Double Maddox Rod Test 

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The Maddox rod is a handheld instrument composed of red parallel plano convex cylinder lens, which refracts light rays so that a point source of light is seen as a line or streak of light. Due to the optical properties, the streak of light is seen perpendicular to the axis of the cylinder.
The double Maddox rod test can also be used to assess torsion and measure cyclotropias.
 It is a subjective test which uses two maddox rods, one before each eye.
 It is used to determine cyclodeviation or torsion.
 This test can be done in all the position of gazes for comparison.
 Traditionally, a red Maddox rod and a clear one were paired, but this was thought to bias the patient’s localization of the cyclodeviation toward the eye with the red rod. Using the same color bilaterally avoids this bias. therefore, nowadays red maddox rods are preferred before both the eyes during the test
Procedures
1. The room lights should be dimmed and only one light source should be visible
2. Maddox rods are placed into the trial frames, one before each eye
3. Cylinders are placed into trial frame vertically (90o), making the two red lines horizontal
4. Patient is instructed to fixate on the light source with both eyes opened
5. When testing at near, the patient is asked to fixate on light source at 33 cm, which is held at eye level. When testing at distance, the patient is to fixate on a light source at 6m.
6. if patient feels difficult to compare the orientation of streaks, place the loose prism in the trail frame. Vertical prism ( base-up, or base-down) can also be added into the trial frames to separate the two red lines (This avoids confusion if the patients claim that they only see one red line).
if the patient does not have any vertical or horizontal separation of streaks, the streaks can be difficult to compare. Thus, loose prisms can be used to separate the images/streaks to let easy comparision. or, if the patient has large horizontal or vertical deviation, prisms can be used to bring the streaks closer together to let the easy comparision.
7. Patient is asked to rotate OR the examiner rotates the cylinders with the axis knob on the trial frame until the 2 red lines are parallel
8. The amount of cyclodeviation is measured in degrees, utilised from the scale on the trial frame
9. if the two streaks are parallel to each other without any rotation of Maddox Rod, patient does not have cyclodeviation.
10. examiner can either use base-out, base-in, base-up or base-down prism depending on the deviation. For example: a patient with an large esotropia may need a base-out prism placed in front of deviated eye to bring the streak corresponding to this eye closer to other streak.
11. This test can be repeated for the secondary and tertiary positions of gaze
Interpretation
Starting from 90◦; look at the superior part of the Maddox rod, if rotation of grooves of the maddox rod towards the nose (nasally) measures the incyclodeviation and if towards the lateral side (temporally) measures the excyclodeviation.
The amount of cyclodeviation is measured in degrees, shown by the scale in the trial frame. For example: In Right Eye, if the axis or grooves of maddox rod is rotated at 80◦, the patient has 10◦ incyclodeviation but if the axis of maddox rod is rotated at 100◦, the patient has 10◦ excyclodeviation.
In most of the cases double maddox rod test helps in detection of the defect of the oblique muscles. For patients with unilateral superior oblique weakness the excyclophoria is generally between 1 to 7 degrees, whereas in bilateral superior oblique weakness the excyclophoria is typically greater than 10 degrees.
Advantages
• Subjective test
• Simple and fast technique
• Can be used on children, if they can respond reliably
• Can be used to test eye muscle balance
Disadvantages
• Cannot be done when there are sensory anomalies present
• Cannot be performed if a patient has suppression, as they are unable to see the light
• Cannot differentiate between tropias and phorias
Chapters
00:00 Start
00:16 what is Maddox Rod
00:34 Double Maddox Rod Test
01:25 Procedures
03:38 Interpretation
04:55 Recording
05:16 Advantages
05:32 Disadvantages
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