Ok. The most likely cause for your condition is called a posterior vitreous
detachment, a common event that occurs in many people.
You have a thick gel material in the middle of your eyes called the vitreous. Over time as it liquefies, this gel material collapses on itself, forms little clumps that you can see as dots, lines or bugs. As these clumps form the vitreous pulls away from the wall of the eye. In the process it can stimulate the retina -- causing the flashes that you may see.
It is recommended that you see your ophthalmologist
to look at the retina to make sure there are no problems such as a retinal hole or tear. In most cases, there are no problems, but this exam is precautionary and allows for preventative treatment of any lesions that are found.
If you notice a sudden increase in floaters, flashes of light (like a lightning storm), or a shadow/veil in the periphery of your vision, this can be worrisome for a retinal detachment
. You would need to contact your ophthalmologist promptly in that case.
My concern in your case is that a PVD usually doesn't seriously impact your vision. This makes me worried that you may have had bleeding inside your eye and the "spider" you are seeing is the blood floating around inside your eye.
A trip to the ER will only be valuable if an ophthalmologist can come in and examine you there....regular ER docs don't have the equipment or the training to deal with this issue.
Does this make sense to you?