- Email: [email protected]
Cyclotorsion in the seated and supine patient
Cyclotorsion in the seated and supine patient Eugene M. Smith, Jr., M.D., Jonathan H. Talamo, M.D.
ABSTRACT We used Maddox double-rod measurements to determine if positionally induced ocular cyclotorsion occurs when a patient moves from the seated to supine position. Maddox double-rod measurements were determined twice while patients (N = 30) viewed a fixation light at a distance of 7 feet in both the seated and supine positions. The difference between axis measurements made in seated and supine positions was not statistically significant. There was also no significant difference between the two measurements made in the seated and in the supine positions. These data show that the eyes do not undergo positionally induced ocular cyclotorsion when a patient moves from a seated to a supine position. Key Words: astigmatism, astigmatic keratotomy, axis, cyclotorsion, exci-
mer laser, keratorefractive surgery, radial keratotomy
Axis of astigmatism and refractive error are determined with patients in the seated position, while astigmatic keratorefractive procedures are performed with patients in the supine position. If eyes undergo a torsional shift when patients move from a seated to a supine position, inaccurate alignment of surgery with respect to axis of astigmatism may occur. Established keratorefractive procedures, such as astigmatic keratotomy, are already in use and additional procedures have been proposed, such as use of an excimer laser with an ablatable mask or software algorithms to create elliptical ablation areas. 1- 3 Best visual outcome may be compromised by misalignment of the treated axis with the patient's actual axis. Our review of the literature revealed many discussions of the actions of the extraocular muscles, yet none specifically addressed the possibility of positionally induced cyclotorsion when a patient moves from a seated to a supine position. 4 - 6 The double Maddox rod can be used to test ocular torsion. 5 •6 We used Maddox double-rod measurements to determine if ocular cyclotorsion occurs when a patient moves from the seated to supine position.
disease or ocular motility disturbance, and best corrected visual acuity of worse than 20/20 in either eye. Patients were fitted with a pair of trial frames containing two Maddox rods. Corrective lenses were added to the frames if needed. Identical fixation lights were placed 7 feet above and in front of the patients. These distances were chosen based on the height limitation of the examination room. The Maddox rod covering the left eye was locked and not allowed to rotate. While viewing the fixation light in the seated position, patients turned the knob on the trial frames to adjust the axis of the Maddox rod covering the right eye until the two linear images were aligned. The axis on the trial frame was recorded to the nearest 0.5 degree. Next, the examiner rotated the Maddox rod covering the right eye at least 45 degrees and asked the patient to readjust the Maddox rod a second time to obtain another measurement to allow analysis of reproducibility. The process was repeated with the patient in the supine position. The same examiner (E.M.S.) did all measurements and fitting of the trial frames.
MATERIALS AND METHODS
RESULTS
The study comprised 30 patients with normal ophthalmologic examinations. Exclusion criteria included age less than 21 years, history of previous or current eye
No statistically significant changes were found between the axis measured in the seated and the supine positions using this Maddox double-rod technique.
From the Department of Ophthalmology, Rhode Island Hospital, Brown University, Providence, (Smith), and the Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston (Talamo). 402
J CATARACT REFRACT SURG-VOL 21, JULY 1995
The mean difference of measurements made in seated and supine positions ( ±SD) was 0.2 ± 1.2 degree (range -2.0 to 4.0 degrees; P = .41, paired, two-tail t-test). There was also no statistically significant difference between the two measurements made in each position. The mean difference between the two measurements made in the seated position was 0.1 ± 1.3 degree (range -3.0 to 4.0 degrees; P = .84). The difference between the two measurements in the supine position was 0 ±: 0.9 degree (range -1.5 to 3.0 ' degrees; P = .92).
believe that surgeons should mark the axis of astigmatism before performing keratorefractive procedures to help ensure proper axis alignment. Possible causes of incorrect alignment with axis of astigmatism include tilting of the patient's head, unmasking of a cyclophoria, unintentional rotation of the operating microscope, or distortion of the globe by a lid retractor. Meticulous attention to axis alignment before performing astigmatic keratorefractive procedures should help achieve the best postoperative results.
DISCUSSION Our data show that the eyes did not undergo positionally induced ocular cyclotorsion when a patient moved from a seated to a supine position. We have previously shown that there are no statistically significant differences between the axis measured in the seated and supine positions using refractive techniques and an accommodative target. 7 This study was done using a Maddox double-rod technique with patients in the seated and supine positions and fixating on an unaccommodative target (a fixation light). One might expect the use of an unaccommodative target to unmask an esophoria, exophoria, or cyclophoria and yield larger differences than refractive techniques using an accommodative target. Although the differences obtained using refractive techniques did not reach statistical significance, 7 they were greater than those obtained using this Maddox rod technique, indicating that the refractive techniques are less precise. Despite finding no differences between the seated and supine positions in axis of astigmatism, we
REFERENCES 1. Brancato R, Carones F, Trabucchi G, et al. The erodible
2. 3. 4. 5. 6. 7.
mask in photorefractive keratectomy for myopia and astigmatism. Refract Corneal Surg 1993; 9(suppl): S125-S130 McDonnell PJ, Moreira H, Garbus J, et al. Photorefractive keratectomy to create toric ablations for correction of astigmatism. Arch Ophthalmol 1991; 109:710-713 McDonnell PJ, Moreira H, Clapham TN, et al. Photorefractive keratectomy for astigmatism; initial clinical results. Arch Ophthalmol 1991; 109:1370-1373 Jampel RS. The fundamental principle of the action of the oblique ocular muscles. Am J Ophthalmol 1970; 69:623-638 Maddox EE. Tests and Studies of the Ocular Muscles, 3rd ed. Philadelphia, Keystone, 1907 Kushner BJ, Kraft S. Ocular torsional movements in normal humans. Am J Ophthalmol 1983; 98:752-762 Smith EM, Talamo JH, Assil KK, Petashnick DE. Comparison of astigmatic axis in the seated and supine positions. J Refract Corneal Surg 1994; 10:615-620
J CATARACT REFRACT SURG-VOL 21, JULY 1995
403
ABSTRACT We used Maddox double-rod measurements to determine if positionally induced ocular cyclotorsion occurs when a patient moves from the seated to supine position. Maddox double-rod measurements were determined twice while patients (N = 30) viewed a fixation light at a distance of 7 feet in both the seated and supine positions. The difference between axis measurements made in seated and supine positions was not statistically significant. There was also no significant difference between the two measurements made in the seated and in the supine positions. These data show that the eyes do not undergo positionally induced ocular cyclotorsion when a patient moves from a seated to a supine position. Key Words: astigmatism, astigmatic keratotomy, axis, cyclotorsion, exci-
mer laser, keratorefractive surgery, radial keratotomy
Axis of astigmatism and refractive error are determined with patients in the seated position, while astigmatic keratorefractive procedures are performed with patients in the supine position. If eyes undergo a torsional shift when patients move from a seated to a supine position, inaccurate alignment of surgery with respect to axis of astigmatism may occur. Established keratorefractive procedures, such as astigmatic keratotomy, are already in use and additional procedures have been proposed, such as use of an excimer laser with an ablatable mask or software algorithms to create elliptical ablation areas. 1- 3 Best visual outcome may be compromised by misalignment of the treated axis with the patient's actual axis. Our review of the literature revealed many discussions of the actions of the extraocular muscles, yet none specifically addressed the possibility of positionally induced cyclotorsion when a patient moves from a seated to a supine position. 4 - 6 The double Maddox rod can be used to test ocular torsion. 5 •6 We used Maddox double-rod measurements to determine if ocular cyclotorsion occurs when a patient moves from the seated to supine position.
disease or ocular motility disturbance, and best corrected visual acuity of worse than 20/20 in either eye. Patients were fitted with a pair of trial frames containing two Maddox rods. Corrective lenses were added to the frames if needed. Identical fixation lights were placed 7 feet above and in front of the patients. These distances were chosen based on the height limitation of the examination room. The Maddox rod covering the left eye was locked and not allowed to rotate. While viewing the fixation light in the seated position, patients turned the knob on the trial frames to adjust the axis of the Maddox rod covering the right eye until the two linear images were aligned. The axis on the trial frame was recorded to the nearest 0.5 degree. Next, the examiner rotated the Maddox rod covering the right eye at least 45 degrees and asked the patient to readjust the Maddox rod a second time to obtain another measurement to allow analysis of reproducibility. The process was repeated with the patient in the supine position. The same examiner (E.M.S.) did all measurements and fitting of the trial frames.
MATERIALS AND METHODS
RESULTS
The study comprised 30 patients with normal ophthalmologic examinations. Exclusion criteria included age less than 21 years, history of previous or current eye
No statistically significant changes were found between the axis measured in the seated and the supine positions using this Maddox double-rod technique.
From the Department of Ophthalmology, Rhode Island Hospital, Brown University, Providence, (Smith), and the Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston (Talamo). 402
J CATARACT REFRACT SURG-VOL 21, JULY 1995
The mean difference of measurements made in seated and supine positions ( ±SD) was 0.2 ± 1.2 degree (range -2.0 to 4.0 degrees; P = .41, paired, two-tail t-test). There was also no statistically significant difference between the two measurements made in each position. The mean difference between the two measurements made in the seated position was 0.1 ± 1.3 degree (range -3.0 to 4.0 degrees; P = .84). The difference between the two measurements in the supine position was 0 ±: 0.9 degree (range -1.5 to 3.0 ' degrees; P = .92).
believe that surgeons should mark the axis of astigmatism before performing keratorefractive procedures to help ensure proper axis alignment. Possible causes of incorrect alignment with axis of astigmatism include tilting of the patient's head, unmasking of a cyclophoria, unintentional rotation of the operating microscope, or distortion of the globe by a lid retractor. Meticulous attention to axis alignment before performing astigmatic keratorefractive procedures should help achieve the best postoperative results.
DISCUSSION Our data show that the eyes did not undergo positionally induced ocular cyclotorsion when a patient moved from a seated to a supine position. We have previously shown that there are no statistically significant differences between the axis measured in the seated and supine positions using refractive techniques and an accommodative target. 7 This study was done using a Maddox double-rod technique with patients in the seated and supine positions and fixating on an unaccommodative target (a fixation light). One might expect the use of an unaccommodative target to unmask an esophoria, exophoria, or cyclophoria and yield larger differences than refractive techniques using an accommodative target. Although the differences obtained using refractive techniques did not reach statistical significance, 7 they were greater than those obtained using this Maddox rod technique, indicating that the refractive techniques are less precise. Despite finding no differences between the seated and supine positions in axis of astigmatism, we
REFERENCES 1. Brancato R, Carones F, Trabucchi G, et al. The erodible
2. 3. 4. 5. 6. 7.
mask in photorefractive keratectomy for myopia and astigmatism. Refract Corneal Surg 1993; 9(suppl): S125-S130 McDonnell PJ, Moreira H, Garbus J, et al. Photorefractive keratectomy to create toric ablations for correction of astigmatism. Arch Ophthalmol 1991; 109:710-713 McDonnell PJ, Moreira H, Clapham TN, et al. Photorefractive keratectomy for astigmatism; initial clinical results. Arch Ophthalmol 1991; 109:1370-1373 Jampel RS. The fundamental principle of the action of the oblique ocular muscles. Am J Ophthalmol 1970; 69:623-638 Maddox EE. Tests and Studies of the Ocular Muscles, 3rd ed. Philadelphia, Keystone, 1907 Kushner BJ, Kraft S. Ocular torsional movements in normal humans. Am J Ophthalmol 1983; 98:752-762 Smith EM, Talamo JH, Assil KK, Petashnick DE. Comparison of astigmatic axis in the seated and supine positions. J Refract Corneal Surg 1994; 10:615-620
J CATARACT REFRACT SURG-VOL 21, JULY 1995
403