Stye and Chalazion
The stye or outer hordeolum is presented as a small nodule that forms when one of the many small glands and ducts of glands in our eyelids (see the anatomy of the eyelid below). simply becomes infected or blocked, which can cause pain or discomfort. The stye appears more often in the upper eyelid near the edge of the eyelid and eyelashes (see illustration), but can also be found in the lower eyelid.
The stye often results from infection with bacteria (staphylococcus) in an eyelash follicle or in the associated Zeis or Moll glands. Staphylococcus is a very common bacterium that is often found on the skin. Sometimes these bacteria reproduce profusely and cause inflammation.
A stye that grows quickly or opens and lets out pus requires special attention. Antibiotic drops or ointment as well as compresses of hot water should be used. This often shortens the healing time and is recommended for people with repeated styes, for those who have an eyelid infection (blepharitis).
Internal Hordeolum
Essentially, it is the same condition as the stye except that the infection is located in a different gland, more central and internal called Meibomian gland. Since it is more internal, it is usually more painful than the stye. The treatment is the same except that antibiotics are more often needed.
Chalazion
Chalazion is most often caused by an accumulation of secretions of a meibomian gland resulting in a blockage of the duct. It is not caused by an infection. When sebum (secretions) accumulates too much, it causes the eyelid to swell and then becomes more and more uncomfortable or painful. Sebum can also harden and form a mass in the eyelid.
The chalazion is more resistant than the stye. Sometimes it takes medical treatment with cortisone injection or incision to extract and heal faster.