The 43rd Richard G. Scobee Memorial Lecture
Fusional Amplitudes: Exploring Where Fusion Falters Katherine J. Fray, C.O.
ABSTRACT Background and Purpose: The stability of binocular vision depends on good fusional amplitudes, but the assessment of fusional amplitudes varies around the world. The author reviewed the literature on fusional amplitudes and surveyed international orthoptists on their assessment of fusional amplitudes. The purpose of the study was to determine whether or not there is variation in fusional amplitudes in normal subjects when looking at the role of examiner encouragement; the order of testing; the method of testing; and the subject’s level of alertness. The preliminary results from this ongoing, prospective study are presented. Patients and Methods: Using a modified crossover design study, the author prospectively assessed fusional amplitudes in fifty participants with normal eye exams who met inclusion criteria. The measurements were done in two separate sessions with each participant being randomized as to the order of fusional vergence testing. All participants were assessed without and with encouragement in the first session. In the second session, all were assessed at different testing distances. Results: Convergence is significantly affected by encouragement and divergence is significantly reduced if assessed after convergence. Numbers were too small to get meaningful data on the effect of fatigue on final outcome measures. Conclusions: We need to develop consistency in assessing fusional amplitudes and agree upon a standard of testing. Variables such as the order of testing, whether or not encouragement is given, and a person’s level of alertness can affect the final outcome. Encouragement should be done especially when assessing convergence fusional amplitudes and divergence should be assessed prior to convergence. Finally, it is important to note a patient’s level of alertness during vergence testing, especially if they are feeling foggy on one visit and are alert on the next. By implementing these strategies into your assessment of fusional amplitudes, the examiner will know if a change in amplitudes is due to treatment effect or just testing method.
INTRODUCTION A highlight of attending Academy is hearing the Richard G. Scobee Memorial Lecture at this annual meeting of the American Association of Certified Orthoptists (AACO). Since 1970, we have had
the privilege of learning from some of the giants in ophthalmology and orthoptics who have dedicated their professional careers to researching binocular vision and ocular motility (Table 1). I am humbled that the AACO and the Scobee Committee selected me to join the company of such
© 2013 Board of Regents of the University of Wisconsin System, American Orthoptic Journal, Volume 63, 2013, ISSN 0065-955X, E-ISSN 1553-4448
American Orthoptic Journal
41
SCOBEE LECTURE
TABLE 1 PREVIOUS SCOBEE LECTURERS (1970-2011) YEAR
LECTURER
YEAR
LECTURER
1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990
Philip Knapp, M.D. Stanley Truhlsen, M.D Goodwin Breinin, M.D. Hermann Burian, M.D. Lisa Cibis, M.D., C.O. John Pratt-Johnson, M.D. Gill Roper-Hall, D.B.O.T, C.O., C.O.M.T. Paul Boeder, Ph.D. Betty Anne Haldi, C.O. Kenneth Swan, M.D. Frankie Stegall, C.O. John Flynn, M.D. Sally Moore, C.O. Gunter von Noorden, M.D. Nancy Capobianco, C.O. Eugene Helveston, M.D. Sara Shippman, C.O. Burton Kushner, M.D. Judy Seaber, C.O. Ronald Burde, M.D. Cindy Avilla, C.O.
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
I.M. Rabinowicz, M.D. Cindy Pritchard, C.O. William Scott, M.D. Paula Edelman, C.O. Thomas France, M.D. Jacqueline Frank, C.O. Malcolm Mazow, M.D. Carol Dickey, C.O. Marilyn Miller, M.D. Kyle Arnoldi, C.O. Monte Del Monte, M.D. Leslie Weingeist France, C.O. David L. Guyton, M.D. Pamela J. Kutschke, C.O. John D. Baker, M.D. Patricia Jenkins, C.O. Edward Buckley, M.D. Carole Panton, C.O., O.C.(C.), D.B.O. Edward Raab, M.D. Gail Morton, C.O. George Ellis, M.D.
distinguished lecturers. After looking at this list, I realized that many have contributed to my education through their writings or direct teachings. I also realized how the one common thread connecting each of us was our passion for the profession of orthoptics, a passion shared by Dr. Scobee. I am truly honored to deliver the 43rd Richard G. Scobee Memorial Lecture. BACKGROUND ON DR. SCOBEE1 This lectureship pays tribute to a man who made significant contributions to our profession and to our field of strabismus. Richard Scobee was born in November
1914 in Texas, where he lived until finishing medical school. He came to St. Louis, Missouri, in 1940 and started his career in ophthalmology. Completing his residency in 1942, he joined the ophthalmology staff at Washington University in St. Louis. Since our country was in the midst of World War II, he was granted a leave of absence to enter the United States Army Air Force in September 1943. He was assigned to the Department of Ophthalmology in the School of Aviation Medicine and soon learned that there were no adequate answers to questions concerning normal and abnormal muscle balance. He sought to fill this void and embarked on his jour-
From the Arkansas Children’s Hospital, and Jones Eye Institute, Department of Ophthalmology, University of Arkansas for Medical Sciences, Little Rock, Arkansas. Requests for reprints should be addressed to: Katherine J. Fray, C.O., Arkansas Children’s Hospital, 1 Children’s Way, Eye Clinic, Slot 111, Little Rock, AR 72202. Presented as part of a Symposium of the Joint Meeting of the American Orthoptic Council, the American Association of Certified Orthoptists, and the American Academy of Ophthalmology, Chicago, Illinois, November 12, 2012.
42
Volume 63, 2013
FRAY
ney of clinical research into the field of ocular motility. He submerged himself looking into problems in ocular motility and continued his work after he returned to St. Louis in 1945. Through the course of his research, he realized the importance of having a good orthoptist. His enthusiasm for orthoptics led to his appointment to the American Orthoptic Council in 1948. There he was inspired to help educate the next generation of orthoptists (Figures 1 and 2). In 1949, he organized an orthoptic training program at Washington University. He also organized the successful summer Orthoptic Basic Science course which continued each year through 1979. I am fortunate to gain a little more insight on Dr. Scobee from certified orthoptist Clara Berryman. In a conversation with Clara (on June 8, 2011) I learned that she was an orthoptic student who attended Dr. Scobee’s 1950 Orthoptic Basic Science course held that year in Boston. After meeting him, she said that she was “impressed with the way he was” and knew that she wanted to train with him if only for a short time before she took her oral/ practical exams. She managed to work with Dr. Scobee for approximately two months, where she learned that he was an excellent clinician and an astute observer. She also learned that he was “always full of energy” and loved to teach. He was instrumental in teaching her how to think critically. Several afternoons a week, Dr. Scobee would review articles, books, and chapters on ocular motility. He would tell the students, “Unless you know the basics, you shouldn’t believe anything in writing.” His enthusiasm for ocular motility was contagious. She said, “He made you excited about things and was very encouraging.” In 1950, Dr. Scobee helped to pioneer the collaboration between the American Academy of Ophthalmology and Otolaryngology (now the American Academy of Ophthalmology) and the American Association of
American Orthoptic Journal
FIGURE 1: Dr. Scobee demonstrates the action of the oculorotary muscles with an ophthalmotrope. (Photo reprinted with permission from the Visual Collections of the Becker Medical Library, Washington University School of Medicine, St. Louis, Missouri.)
FIGURE 2: Dr. Scobee gives instruction on heterotropia and measuring the angle of deviation with a perimeter. (Photo reprinted with permission from the Visual Collections of the Becker Medical Library, Washington University School of Medicine, St. Louis, Missouri.)
Orthoptic Technicians (now the AACO) by founding the orthoptic instruction courses which are held each year at the Academy meeting. Believing that orthoptists should be actively involved in research and writing, he was instrumental in founding the American Orthoptic Journal in 1950 and was the journal’s first editor. Dr. Scobee was a remarkable educator and advocate of the orthoptic profession. It is fitting that
43
SCOBEE LECTURE
he has been referred to as “the Father of American Orthoptics.” His memory lives on through this lectureship and the Scobee Award given to our best and brightest orthoptic students who graduate from American orthoptic training programs. INSPIRATION FOR THIS LECTURE It is evident that Dr. Scobee had many accomplishments in his 10 years after becoming an ophthalmologist until his untimely death in 1952.1 He published almost sixty-five scientific articles and two textbooks during his short career. The second edition of his text The Oculorotary Muscles came out shortly before his death.2 It was here where I sought inspiration for this lecture. I found a drawing depicting fusion as a “benevolent genie” (Figure 3).2 The genie is holding many reins in his hands that run to the two eyeballs. The reins represent the nerves that control eye movements via the muscles. Playing on the reins are tiny gremlins that represent various reflexes, including accommodative- convergence, cortical, postural, and fixation. In the figure legend, Dr. Scobee wrote, “As long as Fusion keeps a firm hand on the reins,
no ocular deviation is permitted.” His illustration of fusion made me think about fusional vergences and the factors that influence our ability to maintain binocular single vision. When doing prism vergence tests, the eyes must make an immediate readjustment to overcome diplopia induced by the prism. This readjustment is part of the fusion reflex and assessing the range of vergence is an important diagnostic tool in the strabismus work-up. I started my investigation of vergence ability by sending a survey to my orthoptic colleagues on the list-serves of the AACO and of the International Orthoptic Association (Table 2). I wanted to see if there were differences in the way fusional amplitudes were assessed by orthoptists around the world. I had a total of ninety responses from seventeen different countries, including seventeen from the United States (Table 3). After reviewing the variety of responses that I received on my survey, I decided that some of the variables needed further investigation. Previous studies have been conducted to evaluate fusional amplitudes; however, these studies did not document parameters such as whether or not the subject was alert and whether or not the subject was encouraged during the testing. In addition, many studies neglected to mention in what order the measurements were taken. CURRENT STUDY
FIGURE 3: Figure 64 from Dr. Scobee’s book with a genie representing fusion. (Reprinted from Scobee RG, The Oculorotary Muscles, 2nd ed., 1952; “Chapter 9: Heterophoria,” p. 126. With permission from Elsevier.)
44
In a prospective study, I sought to investigate the measurement of fusional amplitudes without and with encouragement. I repeated these measurements on a different day, but changed the order of vergence assessment to see if the final outcome was affected. Although the order of testing has been investigated previously, to my knowledge, this is the first study of fusional amplitudes within normal subjects to look at the role of examiner’s en-
Volume 63, 2013
FRAY
TABLE 2 SURVEY QUESTIONS ASKED OF ORTHOPTISTS FOR FUSIONAL AMPLITUDE STUDY 1. How do you measure fusional amplitudes/vergence ability? 2. How do you determine fixing eye? 3. At what distance do you measure the patient? 4. If you measure at distance and near, which measurement do you complete first? 5. When measuring horizontal amplitudes, which do you complete first: convergence or divergence? 6. Do you routinely measure fusional amplitudes or do you measure only if a patient needs further investigation? 7. Do you investigate fusion potential in the opposite direction (e.g., if a patient has convergence insufficiency, do you assess divergence amplitudes)? 8. Do you give encouragement when completing the measurements? 9. Do you note the time of day when you complete the measurements? 10. Do you note whether or not the patient is fatigued? 11. What do you consider to be normal minimum fusional amplitudes (horizontal, vertical, torsional)?
couragement to see if the final outcome is affected. MATERIALS AND METHODS Following protocol approval from the Institutional Review Board at the University of Arkansas for Medical Sciences and Arkansas Children’s Hospital, I obtained written informed consent from fifty participants over the age of 18 who met inclusion criteria. Exclusion criteria included best-corrected visual acuity of less than 20/30 in either eye, a history of manifest or intermittent strabismus, a history of strabismus surgery, or symptoms of disrupted binocular vision or diplopia. The average age of study participants was 37 years old with a range of 20-65 years. The median age was 32 years. The ratio of females to males was approximately 4:1. Each participant had a full orthoptic evaluation while wearing appropriate refractive correction. Alternate prism and cover test was performed at the distances of 6 m and 1/3 m. The average deviation at 6 m was 0.34Δ X (range of 8 Δ X to 4 Δ E) and 1.53 Δ X′ (range of 14 Δ X′ to 4 Δ E′) at 1/3 m. Measured heterophorias were incorporated into the final value of the fusional amplitudes for each study participant.2, 3 In a modified crossover design study,
American Orthoptic Journal
TABLE 3 DISTRIBUTION OF INTERNATIONAL ORTHOPTISTS RESPONDING TO FUSIONAL AMPLITUDE SURVEY (n = 90) COUNTRY
RESPONSES RECEIVED
Australia Austria Belgium Brazil Canada Czech Republic Denmark Germany Hong Kong Japan Netherlands Norway Portugal Sweden Switzerland United Kingdom United States
2 9 2 6 8 1 1 3 3 1 9 8 3 9 3 5 17
fusional amplitudes of convergence and divergence were assessed; however, the ordering in which the participant received each assessment was randomized into one of two sequence groups. One group received convergence assessments followed by divergence in their first session, while the second group had divergence assessed prior to convergence. The order was reversed for both groups in the second session (Table 4).
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SCOBEE LECTURE
TABLE 4 SUMMARY OF THE MODIFIED CROSSOVER DESIGN USED FOR FUSIONAL AMPLITUDE STUDY Sequence Group Session
1
2
Assessment
Encouragement
Testing Distance
1
C→D
D→C
2
D→C
C→D
1 2 1 2
No Yes Yes Yes
6m 6m 1/3 m 6m
C = Convergence; D = Divergence.
The design of this study was modified from the traditional two-period crossover design as each participant was assessed twice under experimental conditions in each session. In the first session, the initial assessment was made without encouragement while the second assessment was made with encouragement. All first session assessments were made with the participant focusing on a 20/40 (6/12) target at a distance of 6 m. The only difference was whether or not encouragement was given. For the second session, the first assessment was performed while the participant focused on a 20/40 target at 1/3 m; while the second assessment was again made focusing on a distant target. All measurements obtained in the second session were performed with encouragement. The only difference was the testing distance (Table 4). At the start of each session, the participant’s level of alertness was assessed using the Stanford Sleepiness Scale (Table 5).4 This scale provided a quick and simple way to quantitate alertness regardless of the time of day in which the assessment was made. VERGENCE TESTING Three of the most popular means to assess fusional amplitudes is via the synoptophore, prism bar, or a Risley rotary prism.5 In Dr. Scobee’s investigation of prism ver-
46
TABLE 5 AN INTROSPECTIVE MEASURE OF SLEEPINESS: STANFORD SLEEPINESS SCALE Scale Rating
Degree of Sleepiness Feeling active, vital, alert or wide awake Functioning at high levels, but not a peak; able to concentrate Awake but relaxed; responsive but not fully alert Somewhat foggy, let down Foggy; losing interest in remaining awake; slowed down Sleepy, woozy, fighting sleep; prefer to lie down No longer fighting sleep, sleep onset soon; having dream-like thoughts Asleep
1 2 3 4 5 6 7 X
From: www.stanford.edu/~dement/sss.html
gence testing, the Risley rotary prism was used.2, 3 He thought that the steady increase in prism power would reveal more vergence power than loose prisms or even the prism bar. Consequently, the first question of my survey pertained to the equipment used to measure fusional amplitudes (Table 2). A total of 97% of the orthoptists reported using a prism bar. Of these, 40% would occasionally use a synoptophore. The Risley rotary prism was used by 3% of the orthoptists with 2% opting to use loose prisms only. Because of the overwhelming number of orthoptists using the prism bar, it was the obvious choice for my prospective study.6
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FRAY
Next, I needed to decide about my measurement technique, and, specifically, on which eye the prism bar should be placed. In response to survey questions pertaining to the fixing eye, 68% of orthoptists said they made note of the fixing eye. Of these, 48% would repeat the measurements fixing with the opposite eye. The fixing eye was determined by cover test (46%), dominance testing or observation (26%), by visual acuity (11%) or by asking the patient (6%). The remaining respondents said that they did not consider the fixing eye but habitually held the prism bar over the same eye (usually the right eye). In the literature, there is some controversy pertaining to the effect of ocular dominance on vergence testing and the selection of the proper eye for fixation. Is there a role in vergence testing? Several investigators found no statistical difference when the prism bar was placed before either eye.2, 6-9 For consistency, I decided to place the prism bar before the non-dominant eye. Ocular dominance was determined by having the participant form the shape of an “O” with one hand and then encircling this with the other hand. The participant was asked to hold up their hands in front of their face and look at my face through the “O”. I was seated about 1-2 m from the participant and I could easily determine the dominant eye using this technique. For vergence testing, I started with the smallest prism on the prism bar held in the frontal position and gradually increased the prism strength. I recorded the blur point (if it was noted), the break point, and the recovery point. For purposes of this study, I did not analyze data pertaining to the blur point. ORDER OF TESTING Does the order of horizontal vergence testing affect the end results? Should you assess divergence amplitudes or conver-
American Orthoptic Journal
gence amplitudes first? 2, 10-11 Forty-two percent of the survey respondents said that divergence amplitudes should always be completed first, whereas 29% routinely assessed convergence amplitudes first. The remaining respondents said that they would tailor the order of their exam to the patient’s symptoms. Thus, if the patient had an esodeviation, they would assess divergence amplitudes first, but would assess convergence amplitudes in a patient with an exodeviation. To test whether or not the order of vergence testing affected the end result, I randomized participants into one of two sequence groups. During the first session, half had convergence tested first and the other half had divergence tested first. The order in which the measurements were performed was switched for the second session (Table 4). Wilcoxon signed-rank tests (WSRT) were used to evaluate the effect of the order in which convergence and divergence measures were made. I found that the order did not appear to affect convergence break or recovery points, but both divergence break and recovery points were significantly affected (break: P = 0.015; recovery: P = 0.024). Divergence break and recovery points seemed to be higher when tested before convergence and lower when tested after convergence (Table 6). ENCOURAGEMENT The role of encouragement has been well documented in the sports research literature12 and psychology literature.13-15 Can a person’s fusional amplitudes be affected by encouragement given by the examiner? Dr. Scobee was a believer in this saying, “If the patient is a child, or even an adult, the use of verbal exhortation is of value in securing an accurate measurement.”2 Seventysix percent of the orthoptists in my survey said that it was important to always give encouragement during fusional amplitude testing. An additional 13% said that they
47
SCOBEE LECTURE
TABLE 6 EFFECT OF ORDERING ON MEASURES OF CONVERGENCE AND DIVERGENCE (n = 50) First
Convergence Divergence
Break Recovery Break Recovery
Second
Mean
Median (IQR)
Mean
Median (IQR)
WSRT P-value
26.5 18.3 7.2 5
25.5 (20, 31.6) 16 (10.9, 21) 7.3 (6, 8) 4.3 (4, 6)
27 18.9 6.7 4.5
25.8 (20, 33.9) 16 (12, 23.5) 6 (6, 8) 4 (4, 5.6)
0.4284 0.2839 0.0447 0.0237
Data is from Session 1, Assessment 2 and Session 2, Assessment 2. IQR = Interquartile range; WSRT = Wilcoxon signed-rank test.
TABLE 7 EFFECT OF ENCOURAGEMENT ON MEASURES OF CONVERGENCE AND DIVERGENCE (n = 50)
Convergence Divergence
Break Recovery Break Recovery
Encouragement
No Encouragement
Mean
Median (IQR)
Mean
Median (IQR)
WSRT P-value
26.7 18.2 6.7 4.6
25.5 (20, 35) 16 (10.9, 24.8) 6 (6, 8) 4 (4, 6)
24.3 16.6 6.7 4.3
25 (16.5, 30) 14 (8.9, 20) 6 (6, 8) 4 (2.9, 6)
0.0014 0.0007 0.7768 0.1320
would occasionally give encouragement, especially if examining a child. The rest of the respondents said that they did not offer any encouragement. WSRT were used to compare convergence and divergence measurements taken when participants were not encouraged (Session 1, assessment 1) to those taken when participants were encouraged (Session 1, assessment 2) (Table 4). It appears that encouragement has a statistically significant effect on convergence break point (P = 0.001) and convergence recovery point (P
Fusional Amplitudes: Exploring Where Fusion Falters Katherine J. Fray, C.O.
ABSTRACT Background and Purpose: The stability of binocular vision depends on good fusional amplitudes, but the assessment of fusional amplitudes varies around the world. The author reviewed the literature on fusional amplitudes and surveyed international orthoptists on their assessment of fusional amplitudes. The purpose of the study was to determine whether or not there is variation in fusional amplitudes in normal subjects when looking at the role of examiner encouragement; the order of testing; the method of testing; and the subject’s level of alertness. The preliminary results from this ongoing, prospective study are presented. Patients and Methods: Using a modified crossover design study, the author prospectively assessed fusional amplitudes in fifty participants with normal eye exams who met inclusion criteria. The measurements were done in two separate sessions with each participant being randomized as to the order of fusional vergence testing. All participants were assessed without and with encouragement in the first session. In the second session, all were assessed at different testing distances. Results: Convergence is significantly affected by encouragement and divergence is significantly reduced if assessed after convergence. Numbers were too small to get meaningful data on the effect of fatigue on final outcome measures. Conclusions: We need to develop consistency in assessing fusional amplitudes and agree upon a standard of testing. Variables such as the order of testing, whether or not encouragement is given, and a person’s level of alertness can affect the final outcome. Encouragement should be done especially when assessing convergence fusional amplitudes and divergence should be assessed prior to convergence. Finally, it is important to note a patient’s level of alertness during vergence testing, especially if they are feeling foggy on one visit and are alert on the next. By implementing these strategies into your assessment of fusional amplitudes, the examiner will know if a change in amplitudes is due to treatment effect or just testing method.
INTRODUCTION A highlight of attending Academy is hearing the Richard G. Scobee Memorial Lecture at this annual meeting of the American Association of Certified Orthoptists (AACO). Since 1970, we have had
the privilege of learning from some of the giants in ophthalmology and orthoptics who have dedicated their professional careers to researching binocular vision and ocular motility (Table 1). I am humbled that the AACO and the Scobee Committee selected me to join the company of such
© 2013 Board of Regents of the University of Wisconsin System, American Orthoptic Journal, Volume 63, 2013, ISSN 0065-955X, E-ISSN 1553-4448
American Orthoptic Journal
41
SCOBEE LECTURE
TABLE 1 PREVIOUS SCOBEE LECTURERS (1970-2011) YEAR
LECTURER
YEAR
LECTURER
1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990
Philip Knapp, M.D. Stanley Truhlsen, M.D Goodwin Breinin, M.D. Hermann Burian, M.D. Lisa Cibis, M.D., C.O. John Pratt-Johnson, M.D. Gill Roper-Hall, D.B.O.T, C.O., C.O.M.T. Paul Boeder, Ph.D. Betty Anne Haldi, C.O. Kenneth Swan, M.D. Frankie Stegall, C.O. John Flynn, M.D. Sally Moore, C.O. Gunter von Noorden, M.D. Nancy Capobianco, C.O. Eugene Helveston, M.D. Sara Shippman, C.O. Burton Kushner, M.D. Judy Seaber, C.O. Ronald Burde, M.D. Cindy Avilla, C.O.
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
I.M. Rabinowicz, M.D. Cindy Pritchard, C.O. William Scott, M.D. Paula Edelman, C.O. Thomas France, M.D. Jacqueline Frank, C.O. Malcolm Mazow, M.D. Carol Dickey, C.O. Marilyn Miller, M.D. Kyle Arnoldi, C.O. Monte Del Monte, M.D. Leslie Weingeist France, C.O. David L. Guyton, M.D. Pamela J. Kutschke, C.O. John D. Baker, M.D. Patricia Jenkins, C.O. Edward Buckley, M.D. Carole Panton, C.O., O.C.(C.), D.B.O. Edward Raab, M.D. Gail Morton, C.O. George Ellis, M.D.
distinguished lecturers. After looking at this list, I realized that many have contributed to my education through their writings or direct teachings. I also realized how the one common thread connecting each of us was our passion for the profession of orthoptics, a passion shared by Dr. Scobee. I am truly honored to deliver the 43rd Richard G. Scobee Memorial Lecture. BACKGROUND ON DR. SCOBEE1 This lectureship pays tribute to a man who made significant contributions to our profession and to our field of strabismus. Richard Scobee was born in November
1914 in Texas, where he lived until finishing medical school. He came to St. Louis, Missouri, in 1940 and started his career in ophthalmology. Completing his residency in 1942, he joined the ophthalmology staff at Washington University in St. Louis. Since our country was in the midst of World War II, he was granted a leave of absence to enter the United States Army Air Force in September 1943. He was assigned to the Department of Ophthalmology in the School of Aviation Medicine and soon learned that there were no adequate answers to questions concerning normal and abnormal muscle balance. He sought to fill this void and embarked on his jour-
From the Arkansas Children’s Hospital, and Jones Eye Institute, Department of Ophthalmology, University of Arkansas for Medical Sciences, Little Rock, Arkansas. Requests for reprints should be addressed to: Katherine J. Fray, C.O., Arkansas Children’s Hospital, 1 Children’s Way, Eye Clinic, Slot 111, Little Rock, AR 72202. Presented as part of a Symposium of the Joint Meeting of the American Orthoptic Council, the American Association of Certified Orthoptists, and the American Academy of Ophthalmology, Chicago, Illinois, November 12, 2012.
42
Volume 63, 2013
FRAY
ney of clinical research into the field of ocular motility. He submerged himself looking into problems in ocular motility and continued his work after he returned to St. Louis in 1945. Through the course of his research, he realized the importance of having a good orthoptist. His enthusiasm for orthoptics led to his appointment to the American Orthoptic Council in 1948. There he was inspired to help educate the next generation of orthoptists (Figures 1 and 2). In 1949, he organized an orthoptic training program at Washington University. He also organized the successful summer Orthoptic Basic Science course which continued each year through 1979. I am fortunate to gain a little more insight on Dr. Scobee from certified orthoptist Clara Berryman. In a conversation with Clara (on June 8, 2011) I learned that she was an orthoptic student who attended Dr. Scobee’s 1950 Orthoptic Basic Science course held that year in Boston. After meeting him, she said that she was “impressed with the way he was” and knew that she wanted to train with him if only for a short time before she took her oral/ practical exams. She managed to work with Dr. Scobee for approximately two months, where she learned that he was an excellent clinician and an astute observer. She also learned that he was “always full of energy” and loved to teach. He was instrumental in teaching her how to think critically. Several afternoons a week, Dr. Scobee would review articles, books, and chapters on ocular motility. He would tell the students, “Unless you know the basics, you shouldn’t believe anything in writing.” His enthusiasm for ocular motility was contagious. She said, “He made you excited about things and was very encouraging.” In 1950, Dr. Scobee helped to pioneer the collaboration between the American Academy of Ophthalmology and Otolaryngology (now the American Academy of Ophthalmology) and the American Association of
American Orthoptic Journal
FIGURE 1: Dr. Scobee demonstrates the action of the oculorotary muscles with an ophthalmotrope. (Photo reprinted with permission from the Visual Collections of the Becker Medical Library, Washington University School of Medicine, St. Louis, Missouri.)
FIGURE 2: Dr. Scobee gives instruction on heterotropia and measuring the angle of deviation with a perimeter. (Photo reprinted with permission from the Visual Collections of the Becker Medical Library, Washington University School of Medicine, St. Louis, Missouri.)
Orthoptic Technicians (now the AACO) by founding the orthoptic instruction courses which are held each year at the Academy meeting. Believing that orthoptists should be actively involved in research and writing, he was instrumental in founding the American Orthoptic Journal in 1950 and was the journal’s first editor. Dr. Scobee was a remarkable educator and advocate of the orthoptic profession. It is fitting that
43
SCOBEE LECTURE
he has been referred to as “the Father of American Orthoptics.” His memory lives on through this lectureship and the Scobee Award given to our best and brightest orthoptic students who graduate from American orthoptic training programs. INSPIRATION FOR THIS LECTURE It is evident that Dr. Scobee had many accomplishments in his 10 years after becoming an ophthalmologist until his untimely death in 1952.1 He published almost sixty-five scientific articles and two textbooks during his short career. The second edition of his text The Oculorotary Muscles came out shortly before his death.2 It was here where I sought inspiration for this lecture. I found a drawing depicting fusion as a “benevolent genie” (Figure 3).2 The genie is holding many reins in his hands that run to the two eyeballs. The reins represent the nerves that control eye movements via the muscles. Playing on the reins are tiny gremlins that represent various reflexes, including accommodative- convergence, cortical, postural, and fixation. In the figure legend, Dr. Scobee wrote, “As long as Fusion keeps a firm hand on the reins,
no ocular deviation is permitted.” His illustration of fusion made me think about fusional vergences and the factors that influence our ability to maintain binocular single vision. When doing prism vergence tests, the eyes must make an immediate readjustment to overcome diplopia induced by the prism. This readjustment is part of the fusion reflex and assessing the range of vergence is an important diagnostic tool in the strabismus work-up. I started my investigation of vergence ability by sending a survey to my orthoptic colleagues on the list-serves of the AACO and of the International Orthoptic Association (Table 2). I wanted to see if there were differences in the way fusional amplitudes were assessed by orthoptists around the world. I had a total of ninety responses from seventeen different countries, including seventeen from the United States (Table 3). After reviewing the variety of responses that I received on my survey, I decided that some of the variables needed further investigation. Previous studies have been conducted to evaluate fusional amplitudes; however, these studies did not document parameters such as whether or not the subject was alert and whether or not the subject was encouraged during the testing. In addition, many studies neglected to mention in what order the measurements were taken. CURRENT STUDY
FIGURE 3: Figure 64 from Dr. Scobee’s book with a genie representing fusion. (Reprinted from Scobee RG, The Oculorotary Muscles, 2nd ed., 1952; “Chapter 9: Heterophoria,” p. 126. With permission from Elsevier.)
44
In a prospective study, I sought to investigate the measurement of fusional amplitudes without and with encouragement. I repeated these measurements on a different day, but changed the order of vergence assessment to see if the final outcome was affected. Although the order of testing has been investigated previously, to my knowledge, this is the first study of fusional amplitudes within normal subjects to look at the role of examiner’s en-
Volume 63, 2013
FRAY
TABLE 2 SURVEY QUESTIONS ASKED OF ORTHOPTISTS FOR FUSIONAL AMPLITUDE STUDY 1. How do you measure fusional amplitudes/vergence ability? 2. How do you determine fixing eye? 3. At what distance do you measure the patient? 4. If you measure at distance and near, which measurement do you complete first? 5. When measuring horizontal amplitudes, which do you complete first: convergence or divergence? 6. Do you routinely measure fusional amplitudes or do you measure only if a patient needs further investigation? 7. Do you investigate fusion potential in the opposite direction (e.g., if a patient has convergence insufficiency, do you assess divergence amplitudes)? 8. Do you give encouragement when completing the measurements? 9. Do you note the time of day when you complete the measurements? 10. Do you note whether or not the patient is fatigued? 11. What do you consider to be normal minimum fusional amplitudes (horizontal, vertical, torsional)?
couragement to see if the final outcome is affected. MATERIALS AND METHODS Following protocol approval from the Institutional Review Board at the University of Arkansas for Medical Sciences and Arkansas Children’s Hospital, I obtained written informed consent from fifty participants over the age of 18 who met inclusion criteria. Exclusion criteria included best-corrected visual acuity of less than 20/30 in either eye, a history of manifest or intermittent strabismus, a history of strabismus surgery, or symptoms of disrupted binocular vision or diplopia. The average age of study participants was 37 years old with a range of 20-65 years. The median age was 32 years. The ratio of females to males was approximately 4:1. Each participant had a full orthoptic evaluation while wearing appropriate refractive correction. Alternate prism and cover test was performed at the distances of 6 m and 1/3 m. The average deviation at 6 m was 0.34Δ X (range of 8 Δ X to 4 Δ E) and 1.53 Δ X′ (range of 14 Δ X′ to 4 Δ E′) at 1/3 m. Measured heterophorias were incorporated into the final value of the fusional amplitudes for each study participant.2, 3 In a modified crossover design study,
American Orthoptic Journal
TABLE 3 DISTRIBUTION OF INTERNATIONAL ORTHOPTISTS RESPONDING TO FUSIONAL AMPLITUDE SURVEY (n = 90) COUNTRY
RESPONSES RECEIVED
Australia Austria Belgium Brazil Canada Czech Republic Denmark Germany Hong Kong Japan Netherlands Norway Portugal Sweden Switzerland United Kingdom United States
2 9 2 6 8 1 1 3 3 1 9 8 3 9 3 5 17
fusional amplitudes of convergence and divergence were assessed; however, the ordering in which the participant received each assessment was randomized into one of two sequence groups. One group received convergence assessments followed by divergence in their first session, while the second group had divergence assessed prior to convergence. The order was reversed for both groups in the second session (Table 4).
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TABLE 4 SUMMARY OF THE MODIFIED CROSSOVER DESIGN USED FOR FUSIONAL AMPLITUDE STUDY Sequence Group Session
1
2
Assessment
Encouragement
Testing Distance
1
C→D
D→C
2
D→C
C→D
1 2 1 2
No Yes Yes Yes
6m 6m 1/3 m 6m
C = Convergence; D = Divergence.
The design of this study was modified from the traditional two-period crossover design as each participant was assessed twice under experimental conditions in each session. In the first session, the initial assessment was made without encouragement while the second assessment was made with encouragement. All first session assessments were made with the participant focusing on a 20/40 (6/12) target at a distance of 6 m. The only difference was whether or not encouragement was given. For the second session, the first assessment was performed while the participant focused on a 20/40 target at 1/3 m; while the second assessment was again made focusing on a distant target. All measurements obtained in the second session were performed with encouragement. The only difference was the testing distance (Table 4). At the start of each session, the participant’s level of alertness was assessed using the Stanford Sleepiness Scale (Table 5).4 This scale provided a quick and simple way to quantitate alertness regardless of the time of day in which the assessment was made. VERGENCE TESTING Three of the most popular means to assess fusional amplitudes is via the synoptophore, prism bar, or a Risley rotary prism.5 In Dr. Scobee’s investigation of prism ver-
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TABLE 5 AN INTROSPECTIVE MEASURE OF SLEEPINESS: STANFORD SLEEPINESS SCALE Scale Rating
Degree of Sleepiness Feeling active, vital, alert or wide awake Functioning at high levels, but not a peak; able to concentrate Awake but relaxed; responsive but not fully alert Somewhat foggy, let down Foggy; losing interest in remaining awake; slowed down Sleepy, woozy, fighting sleep; prefer to lie down No longer fighting sleep, sleep onset soon; having dream-like thoughts Asleep
1 2 3 4 5 6 7 X
From: www.stanford.edu/~dement/sss.html
gence testing, the Risley rotary prism was used.2, 3 He thought that the steady increase in prism power would reveal more vergence power than loose prisms or even the prism bar. Consequently, the first question of my survey pertained to the equipment used to measure fusional amplitudes (Table 2). A total of 97% of the orthoptists reported using a prism bar. Of these, 40% would occasionally use a synoptophore. The Risley rotary prism was used by 3% of the orthoptists with 2% opting to use loose prisms only. Because of the overwhelming number of orthoptists using the prism bar, it was the obvious choice for my prospective study.6
Volume 63, 2013
FRAY
Next, I needed to decide about my measurement technique, and, specifically, on which eye the prism bar should be placed. In response to survey questions pertaining to the fixing eye, 68% of orthoptists said they made note of the fixing eye. Of these, 48% would repeat the measurements fixing with the opposite eye. The fixing eye was determined by cover test (46%), dominance testing or observation (26%), by visual acuity (11%) or by asking the patient (6%). The remaining respondents said that they did not consider the fixing eye but habitually held the prism bar over the same eye (usually the right eye). In the literature, there is some controversy pertaining to the effect of ocular dominance on vergence testing and the selection of the proper eye for fixation. Is there a role in vergence testing? Several investigators found no statistical difference when the prism bar was placed before either eye.2, 6-9 For consistency, I decided to place the prism bar before the non-dominant eye. Ocular dominance was determined by having the participant form the shape of an “O” with one hand and then encircling this with the other hand. The participant was asked to hold up their hands in front of their face and look at my face through the “O”. I was seated about 1-2 m from the participant and I could easily determine the dominant eye using this technique. For vergence testing, I started with the smallest prism on the prism bar held in the frontal position and gradually increased the prism strength. I recorded the blur point (if it was noted), the break point, and the recovery point. For purposes of this study, I did not analyze data pertaining to the blur point. ORDER OF TESTING Does the order of horizontal vergence testing affect the end results? Should you assess divergence amplitudes or conver-
American Orthoptic Journal
gence amplitudes first? 2, 10-11 Forty-two percent of the survey respondents said that divergence amplitudes should always be completed first, whereas 29% routinely assessed convergence amplitudes first. The remaining respondents said that they would tailor the order of their exam to the patient’s symptoms. Thus, if the patient had an esodeviation, they would assess divergence amplitudes first, but would assess convergence amplitudes in a patient with an exodeviation. To test whether or not the order of vergence testing affected the end result, I randomized participants into one of two sequence groups. During the first session, half had convergence tested first and the other half had divergence tested first. The order in which the measurements were performed was switched for the second session (Table 4). Wilcoxon signed-rank tests (WSRT) were used to evaluate the effect of the order in which convergence and divergence measures were made. I found that the order did not appear to affect convergence break or recovery points, but both divergence break and recovery points were significantly affected (break: P = 0.015; recovery: P = 0.024). Divergence break and recovery points seemed to be higher when tested before convergence and lower when tested after convergence (Table 6). ENCOURAGEMENT The role of encouragement has been well documented in the sports research literature12 and psychology literature.13-15 Can a person’s fusional amplitudes be affected by encouragement given by the examiner? Dr. Scobee was a believer in this saying, “If the patient is a child, or even an adult, the use of verbal exhortation is of value in securing an accurate measurement.”2 Seventysix percent of the orthoptists in my survey said that it was important to always give encouragement during fusional amplitude testing. An additional 13% said that they
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TABLE 6 EFFECT OF ORDERING ON MEASURES OF CONVERGENCE AND DIVERGENCE (n = 50) First
Convergence Divergence
Break Recovery Break Recovery
Second
Mean
Median (IQR)
Mean
Median (IQR)
WSRT P-value
26.5 18.3 7.2 5
25.5 (20, 31.6) 16 (10.9, 21) 7.3 (6, 8) 4.3 (4, 6)
27 18.9 6.7 4.5
25.8 (20, 33.9) 16 (12, 23.5) 6 (6, 8) 4 (4, 5.6)
0.4284 0.2839 0.0447 0.0237
Data is from Session 1, Assessment 2 and Session 2, Assessment 2. IQR = Interquartile range; WSRT = Wilcoxon signed-rank test.
TABLE 7 EFFECT OF ENCOURAGEMENT ON MEASURES OF CONVERGENCE AND DIVERGENCE (n = 50)
Convergence Divergence
Break Recovery Break Recovery
Encouragement
No Encouragement
Mean
Median (IQR)
Mean
Median (IQR)
WSRT P-value
26.7 18.2 6.7 4.6
25.5 (20, 35) 16 (10.9, 24.8) 6 (6, 8) 4 (4, 6)
24.3 16.6 6.7 4.3
25 (16.5, 30) 14 (8.9, 20) 6 (6, 8) 4 (2.9, 6)
0.0014 0.0007 0.7768 0.1320
would occasionally give encouragement, especially if examining a child. The rest of the respondents said that they did not offer any encouragement. WSRT were used to compare convergence and divergence measurements taken when participants were not encouraged (Session 1, assessment 1) to those taken when participants were encouraged (Session 1, assessment 2) (Table 4). It appears that encouragement has a statistically significant effect on convergence break point (P = 0.001) and convergence recovery point (P
