ant123ant :

I did see that it's been a while since you've posted this question, but if you're still interested I thought I'd try to give you a little bit of an idea what's going on. I'll do my best to minimize the medical jargon, but not too much so to oversimplify it. If you'd like me to clarify something afterwards, please feel free to ask.

The brain has a ton of nerves that come off of it to send and receive signals all over the body. A specific grouping of those that send and receive signals are the 12 cranial nerves, all of which are named but are abbreviated by counting by Roman numerals I-XII. The Oculomotor nerve, or cranial nerve III, controls eye movements and some movements of your eyelids. The Trigeminal nerve, or cranial nerve V (five), has 3 major branches to the face, essentially one to the forehead area, one from the lower eyes to the upper lip, and then lower lip to the base of your jaw.

Now it's not entirely known what the cause or mechanism of Marcus Gunn syndrome is, but it's believed that some reflexes and muscle movements kinda get criss-crossed, possibly due to nerve damage. The trigeminal nerve and oculomotor nerve signals get crossed, so whenever the jaw muscle is used, the eyelid opens as well. So as a general picture for other people reading this (and let me know if this is applies to you), this will commonly present as somebody sucking on a straw and all of a sudden one eyelid will open wide. The side of the eyelid opening is the side of the nerve injury.

Sorry if that's too difficult to read or understand, but I'd be glad to explain in more detail if you'd like, or to clarify anything I wrote. Good luck with everything. Luckily it won't cause you any major problems and won't get worse so you should hopefully be great.

"Marcus Gunn pupil or relative afferent pupillary defect (RAPD) is a medical signobserved during the swinging-flashlight test whereupon the patient's pupils constrict less (therefore appearing to dilate) when a bright light is swung from the unaffected eye to the affected eye. The affected eye still senses the light and produces pupillary sphincter constriction to some degree, albeit reduced.
The most common cause of Marcus Gunn pupil is a lesion of the optic nerve (between the retina and the optic chiasm) or severe retinal disease. It is named after Scottish ophthalmologist Robert Marcus Gunn."  (Source is Wikipedia)  I hope I answered any questions you might have.  -Xepheria

warmaker : When I was born it took three weeks to find someone who could even identify the condition and then they only knew there is a connection between the jaw and the mouth so I gave up on asking but it has been 16 years now and for all I know a specialist or someone else who has the condition and has learnt about it. Also I don't drink and I spend most of my time studying to get out of poverty in my family and help them.
mikez913 : It is ok I understood all of it, and yes that is the case but in the past three years my eye has been opening less in both movement and frequency could you think why this it?

ant123ant :
Sure I can do my best. Are you saying the reflex doesn't happen as often anymore? Essentially there are multiple nerves and muscles that control the eyelid as a whole, not just the Oculomotor nerve I talked about before. The belief is that over time, all these other muscles and nerves learn to compensate for the bad nerve an gradually become less of an issue.  Hope that helps.

Just FYI, the Marcus Gunn pupil that was described above is completely different from what you have. Marcus Gunn pupil is most commonly due to a type of an infection or a brain injury.

mikez913 : ok and yes the reflex does not happen as much anymore but it is more common when I am tired or feeling sick

ant123ant :

I haven't worked much in ophthalmology, but I can take an educated guess from what I know from general medicine. When you're tired/run down/sick, it'll cause a lot of things in your body to work less than 100% and shift toward other things (building up your immune system, etc...). Meaning, less control is being placed over the eyelid muscles and nerves, so they won't be able to override the bad nerve as strongly as normal. (There's basis for this in a few neuromuscular diseases, that probably isn't necessary to go into here) It doesn't sound like it is anything unexpected, especially if things are improving when you're well. Of course, if all of this is bothering you, a routine check up and physical is ALWAYS a good idea and appropriate step to take.