AssessmentsEye conditions: Inflammation, infections and trauma: Pathology review
USMLE® Step 1 style questions USMLE
A 26-year-old man comes to the emergency department for evaluation of left eye pain and swelling for three hours. He was brought in by local police following an altercation at a bar, where he was punched in the left eye. He reports that he has double vision when looking upward. Temperature is 37°C (98.6°F), pulse is 94/min, respirations are 15/min, and blood pressure is 132/84 mmHg. On examination, the left orbit is ecchymotic with associated swelling. Pupils are equal and reactive to light, and visual acuity is 20/20 bilaterally. Neurologic evaluation demonstrates diminished sensation of the skin to fine touch at the left lower eyelid and left anterior cheek. A CT scan of the face reveals a fracture of the floor of the left orbit with entrapment of orbital contents in the left maxillary sinus. Injury to which of the following nerves is the most likely etiology of this patient’s sensory deficits?
Content Reviewers:Yifan Xiao, MD
While doing your rounds, you meet a 4 day old newborn girl, named Caitlyn, who is brought to the emergency department due to redness and swelling of the eyes. Physical examination shows bilateral eye erythema and purulent discharge. The infant was born at home to a mother who received no prenatal care and is unable to provide any medical history. Some days later, 41-year-old Joshua comes to the ophthalmology clinic complaining of black spots and blurry vision that started about two weeks ago. He mentions that the spots go away when he closes his left eye. On examination, visual acuity is 20/100 in the right eye and 20/20 in the left. Fundus examination is pictured. His medical history includes a diagnosis of HIV infection 8 years ago.
Based on the initial presentation, both Caitlyn and Joshua have some form of inflammatory, infectious or traumatic eye condition. But first, a bit of physiology real quick. If we zoom into the wall of the eye, it is made up of three major layers. There’s a fibrous outer layer that contains the cornea and sclera. The outer surface of the sclera is covered by a mucous membrane, called conjunctiva, which also lines the inside of the eyelids. The middle vascular layer is called uvea and consists of the iris, pupil, choroid, and ciliary body. Finally, the neural layer consists of the retina which helps convert light into neural signals that travel via the optic nerve to the brain for visual processing. Okay, let’s start with stye, also known as hordeolum, which is a common bacterial infection of the sebaceous glands of the eyelids. For your exams, remember that the most common pathogen is Staphylococcus aureus. Styes present as painful, red, pus-filled lumps and are usually located at the lid margin, in which case they are known as external styes, or under the conjunctival side of the eyelid, also called internal styes. For your exams, keep in mind that for unknown reasons, styes tend to be more common in individuals with acne vulgaris and diabetes mellitus. Diagnosis is clinical and treatment usually involves warm compresses, massage and topical antibiotics, usually dicloxacillin. Now, it’s important to differentiate a stye from a chalazion. A chalazion results from the obstruction of sebaceous glands of the eyelids, without any infection. It presents as a slow-growing, painless, rubbery nodule, usually in the middle of the eyelid. Diagnosis is clinical and no treatment is necessary, since it's usually self-resolving. Next is conjunctivitis, which is inflammation of the conjunctiva. For your exams, remember that there are two main types of conjunctivitis, infectious and non-infectious. Infectious conjunctivitis can be further divided into viral and bacterial conjunctivitis. Viral conjunctivitis is the most common one and is typically caused by adenovirus but can be also due to herpes simplex virus or varicella-zoster virus. Bacterial conjunctivitis can be gonococcal, which is caused by Neisseria gonorrhoeae, or chlamydial, which is caused by Chlamydia trachomatis. For your test, remember that gonococcal conjunctivitis tends to be more severe and might be accompanied by various complications. That's because gonococci can penetrate further into the cornea, causing corneal edema, ulceration or even scarring and perforation. In some cases, gonococci could get even deeper and involve the interior of the eye, causing endophthalmitis, or make it into the systemic circulation and spread throughout the body. Now, non-infectious conjunctivitis includes allergic conjunctivitis, which is usually caused by airborne allergens, like pollen, and nonallergic conjunctivitis, caused by chemical or mechanical irritation of the conjunctiva. A high-yield fact is that in newborns, chemical conjunctivitis is most often caused by the use of ophthalmic silver nitrate for prophylaxis against ocular gonococcal infection.
In terms of symptoms, all types of conjunctivitis present with unilateral or bilateral pinkish or red eyes and sometimes, mild eyelid and conjunctival edema, sensitivity to light, and excessive lacrimation. For your exam, you must remember what sets the different types apart, which is their discharge. So, in viral and non-infectious conjunctivitis, the discharge is sparse mucoid or watery, while in bacterial conjunctivitis, it’s purulent, white yellow or green. In newborns, remember that gonococcal conjunctivitis tends to produce a greater amount of purulent discharge than chlamydial conjunctivitis. If there's corneal involvement or endophthalmitis, gonococcal conjunctivitis, may also be accompanied by vision impairment or even vision loss. For allergic conjunctivitis, a telltale sign is excessive eye itchiness or pain. For neonatal conjunctivitis, another high yield clue that helps you differentiate between gonococcal, chlamydial, and chemical conjunctivitis is the time of presentation after birth. So, chemical conjunctivitis typically presents on the first day after delivery, gonococcal conjunctivitis between day 2 and 7, and chlamydial conjunctivitis between days 5 and 14.
Now, diagnosis is usually clinical, but for infectious conjunctivitis, laboratory tests of the conjunctival exudate might be also necessary. Specifically, for viral conjunctivitis, rapid antigen detection tests can be used, whereas in gonococcal conjunctivitis, gram stains can detect the typical gram-negative intracellular kidney bean-shaped diplococci. Keep in mind that Chlamydia does not Gram stain well. That’s mainly because it’s obligate intracellular and its cell wall lacks peptidoglycan, so it can’t retain the dye used during Gram staining. In contrast, Chlamydia is best stained with Giemsa stain, which colors them pinkish-blue. Cultures of the exudate are rarely used, but for your exams, remember that Neisseria gonorrhoeae grows best on a special chocolate medium called Thayer-Martin agar.
For treatment, viral conjunctivitis is typically self-resolving, but ocular lubricant drops, or ointments might be also helpful. On the other hand, bacterial conjunctivitis requires antibiotics. Ceftriaxone is effective for gonococcal conjunctivitis and doxycycline or azithromycin for chlamydia trachomatis infections. For newborns with chlamydia trachomatis, though, oral erythromycin is typically used. If simultaneous gonococcal and chlamydial infection is suspected, combination treatment includes doxycycline or a macrolide plus ceftriaxone. For non-infectious conjunctivitis, allergic conjunctivitis is usually treated with antihistamine drops while non-allergic conjunctivitis is usually self-resolving but flushing the eyes along with removing and avoiding the irritant might be helpful.
Prophylaxis of conjunctivitis should be given to all newborns and involves topical erythromycin or tetracycline. Remember that silver nitrate is typically not used anymore due to its association with chemical conjunctivitis. Another important thing to note is that this regimen doesn’t prevent chlamydial conjunctivitis.
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