Does subconjunctival hemorrhage usually cause many symptoms?

No. Usually it does not, unless it is from excess rubbing from ocular irritation. Consider an evaluation with your eye doctor if it is recurrent because you may have a bleeding disorder or something serious.
Usually none. This is a benign bleeding from a small vein in the space under the clear conjunctiva over the white of the eye. Due to oxygen exposure it stays very red until absorbed. It can spread over a broad area and look very dramatic. Usually there are no symptoms except the redness. If the vision is changed, or there is pain, see your ophthalmologist. Otherwise you can wait it out.

Related Questions

What causes subconjunctival hemorrhage to last so long?

Slow absorption. This benign event in most cases, involves the absorption of blood from the subconjunctival space, which can do this but this is not the ordinary function of this space. So absorption takes a while but will happen. Read more...

What are the most common symptoms of subconjunctival hemorrhage?

Red eye. Subconjunctival hemorrhage, the seepage of a small amount of blood (like a drop) into the space under the conjunctival lining of the eye overtop the white (sclera) is usually benign. The most dramatic thing is the bright red blood which can spread. Some sense a little fullness and slight blur. Pain is rare. Resolution is the rule and no treatment is required. Read more...