The main symptoms of a chalazion are a painless lump on the eyelid and tearing, says American Optometric Association. If the chalazion is large enough, it can press on the eyeball and cause blurred vision. The chalazion may first manifest as a red and tender swelling of the eyelid prior to becoming a painless bump. A chalazion is more common on the upper eyelid than the lower and more common in adults than in children.
A chalazion occurs when an oil gland in the eyelid becomes clogged, which causes it to swell, explains American Optometric Association. This can occur because of a prior infection, but often a chalazion occurs on its own without an infection. One of the more common infections of the eyelid, a stye, occurs closer to the surface of the eyelid than does a chalazion. Rarely, a chalazion can also be a sign of cancer in the eyelid. Whatever the cause, a chalazion can start very small and be barely detectable, but it can grow to the size of a pea.
A chalazion generally goes away on its own within several weeks or a month, says American Optometric Association. Warm compresses can speed up drainage and healing. Squeezing the chalazion is not advisable, and a chalazion that lasts more than a month requires medical attention.