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Fusional Vergence Facility at Near
PURPOSE To test the ability of the patient’s fusional vergence system to respond to rapid changes in disparity over time. This test is especially helpful in diagnosing binocular problems in symptomatic patients with normal fusional vergences.
EQUIPMENT
·12Δ base out and 3Δbase in mounted in a flipper device
·Near target: vertical line of small letters.
·Illumination source.
·Timepiece with second hand.
SET-UP
·The patient wears his habitual near correction.
·The patient holds the near target at 40 cm in good illumination.
·Brightly illuminate the near point card.
STEP-BY-STEP PROCEDURE
1. Place the 12Δ base out lenses in front of the patient’s eyes and ask him to report when the print becomes single and clear.
2. As soon as the print becomes single and clear, flip the lenses to the 3Δbase in position.
3. Repeat steps 1 and 2, noting the number of full cycles that the patient completes in 60 seconds. A full cycle consists of both the BI and BO lenses.
RECORDING
·Record the number of cycles completed in 60 seconds.
EXAMPLE
·Fusional facility at N: 4 cycles per minute
EXPECTED FINDINGS
·Fusional facility at N: 13 cycles per minute |
