Documenta Ophthalmologica 47,1 : 5-12, 1979 OCULOGRAPHIC AUTOMATIC PERIMETRY IN GLAUCOMA VISUAL FIELD SCREENING: A CLINICAL STUDY - PRELIMINARY RESULTS IN GLAUCOMA PATIENTS*
U. TICHO, H. ZAUBERMAN, E. FAIBISH, H. ARMON & J. WEINMAN
(Jerusalem, Israel) ABSTRACT An automatic method for visual field screening using oculographic potentials has been evaluated on 124 eyes of 65 glaucoma patients. The oculographic perimeter records, plotting the central 22~ of the visual field, have been compared with Armaly's manual selective perim~try performed by the Goldman Perimeter. In spite of different testing standards of both methods, equivalent pathological field defects were demonstrated in 72% of the eyes following the first examination. Successive plottings with the automatic method improved the results considerably. The method has proved to be a reliable objective automatic test. Further development is suggested through which the procedure might be useful for glaucoma screening in the future. INTRODUCTION The importance of perimetry as a diagnostic tool in ophthalmology and neurology is well known. Visual field (V.F.) analysis is of particular value in evaluating the condition of glaucoma. Visual field defects may appear at~ time and repeated plottings are essential to control the disease. Since the examination is time consuming, many attempts to automatize perimetry have been made, and some models are already being commercialized. The available units plot the visual field automatically, based on the yes/no response of the patient. An automatic method of perimetry based on eye movement responses has been presented previously (Armon, 1977). The method is based on plotting the visual field by recording the E.O.G. potentials generated by the movement of the polarized eye ball (cornea positive) to the test target (Kris, 1960). Preliminary clinical results are being described. SUBJECTS AND METHODS One hundred twenty-four (124) eyes of 65 patients have been examined. Thirty-five subjects were male and 30 were female. The patients' ages ranged * Supported in- part by the Swiss Fund for Research in Ophthalmology, by the Rogoff Foundation and by Madame L. Teruzzi.
b e t w e e n 4 0 to 70 years, e x c e p t for t h r e e w h o were b e t w e e n six a n d 20 years old. All t h e subjects were n o n s e l e c t e d g l a u c o m a or ocular h y p e r t e n sion p a t i e n t s f r o m o u r o u t - p a t i e n t clinic referrals.
Methods T h e principles o f t h e a u t o m a t i c visual field s y s t e m utilizing electro-oculographic p o t e n t i a l s have b e e n previously described in detail ( A r m o n , 1977).
Fig. 1. An example of a complete visual field tested by the Goldman and automatic perimetry in a normal subject. The subject detected all existing targets (white points) on the automatic perimeter except for two targets which represent bfind spot area. The outer circle contains only 22 targets, therefore the spacing. In the Goldman Perimeter records: X - suprathreshold targets - detected targets
Therefore, only a brief summary of the method, including recent improvements, will be presented. A patient is seated at a distance of 0.5 meter in front of a quadriangular black tangent screen (0.5 m x 0.5 m), to which 100 static red light-emitting diodes (L.E.D.) are attached; eight of'them at 4 ~ eccentricity, 16 points at 8 ~ , 32 at 16~, and 22 at 22 ~ from the fixation point. The patient's chin is placed on a specially designed chin rest while two pairs of electrodes are attached to the skin around his orbits. The non-tested eye is occluded, and the tested eye fixes at a central white spot whenever no target is seen on the screen. Each of the 100 targets are lit alternatively while the patient's is instructed to follow the targets from the central fixation point, avoiding searching movements. The targets are lit automatically by a computer according to a suitable program. The electrodes measure the E.O.G. potentials which are generated by the eye movements. Vertical and horizontal potential components are recorded simultaneously by the two pairs of electrodes. The signals are fed to the computer for analysis after being digitized by an analog to digital converter. After the first run of sequence of all targets, the computer switches on again all those targets which were missed; only targets which were missed twice are recorded as scotomata. The resulting visual field is photographed by a Polaroid camera from a miniature screen display of L.E.D.'s, identical to the test screen. Twenty-two degrees (22 ~) of the central visual field tested by the automatic method have been compared with Armaly's manual selective perimetry (Armaly, 1969). The static perimetry was performed on the Goldman Perimeter with a test target of 1 mm 2 size and 0.096 relative intensity (II/2), except for the blind spot area which was detected by dynamic perimetry. Both V.F. records were analyzed for the presence of equivalent pathologic V.F. defects:
RESULTS
Normal visual field Out of 79 eyes who had a complete visual field plotted by the Goldman Perimeter, 54 (68%) were confirmed by the automatic method and 25 (32%) showed false positive defects (by targets recorded falsely as missed). These results were achieved following the first screening by the automatic method. However, whenever a repetitive plotting could be performed, the false positive results disappeared.
Fig. 2. Left eye - complete visual field. Right eye - equivalent scotoma (altitudinal defect) are demonstrated by both the Goldman and automatic perimetry. In the Goldman Perimeter records: non-detected targets - scotomatous area with border lines detected by dynamic perimetry -
Pathological visual fields F o r t y - f i v e eyes h a d p a t h o l o g i c a l fields d e m o n s t r a t e d b y t h e G o l d m a n Perim e t e r (22 ~ central field). Of those, 37 eyes ( 8 2 % ) d e m o n s t r a t e d e q u i v a l e n t field defects o n t h e a u t o m a t i c p e r i m e t e r , f o l l o w i n g t h e first screening exam i n a t i o n . W h e n e v e r a repetitive e x a m i n a t i o n was possible, t h e results were identical.
Fig. 3. Equivalent field defects in a bilateral aphakic patient recorded by both the Goldman and automatic perimetry. Note in the right eye an enlarged bfind spot; in the left eye a sectorial scotoma. The other eight eyes showed either false positive or false negative defects, but in these cases repetitive examinations were not performed. The following figures are examples of visual field records obtained by both the oculographic automatic method and the Goldman manual perimetry, for the same subject. DISCUSSION The presented method is only one of the many attempts to automatize
visual field testing. The existing non-automatic methods (Goldman, Friedman) are manual, time consuming, and demand the presence of a skilled technician. Their accuracy depends upon the examiner's patience and the Yes/no response of the patient. Computerized automatic perimetry shortens the time of examination, does not involve a skilled technician, and avoids subjective errors due to the examiner. However, the available automatic units (Octopus; Ocutron; Perimatron; Synemed Fieldmaster) still depend upon the subjective yes/no responses of the patient. By our method, an attempt has been made to increase the objectivity of the automatic test by utilizing the E.O.G. potentials. The procedure was
Fig. 4. Equivalent scotoma recorded on the automatic and Goldman perimetry. Note in the right eye an enlarged blind spot with missing targets in the Bjerrum area; in the left eye a Bjerrum scotoma and the nasal step. 10
found to show good correlation to Goldman perimetry. It was demonstrated that the correlation was improved considerably by repeating the tests after the patient became familiar with the procedure. It should be added that at present our testing conditions differ from the Goldman Perimeter standards - the background of the screen is black, the color of the targets is red and the intensity and" size of the targets are not accurately matched with the Goldman Perimeter. In addition the scotomatous borders and the blind spot were detected dynamically by the Goldman Perimeter whereas our automatic method is static throughout. Our procedure at present plots the central field of 22 ~ only. Since glaucoma defects are situated in this range of the field, the method is already being used in our clinic to screen and follow up glaucoma cases. However, there is no reason why this method could not be adapted in the future for peripheral field plotting. It was demonstrated (Camberlin, 1 9 7 1 ) t h a t the
Fig. 5. Subject with complete visual fields. During the first performance of automatic perimetry many targets were missed (Test I). However, a second test revealed a complete visual field (Test II).
11
amplitude of eye movements, especially the vertical movements, might be reduced with age. This phenomenon presents no difficulties to our method since prior to each test the unit is calibrated according to the individual eye movement amplitude. There are two possible reasons for false positive results (targets recorded falsely as missed): 1) Absence of central fixation before a target is presented; 2) Temporary distraction of the patient. These drawbacks are minimized by automatic repeating of targets recognized by the computor as missing on the first run. The probability that the same target will be falsely missed twice is, in our experience, limited. The proposed automatic and objective method requires further improvements, such as control of size, intensity, change in color of the targets and and automatic control of central fixation. It is however encouraging that even at the present stage of the method the results are reliable enough for follow-up examinations in a glaucoma clinic. ACKNOWLEDGEMENT We wish to acknowledge our gratitude to Dr. Y. Mahler and D. Adler, M.Sc. from the Hadassah University Hospital, Jerusalem, for building the interface between the H.P. 2100A computer and the driver of the light-emitting diodes on the test screen. REFERENCES Armaly, M. Ocular pressure and visual fields. Arch. Ophthal. 81: 25-40, 1969. Armon, H., Weinman, J., Peleg, A., Ticho, U., Zauberman, H., Mallek, D. Automatic testing of the visual field usingelectro-oculographic potentials. Docum. Ophthal. 43: 51-63, 1977. Camberlin, W. Restriction in upward gaze with advancing age. Amer. J. Ophthal. 71: 341-346, 1971. Kris, C., Electro-oculography. Med-physics, 3: 692-700, 1960. Octopus - Fully automated computer controlled perimeter. Interzeag AG Rietbachstrasse 5 CH 8952 Schlieren, Switzerland (Brochure). Ocutron, OC 2200, Automatic electronic tonometer, 22500 S. Woodlang Road, Cleveland, Ohio 44122 (Brochure). Perimatron - computerized projection perimeter coherent, 3210 Porter Drive, Palo Alto, California 94304 (Brochure). Synemed Fieldmaster - Fully automatic visual field recorder, Synemed, Inc., 1215 Fourth Street, Berkeley, California 94710 (Brochure). Authors' addresses: U. Ticho, H. Zaubermann, E. Faibish Department of Ophthalmology Hadassah University Hospital Jerusalem, Israel Address for reprint requests: J. Weinman, U. Ticho
12
H. Armon, J. Weinman Rogoff Laboratory for Biomedical Engineering Hebrew University - Hadassah Medical School P.O. Box 1172, Jerusalem, Israel
U. TICHO, H. ZAUBERMAN, E. FAIBISH, H. ARMON & J. WEINMAN
(Jerusalem, Israel) ABSTRACT An automatic method for visual field screening using oculographic potentials has been evaluated on 124 eyes of 65 glaucoma patients. The oculographic perimeter records, plotting the central 22~ of the visual field, have been compared with Armaly's manual selective perim~try performed by the Goldman Perimeter. In spite of different testing standards of both methods, equivalent pathological field defects were demonstrated in 72% of the eyes following the first examination. Successive plottings with the automatic method improved the results considerably. The method has proved to be a reliable objective automatic test. Further development is suggested through which the procedure might be useful for glaucoma screening in the future. INTRODUCTION The importance of perimetry as a diagnostic tool in ophthalmology and neurology is well known. Visual field (V.F.) analysis is of particular value in evaluating the condition of glaucoma. Visual field defects may appear at~ time and repeated plottings are essential to control the disease. Since the examination is time consuming, many attempts to automatize perimetry have been made, and some models are already being commercialized. The available units plot the visual field automatically, based on the yes/no response of the patient. An automatic method of perimetry based on eye movement responses has been presented previously (Armon, 1977). The method is based on plotting the visual field by recording the E.O.G. potentials generated by the movement of the polarized eye ball (cornea positive) to the test target (Kris, 1960). Preliminary clinical results are being described. SUBJECTS AND METHODS One hundred twenty-four (124) eyes of 65 patients have been examined. Thirty-five subjects were male and 30 were female. The patients' ages ranged * Supported in- part by the Swiss Fund for Research in Ophthalmology, by the Rogoff Foundation and by Madame L. Teruzzi.
b e t w e e n 4 0 to 70 years, e x c e p t for t h r e e w h o were b e t w e e n six a n d 20 years old. All t h e subjects were n o n s e l e c t e d g l a u c o m a or ocular h y p e r t e n sion p a t i e n t s f r o m o u r o u t - p a t i e n t clinic referrals.
Methods T h e principles o f t h e a u t o m a t i c visual field s y s t e m utilizing electro-oculographic p o t e n t i a l s have b e e n previously described in detail ( A r m o n , 1977).
Fig. 1. An example of a complete visual field tested by the Goldman and automatic perimetry in a normal subject. The subject detected all existing targets (white points) on the automatic perimeter except for two targets which represent bfind spot area. The outer circle contains only 22 targets, therefore the spacing. In the Goldman Perimeter records: X - suprathreshold targets - detected targets
Therefore, only a brief summary of the method, including recent improvements, will be presented. A patient is seated at a distance of 0.5 meter in front of a quadriangular black tangent screen (0.5 m x 0.5 m), to which 100 static red light-emitting diodes (L.E.D.) are attached; eight of'them at 4 ~ eccentricity, 16 points at 8 ~ , 32 at 16~, and 22 at 22 ~ from the fixation point. The patient's chin is placed on a specially designed chin rest while two pairs of electrodes are attached to the skin around his orbits. The non-tested eye is occluded, and the tested eye fixes at a central white spot whenever no target is seen on the screen. Each of the 100 targets are lit alternatively while the patient's is instructed to follow the targets from the central fixation point, avoiding searching movements. The targets are lit automatically by a computer according to a suitable program. The electrodes measure the E.O.G. potentials which are generated by the eye movements. Vertical and horizontal potential components are recorded simultaneously by the two pairs of electrodes. The signals are fed to the computer for analysis after being digitized by an analog to digital converter. After the first run of sequence of all targets, the computer switches on again all those targets which were missed; only targets which were missed twice are recorded as scotomata. The resulting visual field is photographed by a Polaroid camera from a miniature screen display of L.E.D.'s, identical to the test screen. Twenty-two degrees (22 ~) of the central visual field tested by the automatic method have been compared with Armaly's manual selective perimetry (Armaly, 1969). The static perimetry was performed on the Goldman Perimeter with a test target of 1 mm 2 size and 0.096 relative intensity (II/2), except for the blind spot area which was detected by dynamic perimetry. Both V.F. records were analyzed for the presence of equivalent pathologic V.F. defects:
RESULTS
Normal visual field Out of 79 eyes who had a complete visual field plotted by the Goldman Perimeter, 54 (68%) were confirmed by the automatic method and 25 (32%) showed false positive defects (by targets recorded falsely as missed). These results were achieved following the first screening by the automatic method. However, whenever a repetitive plotting could be performed, the false positive results disappeared.
Fig. 2. Left eye - complete visual field. Right eye - equivalent scotoma (altitudinal defect) are demonstrated by both the Goldman and automatic perimetry. In the Goldman Perimeter records: non-detected targets - scotomatous area with border lines detected by dynamic perimetry -
Pathological visual fields F o r t y - f i v e eyes h a d p a t h o l o g i c a l fields d e m o n s t r a t e d b y t h e G o l d m a n Perim e t e r (22 ~ central field). Of those, 37 eyes ( 8 2 % ) d e m o n s t r a t e d e q u i v a l e n t field defects o n t h e a u t o m a t i c p e r i m e t e r , f o l l o w i n g t h e first screening exam i n a t i o n . W h e n e v e r a repetitive e x a m i n a t i o n was possible, t h e results were identical.
Fig. 3. Equivalent field defects in a bilateral aphakic patient recorded by both the Goldman and automatic perimetry. Note in the right eye an enlarged bfind spot; in the left eye a sectorial scotoma. The other eight eyes showed either false positive or false negative defects, but in these cases repetitive examinations were not performed. The following figures are examples of visual field records obtained by both the oculographic automatic method and the Goldman manual perimetry, for the same subject. DISCUSSION The presented method is only one of the many attempts to automatize
visual field testing. The existing non-automatic methods (Goldman, Friedman) are manual, time consuming, and demand the presence of a skilled technician. Their accuracy depends upon the examiner's patience and the Yes/no response of the patient. Computerized automatic perimetry shortens the time of examination, does not involve a skilled technician, and avoids subjective errors due to the examiner. However, the available automatic units (Octopus; Ocutron; Perimatron; Synemed Fieldmaster) still depend upon the subjective yes/no responses of the patient. By our method, an attempt has been made to increase the objectivity of the automatic test by utilizing the E.O.G. potentials. The procedure was
Fig. 4. Equivalent scotoma recorded on the automatic and Goldman perimetry. Note in the right eye an enlarged blind spot with missing targets in the Bjerrum area; in the left eye a Bjerrum scotoma and the nasal step. 10
found to show good correlation to Goldman perimetry. It was demonstrated that the correlation was improved considerably by repeating the tests after the patient became familiar with the procedure. It should be added that at present our testing conditions differ from the Goldman Perimeter standards - the background of the screen is black, the color of the targets is red and the intensity and" size of the targets are not accurately matched with the Goldman Perimeter. In addition the scotomatous borders and the blind spot were detected dynamically by the Goldman Perimeter whereas our automatic method is static throughout. Our procedure at present plots the central field of 22 ~ only. Since glaucoma defects are situated in this range of the field, the method is already being used in our clinic to screen and follow up glaucoma cases. However, there is no reason why this method could not be adapted in the future for peripheral field plotting. It was demonstrated (Camberlin, 1 9 7 1 ) t h a t the
Fig. 5. Subject with complete visual fields. During the first performance of automatic perimetry many targets were missed (Test I). However, a second test revealed a complete visual field (Test II).
11
amplitude of eye movements, especially the vertical movements, might be reduced with age. This phenomenon presents no difficulties to our method since prior to each test the unit is calibrated according to the individual eye movement amplitude. There are two possible reasons for false positive results (targets recorded falsely as missed): 1) Absence of central fixation before a target is presented; 2) Temporary distraction of the patient. These drawbacks are minimized by automatic repeating of targets recognized by the computor as missing on the first run. The probability that the same target will be falsely missed twice is, in our experience, limited. The proposed automatic and objective method requires further improvements, such as control of size, intensity, change in color of the targets and and automatic control of central fixation. It is however encouraging that even at the present stage of the method the results are reliable enough for follow-up examinations in a glaucoma clinic. ACKNOWLEDGEMENT We wish to acknowledge our gratitude to Dr. Y. Mahler and D. Adler, M.Sc. from the Hadassah University Hospital, Jerusalem, for building the interface between the H.P. 2100A computer and the driver of the light-emitting diodes on the test screen. REFERENCES Armaly, M. Ocular pressure and visual fields. Arch. Ophthal. 81: 25-40, 1969. Armon, H., Weinman, J., Peleg, A., Ticho, U., Zauberman, H., Mallek, D. Automatic testing of the visual field usingelectro-oculographic potentials. Docum. Ophthal. 43: 51-63, 1977. Camberlin, W. Restriction in upward gaze with advancing age. Amer. J. Ophthal. 71: 341-346, 1971. Kris, C., Electro-oculography. Med-physics, 3: 692-700, 1960. Octopus - Fully automated computer controlled perimeter. Interzeag AG Rietbachstrasse 5 CH 8952 Schlieren, Switzerland (Brochure). Ocutron, OC 2200, Automatic electronic tonometer, 22500 S. Woodlang Road, Cleveland, Ohio 44122 (Brochure). Perimatron - computerized projection perimeter coherent, 3210 Porter Drive, Palo Alto, California 94304 (Brochure). Synemed Fieldmaster - Fully automatic visual field recorder, Synemed, Inc., 1215 Fourth Street, Berkeley, California 94710 (Brochure). Authors' addresses: U. Ticho, H. Zaubermann, E. Faibish Department of Ophthalmology Hadassah University Hospital Jerusalem, Israel Address for reprint requests: J. Weinman, U. Ticho
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H. Armon, J. Weinman Rogoff Laboratory for Biomedical Engineering Hebrew University - Hadassah Medical School P.O. Box 1172, Jerusalem, Israel
