Ophthalmology Flashcards
treatment of corneal abrasions?
This is a middle-aged male patient who presented to the emergency department with eye pain after he worked in his yard. Though he was unaware of any eye injury, his eye was likely struck by some kind of projectile given he was working with power equipment. The exhibit clearly shows evidence of a corneal abrasion, which we must assume was caused by a foreign body given the patient’s history. Prophylactic treatment with a broad-spectrum antibiotic ointment or drops, such as erythromycin, trimethoprim/polymyxin B, or sulfacetamide sodium, is recommended for most corneal abrasions. These agents are inexpensive and have few side effects. If a very small abrasion is present, it can be considered to be low risk if it is not caused by a foreign body or trauma, is not located over the central cornea, and is not associated with contact lenses. In these rare cases, observation without antibiotics is reasonable.
All contact lens–associated abrasions (high risk) warrant antibiotic treatment because of their propensity for developing infectious corneal ulcers, also known as microbial keratitis, for which coverage for Pseudomonas is required. An appropriate antibiotic for contact lens wearers would be ciprofloxacin. For patients who do not wear contact lenses, erythromycin is adequate. Ointments are preferred over eye drops because ointments provide lubrication. There is a lack of sufficient evidence to suggest that antibiotics prevent infection or shorten the time to healing. However, antibiotics are often used in clinical practice and are currently recommended. Additionally, antibiotics should not be combined with steroids. Steroids are contraindicated in the setting of corneal abrasions because steroids slow healing and can reduce resistance to infection.
The corneal abrasion is circled in the exhibit below. The green color on the patient’s eyelashes is residual fluorescein dye. As a reminder, fluorescein dye will be washed away from intact corneal epithelium but will be absorbed and remain wherever there is epithelial damage. The dye will appear green under cobalt blue light.
What are the 2 types of endophthalmitis? What bacteria cause each type?
There are 2 types of endophthalmitis: exogenous and endogenous. Exogenous refers to inoculation with bacteria from an outside source, mainly through trauma or surgery. Endogenous refers to inoculation with bacteria from an internal or bloodborne source, such as with bacteremia or fungemia.
The single most common cause of exogenous endophthalmitis is Staphylococcus epidermidis, which is typically normal flora of the skin and conjunctiva and which is generally introduced into the eye during surgical procedures; more than 70% of post-cataract endophthalmitis is caused by this species alone. This organism can also be introduced into the eye during trauma.
The second most common cause of endophthalmitis after cataract surgery is Staphylococcus aureus; this organism causes about 10% of cases. Traumatic endophthalmitis is often associated with Bacillus cereus and other Gram-negative bacteria as well as with Staphylococcus epidermidis and streptococcus.
Endogenous endophthalmitis is most commonly caused by bacteremia and is extremely rare. It is generally associated with endocarditis, and whatever organism, whether it be Staphylococcus or fungus, is isolated in the blood is likely to be present in the eye. The most common bacterial cause of endogenous endophthalmitis in the United States is Staphylococcus aureus followed by various streptococci and Gram-negative organisms, such as Escherichia coli.
Allergic vs viral conjunctivitis?
Viral conjunctivitis may also present with red, watery eyes. Watery exudates and erythematous injection of the conjunctiva will be present on physical exam in addition to preauricular adenopathy. In addition, there is often crusting and matting of the eyelashes upon awakening in the mornings. It is usually caused by adenovirus and treatment is supportive.
The most likely diagnosis in this patient is allergic conjunctivitis. Allergic conjunctivitis is a common cause of red, watery eyes. It usually presents in patients with a history of allergies or atopic dermatitis. It can be associated with seasonal high pollen counts, animals, mites, dust, and other causes of allergies. Patients complain of episodes of itchy, watery eyes that may be alleviated with antihistamines.
How do we treat corneal abrasions?
Corneal abrasions can either be considered traumatic or spontaneous. Spontaneous defects in the corneal epithelium may occur with no injury or foreign body. Patients who have suffered a corneal abrasion in the past are more at risk for a corneal abrasion. Corneal abrasion must be suspected in any patient who complains of photophobia and/or foreign body sensation, but penetrating trauma and infectious infiltrate must be ruled out. History of being a contact wearer is important in making treatment decisions.
Administration of antibiotics is the mainstay of therapy. The purpose of the antibiotic therapy is to prevent superinfection. While it is the most common treatment, there is not good evidence regarding whether topical antibiotics prevent infection or shorten the time to healing. Ointments are preferred over drops because they function better as lubricants.
Non–contact lens wearers should be treated with ophthalmic erythromycin or bacitracin. Contact lens wearers are treated with antipseudomonal coverage such as an aminoglycoside or fluoroquinolone. Antibiotic preparations containing steroids are contraindicated because they slow epithelial healing and reduce host resistance to superinfection.
What is a pterygium?
pterygium. Exposure to wind, sand, and sun can lead to an elastotic degeneration of the conjunctival stroma, resulting in a wing-like growth of tissue over the cornea. Growth into the central axis of vision can impair sight. Constriction of the membrane can also lead to astigmatism, an irregular shape of the cornea leading to further refractive errors. Loss of normal conjunctival surface architecture, such as surface keratinization, and loss of goblet cells will cause symptoms of dry eye. These symptoms include excessive tearing, eye redness, and foreign body sensation. Malignant transformation of this actinic type damage is rare. Treatment includes observation and lubrication of the ocular surface in patients with mild symptoms and surgical excision in more symptomatic cases. Keen clinical observation and understanding of ocular surface anatomy in conjunction with appropriate history taking will provide the clinician with appropriate clinical management and timeliness of referral to a specialist.
