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Measurement of ocular torsion after macular translocation: disc fovea angle and maddox rod
Measurement of Ocular Torsion After Macular Translocation: Disc Fovea Angle and Maddox Rod Sharon F. Freedman, MD, Matthew D. Gearinger, MD, Laura B. Enyedi, MD, Sandra Holgado, MD, CO, and Cynthia A. Toth, MD Purpose: To compare two methods of measuring ocular torsion (the subjective Maddox rod [MR] test versus the objective disc-fovea angle [DFA] test) after macular translocation surgery. Methods: Ocular torsion was measured on consecutive patients after macular translocation at Duke University Eye Center between August 2001 and April 2002. Both MR and DFA measurements of torsion were made at the same clinic visit 4 to 8 weeks after the translocation surgery and again within 3 months after extraocular muscle surgery to decrease torsion. MR and DFA measurements were each performed by a separate examiner who was blinded to the results of the other method. Results: Thirty-five patients (35 eyes) were included for evaluation. Twenty-nine of these patients had intorsion measured by both MR and DFA after macular translocation but before extraocular muscle surgery (MR mean of 40.3 ⫹ 7.2 degrees v DFA mean of 47.0 ⫹ 7.9 degrees [P ⬍ .001]). The intrapatient reproducibility of the MR test was high (using four readings per session), with a mean coefficient variation of 4.8%. Twenty-five patients had residual torsion measured by both MR and DFA after extraocular muscle surgery (MR mean of 4.2 ⫹ 4.7 degrees v DFA of mean 4.8 ⫹ 7.0 degrees). There was good correlation between MR and DFA measurements of torsion (r 2 ⫽ 0.9). Conclusions: DFA measurement correlates well with MR measurement of torsion in patients after full macular translocation. This study verifies the reproducibility of MR to measure large angles of torsion and offers DFA as a simple corroborative test for measuring ocular torsion in patients with poor vision or cooperation. (J AAPOS 2003;7:103-107) acular translocation is a surgical treatment for subfoveal maculopathy that creates large-angle ocular torsion.1 The large magnitude and sudden onset of torsion in elderly patients causes disorientation and hinders use of the translocated eye. Extraocular muscle surgery is usually required to decrease or eliminate torsion and improve the patient’s ability to function with the translocated retina.2-5 The Maddox rod (MR) test is commonly used to quantify torsion after macular translocation.2-4,6-8 Some investigators, however, have reported that MR testing results are highly variable in macular translocation patients.3 In contrast to Fricke et al, we found the MR test to give reproducible, clinically useful measurements of torsion in patients after macular translocation.2,6
M
From Duke University Eye Center,a Durham, NC. Presented in part at the 2002 annual meeting of the American Association of Pediatric Ophthalmology and Strabismus, Seattle, WA. Submitted September 4, 2002. Revisions accepted December 24, 2002. Reprint requests: Sharon Freedman, MD, Duke University Eye Center, Box 3802, Durham, NC 27710. Copyright © 2003 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2003/$35.00 ⫹ 0 doi:10.1016/S1091-8531(03)00010-7
Journal of AAPOS
We therefore wished to re-evaluate the reproducibility of MR test measurements of torsion in a given eye after macular translocation and to evaluate a second, objective method of measuring torsion (the disc-fovea angle or DFA) in these same eyes. Spierer9 described an objective method of measuring ocular torsion by projecting a horizontal light beam from slit lamp onto the retina, connecting the fovea and the optic nerve.9 Although this investigator reported that ocular torsion measured by this test showed good correlation with torsion measured using the Maddox double-rod test10 or by indirect ophthalmoscopy,11 no data were provided.9 A modification of Spierer’s slit-lamp measurement of torsion was reported by Fujikado et al12 in their assessment of patients for myopic neovascular maculopathy after macular translocation. These investigators projected a slit-lamp beam onto the retina using a 90-diopter (D) lens and then rotated the slit until the patient perceived the light to be horizontal; hence, the test was used as a subjective assessment of ocular torsion. No mention of MR was made in this report,12 and we are not aware of any other publication of the results of DFA for measuring ocular torsion associated with macular translocation surgery. Our study was performed to compare an objective measure of ocular torsion (DFA) with a subjective measure (MR) in patients after macular translocation.1 April 2003
103
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FIG 1. A, The scale on the slit-lamp allows measurement of the angle of the slit-beam on the retina. B, Fundus following full macular translocation, demonstrating the disc-fovea angle. The observer views the posterior pole using a 90-diopter lens at the slit lamp (and would therefore see an inverted image), and turns the dial of the slit-beam (white line) until it connects the central portion of the optic nerve with the foveal reflex (“X”). The location of the scar at the site of the original subfoveal neovascular membrane is outlined by a black line.
SUBJECTS AND METHODS Consecutive patients were examined after macular translocation surgery. In each patient, the macula was rotated upward after full retinal detachment and 360-degree retinotomy as previously described.1 Each eye was filled with silicone oil after macular translocation. At the time of extraocular muscle surgery to decrease torsion, the silicone oil was removed. Patient age and visual acuity were recorded. Distance visual acuity (Early Treatment Diabetic Retinopathy Study (ETDRS)-Snellen equivalent by a standard technique) was recorded in a subset of patients both before and 6 months after macular translocation. Snellen acuity was recorded using a video acuity tester (B-VAT) (Mentor O&O, Houston, TX) instrument after macular translocation and while the eye was filled with silicone oil. The subjective degree of intorsion was measured using MR.2 In a darkened room, a red Maddox rod was placed before the operated eye, and the patient stated when the line appeared vertical while viewing a bright light at 13 inches in primary gaze. We chose to perform MR such that the lines appeared vertical to the patient (rods were horizontal). Pilot testing in 17 patients showed that similar results were obtained whether we oriented the Maddox rods vertically (with perceived lines horizontal, as is the usual method) or horizontally (with perceived lines vertical); data are not shown. We found that patients could be
more easily measured with MR when the perceived line was vertical, perhaps partly because of the vertical strabismus created by the macular translocation surgery and also partly because of the large central scotoma always present in the macula of the fellow eye being tested. The patient’s head position was controlled with a level attached to the trial frame. The average of four readings was recorded to the nearest 2.5 degrees, approaching the end point alternately from the incyclo- and excyclo-positions. Double- and single-rod MR usually yielded similar results, but only single-rod MR results were used because some patients could not see both rods during double-rod MR. All clinical decisions regarding surgical intervention for correction of torsion were based on MR (rather than DFA) measurements because this has been our standard method of evaluating torsion since we began performing macular translocation surgery followed by extraocular muscle surgery at our institution in 1998. An objective measurement of torsion, DFA, was performed at the slit lamp as described by Spierer.9 A scale was created that measures the amount of rotation of the slit beam (Figure 1A). A 90-D lens was then used to examine the fundus, and the slit beam was aligned so it connected the center of the optic disc and the center of the fovea (Figure 1B). Two observers recorded DFA results to the nearest 2.5 degrees for most patients, but the data were used only from a single observer (MDG) who recorded the
Journal of AAPOS Volume 7 Number 2 April 2003
DFA for each patient in the study and who was always blinded to the MR measurement. All patients at our institution routinely have extraocular muscle surgery to decrease torsion,2,8 and the silicone oil is removed from the operated eye 4 to 8 weeks after macular translocation. Extraocular muscle surgery involves tenotomy of the superior oblique tendon, advancement of the inferior oblique muscle, and transposition of the lateral and usually also the medial rectus muscles toward the superior and inferior rectus muscle insertions, respectively.8 Because the macular translocation (which creates intorsion) and the extraocular muscle surgery (to decrease torsion) are performed as sequential surgeries, we were able to measure intorsion using both MR and DFA before and after extraocular muscle surgery. MR measurement of torsion was performed for each patient before and after extraocular muscle surgery, but DFA measurements were occasionally not available because of the absence of a second blinded clinician. All MR measurements were made by a single certified orthoptist (SH) or a pediatric ophthalmologist (SFF or LBE). Only paired measurements (ie, MR and DFA readings taken at the same clinical examination) were used for analysis. Data are reported as mean plus standard deviation unless otherwise stated. Statistical comparisons were performed using Student t test (paired or unpaired as appropriate); two-sided P values of ⬍ .05 were considered significant. Linear regression and coefficients of variation were used to evaluate the relationship between MR and DFA measurements, and the coefficient of variation was calculated to evaluate the reproducibility of MR measurements for a given patient. All patients examined were approved by the Institutional Review Board for retrospective evaluation of sensorimotor outcomes associated with macular translocation and extraocular muscle surgery.
RESULTS Thirty-five patients were included, 14 men and 21 women; mean age was 74 years (range, 24 to 90). Results of distance visual acuity by ETDRS testing was available in a subset of 16 patients both before macular translocation (median, 20/180; range 20/50 to 20/320) and 6 months after both macular translocation and extraocular muscle surgery/silicone oil removal (median, 20/90; range 20/40 to 20/250). Vision after macular translocation but before removal of silicone oil was in all 35 cases less than the 6-month visual acuity measurement (median, 8/200; range, 1/200 to 20/100). All 35 eyes underwent torsion measurement using MR after macular translocation surgery and again after extraocular muscle surgery to decrease torsion. All patients had large-angle intorsion measured by MR testing 4 to 8 weeks after macular translocation but before extraocular muscle surgery. Twenty-nine of these 35 patients had both MR and DFA measurements taken before extraocular muscle surgery. Mean intorsion by MR measurement was
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FIG 2. A comparison of Maddox rod (MR) and disc-fovea angle (DFA) measurements of intorsion both before and after surgery. Intorsion is plotted in degrees on the y-axis by the methods of DFA and MR for a group of 29 patients before (Pre-Op) and 25 patients after (Post-Op) extraocular muscle surgery to decrease torsion. Although mean DFA measurement exceeded mean MR measurement in the preoperative time period (P ⬍ .001), there was no significant difference between mean DFA and MR measurements in the postoperative period.
40.3 ⫹ 7.2 degrees (range, 18 to 52). The DFA measurement was usually larger than the MR measurement (mean DFA, 47.0 ⫹ 7.9 degrees; range, 35-68; P ⬍ .001 v mean MR measurement). The mean intrapatient differences (DFA–MR) were 6.6 ⫹ 7.3 degrees; range was 10 to ⫹ 25 (Figure 2). Intrapatient reproducibility of MR measurements before extraocular muscle surgery was high; mean coefficient of variation was 4.9% (range, 0 to 7.2; data not shown). In 25 patients, MR and DFA measurements were also taken for residual torsion after extraocular muscle surgery. This measurement was made between 1 week and 3 months after surgery. Mean residual intorsion by MR measured 4.2 ⫹ 4.7 degrees and by DFA measured 4.8 ⫹ 7.0 degrees (P ⬎ .05) (Figure 2). The mean intrapatient difference (DFA–MR) was 0.6 ⫹ 5.0 degrees (range, ⫺ 8.5 to ⫹ 9.0). Correlation between MR and DFA measurements of torsion was made using a subset of 19 patients who had torsion measured by both MR and DFA methods after macular translocation both before and after extraocular muscle surgery (r 2 ⫽ 0.92; data not shown). The mean coefficient of variation (DFA–MR) was 12.8% before extraocular muscle surgery in this group (Figure 3, preoperative panel). The mean coefficient of variation (DFA–MR) was not calculated after extraocular muscle surgery because the small absolute readings by both DFA and MR methods made standard deviations on these differences large, even though clinically the two methods gave similar results (Figure 3, postoperative panel).
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FIG 3. Maddox rod (MR) test and disc-fovea angle (DFA) test yield congruent measurements of intorsion both before and after surgery. Comparison of intorsion (plotted in degrees on the y-axis) in a subset of 19 patients after macular translocation, whose torsion was measured by both MR and DFA methods both before (Pre-Op) and after (Post-Op) extraocular muscle surgery to decrease torsion.
In recognition of the physiological angle usually present between the optic nerve and the fovea,13,14 we took DFA measurements on five normal individuals whose MR torsion was 0 degrees. The mean DFA was 4.8 degrees of extorsion. We were unable to reliably measure DFA in our patient group before macular translocation surgery because of the large central macular abnormality present in these patients, which precluded precise identification of the fovea in most cases.
DISCUSSION DFA measurement correlates well with MR measurement of torsion in patients after full macular translocation. This study verifies the reproducibility of MR when measuring large angles of torsion and offers DFA as a simple corroborative test for ocular torsion in patients with poor vision or cooperation. In patients tested after macular translocation but before extraocular muscle surgery, the DFA measurement usually exceeded the MR measurement. Our DFA method in a small number of normal individuals showed approximately 5 degrees of extorsion, likely related to the physiological position of the optic nerve relative to the fovea. Because we measured more rather than less intorsion by the DFA method (compared with the subjective angle of torsion by MR) in our patients after macular translocation, factors other than the physiological offset of the optic nerve relative to the macula must be present. We cannot rule out a compensatory sensory adaptation by the patient or another factor yet unidentified. Because all patients in this series had fairly acute-onset intorsion, we would not expect significant monocular adaptation to occur; hence, we obtained similar torsion measurements with both single- and double-rod MR. Nonetheless, the difference between MR and DFA measurements of torsion was not great enough to alter the surgical plan for extraocular muscle surgery to decrease torsion. After extraocular muscle surgery, there was no significant
difference between MR and DFA measurements of residual torsion. We are unable to explain the large variability in MR readings reported by Fricke et al3 in their clinical series of patients undergoing macular translocation surgery. We propose that MR can be performed in patients with agerelated macular degeneration and macular subretinal neovascular membranes, despite their central scotomas, because the projected line on the retina covers a broader area than the fovea alone, allowing the patient to respond even when a central portion of the line is distorted or missing from view. Both the subjective MR and the objective DFA produced clinically useful measurements of torsion, either could be used to guide the clinical management of torsion associated with macular translocation surgery. In the occasional patient for whom MR measurements of torsion after macular translocation seem variable or disparate from the clinician’s impression of the retinal rotation by indirect ophthalmoscopy, DFA measurement provides an additional technique to quantify ocular torsion.
References 1. Toth CA, Freedman SF. Macular translocation with 360-degree peripheral retinectomy: impact of technique and surgical experience on visual outcomes. Retina 2001;21:293-303. 2. Freedman SF, Seaber JH, Buckley EG, Enyedi LB, Toth CA. Combined superior oblique muscle recession and inferior oblique muscle advancement and transposition for cyclotorsion associated with macular translocation surgery. J AAPOS 2000;4:75-83. 3. Fricke J, Neugebauer A, Nobis H, Bartz-Schmidt KU, Rubmann W. Counterrotation of the globe in macular translocation. Graefe’s Arch Clin Exp Ophthalmol 2000;238:664-8. 4. Eckardt C, Eckardt U, Conrad H-G. Macular rotation with and without counter-rotation of the globe in patients with age-related macular degeneration. Graefe’s Arch Clin Exp Ophthalmol 1999; 237:313-25. 5. Aisenbrey S, Lafaut B, Szurman P, et al. Macular translocation with
Journal of AAPOS Volume 7 Number 2 April 2003
6.
7.
8.
9.
360 degree retinotomy for exudative age-related macular degeneration. Arch Ophthalmol 2002;120:451-459. Seaber JH, Machemer R. Adaptation to monocular torsion after macular translocation. Graefe’s Arch Clin Exp Ophthalmol 1997; 235:76-81. Eckardt U, Eckardt C. Orthoptische probleme nach makularotation mit und ohne muskelchirurgie. Klin Monatsbl Augenheilkd 1998; 212:212-7. Freedman SF, Rojas M, Toth CA. Strabismus surgery for large-angle cyclotorsion after macular translocation surgery. J AAPOS 2002;6: 154-62. Spierer A. Measurement of cyclotorsion. Am J Ophthalmol 1996; 122:911-2.
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10. von Noorden GK. Clinical and theoretical aspects of cyclotropia. J Ped Ophthalmol Strabismus 1984;21:126-32. 11. Guyton DL. Clinical assessment of ocular torsion. Am Orthoptic J 1983;33:7-15. 12. Fujikado T, Ohji M, Saito Y, Hayashi A, Tano Y. Visual function after foveal translocation with scleral shortening in patients with myopic neovascular maculopathy. Am J Ophthalmol 1998;125:64756. 13. Madigan WP, Katz NNK. Ocular torsion— direct measurement with indirect ophthalmoscope and protractor. J Pediatr Ophthalmol Strabismus 1992;29:171-4. 14. Bixenman WW, von Noorden GK. Apparent foveal displacement in normal subjects and in cyclotorsion. Ophthalmol 1982;89:58-62.
M
From Duke University Eye Center,a Durham, NC. Presented in part at the 2002 annual meeting of the American Association of Pediatric Ophthalmology and Strabismus, Seattle, WA. Submitted September 4, 2002. Revisions accepted December 24, 2002. Reprint requests: Sharon Freedman, MD, Duke University Eye Center, Box 3802, Durham, NC 27710. Copyright © 2003 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2003/$35.00 ⫹ 0 doi:10.1016/S1091-8531(03)00010-7
Journal of AAPOS
We therefore wished to re-evaluate the reproducibility of MR test measurements of torsion in a given eye after macular translocation and to evaluate a second, objective method of measuring torsion (the disc-fovea angle or DFA) in these same eyes. Spierer9 described an objective method of measuring ocular torsion by projecting a horizontal light beam from slit lamp onto the retina, connecting the fovea and the optic nerve.9 Although this investigator reported that ocular torsion measured by this test showed good correlation with torsion measured using the Maddox double-rod test10 or by indirect ophthalmoscopy,11 no data were provided.9 A modification of Spierer’s slit-lamp measurement of torsion was reported by Fujikado et al12 in their assessment of patients for myopic neovascular maculopathy after macular translocation. These investigators projected a slit-lamp beam onto the retina using a 90-diopter (D) lens and then rotated the slit until the patient perceived the light to be horizontal; hence, the test was used as a subjective assessment of ocular torsion. No mention of MR was made in this report,12 and we are not aware of any other publication of the results of DFA for measuring ocular torsion associated with macular translocation surgery. Our study was performed to compare an objective measure of ocular torsion (DFA) with a subjective measure (MR) in patients after macular translocation.1 April 2003
103
104
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Journal of AAPOS Volume 7 Number 2 April 2003
FIG 1. A, The scale on the slit-lamp allows measurement of the angle of the slit-beam on the retina. B, Fundus following full macular translocation, demonstrating the disc-fovea angle. The observer views the posterior pole using a 90-diopter lens at the slit lamp (and would therefore see an inverted image), and turns the dial of the slit-beam (white line) until it connects the central portion of the optic nerve with the foveal reflex (“X”). The location of the scar at the site of the original subfoveal neovascular membrane is outlined by a black line.
SUBJECTS AND METHODS Consecutive patients were examined after macular translocation surgery. In each patient, the macula was rotated upward after full retinal detachment and 360-degree retinotomy as previously described.1 Each eye was filled with silicone oil after macular translocation. At the time of extraocular muscle surgery to decrease torsion, the silicone oil was removed. Patient age and visual acuity were recorded. Distance visual acuity (Early Treatment Diabetic Retinopathy Study (ETDRS)-Snellen equivalent by a standard technique) was recorded in a subset of patients both before and 6 months after macular translocation. Snellen acuity was recorded using a video acuity tester (B-VAT) (Mentor O&O, Houston, TX) instrument after macular translocation and while the eye was filled with silicone oil. The subjective degree of intorsion was measured using MR.2 In a darkened room, a red Maddox rod was placed before the operated eye, and the patient stated when the line appeared vertical while viewing a bright light at 13 inches in primary gaze. We chose to perform MR such that the lines appeared vertical to the patient (rods were horizontal). Pilot testing in 17 patients showed that similar results were obtained whether we oriented the Maddox rods vertically (with perceived lines horizontal, as is the usual method) or horizontally (with perceived lines vertical); data are not shown. We found that patients could be
more easily measured with MR when the perceived line was vertical, perhaps partly because of the vertical strabismus created by the macular translocation surgery and also partly because of the large central scotoma always present in the macula of the fellow eye being tested. The patient’s head position was controlled with a level attached to the trial frame. The average of four readings was recorded to the nearest 2.5 degrees, approaching the end point alternately from the incyclo- and excyclo-positions. Double- and single-rod MR usually yielded similar results, but only single-rod MR results were used because some patients could not see both rods during double-rod MR. All clinical decisions regarding surgical intervention for correction of torsion were based on MR (rather than DFA) measurements because this has been our standard method of evaluating torsion since we began performing macular translocation surgery followed by extraocular muscle surgery at our institution in 1998. An objective measurement of torsion, DFA, was performed at the slit lamp as described by Spierer.9 A scale was created that measures the amount of rotation of the slit beam (Figure 1A). A 90-D lens was then used to examine the fundus, and the slit beam was aligned so it connected the center of the optic disc and the center of the fovea (Figure 1B). Two observers recorded DFA results to the nearest 2.5 degrees for most patients, but the data were used only from a single observer (MDG) who recorded the
Journal of AAPOS Volume 7 Number 2 April 2003
DFA for each patient in the study and who was always blinded to the MR measurement. All patients at our institution routinely have extraocular muscle surgery to decrease torsion,2,8 and the silicone oil is removed from the operated eye 4 to 8 weeks after macular translocation. Extraocular muscle surgery involves tenotomy of the superior oblique tendon, advancement of the inferior oblique muscle, and transposition of the lateral and usually also the medial rectus muscles toward the superior and inferior rectus muscle insertions, respectively.8 Because the macular translocation (which creates intorsion) and the extraocular muscle surgery (to decrease torsion) are performed as sequential surgeries, we were able to measure intorsion using both MR and DFA before and after extraocular muscle surgery. MR measurement of torsion was performed for each patient before and after extraocular muscle surgery, but DFA measurements were occasionally not available because of the absence of a second blinded clinician. All MR measurements were made by a single certified orthoptist (SH) or a pediatric ophthalmologist (SFF or LBE). Only paired measurements (ie, MR and DFA readings taken at the same clinical examination) were used for analysis. Data are reported as mean plus standard deviation unless otherwise stated. Statistical comparisons were performed using Student t test (paired or unpaired as appropriate); two-sided P values of ⬍ .05 were considered significant. Linear regression and coefficients of variation were used to evaluate the relationship between MR and DFA measurements, and the coefficient of variation was calculated to evaluate the reproducibility of MR measurements for a given patient. All patients examined were approved by the Institutional Review Board for retrospective evaluation of sensorimotor outcomes associated with macular translocation and extraocular muscle surgery.
RESULTS Thirty-five patients were included, 14 men and 21 women; mean age was 74 years (range, 24 to 90). Results of distance visual acuity by ETDRS testing was available in a subset of 16 patients both before macular translocation (median, 20/180; range 20/50 to 20/320) and 6 months after both macular translocation and extraocular muscle surgery/silicone oil removal (median, 20/90; range 20/40 to 20/250). Vision after macular translocation but before removal of silicone oil was in all 35 cases less than the 6-month visual acuity measurement (median, 8/200; range, 1/200 to 20/100). All 35 eyes underwent torsion measurement using MR after macular translocation surgery and again after extraocular muscle surgery to decrease torsion. All patients had large-angle intorsion measured by MR testing 4 to 8 weeks after macular translocation but before extraocular muscle surgery. Twenty-nine of these 35 patients had both MR and DFA measurements taken before extraocular muscle surgery. Mean intorsion by MR measurement was
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FIG 2. A comparison of Maddox rod (MR) and disc-fovea angle (DFA) measurements of intorsion both before and after surgery. Intorsion is plotted in degrees on the y-axis by the methods of DFA and MR for a group of 29 patients before (Pre-Op) and 25 patients after (Post-Op) extraocular muscle surgery to decrease torsion. Although mean DFA measurement exceeded mean MR measurement in the preoperative time period (P ⬍ .001), there was no significant difference between mean DFA and MR measurements in the postoperative period.
40.3 ⫹ 7.2 degrees (range, 18 to 52). The DFA measurement was usually larger than the MR measurement (mean DFA, 47.0 ⫹ 7.9 degrees; range, 35-68; P ⬍ .001 v mean MR measurement). The mean intrapatient differences (DFA–MR) were 6.6 ⫹ 7.3 degrees; range was 10 to ⫹ 25 (Figure 2). Intrapatient reproducibility of MR measurements before extraocular muscle surgery was high; mean coefficient of variation was 4.9% (range, 0 to 7.2; data not shown). In 25 patients, MR and DFA measurements were also taken for residual torsion after extraocular muscle surgery. This measurement was made between 1 week and 3 months after surgery. Mean residual intorsion by MR measured 4.2 ⫹ 4.7 degrees and by DFA measured 4.8 ⫹ 7.0 degrees (P ⬎ .05) (Figure 2). The mean intrapatient difference (DFA–MR) was 0.6 ⫹ 5.0 degrees (range, ⫺ 8.5 to ⫹ 9.0). Correlation between MR and DFA measurements of torsion was made using a subset of 19 patients who had torsion measured by both MR and DFA methods after macular translocation both before and after extraocular muscle surgery (r 2 ⫽ 0.92; data not shown). The mean coefficient of variation (DFA–MR) was 12.8% before extraocular muscle surgery in this group (Figure 3, preoperative panel). The mean coefficient of variation (DFA–MR) was not calculated after extraocular muscle surgery because the small absolute readings by both DFA and MR methods made standard deviations on these differences large, even though clinically the two methods gave similar results (Figure 3, postoperative panel).
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FIG 3. Maddox rod (MR) test and disc-fovea angle (DFA) test yield congruent measurements of intorsion both before and after surgery. Comparison of intorsion (plotted in degrees on the y-axis) in a subset of 19 patients after macular translocation, whose torsion was measured by both MR and DFA methods both before (Pre-Op) and after (Post-Op) extraocular muscle surgery to decrease torsion.
In recognition of the physiological angle usually present between the optic nerve and the fovea,13,14 we took DFA measurements on five normal individuals whose MR torsion was 0 degrees. The mean DFA was 4.8 degrees of extorsion. We were unable to reliably measure DFA in our patient group before macular translocation surgery because of the large central macular abnormality present in these patients, which precluded precise identification of the fovea in most cases.
DISCUSSION DFA measurement correlates well with MR measurement of torsion in patients after full macular translocation. This study verifies the reproducibility of MR when measuring large angles of torsion and offers DFA as a simple corroborative test for ocular torsion in patients with poor vision or cooperation. In patients tested after macular translocation but before extraocular muscle surgery, the DFA measurement usually exceeded the MR measurement. Our DFA method in a small number of normal individuals showed approximately 5 degrees of extorsion, likely related to the physiological position of the optic nerve relative to the fovea. Because we measured more rather than less intorsion by the DFA method (compared with the subjective angle of torsion by MR) in our patients after macular translocation, factors other than the physiological offset of the optic nerve relative to the macula must be present. We cannot rule out a compensatory sensory adaptation by the patient or another factor yet unidentified. Because all patients in this series had fairly acute-onset intorsion, we would not expect significant monocular adaptation to occur; hence, we obtained similar torsion measurements with both single- and double-rod MR. Nonetheless, the difference between MR and DFA measurements of torsion was not great enough to alter the surgical plan for extraocular muscle surgery to decrease torsion. After extraocular muscle surgery, there was no significant
difference between MR and DFA measurements of residual torsion. We are unable to explain the large variability in MR readings reported by Fricke et al3 in their clinical series of patients undergoing macular translocation surgery. We propose that MR can be performed in patients with agerelated macular degeneration and macular subretinal neovascular membranes, despite their central scotomas, because the projected line on the retina covers a broader area than the fovea alone, allowing the patient to respond even when a central portion of the line is distorted or missing from view. Both the subjective MR and the objective DFA produced clinically useful measurements of torsion, either could be used to guide the clinical management of torsion associated with macular translocation surgery. In the occasional patient for whom MR measurements of torsion after macular translocation seem variable or disparate from the clinician’s impression of the retinal rotation by indirect ophthalmoscopy, DFA measurement provides an additional technique to quantify ocular torsion.
References 1. Toth CA, Freedman SF. Macular translocation with 360-degree peripheral retinectomy: impact of technique and surgical experience on visual outcomes. Retina 2001;21:293-303. 2. Freedman SF, Seaber JH, Buckley EG, Enyedi LB, Toth CA. Combined superior oblique muscle recession and inferior oblique muscle advancement and transposition for cyclotorsion associated with macular translocation surgery. J AAPOS 2000;4:75-83. 3. Fricke J, Neugebauer A, Nobis H, Bartz-Schmidt KU, Rubmann W. Counterrotation of the globe in macular translocation. Graefe’s Arch Clin Exp Ophthalmol 2000;238:664-8. 4. Eckardt C, Eckardt U, Conrad H-G. Macular rotation with and without counter-rotation of the globe in patients with age-related macular degeneration. Graefe’s Arch Clin Exp Ophthalmol 1999; 237:313-25. 5. Aisenbrey S, Lafaut B, Szurman P, et al. Macular translocation with
Journal of AAPOS Volume 7 Number 2 April 2003
6.
7.
8.
9.
360 degree retinotomy for exudative age-related macular degeneration. Arch Ophthalmol 2002;120:451-459. Seaber JH, Machemer R. Adaptation to monocular torsion after macular translocation. Graefe’s Arch Clin Exp Ophthalmol 1997; 235:76-81. Eckardt U, Eckardt C. Orthoptische probleme nach makularotation mit und ohne muskelchirurgie. Klin Monatsbl Augenheilkd 1998; 212:212-7. Freedman SF, Rojas M, Toth CA. Strabismus surgery for large-angle cyclotorsion after macular translocation surgery. J AAPOS 2002;6: 154-62. Spierer A. Measurement of cyclotorsion. Am J Ophthalmol 1996; 122:911-2.
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10. von Noorden GK. Clinical and theoretical aspects of cyclotropia. J Ped Ophthalmol Strabismus 1984;21:126-32. 11. Guyton DL. Clinical assessment of ocular torsion. Am Orthoptic J 1983;33:7-15. 12. Fujikado T, Ohji M, Saito Y, Hayashi A, Tano Y. Visual function after foveal translocation with scleral shortening in patients with myopic neovascular maculopathy. Am J Ophthalmol 1998;125:64756. 13. Madigan WP, Katz NNK. Ocular torsion— direct measurement with indirect ophthalmoscope and protractor. J Pediatr Ophthalmol Strabismus 1992;29:171-4. 14. Bixenman WW, von Noorden GK. Apparent foveal displacement in normal subjects and in cyclotorsion. Ophthalmol 1982;89:58-62.