The eyelids can be very swollen due to the following causes: 1. mydriasis, also known as acute blepharitis, which manifests as swollen and painful eyelids. 2. acute allergic conjunctivitis, which can lead to significant eyelid edema with itching. 3. nephrogenic eyelid edema, which can result in eyelid edema when the kidneys are not functioning adequately. 4. cardiogenic edema, which can result in eyelid edema when the heart is not functioning adequately, but without significant pain and other inflammatory manifestations. 5. 5. Eyelid edema due to lacrimal gland prolapse, which is manifested as S-shaped edema. Therefore, when the eyelids are very swollen, you should go to a regular eye care provider in a timely manner for a detailed examination to determine the cause of the edema and to treat it accordingly to avoid delaying the condition.