Physician Assistant Exam: Conditions that Affect External Eye Structures
For the Physician Assistant Exam, you will need to know about issues affecting the conjunctiva, common medical conditions affecting the eyelid and tear ducts, and problems of the orbit, including infection and orbital trauma. You can see a lot of orbital trauma (in an ER or trauma rotation) as a result of motor vehicle accidents.
Conjunctiva are thin membranes that blanket and protect the surfaces of both eyes. Conjunctivitis (pinkeye) is an irritation/infection of the conjunctiva. The most common cause of conjunctivitis is a virus, such as adenovirus. Bacterial conjunctivitis is caused by Streptococcus pneumoniae, Moraxella catarrhalis, or Haemophilus influenzae. Other causes of conjunctival irritation are allergic and fungal. Common presenting symptoms include redness, eye tearing, and pain. There’s also an eye discharge.
Watch out! Viral or bacterial conjunctivitis is contagious! You treat bacterial conjunctivitis with topical antibiotics if it doesn’t resolve on its own in about 3 days.
Pinkeye isn’t the only thing that can happen to the conjunctiva. Pterygium refers to a benign growth on the conjunctiva. The etiology isn’t known, but it may be a reaction to the weather, including excessive sun or wind exposure. The symptoms are tearing, redness, and itching. The treatment is usually conservative. If the growth begins to cover a significant amount of the eye, surgical intervention is warranted.
Bumps around the eyelid
Two eye conditions that have to do with sebaceous glands are often thought of as similar, but they have significant differences. One is the chalazion; the other is the stye.
The chalazion is a cyst-like structure that forms because of a blockage of the meibomian gland, a special type of sebaceous gland in the eye. The affected eye is often tender and swollen and very, very photosensitive.
Chalazions often resolve on their own, especially if they’re small. Interventions can include the use of warm compresses to soften the area and promote drainage. If they continue to enlarge or fail to settle within a few months, then smaller lesions may be injected with a corticosteroid, or larger ones may be surgically removed using local anesthesia.
A stye (a hordeolum) derives from an infected sebaceous gland. It differs from a chalazion, which comes from a blocked sebaceous gland. If untreated, a stye can develop into a chalazion. Rather than being in the eyelid itself, styes are on the lid margin. The treatment is topical warm compresses and topical antibiotics when needed.
Inflammation of the tear duct and eyelid
Dacryoadenitis refers to an inflamed tear duct that may become blocked. The most common cause is infection, either viral or bacterial. A common bacterial cause is Staphylococcus aureus. The upper eyelid is swollen and erythematous, and it can be painful. The treatment often is supportive and involves antibiotics in the case of a bacterial infection.
Blepharitis is inflammation of the eyelids. The lids can be red and swollen, and the skin can be crusty and/or flaky. One of the most common causes is a bacterial infection secondary to your old friend Staph aureus. The treatment is warm compresses and antibiotics.
Orbit the eye
The blowout fracture is a fracture of the orbit, usually as a result of a traumatic event, such as a car accident or a blunt trauma. Basically, the supporting structures of the bone are fractured. The dreaded complication of an orbital fracture is paralysis of the extraocular muscles.
A CT scan gives you a more detailed look at the orbit. Any paralysis of the extraocular muscles is an indication for surgery because there’s likely nerve entrapment. Other significant symptoms include double vision and eye swelling.
Orbital cellulitis is an infection, usually bacterial, of the tissues orbiting the eye, which can include the lid and cheek. The person may also have very significant eye swelling and loss of vision in the affected eye as well as significant pain. The treatment is intravenous antibiotics, although sometimes surgical intervention is necessary.
In clinical practice and on the PANCE, you must differentiate between orbital cellulitis and periorbital cellulitis. Periorbital cellulitis is an infection in front of the orbital septum, whereas orbital cellulitis occurs behind the orbital septum. In addition, the person with periorbital cellulitis doesn’t present with vision loss or pain. The eye isn’t bulging, either. You may see erythema and swelling around the eye, however.