Your symptoms could be caused by glaucoma (increased pressure inside the eye), retinal detachment, or another serious cause. While it might be due to something else that is much less important, you should contact your doctor now just to be sure.
Sudden and persistent changes in vision or intermittent loss of vision are reasons to contact your doctor right away. However, even when vision loss is quite gradual, it's important to get checked out, especially if it is affecting your day-to-day life.
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