Unit 4: Common Viral Infections of the Eye
Viral infections of the eye represent a significant portion of ocular surface and adnexal disorders encountered in clinical practice. Unlike bacterial infections, viral diseases often have a self-limiting course, but they can cause considerable discomfort, decreased vision, and sometimes serious complications. Viruses affect not only the conjunctiva and cornea but may also involve deeper ocular structures such as the uvea, retina, and optic nerve. Optometry students must understand the clinical presentations, diagnostic features, complications, and management approaches of these conditions. This unit provides a detailed exploration of common viral infections of the eye including Herpes Simplex Virus (HSV), Herpes Zoster Ophthalmicus (HZO), Adenoviral Infections, Molluscum Contagiosum, Measles, and Rubella.
Introduction to Ocular Viral Infections
Viral ocular diseases differ from bacterial or fungal infections in several ways. They often spread through respiratory droplets, direct contact, or contaminated surfaces. Unlike bacteria, viruses cannot replicate independently; they invade host cells and utilize cellular machinery to multiply. This makes treatment difficult because antiviral drugs primarily aim to inhibit viral replication rather than kill the virus directly.
Ocular viral infections may present as acute, recurrent, or chronic conditions. Some viral infections such as adenoviral conjunctivitis are highly contagious, leading to outbreaks in schools, hospitals, and workplaces. Others like herpes simplex can remain latent in the nervous system and reactivate periodically. Understanding their pathophysiology and clinical course is crucial for effective diagnosis, prevention, and management.
1. Herpes Simplex Virus (HSV) Eye Infections
Etiology and Pathogenesis
Herpes Simplex Virus type 1 (HSV-1) is the most common cause of ocular herpes. HSV-2, usually associated with genital infections, can also cause ocular disease, particularly in neonates. After primary infection, the virus establishes latency in the trigeminal ganglion. Reactivation can occur due to stress, fever, trauma, or immunosuppression, leading to recurrent ocular involvement.
Clinical Features
- Blepharoconjunctivitis: Vesicular lesions on the eyelids and follicular conjunctivitis.
- Keratitis: Dendritic epithelial ulcer with terminal bulbs is the hallmark sign.
- Stromal keratitis: Can be necrotizing or immune-mediated, leading to scarring and vision loss.
- Endotheliitis: Disciform keratitis with stromal edema and keratic precipitates.
Complications
Recurrent HSV keratitis is a leading cause of corneal blindness worldwide. Chronic stromal disease may result in corneal thinning, perforation, or secondary glaucoma.
Management
- Antivirals: Topical acyclovir 3% ointment or ganciclovir 0.15% gel; oral acyclovir in recurrent disease.
- Supportive therapy: Lubricants, cycloplegics for pain relief.
- Avoid corticosteroids in epithelial disease but carefully used in stromal keratitis with antiviral cover.
2. Herpes Zoster Ophthalmicus (HZO)
Etiology and Pathogenesis
HZO results from reactivation of latent Varicella-Zoster Virus (VZV) within the ophthalmic branch of the trigeminal nerve. It is more common in older adults and immunocompromised patients. The hallmark feature is painful skin eruption along the distribution of the trigeminal nerve.
Clinical Features
- Unilateral vesicular rash on the forehead, upper eyelid, and nose (Hutchinson’s sign: lesions on the tip of the nose predict ocular involvement).
- Conjunctivitis, keratitis (nummular or dendriform), scleritis, uveitis.
- Neurotrophic keratopathy and secondary bacterial infection in chronic stages.
Complications
Post-herpetic neuralgia is a common long-term complication. Ocular complications include chronic keratitis, glaucoma, cataract, and vision loss.
Management
- Oral antivirals (acyclovir, valacyclovir, famciclovir) started within 72 hours of rash onset.
- Analgesics and corticosteroids for inflammation.
- Lubricants and topical antibiotics for secondary prophylaxis.
- Zoster vaccination is preventive in older adults.
3. Adenoviral Infections
Etiology
Adenoviruses are non-enveloped DNA viruses responsible for a spectrum of ocular conditions. They are highly contagious and transmitted via contaminated hands, medical instruments, or swimming pools.
Types of Adenoviral Ocular Disease
- Pharyngoconjunctival Fever (PCF): Associated with fever, sore throat, and conjunctivitis, common in children.
- Epidemic Keratoconjunctivitis (EKC): More severe form with pseudomembranes, subepithelial infiltrates, and decreased vision.
- Non-specific follicular conjunctivitis: Mildest presentation, often self-limiting.
Clinical Features
- Redness, tearing, photophobia, foreign body sensation.
- Preauricular lymphadenopathy (important diagnostic sign).
- Membrane or pseudomembrane formation on tarsal conjunctiva.
Management
- No specific antiviral therapy; treatment is mainly supportive.
- Lubricating eye drops and cold compresses provide relief.
- Topical steroids in severe cases of subepithelial infiltrates.
- Strict hygiene to prevent spread (hand washing, disinfection of instruments).
4. Molluscum Contagiosum
Etiology
Caused by a DNA poxvirus, molluscum contagiosum presents as umbilicated nodules on the eyelid margin. It is more common in children and immunocompromised individuals.
Clinical Features
- Multiple dome-shaped, waxy nodules on the lid margin.
- Conjunctivitis due to viral particles shedding into the tear film.
- Chronic follicular conjunctivitis may be the only presenting symptom.
Management
- Excision or curettage of the lesion is the treatment of choice.
- Cryotherapy or cauterization may also be used.
- Lubricants and supportive care for conjunctivitis.
5. Measles (Rubeola)
Ocular Manifestations
- Conjunctivitis with photophobia, lacrimation, and discharge.
- Keratitis which may progress to corneal ulceration, especially in malnourished children.
- Retinopathy with whitish lesions and optic neuritis in severe cases.
Complications
Vitamin A deficiency worsens ocular morbidity in measles, leading to keratomalacia and permanent blindness in severe cases.
Management
- Supportive therapy with lubricants and antibiotics for secondary infection.
- Vitamin A supplementation is critical.
- Measles vaccination for prevention.
6. Rubella (German Measles)
Ocular Features
- Congenital rubella syndrome causes classic triad: cataract, congenital heart disease, sensorineural deafness.
- Other ocular findings include microphthalmia, glaucoma, and pigmentary retinopathy.
Management
There is no specific antiviral therapy. Prevention through rubella vaccination is the most effective strategy. Optometrists play a role in early detection and visual rehabilitation for children affected by congenital rubella.
Optometric Relevance and Preventive Strategies
Optometrists are often the first point of contact for patients with red eye or visual complaints. Recognizing viral patterns is crucial to avoid unnecessary antibiotic use and to implement proper infection control. Key preventive measures include:
- Hand hygiene and disinfection of instruments such as tonometers.
- Use of disposable diagnostic strips and lenses where possible.
- Educating patients about avoiding close contact and sharing towels, cosmetics, or contact lenses during infection.
- Recommending vaccinations (measles, rubella, zoster) when appropriate.
