Journal of Neuro-Ophthalmology, March 1993, Volume 13, Issue 1

The four-meter confrontation visual field test.

Confrontation visual fields have limited value in testing paracentral vision. We have used a four-meter confrontation test for several years at the Mayo Clinic for screening of the central field. This test can identify paracentral scotomas and macular sparing in a homonymous hemianopia. The optics of this technique parallel those of the two-meter tangent screen examination in which a scotoma is greatly enlarged by doubling the test distance. Although in common usage by some neuro-ophthalmologists, this simple technique is useful as an office screening device for evaluating paracentral vision.

!oumal of Clmical N~lno-orhthalmology 13(l!: 40-43. 1993. © 1993 Raven Press, Ltd . " :w York The Four-Meter Confrontation Visual Field Test Sylvia R. Kodsi, M.D. and Brian R. Younge, M.D. Confrontation visual fields have limited value in testing paracentral vision. We have used a four-meter confron­tation test for several years at the Mayo Clinic for screen­ing of the central field. This test can identify paracentral scotomas and macular sparing in a homonymous hemi­anopia. The optics of this technique parallel those of the two-meter tangent screen examination in which a sco­toma is greatly enlarged by doubling the test distance. Although in common usage by some neuro-ophthalmol­ogists, this simple technique is useful as an office screen­ing device for evaluating paracentral vision. Key Words: Kinetic technique-Static technique­Macular function. From the Department of Ophthalmology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, USA. Presented at the meeting of the American Ophthalmological Society, Hot Springs, Virginia, May 17 to 20, 1992; manuscript will be published in Transactions of the American Ophthalmological Society as a result of the meeting presentation. Address correspondence and reprint requests to Dr. Brian R. Younge, Department of Ophthalmology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. 40 Ophthalmologists and neurologists have seen visual field tests evolve from various confrontation visual field tests to computerized automated pe­rimetry. However, it remains a challenge to iden­tify visual field defects by confrontation tests prior to performing formal visual field tests or when for­mal visual field tests are unavailable. In this article we describe a confrontation visual field test that was originated by Dr. Thomas P. Kearns and has been used at the Mayo Clinic for more than 30 years. We call this the four-meter (4-m) confronta­tion visual field test. This test is extremely valuable as a supplement to the standard confrontation vi­sual field test done at 0.5 m, especially in detecting small paracentral scotomas. It is easy to perform, takes but a few seconds, and costs nothing, and as far as we know, this test has not been described in the literature. An examiner can perform confrontation visual field tests by kinetic or static techniques (1). With kinetic techniques, the examiner's fingers or an ob­ject is moved from the periphery toward fixation and the points where the patient first becomes aware of the target are identified. Confrontation visual field testing by the static method is usually by the finger counting method, which was first described by Welsh in 1961 (2). The examiner pre­sents one or two fingers in each of the four quad­rants of the visual field and the patient identifies the number of fingers seen. Static visual field testing is much more sensitive than kinetic visual field testing for quantitative pe­rimetry. In both the kinetic and the static methods of confrontation visual field testing, previous liter­ature described testing distances of 1 m or less, with the average distance close to 0.5 m (1-5). Al­though confrontation visual field testing at 0.5 m is excellent for detection of large visual field defects, small paracentral or arcuate defects that can occur with occipital lobe infarcts, ischemic optic neuritis, glaucoma, and early chiasmal lesions may escape detection. Often the presenting complaint of these FOUR-METER VISUAL FIELD TEST 41 FIG. 1. Limit of visual field at 1 m increases at 2 m in the normal circumstance. In the tunnel field, the area stays the same at 2 m, a physiologic impossibility. patients is difficulty in reading secondary to miss­ing parts of letters or words. If the examiner uses the 4-m confrontation visual field test in addition to the standard D.S-m test, there is a better oppor­tunity to identify these defects. The 4-m confrontation visual field test originates from the same concept that is used to identify the hysterical patient or malingerer with a markedly constricted visual field. In this situation, a tangent visual field test is performed at testing distances of 1 m and 2 m. If an organic basis exists for the constricted visual field, then the size of the visual field will enlarge appropriately when the results of the I-m test and the 2-m test are compared. How­ever, if there is hysterical field loss or feigned field loss, then the visual field will remain the same size at 1 m and 2 m (Fig. 1). This has also been de­scribed in the past as funnel and tunnel visual fields, respectively (3). Thus, the size of a normal patient's visual field will enlarge as one increases the distance from the patient to the tangent screen if the target size remains relatively constant. It is generally wise always to perform the stan­dard D.S-m confrontation visual field test prior to the 4-m test. This educates the patient in correctly fixating straight ahead and ensures more accurate fixation at the longer distance. The examiner backs away 4 m from the patient to perform the 4-m test. While the patient occludes one eye, the examiner presents one or two fingers in various quadrants. The patient identifies the number of fingers present while maintaining fixation on the tip of the examiner's nose. Also, simultaneous presentation of one or two fingers in the opposing nasal and temporal fields can be used to detect the extinction phenomenon or for comparison of hemifields. In the presence of a homonymous defect, the exam­iner can also perform the 4-m test by moving the finger from the periphery toward the fixation point and identifying the point where the patient first sees the target, thus obtaining an estimate of mac­ular sparing or its absence. Both eyes can be opened if a homonymous scotoma exists, assum­ing the patient fixates binocularly. The area of a scotoma increases by a factor of 64 when the testing distance increases from D.5 m to 4 m (Fig. 2). This increase in the area of the small paracentral scotoma explains why the 4-m con­frontation visual field test can easily identify small paracentral visual field defects that the D.S-m con­frontation visual field test is unable to locate. The increase in area of the visual field at 4 m allows us to identify small paracentral scotomas; however, this increase in area limits the 4-m con­frontation visual field test to detection of central or paracentral defects. To further explain the limita­tions of this test we can return to the example of the optic nerve scotoma. If the examiner's nose is the fixation target, then the average examiner's arms are too short to locate the blind spot with the 4-m confrontation visual field test (Fig. 3). Therefore, the 4-m confrontation visual field test can only detect scotomas that are closer to fixation than the blind spot. The following examples illustrate the value of the 4-m confrontation visual field test. A patient may have a small central homonymous hemiano­pia if a tiny infarct involving the occipital lobe has occurred. This defect may only involve the central 5° to 10° near fixation and may escape detection by standard confrontation test. However, when the examiner moves away from the patient to a dis­tance of 4 m, the scotoma will enlarge enough so that the examiner can easily detect the small cen­tral homonymous hemianopia. 2 meters 2 meters 1 meter 1 meter Tunnel vision Eye Nodal point ~~~f. :J'.I.·...j Optic nerve \ J±j~ z \ ~x , "" 17 mm L------:= 500Jl1m .___ .' 175mml~ Blind 1.5mm 4000 mm spot FIG. 2. The optic nerve is projected in space as a blind spot with dimensions w x x at 500 mm, and these increase to y x z at 4,000 mm. I eli" Neuro-ophthalmol. Vol. 13. No. 1. 1993 42 S. R. KODSI AND B. R. YOUNGE Nodal point \ fovea 17 mm \ 4mm optic nerve 4000 mm Blind spot @ Fingers x Examiner's nose FIG. 3. At 4 m, the distance of the blind spot from the point of fixation, in this case the examiner's nose, is out­side the reach of the examiner's arm. The area of field being tested is within 5° to 10° of fixation. The visual field in Fig. 4 is from a patient with a central left homonymous hemianopia that we were unable to detect by the standard 0.5-m con­frontation visual field test. However, it was easily identified by the 4-m test. The patient's visual field also demonstrates the concept of enlargement of the scotoma by increasing the testing distance while maintaining the size of the target relatively constant. Other examples of difficult visual field defects to detect with the standard confrontation visual field test at 0.5 m would be the small altitu­dinal paracentral defect often seen in ischemic op­tic neuritis or low-tension glaucoma. Again, these scotomas may be too small to detect by confronta­tion visual field testing at 0.5 m; however, at 4 m the examiner can locate the scotoma. Although the major purpose of the 4-m confron­tation visual field test is to detect small paracentral scotomas, it is also of value in the detection of macular sparing in hemianopic and quadrantan­opic defects. The standard confrontation visual field technique will detect the presence of a hom­onymous hemianopia or a quadrantanopia but the examiner may not be able to identify them if mac­ular sparing is present. However, the 4-m confron­tation visual field test will indicate macular sparing if the patient can identify the fingers present in the hemianopic or quadrantanopic field at 4 m. The following case illustrates the examiner's ability to detect macular sparing with the 4-m con­frontation visual field test. A 31-year-old woman was cortically blind secondary to anoxic encepha­lopathy. Her visual acuity was 20/25 in both eyes; however, she did not have any peripheral vision. We were unable to detect the extent of her macular sparing with the standard 0.5-m confrontation vi­sual field test. However, with the 4-m confronta­tion visual field test we found that she had a com­plete right homonymous hemianopia and a left homonymous hemianopia with macular sparing, demonstrated later with tangent visual field test­ing (Fig. 5). Another application of the 4-m confrontation vi­sual field test is in detecting functional vision loss (hysteria or malingering). If a patient is shown to have a markedly constricted visual field of organic 35 2000 18 ~OOO 18 ~ 1000 2000 __eI l""'--_ _1_ 1000 o JChn Neuro-ophthalmol. Vol. 13. No. 1. 1993 2 000 FOUR-METER VISUAL FIELD TEST -L 1000 43 FIG. 5. Residual fields of a patient with cortical blindness due to anoxia. Small resid­ual area of macular sparing to the left of the fixation spot, which at 4 m was easily discerned by the examiner. etiology by standard O.S-m confrontation visual field testing, then the visual field test should not be constricted at 4 m because only the control 10° is being tested. However, a malingerer or a hysterical patient with a constricted visual field will exhibit "tunnel vision" and will also have a constricted field at 4 m. The visual field in Fig. 6 demonstrates tunnel fields in a young woman with functional vision loss who demonstrated a markedly con­stricted visual field at 0.5 m and at 4 m. Additional applications of the 4-m confrontation visual field test include testing the visual field of very young children, elderly demented patients, and patients in intensive care units. All of these individuals may not be able to perform formal vi­sual field tests, and the 4-m test is an extremely useful supplement to the standard O.s-m test in the evaluation of these patients. Lastly, the 4-m visual FIG. 6. Tunnel fields of a patient with hysterical con­striction of the visual fields. This was detected by ex­treme visual field constriction at 0.5 m and at 4 m. field test can be done by color comparison along the vertical or horizontal meridian to detect subtle paracentral scotomas that may occur secondary to an optic neuropathy or glaucoma. In summary, the 4-m confrontation visual field test has been successfully used at the Mayo Clinic for many years in addition to the standard O.S-m confrontation visual field test. The 4-m confronta­tion visual field test is a test of macular function and can identify small central or paracentral scoto­mas that the examiner may not find when the pa­tient is only tested at 0.5 m. It is not meant to supplant or substitute for more formal perimetry but often provides additional clinical information of importance in explaining symptoms. It takes but a few seconds to perform in patients whose history suggests paracentral defects. Also, one may iden­tify macular sparing in homonymous hemianopias and quadrantanopias with the 4-m confrontation visual field test. We recommend the addition of this simple clinical test on appropriately selected patients in addition to the standard O.s-m confron­tation visual field test to obtain the most informa­tion possible by confrontation visual field tests. REFERENCES 1. Trobe JO, Acosta pc, Krischer JP, Trick GL. Confrontation visual field techniques in the detection of anterior visual pathway lesions. All/I Neuro/ 1981;10:2~34. 2. Welsh RC. Finger counting in the four quadrants as a method of visual field gross screening. Arch Ophtlla/mol 1961;66:67~9. 3. Ellenberger C Jr. Perimetry: prillcipit's. techllique. and interpre­tation. New York: Raven Press. 1980:25-9. 4. Anderson DR. Perimetrv with and without automalion. 2nd ed. 51. Louis: CV Mosbv. 1987:64--7l. 5. Harrington DO. Drake MV. The ('lSua/fields: text and atlas of clinical perimdry. 6th ed. St. Louis: CV Mosby. 1990:9-12. I Clill NClIr,l-{'I,htlralmol. Vol. 13. No. 1. 1993