Eyesight Problems?

I have a 5 year old mare who has recently become very spooky which isnt in her nature. She almost always spooks to the left and a friend of mine thinks she might be having issues with her eyes. Is there any way to check her eyes before I call a vet out? She hasnt hurt her eyes in any way and it was pretty sudden that she began spooking.

Eye issues aren't something you want to mess around with, if you suspect a problem, I would call the vet ASAP! Eyes can get worse very fast and if you wait to long could mean complete blindness. I wouldn't wait, just call...ask the vet what to look for, its free to phone :)

The thing is im not sure that's whats wrong with her. I agree she's decided to go spooky and I have no idea why and I do notice that she's mostly spooking to the left but during groundwork and things she has no problem picking on cues on both sides.

Can you see any scratches on or near the eye? Does she wince a lot or does she keep it open? You can try doing quick movements with your hand near her eye to see if she flinches or spooks. My mare fractured her skull and has very little slight in one of her eyes. She severed the tendons that hold the eye in place and broke her brow bone off. I have heard from several people that if the horse can see a little from one eye it's better to just have it removed so they don't spook when they see something. I haven't really had an issue with my mare not being able to see out of that eye. She can't see much so she doesn't spook too bad on that side. I still ride my mare, do barrel competitions and even did poles for the first time during a competition. She relies on me and my cues very much.

Nope. None of those. I've brought her to the front pasture every day and no scratches or scrapes or anything. I tried lunging her today both ways with just physical cues and she took all cues just fine.

If its not her eyes, what could possibly be the reason of her suddenly getting spooky like she is?

I would still call the vet to have her eyes checked. When longeing your horse they can take many cues from the "feel" of the halter and the usual motions that the horse goes through. She may not see your cues at all but feel your cues. Otherwise she may see just portions of you and trust in your ability as a herd leader.