Rearing in dismount...

I agree with getting the saddle etc checked.

I would also try mounting and dismounting from the off side. All horses should allow you to mount and dismount from this side in case there is ever a need for you to do it (at the side of a road or similar). I'd suggest practising on another horse if possible so you can do it smoothly.

My guess is he suddenly looses sight of you in his right eye as you move left to dismount and panics at where you have gone. If you dismount where he can see you then it might well eliminate the problem.
 
Not read everything, and not saying youve not done these things but if it was my horses id :
1. check for pain, saddle, bridle, bit, teeth, back.
2. check its not something to do with his eye, maybe you suddenly appearing to the left is too much to handle??
3. check its not associated with the way you dismount, ie do you slump off, clean his back totally, learn forward alot/not enough aby little things like this.

If your getting the saddle fitter after lunging to fitten then id advise having a physio/dentist to check before you lunge and possibly do the wrong exercises for an underlying problem.

Like i said, not read properly dunno what you have/not done but thats what id do with my horse :)
 
My horse went through this once, just once, very scary! I can't help you fix it, I'm afraid, but to get through the moment, have a helper. Turn your horse's head all the way around to your boot (I guess that's like a one-rein-stop, but I didn't used to know about that) and you can hop off the other side. I don't think a horse can rear with his head turned like that. A helper can keep him from whirling too much. If he stands still, rewards etc! Good luck, stay safe!
 
I'd also have a physio check his back, it might not be the saddle directly.
I presume when he rears, you are hopping straight off (Correct me if I am wrong) after to "get it over and done with". Don't. With this, you are risking twisting his spine.
Sorry to hear about his lameness issues, I hope you resolve them soon.
 
My first thoughts on reading this post was PAIN, sounds like your lad is in alot of pain, it could be his poll, you should have this looked at if everythig else comes back okay, I new an arab that did this, got his poll checked out and it was fantastic after.
 
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