Before we discuss vision disorders, it will be a good idea to review your anatomy and physiology book or do a quick web search to refresh your memory and understanding of the following terms: cornea, sclera, iris, ciliary body, choroid, aqueous humor, vitreous humor, optic disk, and optic nerve. Also review the retina and the cell types found in the retina.

Below is a quick description of a few new terms that you will need to be familiar with:

• Blepharitis: Inflammation of the eyelids that affects the eyelashes or tear production. It most often occurs when the oil glands of the eyelids get clogged or inflamed. The eyes can become irritated, itchy, and people with this condition can wake up with their eyes crusted together.
• Hordeolum: Otherwise known as a stye, this condition occurs when the small glands that line the eyelid get infected. Staphylococcus aureus is usually the perpetrator. The most common symptom is redness and swelling with the appearance of a bump on the eyelid. Styes usually go away on their own, but applying a warm washcloth to the area can ease some of the discomfort.
• Chalazion: A small bump on the eyelid that forms when the small glands that line the eyelid get blocked or clogged. It may be painful at first, but after a bit of time it usually doesn’t hurt. A chalazion is different from a hordeolum in that it isn’t due to infection.
• Keratitis: Inflammation of the cornea that may be caused by infection, disease, injury, or wearing contact lenses too long. It manifests with eye redness, pain, and decreased quality of vision. Prompt medical treatment is important to avoid vision loss.