HSV keratitis treatment centers on antiviral medication, but the specific approach depends heavily on which layer of the cornea is affected. A surface-level (epithelial) infection is typically managed with antiviral drugs alone, while deeper stromal disease usually requires a careful combination of antivirals and anti-inflammatory steroids. The distinction matters because using the wrong treatment at the wrong stage can make things worse, and because the condition tends to come back, making long-term prevention just as important as treating the current flare.
Why the Type of Infection Shapes the Treatment
Herpes simplex virus type 1 (HSV-1) can attack the cornea in several ways, and each pattern calls for a different treatment strategy. The mildest form, epithelial keratitis, involves the virus actively replicating in the thin outermost layer of the cornea, producing the classic branching “dendritic” ulcer that eye doctors look for under a slit lamp. Stromal keratitis, a more serious form, involves inflammation deeper in the corneal tissue. In severe cases, the virus or the immune response it triggers can reach the innermost endothelial layer. Recurrent episodes can shift between these patterns, and scarring from repeated stromal flares is a leading cause of vision loss.
The immune system itself is a major player in the damage. Your body’s inflammatory response to the virus can harm corneal tissue just as much as the virus does directly, which is why treatment is not simply about killing the virus. In stromal and endothelial disease, controlling inflammation is at least as important as antiviral therapy.
Antiviral Options for Epithelial Keratitis
When the virus is actively replicating on the corneal surface, the first goal is to shut down viral reproduction. Several antiviral drugs work well for this, and the choice often comes down to availability, tolerability, and local prescribing habits.
Topical ganciclovir 0.15% gel has become a preferred front-line option in many countries. Compared to acyclovir 0.3% ointment, ganciclovir gel is better tolerated and works at a lower concentration, with no notable systemic side effects. Multiple clinical trials have found it to be at least as effective as acyclovir ointment for healing dendritic ulcers.1Europe PMC. Ganciclovir ophthalmic gel 0.15% for the treatment of acute herpetic keratitis: background, effectiveness, tolerability, safety, and future applications Trifluridine eye drops are another topical antiviral that has been used for decades, though it can be more irritating to the eye surface with prolonged use. Broadly, these topical agents perform similarly in head-to-head comparisons.2PubMed Central. The treatment of herpes simplex virus epithelial keratitis
Oral antivirals are a legitimate alternative. A randomized trial comparing oral valacyclovir to topical acyclovir ointment found that corneal lesions healed faster in the oral valacyclovir group, with lower slit-lamp scores by day ten.3PubMed. Comparison of efficacy of oral valacyclovir and topical acyclovir in the treatment of herpes simplex keratitis: a randomized clinical trial Oral acyclovir performs comparably to topical therapy as well, though combining oral and topical antivirals at the same time does not seem to speed healing beyond what either achieves alone.4PubMed Central. The treatment of herpes simplex virus epithelial keratitis For patients who find eye drops or ointments difficult to use consistently, an oral pill taken two or three times a day can be a practical solution.
Adding Corticosteroids for Stromal Disease
Stromal keratitis is where treatment gets more nuanced. Because the damage here is largely driven by your own immune system’s inflammatory response rather than by the virus directly chewing through tissue, antivirals alone are not enough. Corticosteroid eye drops are needed to tamp down that inflammation, but they must always be paired with antiviral coverage. Using steroids without an antiviral can allow the virus to replicate unchecked and worsen epithelial disease dramatically.
The evidence for this combined approach is strong. A landmark controlled trial found that topical corticosteroids reduced the risk of persistent or worsening stromal disease by about 68% compared to placebo, and the time to resolution of both stromal keratitis and associated uveitis was significantly shorter in the steroid group.5PubMed. A controlled trial of topical corticosteroids for herpes simplex stromal keratitis A systematic review confirmed that patients receiving both prednisolone and acyclovir had higher treatment success rates and significantly longer time to treatment failure than those receiving acyclovir alone.6PubMed. Antiviral and Anti-Inflammatory Therapeutic Interventions for Treating Herpes Stromal Keratitis: A Systematic Review
The tricky part is tapering. Steroid drops are typically started at a higher dose and slowly reduced over weeks to months. Drop the dose too fast and inflammation bounces back; stay on high-dose steroids too long and you risk elevated eye pressure, cataracts, or thinning of the cornea. Your ophthalmologist will adjust the taper based on how the eye responds, often checking pressure at each visit.
Preventing Recurrences
HSV-1 never leaves the body. After the initial infection, the virus retreats into sensory nerve cells in the trigeminal ganglion near the base of the skull and enters a dormant state called latency. The virus’s own genetic machinery and your immune system, particularly certain T cells, work together to keep it quiet. But periodically the virus reactivates, travels back down nerve fibers, and triggers another episode.7PubMed. Control of HSV-1 latency in human trigeminal ganglia–current overview In animal models, neurons have been confirmed as the source of reactivation, and stressors like heat can reliably trigger the virus to start producing infectious particles again.8PubMed Central. Mechanisms of herpes simplex virus type 1 reactivation
Recurrence is the defining challenge of HSV keratitis. Each flare carries a risk of additional corneal scarring, and repeated episodes of stromal keratitis can progressively erode vision. The Herpetic Eye Disease Study, one of the largest trials in this area, showed that taking oral acyclovir (400 mg twice daily) for 12 months cut the recurrence rate roughly in half. The cumulative probability of any ocular HSV recurrence during that year was about 19% in the acyclovir group versus 32% with placebo. Among people with a history of stromal keratitis specifically, the rate of recurrent stromal disease was 14% with acyclovir versus 28% with placebo.9PubMed. Acyclovir for the prevention of recurrent herpes simplex virus eye disease
A longer-term follow-up study found that the protective benefit persisted well beyond the initial year. Patients who continued prophylactic acyclovir had an average recurrence-free survival of over 37 months, compared to about 15 months in those who stopped.10Archives of Ophthalmology. Long-term Acyclovir Use to Prevent Recurrent Ocular Herpes Simplex Virus Infection Many ophthalmologists now recommend at least a year of prophylactic oral antiviral therapy after a stromal keratitis episode, and some patients with frequent recurrences stay on it indefinitely.
What Actually Triggers Flare-Ups
People who have experienced HSV keratitis are often told to avoid stress, sunlight, and illness to prevent recurrences. The reality is more complicated. A large analysis from the Herpetic Eye Disease Study group looked at weekly logs from hundreds of patients and found that common suspected triggers, including systemic infections, sun exposure over 21 hours per week, and contact lens wear, were not significantly associated with recurrences in their statistical models.11JAMA Ophthalmology. Psychological Stress and Other Potential Triggers for Recurrences of Herpes Simplex Virus Eye Infections
That said, UV radiation is not entirely off the hook. A separate study that accounted for the intensity of UV exposure (not just total time outdoors) found that spending eight or more hours per week outdoors when the UV index was four or higher was associated with roughly a threefold increase in ocular HSV recurrence risk.12PubMed Central. Association Between Unprotected Ultraviolet Radiation Exposure and Recurrence of Ocular Herpes Simplex Virus In laboratory mouse models, UVB irradiation is one of the most reliable methods for triggering reactivation, further supporting a biological link between UV exposure and flare-ups.13Scientific Reports. UVB induced reactivation leads to HSV1 in the corneas of virtually all latently infected mice and requires STING to develop corneal disease Wearing UV-blocking sunglasses outdoors is a reasonable precaution, even if the human data is not perfectly consistent.
When Standard Antivirals Stop Working
Most cases of HSV keratitis respond well to acyclovir, valacyclovir, or ganciclovir, but drug resistance does occur. Acyclovir and its relatives depend on a viral enzyme called thymidine kinase to become activated inside infected cells. Mutations in the gene encoding that enzyme can render these drugs ineffective. Studies of resistant corneal HSV-1 isolates have found that the vast majority carry mutations in the thymidine kinase gene.14The Journal of Infectious Diseases. Acyclovir-Resistant Corneal HSV-1 Isolates from Patients with Herpetic Keratitis
Foscarnet is the main alternative when acyclovir resistance is suspected. It inhibits viral DNA replication through a different mechanism that does not require thymidine kinase activation, so it remains effective against resistant strains.15PubMed Central. Foscarnet eyedrops for the treatment of refractory herpetic keratitis Foscarnet is available as an eye drop formulation in some regions, though access varies. Cidofovir is another option that bypasses the thymidine kinase pathway, though it is used less frequently due to potential toxicity concerns.
A newer drug called amenamevir targets the viral helicase-primase enzyme complex instead, and its mechanism is entirely independent of thymidine kinase. Early evidence suggests it retains antiviral activity even in acyclovir-resistant cases, and it has already shown value in treating herpetic infections at other body sites.16PubMed. Pathophysiology and treatment of acyclovir-resistant herpes simplex virus keratitis Other emerging options for refractory disease include experimental helicase-primase inhibitors and the kinase inhibitor BX795.17Journal of Current Ophthalmology. Overcoming Resistance: A Comprehensive Review and Treatment Approach for Acyclovir-Resistant Herpes Simplex Keratitis
Diagnosing HSV Keratitis and Why It Can Be Tricky
Most epithelial HSV keratitis is diagnosed clinically, meaning your ophthalmologist recognizes the characteristic dendritic ulcer pattern under the slit lamp. But deeper forms of the disease, where the virus may not be actively shedding on the corneal surface, are harder to confirm. A large diagnostic study testing tear samples with quantitative PCR found that sensitivity was excellent for epithelial keratitis (about 97%) but dropped sharply for forms without surface ulceration: roughly 14% for endotheliitis, 11% for postherpetic neurotrophic keratopathy, and only 8% for stromal keratitis without ulceration. Patients already receiving antiviral treatment were also more likely to have negative tear samples.18Journal of Clinical Microbiology. Diagnostic performance of real-time quantitative PCR in tear samples in various subtypes of herpes simplex keratitis
This means a negative PCR test does not rule out HSV keratitis, especially in stromal or endothelial disease. Ophthalmologists often treat based on clinical judgment even when lab tests are inconclusive. For patients with atypical presentations or who are not responding to treatment, aqueous humor sampling (a tiny fluid draw from inside the eye) can provide more definitive answers, though it is more invasive than a tear swab.
Neurotrophic Keratopathy as a Complication
Repeated bouts of HSV keratitis can damage the corneal nerves, leading to a condition called neurotrophic keratopathy. The cornea loses its ability to sense irritation, and because normal sensation is essential for the reflex blinking and tear production that keep the surface healthy, the cornea becomes vulnerable to persistent defects and slow-healing ulcers that have nothing to do with active viral replication. This is one of the most frustrating complications because standard antivirals will not help, and the problem feeds on itself: a numb cornea heals poorly, and poor healing leads to more scarring and more nerve damage.
A biological treatment called cenegermin (recombinant human nerve growth factor) has shown promise for this specific complication. In a clinical study of eyes with moderate to severe neurotrophic keratopathy, most of which were caused by herpetic keratitis, complete healing of corneal defects was achieved after eight weeks of treatment, along with significant improvements in corneal sensitivity and thickness.19European Journal of Ophthalmology. Clinical and instrumental assessment of the corneal healing in moderate and severe neurotrophic keratopathy treated with rh-NGF (Cenegermin) Cenegermin is expensive and not available everywhere, but it represents a targeted therapy for a complication that previously had few good options.
When Surgery Becomes Necessary
If repeated episodes of stromal keratitis leave the cornea scarred enough to seriously impair vision, corneal transplantation may be the only option for visual recovery. Two main surgical techniques are used. Penetrating keratoplasty (PK) replaces the full thickness of the cornea, while deep anterior lamellar keratoplasty (DALK) replaces only the front layers, leaving the patient’s own innermost endothelial layer intact.
DALK has emerged as the preferred option for HSV-related scarring. In long-term comparisons, the HSV recurrence rate after DALK was about 10% compared to 20% after full-thickness PK. Even more striking, rejection, which is the major threat to any transplant’s survival, occurred in none of the DALK patients versus 41% of PK patients. Because steroid drops can be tapered sooner after DALK, complications like steroid-induced glaucoma and cataracts were also less common.20PubMed Central. Outcomes of Corneal Transplantation for Herpetic Keratitis: A Narrative Review Visual outcomes were comparable between the two approaches, and DALK showed better overall graft survival.21PubMed. The outcome of deep anterior lamellar keratoplasty in herpes simplex virus-related corneal scarring, complications and graft survival
Prophylactic oral antivirals are typically continued before and after surgery. The virus is still latent in the trigeminal ganglion regardless of what happens to the cornea, and the trauma of surgery itself can provoke reactivation. Post-transplant HSV flares remain one of the main reasons corneal grafts fail in these patients.
Gene Editing and the Prospect of Eliminating Latent Virus
Every current treatment, whether antiviral pills, steroid drops, or corneal transplantation, works around the fact that the virus remains hidden in nerve tissue permanently. The most ambitious frontier in HSV keratitis research aims to change that by destroying the latent viral DNA itself using CRISPR gene-editing technology.
In a first-in-human trial, a CRISPR formulation targeting the HSV-1 genome was injected directly into the cornea of three patients with severe, treatment-resistant stromal keratitis during corneal transplant surgery. The preliminary results suggested acceptable safety, though the trial was designed primarily to assess whether the approach was feasible and safe rather than to measure how well it worked.22PubMed Central. In vivo CRISPR gene editing in patients with herpetic stromal keratitis
Animal studies are further along. In a latent rabbit model of HSV-1 keratitis, a single intravenous dose of an AAV9 vector carrying CRISPR-Cas9 components targeting two essential viral genes eliminated viral shedding in 92% of treated eyes and reduced HSV-1 DNA levels in the trigeminal ganglia.23Molecular Therapy – Methods & Clinical Development. CRISPR-Cas9-mediated genome editing delivered by a single AAV9 vector inhibits HSV-1 reactivation in a latent rabbit keratitis model That 92% figure is striking because it suggests CRISPR could reach and disable the virus even in the nerve tissue where it hides, something no current drug can accomplish. The gap between animal results and a proven human therapy is wide, but the work is progressing faster than many researchers expected.
Vaccines and Why We Still Do Not Have One
Despite more than three decades of clinical trials aimed at preventing genital HSV infection, no approved HSV vaccine exists for any indication, and no formal clinical trials have specifically evaluated a vaccine’s impact on eye disease.24PubMed Central. The Current State of Vaccine Development for Ocular HSV-1 Infection The virus is unusually good at evading the immune system, and the latency mechanism that makes it so hard to cure also makes it hard to vaccinate against. Generating a strong enough immune response to prevent the virus from ever reaching nerve tissue has proven extremely difficult.
A newer approach focuses specifically on ocular herpes, using a therapeutic (post-infection) vaccine strategy rather than trying to prevent initial infection. In a recent study using transgenic rabbits that express human immune molecules, a “prime/pull/keep” vaccine delivered via an AAV8 vector to the eye mobilized and retained CD8+ T cells in the trigeminal ganglion. This was associated with a significant reduction in corneal herpes infection and disease after reactivation was induced.25Journal of Virology. A tissue-targeted prime/pull/keep therapeutic herpes simplex virus vaccine protects against recurrent ocular herpes infection and disease in HLA-A*0201 transgenic rabbits The vaccine used peptide sequences that are preferentially recognized by immune cells from HSV-1-seropositive people who never develop recurrent eye disease, essentially trying to copy the immune profile of people who carry the virus but seem naturally protected from flare-ups. The concept is clever, though it remains in animal testing.
L-Lysine and Other Complementary Approaches
You may have heard that the amino acid L-lysine helps prevent herpes outbreaks. The idea has been around for decades: lysine competes with arginine, another amino acid that HSV needs to replicate, so tipping the balance in favor of lysine could theoretically slow viral activity. A case report documented a patient with recurrent herpetic epithelial keratitis who was given L-lysine supplementation alongside standard antiviral treatment. After adding lysine and limiting arginine intake, the intervals between recurrences lengthened and eventually the flares stopped.26Journal of Exploratory Research in Pharmacology. L-lysine as a Possible Supplement for Treatment of Herpetic Epithelial Keratitis: A Case Report and Literature Review
A single case report is about as weak as evidence gets, and the broader literature on lysine for herpes (mostly studied for cold sores, not eye disease) is mixed. It is unlikely to cause harm, and some patients feel it helps, but it should never replace antiviral therapy for HSV keratitis. The stakes are too high: an undertreated corneal herpes flare can cost you vision in a way that a cold sore never will.
HSV Keratitis as a Leading Cause of Corneal Blindness
HSV keratitis is recognized as the leading infectious cause of corneal blindness in high-income countries.27PubMed Central. Viral eye: Emerging insights into corneal and ocular surface viral infections That ranking may surprise people, given that most associate herpes with relatively minor cold sores. The difference is that the cornea is a uniquely fragile tissue: it is avascular (no blood vessels), it must remain transparent for vision, and even a small amount of scarring in the central visual axis can blur sight permanently. Each recurrence of stromal disease adds another round of immune-mediated scarring, which is why long-term suppressive therapy and prompt treatment of flares are so important. For the same reason, aggressive control of inflammation in stromal disease, rather than relying on antivirals alone, can make the difference between stable vision and progressive loss over years.