Use of Maddox Rod

Aim

Maddox Rod Test is used to measure the lateral and vertical phoria at distance and at near.

Test

The test uses Maddox Rod and the spot light for distance and penlight for near together with the prism lenses from the trial lens set or prism bar. Maddox Rod is used to break the fusion.

Illumination

The test is done in dimly lit room.

Test Distance

Distance test is done with spot light fixed at a distance of 20 feet and the near test is performed at a distance of 40cm.

Patient Position

Patient sits upright in front of the target with corrected correction in front of his eyes.

Critical Factor

Horizontal phoria measurement is reliable only when the accommodation is held constant at the measuring distance. Therefore, keep reminding the patient to look at the light carefully. Vertical phoria is measured with patient’s eyes in the primary position of gaze. It may vary with the direction of gaze.

Step by Step Procedure

1. Place the Maddox Rod horizontally before the patient’s right eye in front of his correction and ask the patient to keep his both eyes open.

2. Now with the right eye the patient sees vertical red line, if the red Maddox Rod is put and with left eye, he sees spot light.

3. If there is no phoria, the vertical line will appear to pass through the spot light.

4. In case the red streak appears to be on the right side of the spot light, a homonymous diplopia is produced indicating esophoria. If the streak appears to be on the left side of the

spot light, there is crossed diplopia, indicating exophoria.

5. The amount of horizontal phoria is measured by placing a prism lens of suitable strength in front of the other eye (left in this case), that ensures the red streak passes through the spot

light and the result is expressed in terms of prism diopter.

6. Now measure the vertical phoria keeping the horizontal prism lens in place. Rotate the Maddox Rod vertically before the right eye.

7. If the patient sees red streak below the spot light, it implies right eye hyperphoria and left eye hypophoria.

8. The prism diopter is measured similarly with prism base down or base up.

 

 9. The amount of prism diopter measured for lateral phoria may be divided half-half between both the eyes with base of the eyes in the same direction. However, care must be taken to split the vertical phoria between right and left eyes. Base orientation is not the same in both eyes for vertical phoria. For example, 3Δ BU in right eye can be splitted as 1.5Δ BU in RE and 1.5Δ BD in LE or unequally.