A corneal dendrite is a specific lesion affecting the cornea, the clear, dome-shaped outer layer at the front of the eye. It is an epithelial lesion, meaning it occurs only in the outermost layer of corneal tissue. The term “dendrite” refers to the lesion’s characteristic physical shape: a branching, treelike figure. This distinctive morphology, often complete with small swellings at the ends of its branches, points directly toward a particular infectious cause.
The Viral Origin of Corneal Dendrites
The presence of a corneal dendrite is the hallmark sign of an active infection called Herpes Simplex Virus Keratitis, caused by Herpes Simplex Virus type 1 (HSV-1). This is the same virus responsible for most cold sores. After initial infection, the virus travels up nerve fibers to become dormant (latent) within the trigeminal ganglion, a cluster of nerve cells near the brain.
Reactivation occurs when specific triggers weaken the immune system or stress the nerve, allowing the virus to travel back down the nerve axon to the eye. Common environmental and systemic triggers include fever, intense sunlight exposure, psychological stress, or recent travel. Once active on the corneal surface, the virus spreads by infecting adjacent epithelial cells, creating the linear, branching pattern.
The true HSV dendrite is defined by its branching structure and the presence of terminal bulbs, which are tiny swellings at the ends of the branches. This appearance differentiates it from “pseudo-dendrites,” which are similar-looking lesions caused by non-infectious conditions like neurotrophic keratitis or a healing epithelial defect. Unlike the viral lesion, pseudo-dendrites typically lack the distinct terminal bulbs and may have tapered edges, making observation of the lesion’s exact shape essential for correct diagnosis and treatment.
Recognizing Symptoms and Diagnostic Methods
Patients experiencing a corneal dendrite typically report uncomfortable, often unilateral, symptoms. Common complaints include moderate pain, a persistent foreign body sensation, and excessive tearing. Corneal inflammation frequently leads to photophobia (heightened sensitivity to light) and blurred vision.
The diagnosis relies primarily on a clinical examination using a slit lamp microscope. To make the lesion visible, an ophthalmologist applies a sterile drop of fluorescein dye to the eye surface. This dye pools within the area where epithelial cells have been destroyed by the virus, highlighting the branching pattern against the surrounding healthy tissue.
The fluorescein stain reveals the classic appearance of the dendrite, including the characteristic linear branches and terminal bulbs. This visual confirmation is usually sufficient for a definitive diagnosis of Herpes Simplex Keratitis. In rare cases, a corneal scraping may be taken for laboratory analysis, such as polymerase chain reaction (PCR), to confirm the presence of viral DNA.
Essential Treatment Strategies
Prompt treatment of a corneal dendrite is essential for eliminating the active infection and preventing deeper damage. Standard management involves antiviral medications, available in both topical and oral forms. Topical antivirals, such as Ganciclovir gel or Trifluridine drops, are applied directly to the eye multiple times daily to halt viral replication within the epithelial cells.
Oral antiviral agents, including Acyclovir, Valacyclovir, or Famciclovir, are frequently prescribed, especially for severe or resistant cases. These systemic medications work throughout the body and offer a convenient alternative to frequent topical drop administration, which can cause localized toxicity. The course of treatment typically lasts one to two weeks, aiming to clear the lesion completely.
A precaution in treating the active dendrite is the strict avoidance of topical corticosteroid drops. While steroids are used to manage inflammation in other types of eye disease, they can worsen an active viral infection by suppressing the local immune response. Using a steroid on a viral dendrite may allow the virus to replicate uncontrollably, causing the lesion to enlarge into a vision-threatening “geographic ulcer” and increasing the risk of corneal perforation.
In some cases, epithelial debridement may be performed as an initial step. This involves gently scraping the infected cells from the cornea using a sterile instrument or applicator. Debridement physically removes the cells containing the active virus, which reduces viral shedding and accelerates healing when combined with antiviral medication.
Preventing Recurrence and Permanent Damage
A significant concern with Herpes Simplex Keratitis is its tendency to recur, which carries the risk of long-term complications. Each recurrent episode can damage corneal tissue, potentially leading to permanent scarring. Scar tissue causes the normally clear cornea to become cloudy, resulting in irreversible vision loss.
Repeated infections can cause neurotrophic keratitis, characterized by damage to the corneal nerves. This nerve damage leads to reduced or absent corneal sensation, impairing the eye’s natural healing and protective reflexes. A damaged surface can then lead to non-healing epithelial defects, increasing the risk of scarring and secondary infection.
For patients who experience frequent or severe recurrences, a long-term preventive strategy may be necessary. This involves low-dose prophylactic oral antiviral therapy, such as Acyclovir or Valacyclovir, taken daily for extended periods. This chronic suppression therapy prevents the virus from reactivating and migrating to the eye, reducing the incidence of future outbreaks and limiting permanent scarring. Managing personal triggers like stress, fatigue, and intense sun exposure is also recommended.