EQUIPMENT NEEDED Penlight Gulden fixation stick Red/green glasses SETUP 1. If the patient wears glasses for close work, these should be used. 2. Hold Gulden fixation stick tongue depressor 40 cm from patient’s face at eye level. 3. Ask the patient to look at the isolated 20/50 target on the Gulden fixation stick. PROCEDURE 1. Slowly move the fixation stick toward the patient at eye level and between the two eyes. 2. Ask the patient to keep the target one for as long as possible. 3. Ask the patient to tell you when he or she sees two targets. 4. Once diplopia occurs, move the fixation stick in another inch or two and then begin to move it away from the patient 5. Ask the patient to try and see “one” again. 6. Also watch the eyes carefully and observe whether the eyes stop working together as a team (one eye will usually drift out). 7. Record the distance at which the patient reports double vision and when the patient reports recovery of single vision. 8. Repeat the test using a penlight and red/green glasses if you suspect that dissociation may reveal a more receded NPC. IMPORTANT POINTS 1. Repeat the test several times if results are not definitive. 2. Watch the patient’s eyes and try to objectively determine when the break and recovery occur