Herpes infection of the cornea

The clear tissue at the front of the eye is known as the cornea, and it must remain crystal clear in order for an individual to see clearly. The herpes viruses can infect the cornea, causing damage to tissue and possibly causing lasting visual impairment if not quickly identified and treated.

Herpes simplex: the cold sore virus

One of the most common infections of the cornea is caused by the herpes simplex virus (HSV type I and HSV type II), or the cold sore virus. The most common question from patients with HSV infection of the cornea is "How did I get this?" The answer is fairly simple. The virus is everywhere, and exposure to it is inevitable. Autopsy studies show that 100% of people over age 60 have the virus in their body, specifically in the trigeminal ganglion that supplies the nerves to the eye. It is a matter of how your body responds to the infection that determines what happens to your eye.

The virus can be latent, having no effect on the cornea, or the virus can cause havoc on the cornea in a variety of ways. HSV can cause a breakdown in the surface layer of the cornea, resulting in microscopic defects that result in eye redness, eye pain, and blurry vision. This condition is treated with oral antiviral medications, such as acyclovir and valacyclovir, and preventative topical antibiotics to limit the risk of a bacterial infection developing in the vulnerable eye.

In addition, the body's immune response to HSV can result in cloudlike whitening patches forming within the cornea. This is known as stromal keratitis and refers to inflammation of the middle layer of the cornea. The common symptoms of stromal inflammation include sensitivity to light and blurry vision. This condition is highly threatening to a person's vision. If not treated quickly and efficiently, it can result in scarring of the cornea with permanent vision loss. The treatment for HSV stromal keratitis is topical steroids under careful supervision by an eye doctor. The steroids are tapered very slowly to reduce the risk of recurrence.

Varicella zoster: the chicken pox and shingles virus

A related infection of the cornea is caused by varicella zoster virus (VZV), or the chicken pox or shingles virus. Exposure to VZV typically occurs during childhood, either with the disease or now more commonly with the vaccination. After this exposure, VZV remains in the body and can reactivate at a later time. The reactivation of VZV, called shingles, or herpes zoster, can cause a painful rash (described as "water droplets on rose petals") anywhere on the body. For the eye to be affected, the rash has to be on the face, typically on the forehead and tip of the nose.

A common misconception is that shingles occurs in only individuals older than 50. In fact, shingles can occur in healthy individuals as young as their 20s or 30s. Similar to HSV, VZV can cause surface layer breakdown of the cornea and stromal inflammation. These conditions are treated with oral antiviral medications and topical steroids, respectively.

The bottom line

HSV and VZV are significant infections of the cornea. If you experience eye pain, eye redness, sensitivity to light, or decreased vision, you should immediately be evaluated by an eye doctor for appropriate treatment to help reduce the risk of visual impairment.