A stye, also known as a hordeolum, is an acute infection of the glands at the base of the eyelids and eyelashes. They occur when oil glands become clogged and infected. Styes present as a red, painful bump on the eyelid. Large styes may cause blurred vision as well.
Styes frequently resolve on their own without treatment. Warm compresses and topical medications can be very helpful and hasten resolution.
A chalazion is a chronic cyst within the eyelid. These lesions tend to be less irritated and painful than a stye, and reflect a chronic issue. Chalazia arise spontaneously, but frequently occur after the acute phase of a stye. Once the acute infection of the stye resolves, residual oils and inflammatory material create a chalazion cyst.
A chalazion is typically a painless swelling of the eyelid. These lesions may cause blurred vision if they become large, a fairly common issue with chalazia.
Treatment initially involves warm compresses to attempt to soften and shrink the lesion, and your doctor may also prescribe topical medications to help treat it. If the chalazion doesn't go away, your eye doctor may need to remove the lesion in the office.