Herpes infections of the eye are most often caused by HSV-1. The virus' ability to hide from the immune system plays a role in this. This is because HSV-1, when evading the immune system's attempts to eradicate it, usually "hides" in the trigeminal ganglion, a nerve center near the ear, where it enters a state of hibernation. When it reawakens, it follows neural pathways back to the facial area, where it can cause an outbreak on the face or in an eye. Varicella-Zoster and Cytomegalovirus are two other types of herpes virus, can also cause herpetic eye infections.
Herpes Keratitis
Herpes Keratitis is the most common form of ocular herpes, which remains the most common viral cause of corneal blindness in the United States. Herpes Keratitis affects the top layer of the cornea, called the epithelium. The University of Wisconsin-Madison, UWM, reports that Herpes Keratitis most often results from HSV-1. In most cases, Herpes Heratitis does not scar the eye.
Stromal Keratitis
When herpes infects deeper in the eye, it can reach the middle layer, or the stroma. There it causes an immune system reaction which can destroy stromal cells, according to The National Eye Institute, NEI. Destruction of stromal cells can lead to scarring of the stroma, reduced sight and even blindness.
Iridocyclitis
When herpes infects the iris, the colored part of the eye behind the cornea, the infection is called Iridocyclitis. Iridocyclitis causes an inflammation of the iris and, according to Herpes.com, can lead to light sensitivity, blurred vision, redness and pain.
Herpes Retinitis
Rarely, the herpes virus will infect deeper inside the eye. When it infects the retina, the inside lining at the back of the eye, Herpes Retinitis results.
Cytomegalovirus Retinitis
Cytomegalovirus, CMV, is one of eight herpes viruses that can infect humans. CMV is usually asymptomatic, meaning the infected person does not notice any symptoms. However, it can cause complications in immuno-compromised patients. When it infects AIDS patients, about 30 percent will contract CMV Retinitis, according to the American Uveitis Society. CMV Retinitis leads to the progressive destruction of the retina, and eventually causes blindness.
Herpes Zoster Eye Infection
The Varicella-Zoster Virus, VZV, is the herpes virus that causes chickenpox and shingles. Once a person has had chickenpox, usually in childhood, it retreats to the nervous system. If it reactivates, most often in older people or those with compromised immune systems, the virus causes shingles, a painful localized rash. The National Eye Institute reports that 40 percent of shingles outbreaks on the head or neck include a corneal infection. The infection can cause decreased sensitivity of the eye or even corneal scarring.
References
- National Eye Institute: Facts about the Cornea and Corneal Disease
- University of Illinois at Chicago Ocular Herpes Simplex
- The Lasik Directory: Herpes and the Eye
- "American Journal of Ophthalmology"; Ocular Herpes Simplex; Jay S. Pepose, MD, PHD, et al; March 2006
- Herpes.com: Ocular Herpes
