You have most probably developed a posterior vitreous detachment which is a normal ageing change. The vitreous gel in the posterior part of the eye liquifies with age and shrinks and may form a clump which is visible to you as a floater. As the vitreous detaches from the retina it may cause a pull on it leading to flashes of light. Usually this goes uneventful but sometimes it may cause a retinal tear which can progress to retinal detachment leading to severe loss of vision. So, you should see an ophthalmologist to confirm the diagnosis and rule out any retinal tear. Thanks.
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