You're definitely not alone here. I found depth perception about the most difficult thing to get a handle on, and I recorded three tree strikes trying to overcome it.

I always thought the aircraft was a lot closer to me than it was, and on final it was sometimes 60 metres wide (further out from me) of the designated runway.

I saw a tip on these forums and it put me right onto the technique. Downwind, the distance out is not all that important, but on final it is, because if you miss the runway you may hit the trees or land in the rough.

Ensure you are standing facing the runway, five metres or so from the edge, and do not move from that position, i.e., you are looking straight across the runway, 90 degrees to the runway direction. Maintain your feet position, and only swivel your body. When you have your model on base leg, fly it till you think it has gone too far, i.e., until you can just see it out to your left (flying a final left to right) and then turn final. Aim it at yourself, and you will get it on the runway every time. It only seems to be flying directly at you as it turns. As it gets closer, it will be over the runway.

This worked for me and I never had another problem. Later I could vary the technique, and fly oblique bases etc., without problems, but it was this tip that got me started.

I find sunglasses make no diffrence to perception, but they do help cut down glare, which they are designed to do, and make seeing the model easier. Seeing it is a very different problem from depth perceptin however.