Von Graefe Phorias & Vergences

FCC = +0.50, which you take out of phoropter. NRA/PRA: +3.00/-2.00. What is the Final Add?

+0.50

You add +1.50 before FCC testing. Pt says vertical once, then equal, then horizontal, FCC =?

+1.25

FCC = +1.25 and NRA/PRA: +2.00/-0.50 so what is the Final ADD?

+2.00

Pt has acc amps of 6.00 D. Target is at 20 cm. How much ADD does pt need?

+2.00

Heterophoria Measurement Using the Von Graefe Technique

- we can only check phorias, cannot do it for a tropia - using the Risley Prisms is how we are going to dissociate the eyes - You have 2 prisms in 2 directions: one of the prisms serve to dissociate, separate the images for both eyes, the other serves as the measuring prism to measure the magnitude of that phoria

First measure Lateral Phoria

1) Instruct pt to look at the dissociating prism - we want to measure whether they have an eso or exo, what their lateral phoria is - so the 6 base up on the left eye serves as the dissociating prism (separates the eye images so they are dissociated) - to pt to look at the bottom target (dissociated image), and you will move the top target - Purpose of the test: to move the prism so that once they are lined up that indicates that you have put the prism where that resting position of that eye is - its a phoria so both eyes have the same resting position - Important to remind the pt to keep those targets clear b/c if not keeping clear (its blurry and they are no longer accommodating) can still do the test but that affects the phoria. Will not converge properly.

Important of Binocular Testing

2 eyes to detect depth, we get out motor and sensory fusion

Methods for Measuring Phorias

3 1/2 main techniques - you can only check for a phoria by dissociating the eye - for each of these techniques we dissociate the eye in different forms, to determine what the resting position of the eye is

Recording

B/c only testing phorias only record the HYPER eye (Left or right)

What will a patient who is suppressing see during vergence testing?

BI or BO - if suppressing pt will see lateral movement

Fusional Vergence Ranges

Do we calculate a blur value? - No! Remember vertical direction their is no accommodation playing a role so this time will only have pt say when image breaks into to and then recovery

Cyclovergence

Dont usually measure these

Troubleshooting

Flash Target Technique - cover one eye, as your changing the prism change 3 prism diopters at a time, and remove for a second, and ask them "Is it lined up? Yes or No" and then cover again, only allow the pt to see the images for 1-2 seconds otherwise it will be moving - can do this if pt has unstable accommodation or is suppressing

Fusional Vergence Technique

For the fusional vergences we are inducing prism in front of the eyes so that we are moving the images off of the fovea, that forces the brain to try and align the eyes on that image BI: the image is going out, so putting the image in front of both eyes outward, both of eyes have to diverge (move out) to line those images to the fovea, the target is no longer straight ahead it is now hitting the nasal retina, forces the eyes to move in the temporal/outward direction

Now what happens when performing the vertical phorias with a 12 diopter XP? (When want them to line up like headlights on a car)

If start to do the vertical phoria and the pt only sees one image, that means they are already fusing - either increase the BI, go from BO, or use the flash technique

Troubleshooting

In order to do this technique we need to dissociate the eyes, we all have the ability to converge and diverge and our brain hates double vision - so we need an adequate combination so that our brain doesn't fuse those images, so its unlikely that we are able to converge or diverge enough to make that image single

Measuring the Vertical Phoria

Is accommodation as issue here? - measuring the vertical phoria, do have to remind the pt to keep the images clear—-> remember we do not accommodate in a vertical direction, we only accommodate in a lateral direction, so if we are to move one eye up and one eye down there is no accommodation playing a role here ——> so we do not need to tell them to keep it clear

What is a phoria?

LATENT DEVIATION of eyes - where eyes go to rest, but with both eyes open you are able to hold your alignment

Von Graefe Vergences Continued- Pt never breaks

Look at your finger, should see two targets If looking at your finger and only see one target then they are suppressing b/c one eye is shut off If not suppressing than they have insanely high vergence ranges Testing ability to converge or diverge all the way When testing your vergence ranges: Have to have equal amount of prisms in both eyes, if you don't you do need to repeat the test (if off by 2 or 3 prisms that is acceptable, any more than that you need to repeat the test)

This is what the pt sees as you move measuring prism:

Move the 15 D prism towards the zero, as you move it the pt is going to tell you when they line up - remember the number where the prism stops - then move past it to decrease fusion (to decrease the ability to fuse) and bring it back from the other direction - then remember the number when they line up again - so you will have 2 numbers, when they lined up the first time, moved past it, and when they lined up the second time), going to average the 2 numbers that is the pts phoria - If both numbers are in the BASE IN side then they have, exophoria - If both numbers are in the BASE OUT side they they have, esophoria and thats the magnitude

BO in Front of Both Eyes Causes Convergences

Now the image is inward, the eyes are lined straight ahead, the image is moving inward now hits the temporal retina and the eye needs to converge in order to have the image lined up on the fovea

Supravergence and Infravergence

People with vertical phorias have a great ability to Supraverge or infraverge, that way your eyes are aligned when open

Procedure for horizontal ranges

Performed after phoria - isolate the letter, same target, so one letter above the best corrected of the worst eye, or 20/20 box - place the zeros so that they are in the up direction - The pt sees one image

Heterophoria Measurement Using the Von Graefe Technique

Performed in the phoropter- do at both distance/near - need a good distance Rx, so performed after retinoscopy, subjective refraction, binocular balance Distance - use singl letter one line above best visual acuity of the poorer seeing eye Near - can use the block of 20/20 letters (can use for all techniques) - other option is to use the vertical line of 20/20 letters (for vertical phorias need horizontal line, for lateral phorias need the vertical line)

Fusional Vergence Ranges

Remember our near triad (convergence, accommodation, Miosis) The target that the pt is viewing is NOT moving but b/c moving the images and the pt is converging or diverging based on which technique you are doing the pt is always going to have their accommodation stopped at a point - you are almost always going to blur before you break - after pt breaks image into 2, increase the prism by about 3-6 prism diopters more, want to make sure eliminating fusion at this point, move target further away, confirm you still see two images, okay so let me know when you see one image

Correct Prism Setup for Vertical Vergence Ranges

Remember that we are talking about phorias, so the resting position is just one eye sits higher relative to the other eye, that means that the right eyes ability to move down to alignment is equal to the left eyes ability to move up to alignment, so your right eye infravergence ranges should be equal to your left eyes supravergence ranges and the opposite is true in the other direction

Expected Values

Same as cover test

Fusional Vergence Ranges

So for the fusional vergence ranges what we are doing is causing retinal disparity, we are moving the image no longer on the fovea, so the the pt has to overcome the retinal disparity by moving the eyes in or out Do BI on one eye and BO on the other eye - the image is moved to one side (basically doing EOMS), making both eyes move together in the same direction - have to put the same prism amount, the base ins need to go together so both eyes need to move out or both eyes move in The target is a non-moving target, we are moving the prisms, the plane of accommodation has to stay on that target to maintain that clear vision If doing lateral vergence ranges, the BIs and BOs you always need to control the accommodation

Convergence

So the eyes rotate inwards so that the target lands onto the fovea - so anytime your looking at a target, that sends a signal to the brain, wherever that image lands on the retina, if its not directly on the fovea thats what sends the signal to the brain

Convergence

So when we are converging, what happens is you have a target up close and now that is stimulating your temporal retina in both eyes, and your brain says that is not clear, not where its supposed to land, I need this to land on the fovea

Phoropter Configuration for distance Von Graefe Phoria Technique

Standard to use this: Starting point - you may have pts that have huge superhuman abilities to move the eyes in, out, up, down in converge and diverge and you may need to adjust this - Right eye: Zero is at the top (Base out/Base in) - we always do 15 prism D BI on one eye - the other eye has the 0 at the 180 (Base up/Base down) So one eye has 15 prism D base in, the other eye has 6 prism D base up - The right eye is going to see an image that is out - The left eye is going to see the image that is down

Esophoria

Tendency of eyes to rest inward

Exophoria

Tendency of eyes to rest outward

What happens if the pt has 12 prism diopters XP (high exophoria)?

The BI prism at 15 is not enough, its like when your doing cover test and when you are getting closer to neutrality where the eye is resting, that eye does not have to move as much. So instead of that image being straight ahead (15 prism diopters BI— should move it all the way out) for a 12 prism diopter XP its only going to move it a little bit out (not quite as far as like) Troubleshoot: Increase the 15 to 20 BI, that will move the image further out.

How are ocular deviations made latent? How come we are not all manifesting tropes?

The reason why people with high phorias dont ever trope, is because they have good convergence and divergence. - the ability of the eye to move inward or outward - we talked about this with PRA/NRA, PFV and NFV Ex: have very high exophoria, you dont trope, you must have a very high ability to converge, because with both eyes open your eyes are aligned

Excylophoria/Encyclophoria

The temporal or nasal rotation of the top of the vertical meridian of one eye respectively - resting position of the eye tends to be rotated inward or outward

Fusional Vergence Ranges

The zeros are at the 180, now we will just move one of the prism - if you move both prisms in the base up direction, then the pt will see the image move down, not really inducing any type of vergence - moving in the base up direction testing that eyes ability to infraverge - base down direction, ability of that eye to supraverge

What happens if the pt has 12 prism diopters XP (high exophoria)?

Troubleshoot: Other option is to move to BO direction (can be any number, ex: 15 BO). Other Technique is to do the flash technique: You are going to cover one eye, as you have your 15 BI and your 6 BU, cover one eye with your hand, move the prism with your other hand in 3 prism diopters, and then just Unocclude for a second and ask "Are they lined up? Yes or No" - cover the dissociating prism - if you give the pt more than one second they are going to find it aligned it your doing the lateral phoria - so you can use the flash technique if increasing the dissociation doesn't work

Hyperphoria

Upward resting of one eye relative to the other

This is what your patient is now seeing:

We have now dissociate the eyes, we have given each eye a different target - if you do this and your pt immediately says I still see one image, one possibility is that they have fused those images, so to make sure that they see two images we can increase the dissociated prism, so we measure the vertical and lateral so whichever is the dissociating prism we can increase that to make sure we separated them more

Fusional Vergence Ranges

When do this technique going to have pt look at one image and as you change the lenses you want the patient to keep it clear, tell you when they first see blurry vision, and then when the image breaks into 2, then ask pt to tell you when it comes back to one image - record 3 values, when pt first blurs (accommodation kicked out), when break into 2 (experience diplopia), record when image becomes one again - has to be performed in smooth fashion (cannot take break) - when recording numbers adding prism from both eyes - should be moving at an equal pace