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Maddox Rod Phoria
PURPOSE To measure the lateral and vertical phoria at distance and at near.
INDICATIONS
The Maddox rod phoria test is an alternative to the von Graefe phoria technique. It is used when the patient is unable to see two targets on the von Greafe test or when the phoria test must be done in space rather than behind the phoropter. Since this test can be done in free space with the patient wearing glasses, it is particularly useful for ruling out a prisminduced vertical phoria due to a patient’s head tilt behind the phoropter lenses.
EQUIPMENT
·Penlight for near testing and muscle light for distance testing.
·Maddox rod (red or while).
·Prisms (Risley prisms, prism bars, or hand held prisms).
SET-UP
The Maddox rod phoria test can be done at distance and at near, using the phoropter and Risley prisms, or in space, using a hand held Maddox rod and loose prisms or a prism bar.
Set- for Testing in the Phoropter
·The examiner turns on the muscle light for distance testing. The examiner holds the penlight at 16 in for near testing.
·The patient’s distance correction and distance PD are placed in the
phoropler for distance testing. The patient’s near correction and near
PD are placed in the phoropter for near testing.
·The Maddox rod is placed over the patient’s right eye as follows:
a. for measuring the lateral phoria, the grooves on the Maddox rod are oriented horizontally. The patient sees a vertical streak.
b. for measuring the vertical phoria, the grooves on the Maddox rod are oriented vertically. The patient sees a horizontal streak (see Figure 4-22).
·The Risley prism is placed over the patient’s right eye as follows:
a. for measuring the lateral phoria, the prism is oriented base in with sufficient prism to move the streak to the right of the spot of light.
b. for measuring the vertical phoria, the prism is oriented base with sufficient prism to move the streak below the spot of light.
Set- for Testing in Space
·The examiner turns on the muscle light for distance testing. The examiner holds the penlight at 16 in for near testing.
·The patient wears his distance glasses for distance testing. The patient wears his near correction for near testing.
·The patient holds the Maddox rod over his right eye as follows:
a. for measuring lateral phoria, the grooves on the Maddox rod are oriented horizontally. The patient sees a vertical streak.
b. for measuring vertical phoria, the grooves on the Maddox rod are oriented vertically. The patient sees a horizontal streak.
·The examiner holds the prism bar over the patient’s right eye as follows:
a. for measuring the lateral phoria, the prism is oriented base in with sufficient prism to move the streak to the right of the spot of light.
b. for measuring the vertical phoria, the prism is oriented base with sufficient prism to move the streak below the spot of light.
STEP-BY-STEP PROCEDURE
1. Instruct the patient to look at the light but to be aware of the red or white line.
2. For the lateral phoria measurement, reduce the base in prism until the patient reports that the streak is in the center of the light.
Note the amount of prism and the direction of the base.
3. For the vertical phoria measurement, reduce the base prism until the patient reports that the streak is in the center of the light.
Note the amount of prism and the direction of the base.
RECORDING
·Record D for distance and N for near.
·Record the lateral and vertical phorias separately.
·Record the size of the deviation in prism diopters.
·Record the direction of the deviation.
·Indicate the type of Maddox rod used (red or white).
EXAMPLES
·DLP c red MR ortho; DVP c red MR ortho
·NLP c red MR 6Δ exo; NVP c red MR 2Δ R hyper |
