Keratitis: Corneal Inflammation and Infection

Bacterial keratitis occurs when bacteria infect the cornea. This type is often fast-moving, painful, and associated with severe redness. The most common bacteria causing this infection is Pseudomonas aeruginosa, especially in contact lens wearers. Other bacteria like Staphylococcus and Streptococcus can also infect the cornea. This type develops quickly and needs immediate treatment with antibiotic eye drops to prevent permanent scarring.

Viral keratitis is caused by viruses that infect the cornea, most commonly the herpes simplex virus, which is the same virus that causes cold sores. This type often creates a characteristic branching pattern on the cornea that doctors call a dendritic ulcer. Herpes simplex keratitis is the leading infectious cause of corneal blindness in developed nations. The varicella-zoster virus, which causes chickenpox and shingles, can also infect the cornea. Viral keratitis can flare up repeatedly throughout your life and may be triggered by stress, illness, or sun exposure.

Fungal keratitis happens when fungi, microscopic organisms similar to mold or yeast, infect the cornea. This type is less common than bacterial keratitis but can be more difficult to treat and takes longer to heal. Fungal infections often occur after eye injuries involving plant material, like getting poked by a tree branch, or from poor contact lens hygiene. The infection develops more slowly than bacterial keratitis and requires weeks or even months of treatment with antifungal medications. These infections often show gray-white infiltrates with feathery margins and a dry, elevated appearance.

Acanthamoeba keratitis is caused by a tiny organism called Acanthamoeba, found in water, soil, and air. This type is most commonly seen in contact lens wearers, especially those who expose their lenses to tap water, swim while wearing lenses, or do not clean them properly. Acanthamoeba keratitis causes severe pain that is often out of proportion to how the eye looks and can be extremely difficult to treat, often requiring many months of special medications. The ulcers caused by Acanthamoeba tend to be larger than those caused by bacteria, with an average size of over 6 millimeters.

Exposure keratitis is a noninfectious form that occurs when your eye does not close completely, causing the cornea to dry out and become inflamed. This can happen due to eyelid problems, facial nerve paralysis, or conditions that affect your ability to blink normally. Without proper closure, the cornea is exposed to air constantly and cannot maintain adequate moisture, leading to damage of the corneal surface.

Contact lens-related keratitis can be either infectious or noninfectious and occurs when lenses are worn too long, do not fit properly, or are not cleaned correctly. Even without infection, extended lens wear can deprive the cornea of oxygen and cause inflammation. Studies show that wearing extended-wear contact lenses overnight increases your risk of severe keratitis by more than four times compared to wearing daily disposable lenses. Overnight wear increases the risk of microbial keratitis by 5 to 15 times.

Also called photokeratitis, this noninfectious type results from excessive exposure to ultraviolet light from sources like intense sunlight, snow reflection, welding torches, or tanning beds. Both eyes are typically affected, and symptoms usually appear several hours after the exposure. This type generally heals within one to three days with proper lubrication and eye protection.

Neurotrophic keratitis is a noninfectious condition where the corneal nerves are damaged, reducing sensation in the cornea. Without normal feeling, the cornea does not heal well and is more susceptible to injury and infection. This can result from herpes infections, diabetes, or other conditions that damage corneal nerves.

Our ophthalmologists will ask detailed questions about your symptoms, including when they started, how quickly they developed, and whether they are getting better or worse. Important questions include:

• Do you wear contact lenses, and if so, what type and wearing schedule
• Have you slept in your lenses or exposed them to water
• Have you had any recent eye injuries or trauma
• Have you been gardening or had exposure to plant material
• Have you had any recent eye surgery
• Do you have any other eye conditions like dry eye or blepharitis
• Have you traveled recently or been in hot tubs or pools
• Do you have any medical conditions that affect your immune system

The slit lamp is a specialized microscope that allows our ophthalmologists to examine all the structures of your eye in detail under high magnification. Using this instrument with special lighting and stains, we can see the size, depth, and location of any ulcers or areas of infection on your cornea. We can also assess whether the infection has spread to deeper layers of the cornea or other parts of the eye.

We place a special orange dye called fluorescein on the surface of your eye, which temporarily stains areas where the corneal surface has been damaged. When viewed under blue light with the slit lamp, damaged areas glow bright green, making it easy to see the extent and pattern of corneal damage. Different types of keratitis create characteristic staining patterns that help with diagnosis.

In moderate to severe cases, or when the diagnosis is unclear, our ophthalmologists may need to take a tiny sample from your cornea to identify the exact organism causing the infection. This procedure, called a corneal scraping, is performed while your eye is numbed with anesthetic drops. The sample is sent to a laboratory where technicians use special stains and grow the organisms on culture plates to identify them and determine which medications will work best. Studies show that about 74 percent of cases have a positive culture, which helps guide treatment decisions.

We will test your vision to see how much the keratitis has affected your ability to see clearly. This baseline measurement helps us track your improvement during treatment and assess whether any permanent damage has occurred.

We check the pressure inside your eye because severe keratitis can sometimes cause increased pressure, which requires additional treatment. We also want to ensure the infection has not spread to the interior of the eye, which would be a serious complication.

In cases where the infection appears aggressive or is progressing rapidly, we often do not wait for culture results before starting treatment. Beginning appropriate medication immediately can prevent further damage while we wait for laboratory confirmation of the specific organism involved.

The most common complication of keratitis is permanent scarring of the cornea. When the infection or inflammation damages the corneal tissue, scar tissue forms as it heals. This scarring can create a hazy or cloudy area on the cornea that blocks or distorts light entering your eye, causing lasting vision impairment. The location and size of the scar determine how much it affects your vision, with central scars having the greatest impact.

Severe keratitis can cause the cornea to heal unevenly, changing its shape and creating irregular astigmatism. This makes your vision distorted and blurry in ways that cannot always be fully corrected with regular glasses or contact lenses. You may need specialized contact lenses or other treatments to improve vision quality.

In severe cases, the infection can cause the cornea to become dangerously thin or even develop a hole, called a perforation. This is a medical emergency that requires immediate surgical intervention to prevent further damage and possible loss of the eye. The infection can literally melt through the corneal tissue if not controlled.

If the infection penetrates through the cornea, it can spread to the inside of the eye, causing a serious condition called endophthalmitis. This internal eye infection can cause permanent vision loss or loss of the eye if not treated aggressively with antibiotics or antifungals, sometimes requiring injection of medications directly into the eye or surgical intervention.

Some people develop ongoing inflammation that continues even after the infection is gone. This chronic inflammation may require long-term treatment with anti-inflammatory medications and can lead to progressive corneal damage over time.

Research shows that about 41 percent of patients with severe keratitis have very poor vision at the time they first seek treatment, with vision worse than 20/200, which is considered legally blind. This highlights how quickly keratitis can damage your vision and why getting treatment early is so important. While many people recover good vision with prompt treatment, those who delay care or have severe infections may experience permanent vision loss.

When scarring is severe or the cornea is extensively damaged, you may need a corneal transplant surgery to restore vision. This procedure involves replacing your damaged cornea with healthy donor corneal tissue. While corneal transplants can successfully restore vision, they require surgery, have risks, and need long-term follow-up care.

Certain types of keratitis, particularly viral keratitis from herpes simplex virus, have a high tendency to recur multiple times throughout your life. Each recurrence brings additional risk of corneal scarring and vision loss. Long-term preventive medication can reduce but not completely eliminate the risk of recurrence.

Whether keratitis is contagious depends on the cause. Infectious keratitis caused by bacteria, viruses, or fungi can potentially spread through direct contact, though this is relatively uncommon. Most people develop keratitis through their own risk factors like contact lens wear or eye injury rather than from another person. Noninfectious keratitis from trauma, dry eyes, or wearing lenses too long is not contagious. If you have viral keratitis from herpes virus, avoid touching your eye and then touching others or shared surfaces, as the virus can spread.

Yes, keratitis can recur, especially certain types. Viral keratitis caused by herpes simplex virus has a particularly high tendency to return multiple times throughout your life. Triggers for recurrence include stress, illness, weakened immune system, or exposure to bright sunlight. Each recurrence carries risk of additional corneal scarring. If you have had herpes keratitis, our ophthalmologists may prescribe long-term preventive antiviral medication to reduce future episodes. People who continue risky behaviors like improper contact lens use remain at risk for developing keratitis again.

This depends on the severity of your condition and your symptoms. Many people with keratitis experience significant pain, light sensitivity, and blurred vision that make it difficult to function normally. During the first few days of treatment, especially when using eye drops every hour around the clock, most people need to take time off. The dilating drops used for pain management will blur your vision, making it hard to read, use a computer, or drive. As your condition improves and your treatment schedule becomes less frequent, you may be able to return to normal activities, but discuss this with our ophthalmologists based on your specific situation.

Not all cases of keratitis result in permanent vision loss, but it is a serious risk if not treated promptly or if the infection is severe. Many people who receive early treatment for mild keratitis recover completely with no lasting vision problems. However, keratitis is one of the leading causes of corneal blindness worldwide. Research shows about 41 percent of patients with severe keratitis have very poor vision when they first seek treatment. The key to preventing permanent damage is getting treatment as quickly as possible when symptoms first appear. Scarring from keratitis can cause lasting vision impairment, though corneal transplant surgery can sometimes restore vision in severe cases.

While possible, getting keratitis in both eyes simultaneously is quite rare. Research shows that simultaneous infection of both eyes occurs in less than 3 percent of severe keratitis cases. Most people develop keratitis in just one eye. Interestingly, when keratitis occurs in only one eye, it is more common in the left eye than the right eye, though the reason for this is not fully understood. If you develop keratitis in one eye, be extra careful with your other eye to avoid spreading infection or exposing it to the same risk factors.

You should avoid wearing eye makeup during keratitis treatment. Makeup can introduce additional bacteria or irritants to your infected eye, potentially worsening the infection. Makeup applicators like brushes and sponges can harbor bacteria, and putting them near an infected eye increases contamination risk. Particles from makeup can interfere with your medication or get trapped under your eyelid, causing additional irritation. Once our ophthalmologists confirm your infection has completely cleared, throw away any eye makeup you were using before the infection and purchase new products to avoid reinfecting yourself.

Keratitis and pink eye, also called conjunctivitis, are different conditions, though they share some similar symptoms like redness and discharge. Pink eye is inflammation of the conjunctiva, the thin clear tissue covering the white part of your eye and lining your eyelids. Keratitis is inflammation of the cornea, the clear dome covering the colored part of your eye. Keratitis is generally more serious than pink eye because the cornea is essential for clear vision, and damage can cause permanent vision loss. Keratitis typically causes more severe pain and light sensitivity than pink eye and requires more aggressive treatment. Pink eye often resolves on its own or with simple treatment, while keratitis may require intensive medication and close monitoring.

Yes, children can develop keratitis, though it is somewhat less common than in adults. Children can get keratitis from eye injuries while playing, from viral infections like herpes simplex or chickenpox virus, or from contact lens wear if they are old enough to wear contacts. Parents should watch for signs like eye pain, redness, light sensitivity, or squinting in children and seek prompt evaluation if these symptoms appear.