Spectacles must not be worn because they can cause false defects in the visual field due to their shape 6).
Refractive correction must be made with a test lens. Each eye is tested separately while the opposite eye is covered with a patch. The individual must be able to maintain a constant gaze toward a fixed location for several minutes. Several basic conditions must be met for a successful map of the visual field to be produced by any method. For dim night lighting (scotopic) conditions, the mid periphery is the most sensitive region of the visual field. The average blind spot is 7.5° in diameter, vertically centered 1.5° below the horizontal meridian 5). Definitive location varies slightly on an individual basis. A physiologic scotoma (a blind spot) exists at 15° temporally where the optic nerve leaves the eye. At this location, no photoreceptors are present, creating a normal absolute scotoma 4). Nerve fibers pass through the sclera at the optic nerve head, typically 10-15º nasal to fixation. The field of vision is often depicted as a three dimensional hill, with the peak sensitivity to stimuli occurring at the point of fixation under photopic conditions, decreasing rapidly in the 10º around fixation, and then decreasing very gradually for locations further in the periphery 3). From the point of fixation, stimuli can typically be detected 60º superiorly, 70º inferiorly, 60º nasally, and 100 degrees temporally (laterally) 2), though the true extent of the visual field depends on several features of the stimulus (size, brightness, motion) as well as the background conditions. Under normal daylight (photopic) conditions, the smallest or least intense visible objects are only seen in the central region of the visual field. The normal eye can detect stimuli over a 120º range vertically and a nearly 160 degree range horizontally. If there is uncertainty, consult with colleagues.Consider the findings in the context of the physical exam findings and the results of other tests and imaging. Generally six or more visual field tests are necessary to evaluate disease progression. Do not take a shortcut by comparing these fields to only the most recent visual field, as this may be misleading. Compare these visual fields with each of the patient’s previous visual field tests to identify progression of visual field loss.Refer to the chart to determine the likely region of damage to the visual pathway. Identify the shape of the visual field defect.Refer to the patterns of visual field defects chart to determine the likely region of damage to the visual pathway. Locate the region of the visual field deficit.Damage in the visual fields of both eyes could be due to damage at the level of the optic chiasm and beyond, or due to separate damage in the visual pathways of each eye anterior to the chiasm. the cornea, vitreous, retina, or optic nerve of only one eye). Is the visual field damage present in one or both eyes? If only one eye is affected, the damage is located in front of the optic chiasm (i.e.If one or both of the eyes exhibit abnormal fields, continue to step 3. If the fields are within normal limits, there is no further analysis. Look at the sensitivity map to determine whether the field is within normal limits.Look for signs of unreliable fields: Are there many false positives (> 15% using SITA), or losses of fixation (> 33%)? Is there a lens rim artifact or uncorrected ptosis? If the fields appear reliable, continue to step 2.These guidelines must be followed in this order for the most accurate results. Available techniques can test the full field (including confrontation, tangent screen, Goldmann perimetry and automated perimetry), or assess just the central field of vision, such as the Amsler Grid. Several methods for assessing visual field loss are available, and the choice of which to use depends on the patient’s age, health, visual acuity, ability to concentrate, and socio-economic status. In glaucoma – as well as other conditions – it is vital to repeat visual field testing to track any changes over time.Įxamining visual fields is an integral part of a full ophthalmic evaluation. Careful detection of visual field defects can be diagnostic of many eye and/or neurological conditions, including glaucoma or retinitis pigmentosa. Central and peripheral vision is tested by using visual field tests. Visual field test looks for visual field defects and their location. Features of glaucomatous visual field defects.Interpreting the Humphrey visual field test.Humphrey visual field test results interpretation.Goldmann visual field test results interpretation.Testing to confrontation with both eyes open.