Ulcerative keratitis is a serious inflammatory eye condition that involves the formation of open sores on the cornea, the clear front surface of the eye. This condition can arise from various causes, including infections and autoimmune disorders, and requires prompt medical attention to prevent potentially severe complications, including permanent vision loss.

Understanding Ulcerative Keratitis

Ulcerative keratitis, also known as keratitis, refers to inflammation and ulceration of the cornea—the transparent, dome-shaped layer covering the pupil and iris at the front of the eye. The cornea functions like a protective windshield for the eye, shielding the inner structures from external elements. When this delicate tissue becomes damaged or inflamed, open sores or ulcers can form, creating vulnerable spots that may become infected or worsen without proper care.^[1]

A specific type of this condition is called peripheral ulcerative keratitis, or PUK, which affects the outer edge of the cornea near the junction with the white part of the eye. This variant often occurs in people with underlying health conditions, particularly autoimmune diseases where the body’s immune system mistakenly attacks its own tissues. The ulcers in peripheral ulcerative keratitis typically appear crescent-shaped and are located at the margin of the cornea.^[2]

How Common Is This Condition?

Ulcerative keratitis is considered rare, though exact numbers vary depending on the specific type. For peripheral ulcerative keratitis specifically, medical research estimates the incidence to be between 0.2 to 3 individuals per million people each year.^[2] This means that in a city of one million people, only two or three cases might be diagnosed annually, making it an uncommon but medically significant condition.

The condition does not appear to favor any particular age group, race, or ethnicity based on current evidence. However, certain patterns emerge when looking at associated health conditions. For instance, among cases of peripheral ulcerative keratitis linked to autoimmune diseases, rheumatoid arthritis accounts for a substantial portion—approximately 34 percent of all noninfectious cases.^[12] This connection highlights how the condition often appears as part of a broader health picture rather than as an isolated eye problem.

What Causes Ulcerative Keratitis?

The causes of ulcerative keratitis fall into two main categories: infectious and noninfectious. Understanding which category applies is crucial because it determines the appropriate treatment approach and can influence the outcome significantly.

Infectious causes include bacteria, viruses, fungi, and parasites. Bacterial infections are among the most common, with organisms like Pseudomonas, Staphylococcus, and Streptococcus species frequently responsible. These bacteria exist all around us but typically only cause problems when the cornea has already sustained an injury that allows them to establish an infection.^[3] Viral infections can stem from herpes simplex virus (the same virus that causes cold sores), varicella-zoster virus (responsible for chickenpox and shingles), or even common cold viruses.^[5]

Fungal infections, while less common, typically occur after eye injuries involving plants or soil, such as when gardening. The most common fungi involved include Aspergillus and Candida species. Parasitic infections, particularly those caused by Acanthamoeba organisms, represent another infectious pathway. These microscopic parasites live in various environments, including tap water, and pose particular risks to contact lens wearers.^[3]

Noninfectious causes center primarily on autoimmune processes. In peripheral ulcerative keratitis, the condition is probably caused by an autoimmune reaction—a situation where antibodies or cells produced by the body mistakenly attack the body’s own tissues.^[1] This occurs in systemic rheumatic disorders, which are conditions affecting connective tissue throughout the body. Connective tissue is the structural material that provides strength to joints, tendons, ligaments, and blood vessels.^[1]

Specific systemic conditions associated with peripheral ulcerative keratitis include rheumatoid arthritis, granulomatosis with polyangiitis (formerly called Wegener granulomatosis), systemic lupus erythematosus, and relapsing polychondritis. When vasculitides or collagen vascular diseases are involved, they can account for up to 53 percent of PUK cases.^[2] Eye injuries from trauma, burns, scratches, or even improper contact lens use can also lead to ulcer formation without infection.^[3]

Risk Factors for Developing Ulcerative Keratitis

Several factors increase the likelihood of developing ulcerative keratitis. Contact lens wear represents one of the most significant modifiable risk factors, especially when lenses are worn improperly. Wearing contact lenses for too long, sleeping in them, or using lenses that don’t fit correctly can damage the corneal surface and create entry points for infection.^[3] Contact lens wearers who swim while wearing their lenses face additional risk from waterborne parasites like Acanthamoeba, which can survive even in chlorinated pools.

People with existing autoimmune or rheumatic diseases carry substantially higher risk for peripheral ulcerative keratitis. Those with long-standing or severe rheumatoid arthritis, systemic lupus erythematosus, or ANCA-associated vasculitides need to be particularly vigilant about eye symptoms.^[1] The presence of these conditions means the immune system is already prone to attacking the body’s own tissues, and the peripheral cornea can become a target site.

Previous eye injuries or surgeries create vulnerable areas on the cornea that may be more susceptible to ulcer formation. Burns, scratches, cuts, or punctures can leave imperfections in the corneal surface that don’t heal properly and remain prone to infection or inflammation.^[3] People with certain eye conditions that prevent complete eyelid closure, a condition called lagophthalmos, face increased risk because their corneas remain exposed and may dry out.^[3]

Individuals with compromised immune systems, whether from medical conditions or medications that suppress immunity, cannot fight off infections as effectively. This makes them more vulnerable to fungal and other opportunistic infections of the cornea.^[3] Vitamin A deficiency and conditions causing severe dry eyes can also predispose people to developing keratitis.^[1]

Recognizing the Symptoms

The symptoms of ulcerative keratitis can range from mild discomfort to severe, debilitating pain. Understanding these warning signs helps ensure timely medical attention, which is critical for preventing complications.

Eye pain stands out as one of the most common and prominent symptoms. This pain can vary considerably—some people experience mild discomfort or aching, while others suffer severe, sharp pain that makes it difficult to open the affected eye.^[3] In peripheral ulcerative keratitis specifically, patients often report significant eye pain along with redness and irritation.^[6]

Blurred vision develops as the ulcer disrupts the normally clear corneal tissue. The degree of vision impairment depends on the ulcer’s size, depth, and location. When ulcers affect the center of the cornea or become large, vision problems become more pronounced.^[1] Some people describe their vision as hazy or cloudy rather than simply blurred.

Increased sensitivity to bright light, medically termed photophobia, makes it uncomfortable or painful to be in well-lit environments or sunlight. This symptom often accompanies the pain and redness, creating a cluster of discomforts that significantly impact daily activities.^[1] Many patients find themselves squinting or avoiding bright spaces altogether.

The sensation that something foreign is trapped in the eye—like a hair, dust particle, or eyelash—occurs frequently. This feeling persists even when nothing is actually present and results from the irritation caused by the ulcer itself.^[1] The affected eye often appears red or bloodshot due to inflammation and increased blood flow to the area.^[3]

Excessive tearing or watery eyes develop as the eye attempts to flush out what it perceives as an irritant. In cases involving infection, pus or thick discharge may accumulate, particularly after sleep. The eyelids may become swollen or inflamed, a condition called blepharitis.^[3] In some cases, a white or gray spot becomes visible on the cornea, though this isn’t always apparent without specialized examination equipment.

Preventing Ulcerative Keratitis

While not all cases can be prevented, several practical measures significantly reduce the risk of developing ulcerative keratitis, particularly the infectious varieties.

For contact lens wearers, proper hygiene and care practices are paramount. Never wear contact lenses longer than recommended by the manufacturer or your eye care provider. Extended-wear lenses that can be slept in for days or weeks at a time carry the highest risk for bacterial infection.^[1] Always remove lenses before swimming in pools, lakes, or oceans, as water exposure while wearing contacts dramatically increases the risk of parasitic infection from Acanthamoeba.^[3]

Clean and store contact lenses properly using appropriate sterile solutions. Never use tap water to rinse or store contact lenses, as tap water can harbor Acanthamoeba parasites that survive in water supplies.^[3] Replace contact lens cases regularly and allow them to air dry between uses. If eyes become red, painful, or irritated while wearing contacts, remove them immediately and consult an eye care professional.

When experiencing illnesses that can affect the eyes, such as cold sores or other herpes infections, avoid touching the eyes and maintain meticulous hand hygiene. Viruses can easily transfer from other body sites to the eyes through contaminated hands.^[5] If you work with plants, soil, or engage in gardening activities, wear protective eyewear to prevent corneal injuries from plant materials that might introduce fungal organisms.

People with autoimmune or rheumatic diseases should maintain regular follow-up with their healthcare providers and remain alert to any new eye symptoms. Controlling the underlying systemic disease through appropriate medical treatment may help reduce the risk of developing peripheral ulcerative keratitis.^[1] If you develop any eye injury, even seemingly minor scratches, seek prompt evaluation, as these create vulnerable spots prone to infection or ulcer formation.

How the Condition Affects the Eye

Understanding the physical changes that occur in ulcerative keratitis helps explain why this condition requires urgent attention and can cause such significant symptoms.

The peripheral cornea has unique anatomical features that make it particularly susceptible to certain types of inflammation. Unlike the central cornea, which lacks blood vessels and receives nutrition from surrounding fluids, the peripheral cornea has direct blood supply extending about half a millimeter onto the cornea from surrounding capillaries.^[6] This vascular supply, while helpful for delivering nutrients, also provides a route for inflammatory cells and immune complexes to reach the corneal tissue.

In peripheral ulcerative keratitis associated with autoimmune disease, inflammatory markers and immune complexes like IgM and C1 deposit in the peripheral cornea.^[12] White blood cells recruited to the area release proteolytic enzymes—substances that break down proteins. Since the cornea consists largely of organized collagen proteins, these enzymes begin digesting the corneal structure itself, leading to the characteristic thinning and ulceration.^[12]

The process typically begins with a crescent-shaped area of clouding in the peripheral cornea as white blood cells infiltrate the tissue. Shortly after this clouding appears, the overlying epithelial layer breaks down, creating an open ulcer that stains with fluorescein dye during examination.^[7] This sequence differs from infectious ulcers, which typically start with the epithelial defect before developing deeper infiltration.

As the condition progresses, stromal lysis—the breakdown of the cornea’s middle structural layer—continues. This leads to progressive thinning of the corneal tissue. In severe cases, the cornea can thin to just a fraction of its normal thickness. In one documented case, imaging showed the peripheral cornea had thinned by 76 percent, leaving only 0.17 millimeters of tissue remaining at the thinnest point.^[6] Such extreme thinning creates risk for corneal perforation, a medical emergency where the eye’s outer barrier breaks completely.

The ulcer itself is usually oval or crescent-shaped and located at the corneal margin. In peripheral ulcerative keratitis, about 36 percent of patients also develop scleritis, inflammation of the white part of the eye adjacent to the cornea.^[12] When scleritis accompanies peripheral ulcerative keratitis, the prognosis tends to be more serious.

In infectious keratitis, different mechanisms drive the tissue damage. Bacteria, fungi, viruses, or parasites directly invade the corneal tissue, triggering inflammation as the body attempts to fight the infection. The microorganisms themselves, combined with the inflammatory response, cause tissue destruction. Some bacteria produce enzymes or toxins that directly damage corneal cells, while others trigger excessive immune responses that inadvertently harm the eye’s own tissues in the process of fighting infection.

Regardless of the underlying cause, the corneal damage disrupts the normally smooth, transparent corneal surface. This disruption scatters light entering the eye instead of allowing it to pass through cleanly, resulting in the blurred or hazy vision patients experience. Pain arises from exposure of nerve endings in the damaged cornea, and these nerves also trigger the reflex tearing and light sensitivity that characterize the condition.