Maddox Rod Test- Everything You Need to Know.

What is Maddox Rod Test?

Maddox Rod is subjective test performed with placing Maddox rod in one or both eyes which separate both eyes images and helps to identify what type of deviation is present.

What is a Maddox Rod?

• Maddox Rod is a glass rod (series of parallel glass rods) that converts the image of a spot-light source into a streak of light perpendicular to the axis of the rod due to its optical property.
• The position of this streak in relation to the spot-light source seen by the fellow eye indicates the presence and amount of Tropia/Phoria.
• The power of the Maddox is Plano-Convex and available in Red, White or Green.

Types of Maddox Rod Test:

• Maddox Rod test can be of two types:
  • 1. Single Maddox Rod Test.
  • 2. Double Maddox Rod.

Single Maddox Rod Test:

• In single Maddox Rod Test, Maddox Rod is placed only in one eye (Deviated Eye or suspected eye).
• With the help of single Maddox rod test we can measure only Horizontal & Vertical Deviation.
• Torsional Deviation can’t be measured in single Maddox rod test as only one streak of light is formed and compared with spot-light. Spot-light doesn’t give any clue about orientation of eyes.

Double Maddox Rod Test:

• In Double Maddox Rod Test. Two different color Maddox Rod are used for both eyes.
• Double Maddox Rod helps us to identify Horizontal, Vertical and Tortional deviation.
• Due to forming two streak of light, it’s possible to measure Torsional deviation with doble Maddox rod test.

Principle Maddox Rod Test:

• The test is based on the principle of diplopic projection.
• When Maddox is placed in front of one, patient sees a red streak of light and in other eye sees a spot-light (Diplopic Projection)
• When both eyes image is separated it’s easier to compare what type of deviation is there and which eye is affected.
• If there is no no Deviation then the Spot-Light will at the center of the Red Streak.

Procedure of Maddox Rod Test:

Requirements to Perform Maddox Rod Test:

• Patients.
• Trial Frame
• Fixation Target (Point light source)
• Maddox rod streak or trial lens form

Test Distance for Maddox Test:

• When testing at near, the patient is 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.

Measuring horizontal deviations with Maddox Rod Test:

• When performing the clinical test, the room lights should be dimmed and only one light source should be visible. 
• Patient is instructed to fixate on the light source with both eyes opened. 
• The Maddox rod is then placed over the fixating eye (let’s consider Rt eye). 
• To measure Horizontal deviation red lines are placed horizontally so that a vertical line can be formed.
• The patient is then asked whether the white light is superimposed on the red line or not.
• Patient may see the light sources right or left to the red line.

Measure the Vertical deviation with Maddox Rod Test:

• The Maddox rod is placed in front of the Fixating eye (let’s consider Right Eye) making the red lines vertical so that a Horizontal Red streak can form.
• The patient is then asked whether the white light is superimposed on the horizontal red line or not.
• Patient may see the point light source up or down to the horizontal red line.

Interpretations of Maddox Rod Test:

Patient Response:

• Point light source is superimposed at the center of Red line

Interpretation:

• Orthophoria/Normal retinal Correspondence/Simultaneous macular perception

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Patient Response:

• With Maddox Rod in RE (fixating eye), Point light source is right side of patient (left side of examiner) in relation to red line. (LE image going Inward)

Interpretation:

• Left Eye Exotropia or Crossed Diplopia.
• Eye deviates opposite to image (As image moved inward Eye will move Outward or Exotropia).

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Patient Response:

• With Maddox Rod in RE (fixating eye), Point light source is left side of patient (right side of examiner) in relation to red line (LE image going Outward).

Interpretation:

• LE Esotropia or uncrossed diplopia

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Patient Response:

• With Maddox Rod in RE (fixating eye), Point light source is Up of the red line (LE Image shifted Upward)

Interpretation:

• Left Hypotropia or Right Hypertropia
• Eye deviates opposite to image (As image moved Upward in Left Eye, LE will move Downward or Hypotropia).

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Patient Response:

• Point light source is Down of the red line

Interpretation:

• Left Hypertropia or Right Hypotropia
• Eye deviates opposite to image (As image moved Downward in Left Eye, LE will move Upward or Hypertropia).

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Questions For You (MCQs on Maddox Rod):

Q-1: Maddox Rod is Place in which eye during the Maddox Test Procedure?

1. Fixating Eye.
2. Deviated Eye.
3. No Maddox Rod is Required.

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Q-2: What is the Power of Maddox Rod line?

1. Plano-Convex.
2. Plano-Concave.
3. Plus +0.25D.
4. Plano -0.25D

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Q-3: What is the Diagnosis of Below Response?

1. RE Esotropia.
2. LE Esotropia.
3. RE Exotropia.
4. LE Exotropia.

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Q-4: After Placing a Maddox Rod in RE, Patient is saying that only a Spot-Light is visible (No Red Streak) and when Maddox Rod place in LE, patient is saying that only a Red Streak is visible (No Spot-Light). What is your Diagnosis?

1. Alternate Deviation.
2. RE Suppression.
3. LE Suppression.
4. Malingering Patient.

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