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Exophoria and Exotropia and Strabismus- Aren't they the same?!

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Exophoria and Exotropia and Strabismus- Aren't they the same?!

Old 15th Jun 2009, 21:14
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Exophoria and Exotropia and Strabismus- Aren't they the same?!

Hello to you all!,

Hope you are all well...

Exophoria and Exotropia and Strabismus.

Outlined above are three conditions and if I understand correctly, they have the same symptoms...whereby the eye just deviates from a normal position outwards while the other eye remains unchanged.

But they are three different conditions? I don't get why they are all different? Why are they not under one name. They both have the same outcome (deviation of the eyeball).

The CAA Class One Medical Requirements are as follows;

"You must have normal fields of vision.
You must not suffer from double vision.
Any degree of heterophoria (eye muscle imbalance) in excess of:
8Δ exo, 10Δ eso or 2Δ hyperphoria - measured at 6 m
12Δ exo, 8Δ eso or 1Δ hyperphoria - measured at 33 cm
will require further evaluation by an eye specialist at Gatwick.

Now I don't think the are talking about strabismus, but it is the same essentially right?

What is the difference between these disorders? I'm trying to figure out which one I have (both my eyes deviate sometimes...but I can control it but sometimes it'll deviate by itself..). I also have myopia

But more importantly what does this mean for an individual that wants to be a commercial airline pilot? Is there not surgery available for these disorders? Can they be fixed or do we write off a whole career?

Anyway's guys watch this space, I'm going to go to Vision Express tomorrow to discuss this with an Optician to see what he says (I'll take the class 1 medical vision requirements with me and see what they say).

If anyone can answer this question I (and a many others) would greatly appreciate it!

Speak soon guys, I'll keep ya'll updated as to what the Optician says!

Captain Bolt!

N.B. Some may say that Lazy Eye is also a disorder in which an eye deviates outwards, however I found out today that it is a completely different disorder...! Learn something new everyday lol...!
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Old 23rd Jun 2009, 10:29
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"Phorias" and "Tropias" are different things. A phoria is a tendency for one (or both) eyes to deviate if fusion cannot be maintained. So, for example, if you covered one eye the other might turn inwards or outwards.

This is where the "exo" and "eso" come in. They're from the Greek meaning "out" and "in". So an exophoria would be the tendency for an eye to turn outwards when fusion is broken. For reference, hyperphoria refers to the vertical plane. (I think.)

A tropia, on the other hand, is a manifest defect in the eye and is a constant imbalance pulling the eye in or out. Strabismus = squint = general term.

I believe the CAA have issues with phorias because of the potential for double vision to occur, whereas with a tropia the patient is generally adapted to it and the risk of double vision is tiny.

I had a pretty bad squint (exotropia) corrected with surgery. No complications and the CAA handed me my Class 1 about 3 months after the operation. The consultant had to write them a report but that was about it.

The head optometrist at the CAA is a fantastic guy and incredibly supportive. Best thing to do is ask your own optometrist for a report and send it off to the CAA and see what they say.

Best of luck,


PS - Apologies if I've screwed up any of my definitions. ;-)
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Old 24th Jun 2009, 19:09
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David, Were You forced to to do the strabismus (exotropia) surgery by the FAA ? I mean if u didn't get it done, would you have been granted a class 1? Does it still deviate? was it intermittent or constant? was it alternating? How come tropias are not mentioned in the FAR?

Thanks alot
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Old 24th Jun 2009, 21:25
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I actually hold a JAA Class 1, not FAA so I can't really answer your question. It was purely a cosmetic decision - I hated not being able to maintain proper eye contact with people and am delighted with the way it turned out. So I would have been issued a certificate regardless.

I had an alternating exotropia, so an eye always appeared to turn outwards. No idea why it's not mentioned in the FAR, but realistically it has no impact on your flying. There is a side-effect of a loss of stereopis which probably is mentioned (it's covered in the UK ATPL exams) but I never noticed a problem.

The only FAA medical I hold is class 3, and while the doctor issuing it was curious about the surgery, it had no impact on the medical. Although being Class 3, you could probably get away without having any eyes at all... ;-)
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