The black line you see is caused by vitreous opacity. There are several diseases: uveitis, vein occlusion, and if the vision drops rapidly, it may also be retinal detachment. Anyway, we should speed up the treatment.

After you left the hospital, the sunshine was very strong because you dilated your pupils. That's what the hospital ordered for you. The liquid medicine in your eyes is a mydriatic. Generally, it will recover in an hour or two after pupil dilation.

I think if you are not sure about the cause of your illness, you will be asked to have a fluoroscopy.