixation. When a reading problem is found, a careful ophthalmoscopic examination of the macula will often reveal the cause, but if the ocular fundus is unremarkable in appearance, there is likely to be a homonymous hemianopic visual field defect that divides the central visual field, including the point of fixation and the perifoveal field on the affected side. The common goal of these methods is to determine, as precisely as possible, the sensitivity of visual perception as a function of location in the visual field.
By choosing appropriate stimulus sizes and luminous intensities, the hill of vision's (con-ceptional) three-dimensional shape and size can be documented by plotting the various isopters. Given such cooperation, one can determine not only the depth of a defect, but also its size, shape, and location (¦ Fig.
The numerical labels in the left half of the diagram refer to the corresponding numbers of the Compendium of Visual Field Defects.
Conversely, if there is a suspicion of a hom-onymous visual field defect, if there are any ophthalmo-scopic signs of macular disease, complaints of reading problems or of amblyopia, tests of reading ability are a necessary part of the clinical evaluation. Using the same colored object, confrontation perimetry can be done, while monitoring the patient's fixation, by holding the object in various locations in the visual field. The correct physiologic term for sensitivity is differential luminance sensitivity ([DLS] also incremental luminance sensitivity). Particularly noteworthy responses are descriptions of sudden change in the color's appearance, when the object is moved into or out of the region of a visual field defect.
Automated static perimetry, in which static test object locations are distributed across a contiguous area of the visual field produces loci of DLS for each location in the pattern. Their angles of meridional orientation are analogous to those of the geographic meridians of the globe.
It is particularly suited to the examination of patients capable of only poor cooperation, permitting a high level of efficiency when examining large visual field defects.
This can sometimes be quite striking, particularly when crossing the vertical meridian in instances of hemianopie deficits in the visual field. The stimulus strength is expressed as a function of the incremental addition of the stimulus light to the adapting surround on which it is projected.
4.2) and for monitoring the temporal course of lesions affecting the afferent visual pathway. This chapter describes the various methods of perimetric testing, provides a classification system (¦ Fig. 4.3) of the visual field defects that are associated with neuro-ophthalmic disease, describes their various differential diagnoses, and shows which additional diagnostic tests they may indicate.

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