![]() These demonstrate the presence of localized field defects and their pattern. Zone 5: This zone comprises the pattern deviation numerical plot and the pattern deviation probability plot. The upper 95% of these values are arbitrarily taken as normal, and the lower 5% are considered abnormal. The normative database is calculated by collecting responses from a group ofhealthy subjects. It compares the dB value of the patient at all the retinal points tested to the normative data stored in the machine for that particular age. The total deviation numerical plot indicates the depth of the field defect. Zone 4: This zone comprises the total deviation numerical plot and total deviation probability plot. It indicates the progression of the visual field both in extent and in-depth over time at a glance, given the reliability indices are within normal limits. The greyscale is useful when comparing the fields of a patient on follow-up. They usually indicate a “trigger happy” patient who has responded without seeing the stimulus (false positive). The points with sensitivity greater than 40 dB are seen as white scotomas on the greyscale and require careful interpretation. The values closer to 0 dB are illustrated as black points of varying shades, whereas points close to 50 dB are illustrated as white points. It is not used for the final interpretation of the field test but is important for patient education. Zone 3: The greyscale graph is a color-coded representation of the retinal sensitivity of the patient. A good visual acuity with a less foveal threshold would indicate damage to the fovea, and a poor visual acuity with a good foveal threshold would indicate a refractive error that has not been corrected before performing the test. The foveal threshold should correspond to the visual acuity of the patient. Zone 2: This zone mentions the foveal threshold and the reliability indices. Zone 1: This section consists of the patient’s information like the patient’s name, date of birth, visual acuity, the refractive correction used for the patient for doing the test, and the patient’s pupil size Humphrey visual field test printout can be divided into eight zones for ease of understanding Reading the Humphrey visual field test printout. Instead the stimuli that are likely near threshold are tested. By taking into account a user’s results in nearby locations, stimuli that are unlikely to be seen, or extremely likely to be seen are not tested exhaustively. SITA allows for more rapid analysis than would be possible without forecasting. SITA is a forecasting procedure that uses Bayesian statistical properties that is similar to the methods used for providing weather information and predictions. The Swedish Interactive Thresholding Algorithm (SITA) is frequently used. If the patient is unable to see even the brightest, unattenuated stimlulus, it is reported as <0 dB. It is reported in decibels (dB) of attenuation, or dimming, extending from 0 dB (the brightest, unattenuated stimulus) to 51 dB (the dimmest, maximally attenuated stimulus). The luminous intensity of the stimuli can be varied over a range of 0.08 to 10,000 apostilbs (asb). Goldmann sizes I, II, and III are rarely used clinically. Goldmann size III (about ½ degree in diameter) is generally used, but Goldmann size V (approximately 2 degrees in diameter) is available for patients with decreased visual acuity (< 20/200) or other visual impairment. Stimuli vary in size and luminous intensity. Different locations within a given region of the visual field are tested until the threshold, or the stimulus intensity seen 50% of the time, is seen at each test location. When the patient sees a presented stimulus, he presses the button on a handheld remote control. It assesses the ability to see a non-mobile stimulus which remains for a brief moment (200 ms) in the visual field. As stated above, this test is an example of static perimetry. If the eyelid or lashes obstruct the visual axis, the lid may be taped to the forehead to lift it out of the way.ĭuring Humphrey Visual Field (HVF) testing, the patient places his head in the chinrest and fixes his gaze toward a central fixation point in a large, white bowl. To correct an astigmatism >0.75 diopters, a cylindrical lens must be used. Standard adjustments for presbyopia are available based on age alone. In addition, correction must be made for presbyopia, to reduce accommodative strain.
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