Eye Infections | Clinical Medicine
•March 10, 2026
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Why It Matters
Accurate identification of eye infection types ensures timely, targeted treatment, preventing vision‑threatening complications and boosting performance on board examinations.
Key Takeaways
- •Identify lid and lacrimal infections by obstruction and inflammation patterns
- •Staphylococcus aureus is the most common pathogen in eye infections
- •Contact lens wearers risk Pseudomonas aeruginosa conjunctivitis requiring fluoroquinolones
- •Distinguish bacterial, viral, and gonococcal conjunctivitis for proper treatment
- •Dacryocystitis arises from nasolacrimal duct obstruction causing fluid stasis
Summary
The video provides a concise review of eye infections, emphasizing their relevance for USMLE Step 2 and clinical rotations. It categorizes disorders into lid‑and‑lacrimal conditions—such as dacryocystitis, hordeolum (stye), and blepharitis—and conjunctival infections, outlining the anatomy of the lacrimal drainage system and how obstruction leads to stasis and bacterial overgrowth. Key insights include the predominance of Staphylococcus aureus across most lid infections, the role of Group A β‑hemolytic streptococcus in dacryocystitis, and the special risk posed by contact‑lens wearers to Pseudomonas aeruginosa, which mandates fluoroquinolone therapy. The presenter also differentiates bacterial, viral, and gonococcal conjunctivitis, noting typical adult pathogens (Staph aureus) versus pediatric agents (H. influenzae, Streptococcus pneumoniae) and the unique management of gonococcal disease in neonates or sexually active patients. Illustrative examples highlight a blocked eyelash follicle producing an anterior hordeolum, the red‑eye presentation of conjunctivitis with both bulbar and palpebral involvement, and the direct inoculation route for gonococcal infection during vaginal delivery. The speaker stresses that many mild infections resolve without antibiotics, while specific scenarios—contact‑lens‑associated keratitis or gonococcal conjunctivitis—require prompt, targeted treatment. For learners and clinicians, recognizing the pattern of redness, swelling, and discharge guides appropriate empiric therapy and avoids unnecessary antibiotic use. Mastery of these concepts not only improves patient outcomes but also prepares students for high‑yield exam questions on ocular pathology.
Original Description
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Ninja Nerds!
In this lecture, Professor Zach Murphy will present on Eye Infections. We will begin by examining the pathophysiology of common eyelid and lacrimal system infections, including dacryocystitis, hordeolum, and blepharitis, with a focus on how obstruction and bacterial overgrowth contribute to localized inflammation.
We will then transition into conjunctival infections, comparing bacterial and viral conjunctivitis and highlighting key organisms like Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, adenovirus, as well as high-stakes causes such as Neisseria gonorrhoeae and Chlamydia trachomatis. From there, we will build into corneal infections, including bacterial keratitis, HSV keratitis, and VZV keratitis, focusing on classic fluorescein staining patterns like dendritic lesions and pseudodendrites, along with the clinical clues that point to sight-threatening disease.
Next, we will cover periorbital and orbital infections, distinguishing between preseptal cellulitis and orbital cellulitis using red flag findings, such as pain with eye movements, proptosis, restricted extraocular movements, and decreased visual acuity. We will also discuss endophthalmitis, especially in the setting of recent ocular surgery or penetrating trauma, and why rapid recognition is critical to preserving vision.
Finally, we will walk through a practical diagnostic and management approach, including when to obtain cultures or NAAT testing, when slit lamp and fluorescein staining are necessary, and when CT or MRI imaging of the orbits and sinuses is required. We will close by reviewing serious complications like cavernous sinus thrombosis and vision loss, and the treatments used to prevent irreversible outcomes.
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Table of Contents:
0:00 Lab
1:01 Pathophysiology and Causes of Eye Infections
57:03 Lid and Lacrimal Infections
58:50 Conjunctival Infections
1:03:03 Corneal Infections
1:05:29 Periorbital/Orbital Infections
1:07:35 Intraocular Infections
1:10:23 Complications of Eye Infections
1:30:08 Diagnostic Approach to Eye Infections
1:52:52 Treatment of Eye Infections
2:05:08 Comment, Like, SUBSCRIBE!
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