As we know, the eyes and nose nerves are interlinked. Your symptom of sneezing when seeing the sun may belong to the sensitivity to the light of the eyes. You could go to the hospital to have a check. The eyes are the very important parts for our whole body. You should take high notice of it and protect them carefully.
Sneeze is a reflex which can't be controled by oneself. It occurs when the nose is stimulated by something. When the nerve cells are passed on to the brain, the brain control your nose to sneeze. During the process of nerve cells transmission, some of the cells can be leaked and affected reflex area near it.
When our eyes contact strong light, nerve cells of eye reflex, that is, closing our eyes will be transmitted to our brain. On their way to the brain, some nerve cells are leaked and cause sneeze reflex.
I think your sneeze cannot be related to eye problems. If there has some problems with your eyes, you will be sensitive to sunlight and feel burning in eyes when you see sun. We called it photophobia. However, it is impossible to cause sneeze. Your sneeze may be due to cold or fever.