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Tangent Screen Perimetry using Twin Test Objects
NOTES, CASES, INSTRUMENTS TANGENT SCREEN PERIMETRY USING TWIN T E S T O B J E C T S J . T E R R E N C E C O Y L E , M.D., A N D D. F R A N K L I N M I L A M , J R . ,
M.D.
Bellevue, Washington A T-shaped carrier with a test object placed at each end o f t h e horizontal crossbar helps in detecting and analyzing visual field defects. T h e carrier is a 6 0 - c m long, / 4 - c m diameter aluminum tube hinged at one end to a 30-cm long, 2 x 2-cm oak crossbar. T h e crossbar may b e swiveled to lie parallel to the aluminum rod for storage or positioned to form a T when used. T h e carrier is matte black. O n one side of the crossbar, two 3-mm white test objects are placed 14 c m apart, and on the opposite side, two 3-mm red test o b jects are placed 6 c m apart. 3
METHOD
Glaucoma—The patient monocularly fixates on the center o f a tangent screen at a distance o f 1 meter. T h e carrier with the dual white test objects is brought in from the nasal periphery along the horizontal meridian. T h e upper test object lies 7 c m above, and the lower test object 7 cm below, the horizontal. I f the patient sees only one test object, the examiner notes that point and continues to move the carrier toward fixation until the second test object is seen. T h e presence and extent o f a nasal steppe is immediately known. T h e technique is especially sensitive when performed using reduced illumination.
tical meridian. W h e n the test objects, 14 c m apart on the crossbar, are centered over the 13-cm b l i n d spot, the patient should see both test objects (Figure, No. 1). I f only one object is seen, the patient may have an enlarged b l i n d spot. T h e carrier is then passed from the blind spot along the horizontal meridian to fixation. T h e upper and lower test objects should always b e seen equally. I f not, the patient may have an arcuate scotoma. T h e techn i q u e o f b l i n d spot evaluation is helpful in subsequent field studies. A patient who six months earlier saw the test objects above and b e l o w the b l i n d spot and now can only see one test object has lost additional visual field. Cortical lesions—The twin white targets are introduced at the 6 or 12 o'clock positions and advanced toward fixation while they straddle the vertical meridian. Angling the crossbar to 3 0 degrees facilitates moving the test objects in the vertical axis (Figure, No. 2 ) . A field defect is limited by the vertical meridian i f the patient consistently sees a test object on one side before he recognizes it on the other. T h e test is helpful in detecting
At a distance o f 1 meter from a tangent screen, the b l i n d spot o f an emmetropic patient with a normal optic nerve head measures approximately 13 cm in the verReprint requests to J. Terrence Coyle, M.D., Eye Clinic of Bellevue, Ltd., P.S., 1300 - 116th Avenue N.E., Bellevue, WA 98004.
Figure (Coyle and Milam). Tangent screen perimetry with twin test objects.
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AMERICAN JOURNAL O F OPHTHALMOLOGY
field loss adjacent to the superior vertical meridian in patients with temporal lobe lesions. Macular sparing—A third 3-mm white test object is added at the center of the crossbar midway between the other two test objects. T h e carrier is positioned in the hemianopic field with the middle test object on the horizontal meridian and then moved toward fixation (Figure, No. 3). I f the patient sees the middle test object first, he has macular sparing. I f he sees all three test objects simultaneously, he does not have macular sparing. Paracentral scotoma—The T-carrier is flipped over to expose the two 3-mm red test objects that are spaced 6 cm apart. T h e crossbar is angled (Figure, No. 4 ) , and the test objects introduced close to fixation in the vertical meridian. Both test objects should be seen as equally red. By moving the crossbar slowly in the vertical and horizontal positions, and noting where the two test objects appear the same, the examiner is able to outline the limits o f any scotoma. 1
field screening device which facilitated identification of a nasal steppe, a paracentral scotoma, an enlarged blind spot, an arcuate scotoma, macular sparing, or hemianopic defects. ACKNOWLEDGMENT
The T-carrier with test objects is available from Steve Mattausch, 18100 NE 95th, # 1 4 , Redmond, WA 98052. REFERENCES 1. Harrington, D.: The Visual Fields, 3rd ed. St. Louis, C. V. Mosby, 1971, p. 129. 2. Chamlin, M.: Methodology and technique in visual field studies. Survey Ophthalmol. 13:97, 1968. 3. Bender, M. B., and Furlow, L. T.: Phenomena of visual extinction in homonomous fields and the psychologic principles involved. Arch. Neurol. Psychiatr. 53:29, 1945.
A S T A B L E B A S E F O R AN OPERATING MICROSCOPE G E O F F R E Y E . K I N G , M.D., THOMAS E. LAMB, AND E D W A R D F I N E B E R G , M.D. Augusta,
DISCUSSION
T h e T-carrier effectively detects visual field defects because it allows the patient to compare the intensity o f two test objects simultaneously. I f one of those test objects lies in an area of depressed peripheral vision, it will not be seen as clearly as its twin test object that lies in an area of normal peripheral vision. Relative scotomatous areas are immediately perceived by the patient. T h e phenomenon of extinction may also contribute to the sensitivity of the twin test object technique. Extinction is suppression or neglect of a previously seen test object in a depressed visual field when another test object is presented simultaneously in an area o f normal visual field. 8
3
SUMMARY
A T-shaped carrier with twin test objects is an inexpensive efficient visual
JUNE, 1977
Georgia
T h e operating microscope has b e c o m e an indispensable piece of equipment that is needed for many new microsurgical procedures. T h e standard 1,880-mm Zeiss floorstand has safely supported an isolated microscope head. However, the addition o f accessories such as television cameras, stereoscopic viewing tubes, and X Y positioning systems have made the unit top heavy. We were concerned that the fully equipped unit would fall during surgery, during movement from one room to another, or during cleanup. Our fear was From the Section of Biomedical Engineering, Division of Systems and Computer Services (Dr. King and Mr. Lamb), and the Department of Ophthalmology (Dr. Fineberg), Medical College of Georgia, Augusta, Georgia. Reprint requests to Geoffrey E . King, M.D., Biomedical Engineering, Medical College of Georgia, Augusta, GA 30902.
M.D.
Bellevue, Washington A T-shaped carrier with a test object placed at each end o f t h e horizontal crossbar helps in detecting and analyzing visual field defects. T h e carrier is a 6 0 - c m long, / 4 - c m diameter aluminum tube hinged at one end to a 30-cm long, 2 x 2-cm oak crossbar. T h e crossbar may b e swiveled to lie parallel to the aluminum rod for storage or positioned to form a T when used. T h e carrier is matte black. O n one side of the crossbar, two 3-mm white test objects are placed 14 c m apart, and on the opposite side, two 3-mm red test o b jects are placed 6 c m apart. 3
METHOD
Glaucoma—The patient monocularly fixates on the center o f a tangent screen at a distance o f 1 meter. T h e carrier with the dual white test objects is brought in from the nasal periphery along the horizontal meridian. T h e upper test object lies 7 c m above, and the lower test object 7 cm below, the horizontal. I f the patient sees only one test object, the examiner notes that point and continues to move the carrier toward fixation until the second test object is seen. T h e presence and extent o f a nasal steppe is immediately known. T h e technique is especially sensitive when performed using reduced illumination.
tical meridian. W h e n the test objects, 14 c m apart on the crossbar, are centered over the 13-cm b l i n d spot, the patient should see both test objects (Figure, No. 1). I f only one object is seen, the patient may have an enlarged b l i n d spot. T h e carrier is then passed from the blind spot along the horizontal meridian to fixation. T h e upper and lower test objects should always b e seen equally. I f not, the patient may have an arcuate scotoma. T h e techn i q u e o f b l i n d spot evaluation is helpful in subsequent field studies. A patient who six months earlier saw the test objects above and b e l o w the b l i n d spot and now can only see one test object has lost additional visual field. Cortical lesions—The twin white targets are introduced at the 6 or 12 o'clock positions and advanced toward fixation while they straddle the vertical meridian. Angling the crossbar to 3 0 degrees facilitates moving the test objects in the vertical axis (Figure, No. 2 ) . A field defect is limited by the vertical meridian i f the patient consistently sees a test object on one side before he recognizes it on the other. T h e test is helpful in detecting
At a distance o f 1 meter from a tangent screen, the b l i n d spot o f an emmetropic patient with a normal optic nerve head measures approximately 13 cm in the verReprint requests to J. Terrence Coyle, M.D., Eye Clinic of Bellevue, Ltd., P.S., 1300 - 116th Avenue N.E., Bellevue, WA 98004.
Figure (Coyle and Milam). Tangent screen perimetry with twin test objects.
923
924
AMERICAN JOURNAL O F OPHTHALMOLOGY
field loss adjacent to the superior vertical meridian in patients with temporal lobe lesions. Macular sparing—A third 3-mm white test object is added at the center of the crossbar midway between the other two test objects. T h e carrier is positioned in the hemianopic field with the middle test object on the horizontal meridian and then moved toward fixation (Figure, No. 3). I f the patient sees the middle test object first, he has macular sparing. I f he sees all three test objects simultaneously, he does not have macular sparing. Paracentral scotoma—The T-carrier is flipped over to expose the two 3-mm red test objects that are spaced 6 cm apart. T h e crossbar is angled (Figure, No. 4 ) , and the test objects introduced close to fixation in the vertical meridian. Both test objects should be seen as equally red. By moving the crossbar slowly in the vertical and horizontal positions, and noting where the two test objects appear the same, the examiner is able to outline the limits o f any scotoma. 1
field screening device which facilitated identification of a nasal steppe, a paracentral scotoma, an enlarged blind spot, an arcuate scotoma, macular sparing, or hemianopic defects. ACKNOWLEDGMENT
The T-carrier with test objects is available from Steve Mattausch, 18100 NE 95th, # 1 4 , Redmond, WA 98052. REFERENCES 1. Harrington, D.: The Visual Fields, 3rd ed. St. Louis, C. V. Mosby, 1971, p. 129. 2. Chamlin, M.: Methodology and technique in visual field studies. Survey Ophthalmol. 13:97, 1968. 3. Bender, M. B., and Furlow, L. T.: Phenomena of visual extinction in homonomous fields and the psychologic principles involved. Arch. Neurol. Psychiatr. 53:29, 1945.
A S T A B L E B A S E F O R AN OPERATING MICROSCOPE G E O F F R E Y E . K I N G , M.D., THOMAS E. LAMB, AND E D W A R D F I N E B E R G , M.D. Augusta,
DISCUSSION
T h e T-carrier effectively detects visual field defects because it allows the patient to compare the intensity o f two test objects simultaneously. I f one of those test objects lies in an area of depressed peripheral vision, it will not be seen as clearly as its twin test object that lies in an area of normal peripheral vision. Relative scotomatous areas are immediately perceived by the patient. T h e phenomenon of extinction may also contribute to the sensitivity of the twin test object technique. Extinction is suppression or neglect of a previously seen test object in a depressed visual field when another test object is presented simultaneously in an area o f normal visual field. 8
3
SUMMARY
A T-shaped carrier with twin test objects is an inexpensive efficient visual
JUNE, 1977
Georgia
T h e operating microscope has b e c o m e an indispensable piece of equipment that is needed for many new microsurgical procedures. T h e standard 1,880-mm Zeiss floorstand has safely supported an isolated microscope head. However, the addition o f accessories such as television cameras, stereoscopic viewing tubes, and X Y positioning systems have made the unit top heavy. We were concerned that the fully equipped unit would fall during surgery, during movement from one room to another, or during cleanup. Our fear was From the Section of Biomedical Engineering, Division of Systems and Computer Services (Dr. King and Mr. Lamb), and the Department of Ophthalmology (Dr. Fineberg), Medical College of Georgia, Augusta, Georgia. Reprint requests to Geoffrey E . King, M.D., Biomedical Engineering, Medical College of Georgia, Augusta, GA 30902.