Brief Answer:
Dissection probable, can be treated succesfully, but is an emergency.

Detailed Answer:
I read your question carefully and I understand your concern.

So from what I understand after the accident you have developed a myosis and a ptosis in the right eye (terms for constriction of the pupil and drooping of the eyelid). That is part of what is called a Horner syndrome. It can have many causes, the lung cancer as well as was told to you, but given its appearance after the accident makes it most probably in the setting of a right carotid artery dissection (tumors do not appear after car accidents).

A dissection means a tear in the wall of a blood vessel, in this case in the right carotid artery, which leads to formation of a false lumen. The Horner syndrome happens due to compression of some nerve fibers passing in close contact with the artery. Neck artery dissection happens typically after trauma like yours.

Now the risk of a dissection is that it may lewd to narrowing of the artery lumen or formation of thrombi which can detach and travel to brain vessels. So both these phenomena may lead to a stroke. For that reason it is vital to be diagnosed and started treatment early so that a stroke can be prevented. If caught in time, before a serious stroke has happened (looks like your case as if you had a major stroke you'd have other symptoms), through treatment with blood thinners stroke can be prevented and generally the prognosis is good as the tear will heal gradually.

So it is vital now to confirm the diagnosis. You should go to ER again with the new symptoms and the ophthalmologist report, to diagnose the dissection should have imaging of neck vessels. That can be done through neck vessels Doppler ultrasound, through angio CT or angio MRI (CT or MRI of the neck vessels - different from plain head ct you have had). If diagnosis is confirmed as I said treatment with blood thinners will be required, generally for about 6 months.

As for your question whether it can heal by itself, well it can, but there would be the high risk of stroke, I do not suppose you want to take that chance when it can be treated with good success at this stage.

I remain at your disposal for other questions (although in my opinion you should be heading to the ER now).

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Brief Answer:
Read below

Detailed Answer:
My opinion remains the same. Of course I can not examine you myself but if the myosis and ptosis are clear on examination coupled with the appearance after the accident the probability of a dissection is very high and as you might well have heard a stroke is a highly disabling and even life threatening condition.

Auscultation with a stethoscope doesn't offer any guarantee whatsoever. Even the ultrasound doesn't exclude it, it detects the dissection in about 80-86% of cases (and that depends also on the ability of the examiner), so even if it results clear I still would recommend the angio CT or angio MRI.

If you're really set on waiting, may I suggest that you at least take some Aspirin with a dosage of 325 mg which would offer protection and even if you do not have a dissection after all can always be interrupted once you are through with tests.

I hope things work out for the best.

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