Journal of Pediatric Ophthalmology and Strabismus

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SHORT SUBJECTS 

A New Test for the Measurement of Torsion

Zoran Georgievski, BAppSc(Orth)Hons

Abstract

INTRODUCTION

Little over a decade ago at the annual meeting of the American Association for Pediatrie Ophthalmology and Strabismus, the Costenbader lecturer, Gunter von Noorden asked, "Why has cyclotropia been a stepchild of clinical investigation for so long?"1 Without doubt, part of the neglect in this field of strabismology has been due to the complexity of the measurement procedure found in some tests. Today, measurement of torsion is recognized to be an integral part of the examination of incomitant strabismus, since its presence and extent are important factors in planning treatment.

I have designed a new test for the measurement of torsion called the Torsionometer. It offers the advantages of portability, speed, and ease of use for both patient and examiner. The Torsionometer is a subjective test consisting of a white plate with a vertical red line beside a green one, which the patient rotates using a dial. The patient's view of the test has been designed so that there are minimal cues about objective parallelism. On the back of the test plate is a measurement scale corresponding to the orientation of the green line relative to the red line (Fig 1). This enables the examiner alone to read the amount of torsion present. The test is carried out in free-space with the patient wearing a pair of reversible complementary red and green goggles, such that each eye is presented with a different line image. The test plate and its surrounds provide material that is visible to both eyes so that cyclofusion, a most effective compensating mechanism in cyclodeviations,2 is not precluded. Therefore, the torsion of longstanding cyclotropia may be understated, revealing only that amount which is symptom-producing and clinically significant.

Measurement is relatively quick and uncomplicated. The test plate is held at a 40-cm viewing distance, perpendicularly to the patient's line of sight. To begin testing, the green line is rotated maximally in one direction and the patient attempts to make it subjectively parallel with the red line, using the finger-grip on the front of the test. The amount of torsion, if any, is then read off the scale. Up to 25° of excyclo- or incyclotorsion can be measured. Torsion can also be measured in secondary positions of gaze, eg, in downgaze, where it is often a problem, especially in bilateral fourth nerve palsy.3 The goggles provided enable unrestricted measurement in the reading position or extreme downgaze, which is often necessary.

1. von Noorden GK. Clinical and theoretical aspects of cyclotropia. J Pediatr Ophthalmol Strabismus. 1984; 21:126-132.

2. von Noorden GK. Binocular Vision and Ocular Motility. Theory and Management of Strabismus. 4th ed. St Louis, Mo: CV Mosby; 1990: 85.

3. Kraft SP, O'Reilly C, Quigley PL, Allen K, Eustis HS. Cyclotorsion in unilateral and bilateral superior oblique paresis. J Pediatr Ophthalmol Strabismus. 1993; 30: 36 1-36 7.

4. Georgievski Z. Comparison of 3 standard clinical tests and a new test for the measurement of torsional diplopia. In: Lennerstrand G, ed. Update on Strabismus and Pediatrie Ophthalmology. Boca Raton, FI: CRC Press; 1995:171-174.

TABLE

Correlation Matrix of R Statistic (of lntraclass Correlation Analyzes) for the Torsionometer, Synoptophore, DMR, and MOW Tests…

INTRODUCTION

Little over a decade ago at the annual meeting of the American Association for Pediatrie Ophthalmology and Strabismus, the Costenbader lecturer, Gunter von Noorden asked, "Why has cyclotropia been a stepchild of clinical investigation for so long?"1 Without doubt, part of the neglect in this field of strabismology has been due to the complexity of the measurement procedure found in some tests. Today, measurement of torsion is recognized to be an integral part of the examination of incomitant strabismus, since its presence and extent are important factors in planning treatment.

I have designed a new test for the measurement of torsion called the Torsionometer. It offers the advantages of portability, speed, and ease of use for both patient and examiner. The Torsionometer is a subjective test consisting of a white plate with a vertical red line beside a green one, which the patient rotates using a dial. The patient's view of the test has been designed so that there are minimal cues about objective parallelism. On the back of the test plate is a measurement scale corresponding to the orientation of the green line relative to the red line (Fig 1). This enables the examiner alone to read the amount of torsion present. The test is carried out in free-space with the patient wearing a pair of reversible complementary red and green goggles, such that each eye is presented with a different line image. The test plate and its surrounds provide material that is visible to both eyes so that cyclofusion, a most effective compensating mechanism in cyclodeviations,2 is not precluded. Therefore, the torsion of longstanding cyclotropia may be understated, revealing only that amount which is symptom-producing and clinically significant.

Measurement is relatively quick and uncomplicated. The test plate is held at a 40-cm viewing distance, perpendicularly to the patient's line of sight. To begin testing, the green line is rotated maximally in one direction and the patient attempts to make it subjectively parallel with the red line, using the finger-grip on the front of the test. The amount of torsion, if any, is then read off the scale. Up to 25° of excyclo- or incyclotorsion can be measured. Torsion can also be measured in secondary positions of gaze, eg, in downgaze, where it is often a problem, especially in bilateral fourth nerve palsy.3 The goggles provided enable unrestricted measurement in the reading position or extreme downgaze, which is often necessary.

Figure 1: Examiner's and patient's view of the Torsionometer.

Figure 1: Examiner's and patient's view of the Torsionometer.

CLINICAL TRIAL

In a concurrent validity study, the reliability of the Torsionometer was tested against three standard clinical methods: the synoptophore, the double Maddox rod (DMR), and the Maddox wing (MOW) tests.4 Thirty-three adult patients, all of whom described a torsional component to their diplopia, underwent measurement. A total of 68 sets of measurements were statistically analyzed. The measurements obtained with the Torsionometer correlated highly with those of the other tests (Table), particularly with the DMR test (Fig 2). The conclusion was that the measurements with this device are accurate and reliable.

The Torsionometer is produced by Clement Clarke International Ltd., Airmed House, Edinburgh Way, Harlow, Essex CM20 2ED, Great Britain.

Figure 2: Scattergram demonstrating correlation between the Torsionometer and the DMR test. Each point overlap is represented by a sunpower petal.

Figure 2: Scattergram demonstrating correlation between the Torsionometer and the DMR test. Each point overlap is represented by a sunpower petal.

Table

TABLECorrelation Matrix of R Statistic (of lntraclass Correlation Analyzes) for the Torsionometer, Synoptophore, DMR, and MOW Tests

TABLE

Correlation Matrix of R Statistic (of lntraclass Correlation Analyzes) for the Torsionometer, Synoptophore, DMR, and MOW Tests

REFERENCES

1. von Noorden GK. Clinical and theoretical aspects of cyclotropia. J Pediatr Ophthalmol Strabismus. 1984; 21:126-132.

2. von Noorden GK. Binocular Vision and Ocular Motility. Theory and Management of Strabismus. 4th ed. St Louis, Mo: CV Mosby; 1990: 85.

3. Kraft SP, O'Reilly C, Quigley PL, Allen K, Eustis HS. Cyclotorsion in unilateral and bilateral superior oblique paresis. J Pediatr Ophthalmol Strabismus. 1993; 30: 36 1-36 7.

4. Georgievski Z. Comparison of 3 standard clinical tests and a new test for the measurement of torsional diplopia. In: Lennerstrand G, ed. Update on Strabismus and Pediatrie Ophthalmology. Boca Raton, FI: CRC Press; 1995:171-174.

TABLE

Correlation Matrix of R Statistic (of lntraclass Correlation Analyzes) for the Torsionometer, Synoptophore, DMR, and MOW Tests

10.3928/0191-3913-19960101-16

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