A Case of Herpes Simplex Virus Keratitis in The Emergency Department

A Case of Herpes Simplex Virus Keratitis in The Emergency Department – A Medical Student Clinical Pearl

Patrick Gallagher, MED III

MUN Class of 2022

Reviewed by Dr. Robin Clouston

Copyedited by Dr. Mandy Peach


A 53-year-old female presents to the emergency department with a two-day history of left-eye pain, which she describes as “something being stuck in her eye.” The patient endorses left eye tearing, pruritis, and photophobia. She notes that her eye has been “blurry” since she awoke this morning. The patient denies any infectious symptoms at present but states that a cold sore erupted on her upper lip seven days ago. She does not use contact lenses.

Past medical history: T2DM and hypothyroidism.

Past surgical history: None.

Medications: Metformin 500 mg OD and Synthroid 125 mcg OD.

Physical exam:

Upon inspection, the patient has conjunctival injection and tearing in the left eye. Mild periorbital edema and erythema is noted. The patient’s pupils are equal and reactive to light, and visual acuity is 20/20 in the left eye and 20/40 on the left eye. Extraocular eye movements and visual fields are normal. The patient has decreased corneal sensation.

On slit lamp examination using fluorescein-based dye, a small branching dendritic ulcer was seen (Figure 1).

Figure 1: Dendritic ulcer noted on slit-lamp exam with fluorescein-based dye.


What is the differential diagnosis of dendrites?

• Herpes simplex keratitis
• Acanthamoeba keratitis
• Other keratitis caused by Varicella zoster virus (VZV), cytomegalovirus (CMV), Epstein–Barr virus (EBV), or adenovirus.
• Dendritiform keratopathy
• Ramous epithelial changes
• Limbal stem cell deficiency
• Drug induced corneal changes (epinephrine, antivirals, beta-blockers) 1,2

Herpes simplex virus keratitis :

Herpes simplex is a DNA virus that can cause a wide variety of infections, most commonly involving the mouth, genitalia, and eyes3. While HSV-1 and HSV-2 can involve the eye, HSV-1 is the most common cause of keratitis1. Herpes simplex keratitis (HSK) is characterized by recurrent infections of the corneal epithelium and stroma2. HSK can be classified as primary or recurrent and further divided into three subtypes: epithelial, stromal, and endothelial3. Epithelial keratitis is the most commons subtype of ocular herpes (50% to 80%)2.

Herpes simplex virus (HSV) infections are the leading cause of infectious corneal blindness in developed countries3. It is estimated that 1.5 million people worldwide experience HSV keratitis every year2.


Primary HSV eye infections occur when the virus enters mucous membranes by direct contact. This initial infection is usually subclinical, but it can cause unilateral blepharitis, follicular conjunctivitis, and occasional epithelial keratitis (Figure 2)4. The initial infection is typically asymptomatic, and it occurs in children less than five years old5.

Figure 2: Pictorial representation of blepharitis (inflammation of the eyelid), keratitis (inflammation of cornea), conjunctivitis (inflammation of conjunctiva), and ocular anatomy. Diagram retrieved from 7

After the initial infection, the virus can remain latent in the ophthalmic division of the trigeminal ganglion for the lifetime of the host. HSV reactivation in the latently infected ganglia can lead to corneal scarring, thinning, stromal opacity, and neovascularization5. The cumulative effect of numerous infections results in vision loss and eventually blindness if left untreated.

History and physical:

Diagnosis of HSK is primarily diagnosed by clinical presentation on slit lamp exam using fluorescein and either rose bengal or lissamine green3. However, it is crucial to complete a thorough history and physical exam to narrow the differential diagnosis (Table 1).

Table 1: Key points on history and physical

Figure 3: Slit-lamp corneal findings for patient’s diagnosed with HSV epithelial keratitis. A: Classic dendritic lesion with terminal bulbs. B: More advanced dendritic lesion presenting as geographic ulcer. Figure modified from 6.


The diagnosis of HSVK is based off of clinical findings and does not require additional investigations; however, for atypical lesions, polymerase chain reaction has been used to confirm HSVK. Enzyme-linked immunosorbent assay and viral cultures are also effective in the diagnosis of the HSVK subgroups3.

Treatment/management of HSVK in the emergency department:

In the emergency department, typical findings on the slit lamp exam is diagnostic for epithelial HSVK.

Care providers should initiate treatment immediately to reduce the risk of complications; however, the patient must be referred to ophthalmology within the next few days for follow-up.

Topical and oral antiviral treatments effectively treat epithelial HSVK, although no topical ophthalmic antivirals are currently available in Canada7. It is crucial to adjust the dose of oral antivirals according to the patient’s renal function. See Table 2 for available oral antiviral treatments. For symptomatic management, artificial tears or eye lubricants can ease eye discomfort and over-the-counter analgesics can help relieve pain7.

Table 2: Oral antiviral treatment for epithelial HSVK in adults. Modified from 7

Back to the case:

Given our patient’s classic symptoms of epithelial HSVK (conjunctival injection, tearing, vision changes, foreign body sensation, photophobia, hx of HSV infection) and finding of dendritic ulcers on slit lamp examination, we treated this case as epithelial HSVK until proven otherwise. Therefore, we prescribed the patient valacyclovir 1000mg PO TID and arranged an urgent ophthalmology consult for the following day.


  1. Roozbahani, M., & Hammersmith, K. M. (2018). Management of herpes simplex virus epithelial keratitis. Current opinion in ophthalmology, 29(4): 360-364.

  2. Wilhelmus, K. R. (2015). Antiviral treatment and other therapeutic interventions for herpes simplex virus epithelial keratitis. Cochrane Database of Systematic Reviews, 1.

  3. Azher, T. N., Yin, X. T., Tajfirouz, D., Huang, A. J., & Stuart, P. M. (2017). Herpes simplex keratitis: challenges in diagnosis and clinical management. Clinical Ophthalmology, 11:185–191.

  4. Sibley, D., & Larkin, D. F. (2020). Update on Herpes simplex keratitis management. Eye, 34: 2219–2226.

  5. Toma, H. S., Murina, A.T., Areaux, R.G., Neumann, D.M., & Bhattacharjee, P.S. (2008). Ocular HSV-1 Latency, Reactivation and Recurrent Disease. Seminars in Ophthalmology, 23(4), 249–273.
  6. Leon, S., & Pizzimenti, J. (2017). Be a Hero to Your HSVK Patients. Review of Optometry-Leadership in clinical care. Retrieved from https://www.reviewofoptometry.com/article/ro0717-be-a-hero-to-your-hsvk-patients2
  7. Institut national d’excellence en santé et en services sociaux. (2018). Herpes Simplex Eye Disease. INESSS Guides. Retrieved from https://www.inesss.qc.ca/fileadmin/doc/INESSS/Outils/GUO/Herpes/Guide_HerpesSimplex_web_EN_VF.pdf


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