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Fixation Devices for Evaluation of Ocular Alignment
FIXATION DEVICES FOR EVALUATION O F OCULAR ALIGNMENT DAVID S. FRIENDLY,
M.D.
Washington, D.C.
Accurate evaluation of ocular alignment at distance is an important part of the pédiatrie eye examination. Regardless of the quantita tive method used, central, steady, and rela tively prolonged fixation are prerequisite for mensuration. It is unfortunate that fixation at distance is more difficult both to obtain and to maintain than is fixation at near, be cause the distant measurement is far more critical than the near measurement in deter mining the appropriate amount of surgical correction. Yet even the experienced exam iner is at times unable to obtain meaningful distant measurements utilizing conventional fixation targets. The purpose of this paper is to describe two fixation devices which have been found attractive to pédiatrie patients. Both devices are designed for use at 20 feet. The first of these is primarily intended for infants and children under the age of three or four years, while the second is intended for chil dren older than that, but not sufficiently cooperative or intelligent to permit the use of targets which provide better accommoda tion control, such as projected vertical rows of small Snellen optotypes. DEVICE PRIMARILY INTENDED FOR INFANTS AND YOUNG CHILDREN
Technical description—The device (Fig. 1) consists of an electrical assembly and an enclosure containing three sequentially acti vated and illuminated noisy toy animals each of which operates in two modes.* The mov ing legs of the toy animals slip over smoothly surfaced "floors" of each of the three areas. The enclosure (Fig. 2) may be Reprint requests to David S. Friendly, M.D., Children's Hospital of the District of Columbia, 2125 13th Street, N.W., Washington, D.C. 20009. * A modified version of this device is available through the Da-Laur Corporation, 75A Spring Street, West Roxbury, Massachusetts 02132.
constructed for either horizontal or vertical display, depending on the examiner's personal preference and available space. The electrical assembly (Fig. 3) features a foot-switch operated stepping relay that ener gizes each of three control triple-pole, dou ble-throw (3PDT) relays in a predeter mined specific sequence. "Off" positions are provided between the "on" positions of the stepping relay. Each 3PDT relay distributes line alternating current (AC) to the incandes cent lights of one area of the enclosure and to the primary coil of the power trans former. The 3PDT relays also distribute ap proximately 3.0 volts of direct current (DC) to the appropriate toy. The diodes across the coils of the three control relays prevent arc ing at the stepping relay contacts, thus pro longing the life of this relay. The center tap and one of the two side taps of the secondary coil of the 6.3 volt power transformer provide 3.15 volts AC which is rectified by a solid state bridge cir cuit. Rippling DC current then passes through a polarity reversing relay which is operated by a mismatched (for purposes of identification) second foot switch—thereby enabling each toy to operate in two separate modes or cycles. A single two-position rocker-type foot switch may be substituted for the two mismatched foot switches if de sired. A convenient parts layout is illustrated (Fig. 4). Note the presence of a 14-position terminal strip which facilitates connecting the electrical assembly to the enclosure. Operation and maintenance—The controls are as simple as possible—two foot switches operate the device. Depressing one of the foot switches energizes the stepping relay, thereby activating and illuminating a partic ular toy animal. Depressing this same switch a second time turns off all power. The device may remain in this mode for an indefinite period without consumption of current and
587
588
AMERICAN JOURNAL OF OPHTHALMOLOGY
APRIL, 1972
without damage to the electrical components. A third depression of this same switch acti vates and illuminates the next area ; a fourth depression turns the power completely off, etc. Depression of the mismatched second foot switch changes the action of the toy selected by reversing the polarity of the direct current. There are no manual controls and the power cord does not need to be disconnected from the 117-volt AC wall outlet between office hours. Two electrical cords extend from the unit ; one of these is connected to a 117-volt AC power source, while the other (which con-
Fig. 1 (Friendly). Time-lapse photograph of fix ation device. The electrical assembly may be mounted on top of the enclosure.
Fig. 2 (Friendly). Dimensions of enclosure. The two illuminating bulbs are recessed behind the upper panelling of each area. The panelling should over hang each "ceiling" by 1.5 inches to shield the bulbs.
VOL. 73, NO. 4
FIXATION DEVICES
tains three leads) connects the two remote foot switches (or single rocker switch) to the electrical assembly. Ease of maintenance was given priority in the design and construction of this device. The physician or his assistant can easily and rapidly remove and replace worn toys and light bulbs—substitutes are widely available. The toys are 3.0-volt battery-operated two-cycle types that are sold in most large department stores. Selection and stocks are usually most ample in November and early December. The quality control of these inex pensive imports is poor and the life expec tancy is rather unpredictable ; thus, provision has been made for simple replacement. This is accomplished by cutting the wires (twin lead) which attach to the hand-held battery pack which is supplied with these toys. The battery pack is discarded and each lead from
WIRING DIAGRAM FOR THREE UNIT TWO CYCLE DISPLAY CABINET
589
Fig. 4 (Friendly). Parts layout for electrical as sembly. The center secondary tap and either of the two side secondary taps of the power transformer are used. The 3PDT relays and foot switches are wired so that they are normally off. The opposite "on" position contacts of SA IN 12A are wired to gether, thus converting the 12 positions to six effec tive positions. This modification is not shown in the wiring diagram.
the toy is bared and connected to the proper terminal in the rear of the enclosure. The toy animals are restrained by two easily removed tethers which encircle their hind legs. The lengths of these tethers may be adjusted by means of the anchoring tack in the rear of the enclosure (Fig. 5). The light bulbs are 25-watt, small-socket, 117-volt decorator types that can be obtained from most hardware stores. Two recessed bulbs illuminate each area. DEVICE INTENDED FOR OLDER CHILDREN
Fig. 3 (Friendly). Key to wiring diagram for electrical assembly: Rl,2,3: KA 14 AY 120 volt 3PDT relays (Potter and Brumfield) ; R4: Guard ian 660-2C-120A reversing relay; R5: SA IN 12A 120 volt stepping relay (Potter and Brumfield) ; SI and S2: mismatched 1PST foot switches or Linemaster 476 S switch; power transformer: Stancor P-6466; diodes: 1/2 amp 200 volts PIV.
Technical description and operation—This device (Fig. 6 ) , which was first brought to our attention by Dr. Mary Fletcher of Houston, Texas, consists of a silent Super-8 projector which shows continuous loop film. Although several models are currently available, our experience is limited to Tech nicolor* Model 510 with a right-angle * Technicolor Commercial and Education Divi sion, 1300 Frawley Drive, Costa Mesa, California 92627.
590
AMERICAN JOURNAL OF OPHTHALMOLOGY
I À
APRIL, 1972
COMMENT
/
■O
Fig. 5 (Friendly). Back of enclosure, showing terminals for leads from toys and anchoring tacks for securing tethers.
screen. The projector is a compact, light, inexpensive type which utilizes film car tridges, a 150-watt projection lamp and im peller fan. Four-minute continuous films can be shown without threading or rewinding. A wall shelf that is 20 feet from the patient provides a convenient location for both the projector and right-angle screen. A foot switch is preferred for remote operation of the projector. Although a large variety of films are avail able through retail photographic supply stores, color cartoons have been found dis tinctly preferable. Projectors utilizing Super 8 motion pic tures in loop form with sound tracks may be purchased at considerably higher prices. Sound movies are not superior to silent films, since projection devices are reserved for older children who do not usually require the additional auditory stimulation. Also, the subject material of commercially available Super 8 sound movies is not as appropriate as that of the silent films.
Not infrequently, the accurate determina tion of ocular alignment by cover tests at distance is frustrated by a combination of patient fatigue, anxiety, inattentiveness, and short attention span. Infants and young chil dren should not be seen during periods nor mally reserved for rest, nor should they be obliged to wait unduly for examination.1 Almost all pédiatrie patients have anxiety about the office visit and this may be height ened by an "operating room" office decor or a lack of sensitivity on the part of the physi cian or assistants. White uniforms generally do not add to a sense of well-being. These and other environmental factors frequently bring to mind unpleasant past medical expe riences. Patient cooperation will be enhanced by attention to such details as the time of day of the examination, the length of the waiting period, the office design, the type of profes sional dress, and the manner of professional conduct. Nevertheless, patient inattentive ness may still result in an unsatisfactory ocular motility evaluation. It is in their ability to hold the child's at tention that fixation devices may play a deci sive role. Ennui develops with extraordinary rapidity in young children, hyperactive chil dren, retarded children, and those who are emotionally disturbed. Therefore, a variety of fixation targets is essential.2 For these
ft <^!$<^#
Fig. 6 (Friendly). Technicolor Model 510 with right-angle screen.
VOL. 73, NO. 4
FIXATION DEVICES
children, sound stimulation is advantageous and should be incorporated in the device uti lized. Older children do not require sound stimulation and respond well to silent mov ies. T h e examiner should attempt to interest the patient in the fixation object by making observations about the target, by asking questions about it, or by increasing aware ness of the fixation target by means of a story in which the object plays a leading role. P r o viding a modicum of control 3 over the fixa tion object, such as by saying, "Tell the dog to bark !" also increases attention. T h e examiner's fingers are generally the least offensive occluders. Black occluder paddles such as are used for older children and adults are distracting and at times frightening to the infant and young child. Foot switches have been found far superior to line or wall-mounted switches, because both of the examiner's hands must be free to manipulate prisms and covers and also be cause distracting movements should be avoided. T h e devices described have been found helpful in obtaining and maintaining ocular fixation, but no claim is made or implied for uniform success. O n e must always use judg ment, and if reasonable attempts to evaluate ocular alignment should fail it is occasionally prudent to cease testing altogether. W h e n confronted with a hopelessly obstreperous child, it is generally wiser to admit defeat
S91
and to a r r a n g e a second appointment for this portion of the examination than to jeopar dize future cooperation by badgering the pa tient. SUMMARY
Since surgery is largely based on the ocular alignment at distance, it is particularly im portant to obtain accurate and prolonged fixa tion at this testing distance. F o r this purpose, an enclosure for three noisy, brightly illumi nated, animated toys was developed. T h e toys are inexpensive, readily available, battery op erated types. An electrical assembly has been devised which eliminates the need for batteries and permits remote control operation of the toys, utilizing 117-volt alternating current. T h e toys and illuminating bulbs, which are also easily obtained, may be replaced without difficulty by the examiner or his assistant. Older children who will not fixate on dis tant Snellen optotypes will frequently fixate Super-8 color cartoons. A remotely controlled, shelf-mounted Technicolor model 510 projec tor with a right-angle screen has proved satisfactory for this purpose. REFERENCES
1. Parks, M. M. : Ocular motility diagnosis. Int. Ophth. Clin. 3:811, 1963. 2. Jampolsky, A. : Animated fixation targets for strabismus examination. Tr. Am. Acad. Ophth. Otolaryng. 64:213, 1960. 3. Jampolsky, A.: A simplified approach to stra bismus diagnosis. In Transactions of the New Orleans Academy of Ophthalmology. St. Louis. C. V. Mosby, 1971.
M.D.
Washington, D.C.
Accurate evaluation of ocular alignment at distance is an important part of the pédiatrie eye examination. Regardless of the quantita tive method used, central, steady, and rela tively prolonged fixation are prerequisite for mensuration. It is unfortunate that fixation at distance is more difficult both to obtain and to maintain than is fixation at near, be cause the distant measurement is far more critical than the near measurement in deter mining the appropriate amount of surgical correction. Yet even the experienced exam iner is at times unable to obtain meaningful distant measurements utilizing conventional fixation targets. The purpose of this paper is to describe two fixation devices which have been found attractive to pédiatrie patients. Both devices are designed for use at 20 feet. The first of these is primarily intended for infants and children under the age of three or four years, while the second is intended for chil dren older than that, but not sufficiently cooperative or intelligent to permit the use of targets which provide better accommoda tion control, such as projected vertical rows of small Snellen optotypes. DEVICE PRIMARILY INTENDED FOR INFANTS AND YOUNG CHILDREN
Technical description—The device (Fig. 1) consists of an electrical assembly and an enclosure containing three sequentially acti vated and illuminated noisy toy animals each of which operates in two modes.* The mov ing legs of the toy animals slip over smoothly surfaced "floors" of each of the three areas. The enclosure (Fig. 2) may be Reprint requests to David S. Friendly, M.D., Children's Hospital of the District of Columbia, 2125 13th Street, N.W., Washington, D.C. 20009. * A modified version of this device is available through the Da-Laur Corporation, 75A Spring Street, West Roxbury, Massachusetts 02132.
constructed for either horizontal or vertical display, depending on the examiner's personal preference and available space. The electrical assembly (Fig. 3) features a foot-switch operated stepping relay that ener gizes each of three control triple-pole, dou ble-throw (3PDT) relays in a predeter mined specific sequence. "Off" positions are provided between the "on" positions of the stepping relay. Each 3PDT relay distributes line alternating current (AC) to the incandes cent lights of one area of the enclosure and to the primary coil of the power trans former. The 3PDT relays also distribute ap proximately 3.0 volts of direct current (DC) to the appropriate toy. The diodes across the coils of the three control relays prevent arc ing at the stepping relay contacts, thus pro longing the life of this relay. The center tap and one of the two side taps of the secondary coil of the 6.3 volt power transformer provide 3.15 volts AC which is rectified by a solid state bridge cir cuit. Rippling DC current then passes through a polarity reversing relay which is operated by a mismatched (for purposes of identification) second foot switch—thereby enabling each toy to operate in two separate modes or cycles. A single two-position rocker-type foot switch may be substituted for the two mismatched foot switches if de sired. A convenient parts layout is illustrated (Fig. 4). Note the presence of a 14-position terminal strip which facilitates connecting the electrical assembly to the enclosure. Operation and maintenance—The controls are as simple as possible—two foot switches operate the device. Depressing one of the foot switches energizes the stepping relay, thereby activating and illuminating a partic ular toy animal. Depressing this same switch a second time turns off all power. The device may remain in this mode for an indefinite period without consumption of current and
587
588
AMERICAN JOURNAL OF OPHTHALMOLOGY
APRIL, 1972
without damage to the electrical components. A third depression of this same switch acti vates and illuminates the next area ; a fourth depression turns the power completely off, etc. Depression of the mismatched second foot switch changes the action of the toy selected by reversing the polarity of the direct current. There are no manual controls and the power cord does not need to be disconnected from the 117-volt AC wall outlet between office hours. Two electrical cords extend from the unit ; one of these is connected to a 117-volt AC power source, while the other (which con-
Fig. 1 (Friendly). Time-lapse photograph of fix ation device. The electrical assembly may be mounted on top of the enclosure.
Fig. 2 (Friendly). Dimensions of enclosure. The two illuminating bulbs are recessed behind the upper panelling of each area. The panelling should over hang each "ceiling" by 1.5 inches to shield the bulbs.
VOL. 73, NO. 4
FIXATION DEVICES
tains three leads) connects the two remote foot switches (or single rocker switch) to the electrical assembly. Ease of maintenance was given priority in the design and construction of this device. The physician or his assistant can easily and rapidly remove and replace worn toys and light bulbs—substitutes are widely available. The toys are 3.0-volt battery-operated two-cycle types that are sold in most large department stores. Selection and stocks are usually most ample in November and early December. The quality control of these inex pensive imports is poor and the life expec tancy is rather unpredictable ; thus, provision has been made for simple replacement. This is accomplished by cutting the wires (twin lead) which attach to the hand-held battery pack which is supplied with these toys. The battery pack is discarded and each lead from
WIRING DIAGRAM FOR THREE UNIT TWO CYCLE DISPLAY CABINET
589
Fig. 4 (Friendly). Parts layout for electrical as sembly. The center secondary tap and either of the two side secondary taps of the power transformer are used. The 3PDT relays and foot switches are wired so that they are normally off. The opposite "on" position contacts of SA IN 12A are wired to gether, thus converting the 12 positions to six effec tive positions. This modification is not shown in the wiring diagram.
the toy is bared and connected to the proper terminal in the rear of the enclosure. The toy animals are restrained by two easily removed tethers which encircle their hind legs. The lengths of these tethers may be adjusted by means of the anchoring tack in the rear of the enclosure (Fig. 5). The light bulbs are 25-watt, small-socket, 117-volt decorator types that can be obtained from most hardware stores. Two recessed bulbs illuminate each area. DEVICE INTENDED FOR OLDER CHILDREN
Fig. 3 (Friendly). Key to wiring diagram for electrical assembly: Rl,2,3: KA 14 AY 120 volt 3PDT relays (Potter and Brumfield) ; R4: Guard ian 660-2C-120A reversing relay; R5: SA IN 12A 120 volt stepping relay (Potter and Brumfield) ; SI and S2: mismatched 1PST foot switches or Linemaster 476 S switch; power transformer: Stancor P-6466; diodes: 1/2 amp 200 volts PIV.
Technical description and operation—This device (Fig. 6 ) , which was first brought to our attention by Dr. Mary Fletcher of Houston, Texas, consists of a silent Super-8 projector which shows continuous loop film. Although several models are currently available, our experience is limited to Tech nicolor* Model 510 with a right-angle * Technicolor Commercial and Education Divi sion, 1300 Frawley Drive, Costa Mesa, California 92627.
590
AMERICAN JOURNAL OF OPHTHALMOLOGY
I À
APRIL, 1972
COMMENT
/
■O
Fig. 5 (Friendly). Back of enclosure, showing terminals for leads from toys and anchoring tacks for securing tethers.
screen. The projector is a compact, light, inexpensive type which utilizes film car tridges, a 150-watt projection lamp and im peller fan. Four-minute continuous films can be shown without threading or rewinding. A wall shelf that is 20 feet from the patient provides a convenient location for both the projector and right-angle screen. A foot switch is preferred for remote operation of the projector. Although a large variety of films are avail able through retail photographic supply stores, color cartoons have been found dis tinctly preferable. Projectors utilizing Super 8 motion pic tures in loop form with sound tracks may be purchased at considerably higher prices. Sound movies are not superior to silent films, since projection devices are reserved for older children who do not usually require the additional auditory stimulation. Also, the subject material of commercially available Super 8 sound movies is not as appropriate as that of the silent films.
Not infrequently, the accurate determina tion of ocular alignment by cover tests at distance is frustrated by a combination of patient fatigue, anxiety, inattentiveness, and short attention span. Infants and young chil dren should not be seen during periods nor mally reserved for rest, nor should they be obliged to wait unduly for examination.1 Almost all pédiatrie patients have anxiety about the office visit and this may be height ened by an "operating room" office decor or a lack of sensitivity on the part of the physi cian or assistants. White uniforms generally do not add to a sense of well-being. These and other environmental factors frequently bring to mind unpleasant past medical expe riences. Patient cooperation will be enhanced by attention to such details as the time of day of the examination, the length of the waiting period, the office design, the type of profes sional dress, and the manner of professional conduct. Nevertheless, patient inattentive ness may still result in an unsatisfactory ocular motility evaluation. It is in their ability to hold the child's at tention that fixation devices may play a deci sive role. Ennui develops with extraordinary rapidity in young children, hyperactive chil dren, retarded children, and those who are emotionally disturbed. Therefore, a variety of fixation targets is essential.2 For these
ft <^!$<^#
Fig. 6 (Friendly). Technicolor Model 510 with right-angle screen.
VOL. 73, NO. 4
FIXATION DEVICES
children, sound stimulation is advantageous and should be incorporated in the device uti lized. Older children do not require sound stimulation and respond well to silent mov ies. T h e examiner should attempt to interest the patient in the fixation object by making observations about the target, by asking questions about it, or by increasing aware ness of the fixation target by means of a story in which the object plays a leading role. P r o viding a modicum of control 3 over the fixa tion object, such as by saying, "Tell the dog to bark !" also increases attention. T h e examiner's fingers are generally the least offensive occluders. Black occluder paddles such as are used for older children and adults are distracting and at times frightening to the infant and young child. Foot switches have been found far superior to line or wall-mounted switches, because both of the examiner's hands must be free to manipulate prisms and covers and also be cause distracting movements should be avoided. T h e devices described have been found helpful in obtaining and maintaining ocular fixation, but no claim is made or implied for uniform success. O n e must always use judg ment, and if reasonable attempts to evaluate ocular alignment should fail it is occasionally prudent to cease testing altogether. W h e n confronted with a hopelessly obstreperous child, it is generally wiser to admit defeat
S91
and to a r r a n g e a second appointment for this portion of the examination than to jeopar dize future cooperation by badgering the pa tient. SUMMARY
Since surgery is largely based on the ocular alignment at distance, it is particularly im portant to obtain accurate and prolonged fixa tion at this testing distance. F o r this purpose, an enclosure for three noisy, brightly illumi nated, animated toys was developed. T h e toys are inexpensive, readily available, battery op erated types. An electrical assembly has been devised which eliminates the need for batteries and permits remote control operation of the toys, utilizing 117-volt alternating current. T h e toys and illuminating bulbs, which are also easily obtained, may be replaced without difficulty by the examiner or his assistant. Older children who will not fixate on dis tant Snellen optotypes will frequently fixate Super-8 color cartoons. A remotely controlled, shelf-mounted Technicolor model 510 projec tor with a right-angle screen has proved satisfactory for this purpose. REFERENCES
1. Parks, M. M. : Ocular motility diagnosis. Int. Ophth. Clin. 3:811, 1963. 2. Jampolsky, A. : Animated fixation targets for strabismus examination. Tr. Am. Acad. Ophth. Otolaryng. 64:213, 1960. 3. Jampolsky, A.: A simplified approach to stra bismus diagnosis. In Transactions of the New Orleans Academy of Ophthalmology. St. Louis. C. V. Mosby, 1971.