7. Von Graefe Phorias

Procedure for Von Graefe vertical at near

1. Ask patient "Do you see two charts, one up and one down?" 2. Instruct patient "I want you to look at the lower target, and tell me when the other target is right beside it, like headlights on a car. Keep looking at the lower target and keep it clear." 3. Gradually reduce the BD prism until the patient reports vertical alignment of targets. Confirm your endpoint 4. Quickly continue changing the prism in the same direction, overshooting alignment. Tell the patient: "I've gone too far, right?' 5. Decrease BU prism until alignment is achieved again from the opposite direction

Procedure for Von Graefe lateral at near

1. Ask patient "Do you see two charts, one up and one down?" 2. Instruct patient "Look at the upper target and keep it clear. I'm going to move the lower target over. I want you to tell me when it is directly below the upper one, like buttons on a shirt. Keep looking at the upper target." 3. Gradually reduce the BI prism (approx 2 ∆ /sec) until the patient reports vertical alignment of targets. Confirm your endpoint 4. Quickly continue changing the prism in the same direction, overshooting alignment. 5. Tell the patient: "I've gone too far, right?' 6. Increase BI prism until alignment is achieved again from the opposite direction

Procedure for Von Graefe vertical at distance

1. Ask patient "Do you see two charts, one up and one down?" 2. Instruct patient "We're going to do the same sort of thing, except that now I want you to look at the lower target, and tell me when the other target is right beside it, like headlights on a car. Keep looking at the lower target and keep it clear." 3. Gradually reduce the BD prism until the patient reports vertical alignment of targets. Confirm your endpoint 4. Quickly continue changing the prism in the same direction,overshooting alignment. Tell the patient: "I've gone too far, right?' 5. Decrease BU prism until alignment is achieved again from the opposite direction

Procedure for Von Graefe lateral at distance

1. Instruct patient "Look at the upper target and keep it clear. I'm going to move the lower target over. I want you to tell me when it lines up directly below the upper one, like buttons on a shirt. Keep looking at the upper target." 3. Gradually reduce the BI prism (approx 2 ∆/sec) until the patient reports vertical alignment of targets. 4. confirm endpoint by overshooting. Tell the patient: "I've gone too far, right?' 5. Increase BI prism until alignment is achieved again from the opposite direction

Procedure for flash technique

1. Place occluder (or hand) over the eye with the measuring prism. 2. Instruct patient to make sure the image is clear. "When I uncover your eye, I want you to tell me where the lower letter/target is at first: to the left or right of the upper letter/target" (for lateral phoria). 3. Quickly uncover the eye and question patient as to relative positions. 4. Re-cover the eye and adjust appropriate prism to align the images 5. Repeat until alignment is achieved • Record as before, but note that the "flash technique" was used

Set-Up for Von Graefe vertical at distance

Distance correction in phoropter with distance PD • Target = horizontal line of letters (that includes letters that are one line larger than BVA) or a single letter one line larger than BVA • place Risley prisms in front of both eyes • 6∆ BD OD = measuring prism • 12∆ BI OS = dissociating prism

Set-Up for Von Graefe lateral at distance

Distance correction in phoropter with distance PD • Target = vertical line of letters (that includes letters that are one line larger than BVA) or a single letter one line larger than BVA • place Risley prisms in front of both eyes • 6∆ BD OD = dissociating prism • 12∆ BI OS = measuring prism

T/F During Von Graefe phoria testing vertical, the alignment values must be within 3 ∆

F, within 2 ∆

During lateral Von Graefe phorias, your patient reports the lower target to the bottom right of the top target. What does this mean

If the lower image is to the right to start with, the pt needs more BI prism to bring the lower target toward the left to line up -pt has an exo deviation

The results for Von Graefe lateral should be recorded as the average of the two values at which the patient saw alignment. What if they are not within 3 ∆?

If they are not within 3 ∆ of each other, repeat the test from the beginning, emphasizing patient instructions and fixation. Average the 2 closest values obtained.

Set-up for Von Graefe vertical at near

Near correction in phoropter with near PD • Near point card placed at 40 cm on near point rod. Make sure pt can see line clearly! • Target = horizontal LoL on rotary chart with stand lamp • Place Risley prisms in front of both eyes • 6 ∆ BD OD = measuring • 12 ∆ BI OS = dissociating

Set-Up for Von Graefe lateral at near

Near correction in phoropter with near PD • Near rotary card placed at 40 cm on near point rod. • Target = vertical line of letters on rotary chart (make sure line is clear for patient) • Bright lighting with stand lamp directed at target • Place Risley prisms in front of both eyes • 6 ∆ BD OD dissociating prism • 12 ∆ BI OS measuring prism

Von Graefe phorias, vertical expected values at distance

ORTHO to 0.25^

Von Graefe phorias, vertical expected values at near

ORTHO to 0.25^

Von Graefe phorias, lateral expected values at distance

ORTHO to 2^exo

Von Graefe phorias, lateral expected values at near

ORTHO to 6^exo

What is the purpose of the Von Graefe test

Subjective test to measure the presence, direction, and magnitude of a deviation • Used to confirm or supplement a cover test • Does NOT differentiate between phorias and tropias • Uses lateral and vertical risley prism simultaneously to dissociate the eyes AND to measure the deviation

T/F For lateral testing we record to the nearest 1 ∆ while in vertical testing we record to the neart 0.5 ∆

T

T/F If the average value during lateral testing gives you a 0.5 ∆, record the higher of the two numbers.

T

T/F No bracketing is required for the flash technique

T

When would the flash technique be preferred

When a patient is unable to control his/her fusional eye movements, despite attempts to separate the targets with an alternate set up • Useful for patients with suppression • Used mainly with lateral phorias

Troubleshooting with Von Graefe -your patient states they do not see 2 separate images

make sure both eyes are unoccluded and alternately occlude each eye to make sure the patient can locate each of the images • If the patient still does not see two separate targets, try switching the BI to BO prism or increasing the amount of BI prism (e.g., swap the 12 ∆ BI to 12 ∆ BO OS, or increase the 12 ∆ BI to 30 ∆ BI OS).

During lateral Von Graefe phorias, your patient reports the lower target to the far to the bottom left of the top target. What does this mean

the pt needs less BI or more BO prism to bring the lower target to line up -patient has an eso deviation

What 4 tests measure eye alignment

• Cover test • Bruckner, Hirschberg, Krimsky • Maddox Rod • Von Graefe Phorias