The cornea is the transparent outer surface at the front of the eye, which plays a major role in focusing light onto the retina. Keratitis refers to any inflammation or damage to this surface, often resulting from injury, infection, or dryness. Punctate keratitis, also known as superficial punctate keratitis (SPK), is a specific pattern of corneal disruption marked by multiple, scattered, pinpoint areas of damage to the outermost layer of the cornea.
Understanding the Cornea and Punctate Keratitis
The cornea is covered by the epithelium, a delicate, fast-healing layer of cells that acts as the eye’s primary protective barrier. Punctate keratitis is characterized by damage within this epithelial layer, appearing as tiny, scattered spots. The term “punctate” describes the dot-like nature of these lesions across the corneal surface.
When an eye care professional examines the cornea using a specialized microscope called a slit lamp, they use fluorescein, a yellow dye. This dye pools into the areas where epithelial cells are missing or damaged, making the minute erosions visible as glowing dots. The presence of these lesions indicates that the corneal surface integrity has been compromised.
Primary Causes of Corneal Damage
Punctate keratitis is a sign of an underlying problem, most commonly tear film instability associated with dry eye syndrome. When the tear film is poor or insufficient, epithelial cells are left exposed and dry, leading to damage and the characteristic punctate pattern. This mechanism, known as keratoconjunctivitis sicca, is observed when the eyes do not produce enough tears or tears of adequate quality.
Infectious agents, particularly viruses, are another significant cause, such as those responsible for epidemic keratoconjunctivitis (EKC), often caused by adenoviruses. These viral infections directly disrupt the corneal epithelium, leading to inflammation and the formation of punctate lesions. Less commonly, certain bacteria, fungi, or parasites can also cause infectious keratitis, especially when associated with contact lens wear.
Mechanical and environmental factors frequently trigger the condition, especially the improper use of contact lenses. Overwearing lenses, sleeping in them, or poor cleaning hygiene can stress the cornea and increase the risk of damage. Exposure to intense ultraviolet (UV) light, such as from arc welding or sunlamps, can cause photokeratitis, where the epithelial damage is distinctly punctate. Toxicity from topical eye medications, especially preservatives within eye drops, can also irritate the ocular surface and induce this pattern.
Recognizing the Signs and Symptoms
Patients with punctate keratitis typically experience uncomfortable symptoms related to corneal surface disruption. One common complaint is a foreign body sensation, often described as a gritty feeling, because the damaged epithelium exposes underlying nerve endings.
Light sensitivity (photophobia) is another frequent symptom. The eyes may appear red and watery due to irritation and excessive tearing, which is a reflex response to the surface damage. Vision may become slightly blurry or fluctuate, as the scattered epithelial defects interfere with the cornea’s normally smooth surface.
Managing and Treating the Condition
The successful management of punctate keratitis relies on accurately identifying and addressing the specific underlying cause. Treatment for cases related to dry eye syndrome typically involves the frequent use of preservative-free artificial tears and lubricating ointments to restore the health of the ocular surface. This lubrication helps the epithelium time to regenerate.
If the cause is linked to contact lens use, immediate cessation of wear is required until the cornea has fully healed. For viral causes, such as EKC, the condition often resolves spontaneously over a few weeks, though supportive care or specific antiviral medications may be prescribed. When a secondary bacterial infection is suspected, a topical antibiotic ointment or drops may be used to prevent complications.
In cases of severe inflammation or specific non-infectious types, such as Thygeson’s superficial punctate keratitis, a specialist may prescribe a low-dose topical corticosteroid to reduce the inflammatory response. Steroids are used cautiously, as they can potentially prolong certain conditions or increase the risk of complications like glaucoma. Therapeutic soft contact lenses may also be used as a “bandage” to protect the exposed corneal nerves and provide symptomatic relief while the tissue heals.