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What is Herpetic Simplex Keratitis?

Herpetic Simplex Keratitis (HSK) is an eye infection of the cornea, the clear dome that covers the front of the iris and pupil. It is also known as Herpes Simplex Keratitis.

What are the symptoms of Herpetic Simplex Keratitis?

Some common symptoms include:

  • Eye pain
  • Tearing
  • Redness
  • Blurry vision
  • Sensitivity to light
  • Sensation of foreign objects

What causes this infection?

HSV-1 causes Herpetic Simplex Keratitis

HSV-1 causes Herpetic Simplex Keratitis

Herpes Simplex Virus (HSV) causes this infection. There are two types of HSV; HSV-1 and HSV-2. Herpes Simplex Keratitis is usually caused by HSV-1 which can also cause cold sores around the mouth. HSV-2 primarily causes genital herpes.

Who is most susceptible to Herpetic Simplex Keratitis?

Primary herpes simplex eye infections typically occur in children. Symptoms are usually mild and can heal without damaging the eye. Sometimes the symptoms may be so mild that they may not even be noticed.

Are further complications possible?

After the original infection, HSV-1 goes into a dormant state, living in nerve cells of the skin or eye. HSV-1 can travel back to the cornea and cause more severe damage when reactivated by triggers. Some examples of these triggers are:

  • Stress
  • Trauma
  • Overexposure to UV light
  • Immunosuppression.

These triggers may prompt a return of symptoms leading to temporary or permanent visual loss. Herpetic Simplex Keratitis is a leading cause of blindness worldwide.

Is Herpetic Simplex Keratitis contagious?

Yes and no. While HSV-1 is highly contagious and easily transmitted by skin contact,
once into the eyes the Herpes Simplex Keratitis (HSK) doesn’t spread as easily. Hence
HSK usually does not spread from one eye to the other, and spreading the virus from an
HSK infected eye to another person is rare.

What is Herpetic Whitlow? And can you contract Herpetic Simplex Keratitis from a herpetic whitlow infection?

Herpetic whitlow is a type of herpes lesion on a finger or thumb which can be caused by HSV-1 or HSV-2. It is most common in children who suck their thumbs.

Yes. Herpes Simplex Keratitis is usually contracted by direct contact with the virus. One can get this infection after touching their eye with herpes infected hands. Such sources of infection may be herpetic whitlow or cold sores on the mouth. It’s no surprise that most of the primary HSK happens in children.


Does Herpetic Simplex Keratitis have a cure?

No, there is no complete cure for Herpes Simplex Keratitis. Once HSV-1 is in the body, it establishes latency and stays with you for the rest of your life.

Are there any current treatments available?

Current treatment usually involves topical antiviral eye drops or oral antiviral medicine. These can limit the course of the active outbreak and help maintain the virus in latency.

How do these antiviral drugs work?

The antiviral drugs for HSV-1 work by inhibiting viral replication. They prevent cells from generating more viruses. They do not, however, clear the existent viruses.

Are there treatments for more severe cases?

Severe cases of Herpetic Simplex Keratitis can involve scarring or vision loss. A cornea transplant may be required for these situations.


How can we prevent outbreaks of Herpetic Simplex Keratitis?

Even though there is no cure for HSV-1, there are still things we can do to prevent outbreaks of HSK.

Most importantly, visit your eye doctor at the first sign of symptoms.

If you have any active cold sores or blisters:

  • avoid touching your eyes without washing your hands properly
  • avoid wearing contact lenses


How is Herpetic Simplex Keratitis diagnosed?

To be diagnosed with HSK, a doctor will review the patient’s health history and clinical symptoms from an eye exam.

When viral eye infections are suspected, further confirmation can be done using:

  • Polymerase Chain Reaction (PCR) Assay
    • PCR of HSV-1 detects the presence of HSV-1 DNA
    • takes hours to get results
  • Immunofluorescent Antibody Assay (IFA)
    • IFA detects the presence of HSV-1 antigens
    • takes hours to get results
  • Enzyme-Linked Immunosorbent Assay (ELISA)
    • ELISA detects the presence of HSV-1 antigens
    • takes hours to get results
  • Viral Cultures
    • most direct evidence of an active infection
    • takes many days to get results

Doctors usually need to get corneal scrapings from patients as samples for HSV-1 tests. Such tests are thus only done when necessary.

What is a Giemsa stain?

A Giemsa stain is a simpler, more rapid test that your eye doctor can perform. This is a less sensitive test. The doctor adds special dyes to the cornea scrapings to stain the multinucleated giant cells caused by HSV-1 infection.

How to determine which test is needed?

As all HSK cases are different, the eye doctor will determine the diagnostic method based on symptoms and the patient’s health history.

Please note that the CDC does not recommend HSV testing for people without symptoms of HSV.

Current Research

Are you aware of any current research on Herpetic Simplex Keratitis?

There is some interesting research being done by a group in Spain. They are working on the improvement of antiviral drug delivery to the cornea. Contact lenses have recently been developed that are imprinted with hydrogel. These lenses are loaded with an antiviral drug that can increase the efficiency of the treatment.7

There has also been recent improvement in HSV-1 PCR sensitivity. Reports show successful detection of HSV-1 DNA in collected tears from HSK patients. This is a big step in making non-invasive tests possible.6

Other Herpetic Eye Diseases

Are there any other herpetic eye diseases?

Yes. Another herpetic eye disease is Herpes Zoster Ophthalmicus (HZO). HZO is caused by Varicella Zoster Virus (VZV), or Human Herpes Virus 3 (HHV-3). VZV is also the virus that causes chickenpox and shingles. HZO is thus also called “eye shingles”.

How are HSK and HZO similar?

Similar to HSV-1 (the virus that causes HSK), VZV establishes latency in neuron cells and can cause an outbreak when our bodies experience mental or physical stress or have weakened immune systems. HZO and HSK share some symptoms such as eye pain, tearing, redness, and sometimes blurry vision or cloudiness of the cornea.

How is HZO different from HSK?

HZO has some unique symptoms such as headache, fever, rash or sores on the forehead or the tip of the nose.

What happens when both HZO and HSK are suspected?

When both HZO and HSK are suspected, further lab tests as mentioned above can be done. These tests may further confirm the identity of the virus.

What is a common treatment for HZO?

An oral antiviral is the most common treatment for HZO (instead of topical antivirals). This is because HZO is usually accompanied by zoster outside of the eye area.
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  1. Basics of HSV (Herpes Simplex Virus) Keratitis. Centers for Disease Control and Prevention.
  2. Herpes Simplex Keratitis – Eye Disorders. Merck Manuals Consumer Version. Published May 2020.
  3. Wald A, Corey L. Chapter 36, Persistence in the population: epidemiology, transmission. Human Herpesviruses: Biology, Therapy, and Immunoprophylaxis. Published 2014.
  4. Azher T, Yin X-T, Tajfirouz D, Huang A, Stuart P. Herpes simplex keratitis: challenges in diagnosis and clinical management. Clinical Ophthalmology. 2017; Volume 11:185-191. doi:10.2147/opth.s80475
  5. Farhatullah S. Diagnosis of herpes simplex virus-1 keratitis using Giemsa stain, immunofluorescence assay, and polymerase chain reaction assay on corneal scrapings. British Journal of Ophthalmology. 2004;88(1):142-144. doi:10.1136/bjo.88.1.142
  6. Hirota A, Inada N, Shiraki Y, Shoji J, Yamagami S. Herpes Simplex DNA in Tears of Atypical Dendritic Keratitis and Multiple Punctate Subepithelial Stromal Opacity: A Case Report. Cornea. 2020;39(9):1177–1180. doi:10.1097/ICO.0000000000002293
  7. Varela-Garcia A, Gomez-Amoza JL, Concheiro A, Alvarez-Lorenzo C. Imprinted Contact Lenses for Ocular Administration of Antiviral Drugs. Polymers. 2020;12(9). doi:10.3390/polym12092026
  8. Herpes Eye Disease. WebMD.