3. Torsion and causes
Intorsion occurs when the 12 o'clock meridian is rotated nasally
Extorsion occurs when the 12 o'clock meridian is rotated temporally
CAUSES:
Paresis or overaction of any of the four cyclovertical muscles
Thyroid-related orbitopathy
Brown syndrome
Orbital blow-out fractures.
Local myotoxicity from retrobulbar /peribulbar anesthesia
Fourth cranial nerve palsy .
Skew deviations
Craniofacial anomalies-plagiocephaly
Guyton and Weingarten proposed that absent or poor fusion predisposes to abnormal torsion
4. Tests for torsion
SUBJECTIVE:
Double maddox rod test
Perimetry
Bagolini glasses
Synaptophore
OBJECTIVE:
Indirect ophthalmoscopy
Slit lamp biomicroscopy
5. Double Maddox rod test
-Red and green Maddox rods - cylinders vertical - placed one in front of either eye .
- Each eye will therefore perceive -horizontal line of light .
-In the presence of cyclodeviation , the line perceived by the paretic eye will be
tilted and distinct from that of the other eye .
-One Maddox rod is then rotated till fusion ( superimposition ) of the line is achieved
6. -The amount of rotation can be measured in degrees and indicates the
extent of cyclodeviation .
-Unilateral fourth nerve palsy is characterized < 10° of cyclodeviation
-Bilateral fourths may have >than 20° of cyclodeviation.
-This can also be measured with a synoptophore .
7. Evaluation of Ocular Torsion
Anatomic (objective) torsion refers to anatomic rotation of eye.
Subjective torsion refers to the patient’s perception of rotation.
Comparison of anatomic and subjective torsion can help determine the
time of onset of cyclovertical strabismus.
8. Foveal location in normal patients
0.3 to 0.6 disc diameters below a horizontal line extending temporally from the
geometric center of the optic nerve head
Creates a mean angle of 7.25° to 12.5° from the horizontal axis at the geometric
center of the optic disc
10. Disc foveal angle (DFA) which is formed at the optic disc center between the
horizontal meridian and the line joining the center of disc and foveal center
11. Bagolini’s striated glasses
Principle of the test is similar to that of double Maddox rod test.
The glasses are placed in the trial frames with the striations vertical- two horizontal line images when viewing a
spotlight.
Patient has a vertical deviation, the lines will be seen one above the other. If there is little or no vertical separation,
vertical prism can be used to separate the lines.
The patient is asked if one or both lines are tilted.
The lines can be straightened subjectively by rotating the glasses in the trial frame and the degree of cyclotropia
recorded
12. VISUAL FIELDS
Monocular and binocular visual fields were measured kinetically with Goldmann perimeter (and Dichoptic Visual
Fields (DVF) system.
The DVF allows presentation of different perimetric stimuli to each eye independently under binocular (or
monocular) fixation conditions using a liquid crystal shutter goggles.
The ferroelectric liquid crystal shutter goggles permit about 60° diameter of visual field to be tested with the DVF.
The subject is fixated on a 1.2° central fixation cross seen binocularly and instructed to press a button when a 1.2°
square target seen only monocularly was detected.
13. Perceived visual directions were mapped over the central 50° diameter of the visual field (pericentral field) by
modifying the DVF.
A fixation target (1.2° cross centered inside a 3° box) is presented on a gray background .
A 3° open square frame presented in one of 16 preselected peripheral positions.
The fixation target and the open frame were always viewed by the same eyes.
A 1.2° filled square target was moved with the computer mouse by the examiner as directed by the subject
verbally until the subject perceived the square target to be aligned to the center of the open frame.
14. Test conditions were used to map retinal
correspondence:
Primary deviation:
Fixation target and open frame viewed by the dominant/non-deviating eye and the square target was presented to
the non-dominant/deviating eye.
The dominant eye selected using the sighting dominance test
Secondary deviation:
Fixation target and open frame were viewed by the non-dominant/deviating eye and the square target was
presented to the dominant/non-deviating eye.
Binocular viewing:
Fixation target, open frame and the square target were all viewed by both eyes. This simulated the natural viewing
conditions.
