How Do You Get Keratitis In The Eye??

What Is The Role Of Contact Lenses In Causing Keratitis?

The most common predisposing factor for developing bacterial keratitis, particularly in developed countries, is the improper use of contact lenses. Contact lens wear is associated with a risk of microbial keratitis that's significantly higher compared to non-wearers. This risk is tied to several poor hygiene practices that allow bacteria to colonize the lens, the lens case, and the tear film, eventually infecting the eye.Specifically, behaviors such as sleeping in contact lenses (extended wear), using lenses past their recommended replacement date, and failing to clean and disinfect lens cases properly are major contributors. These practices can reduce the oxygen supply to the cornea, increase micro-trauma to the corneal surface, and create a contaminated reservoir where virulent bacteria can thrive and adhere to the lens surface, which is then directly placed on the eye.

What Types Of Microorganisms Cause Infectious Keratitis?

The two bacteria most commonly responsible for bacterial keratitis are Pseudomonas aeruginosa and Staphylococcus aureus. Pseudomonas aeruginosa is a highly virulent, Gram-negative bacterium frequently associated with contact lens wear. It's notorious for its ability to produce enzymes that rapidly digest the corneal tissue (keratolysis), leading to extensive and severe ulcers in a short period, sometimes within 24 to 48 hours.

Staphylococcus species (S. aureus and S. epidermidis), which are common inhabitants of human skin and mucous membranes, are also frequent causes, especially in non-contact lens wearers with compromised ocular surfaces. S. aureus is often implicated in cases following ocular trauma or in eyes with pre-existing surface diseases like dry eyes or chronic blepharitis. Other bacteria, including Streptococcus pneumoniae and certain species of the Enterobacteriaceae family, also cause this infection.

How Does Trauma And Underlying Disease Lead To Keratitis?

Bacterial keratitis is rare in an eye with an entirely healthy surface. Various local ocular conditions that compromise the cornea's defense mechanisms serve as independent risk factors. These conditions cause an epithelial defect or otherwise weaken the cornea's ability to resist microbial attack.

Local factors include ocular trauma (such as a foreign body injury or scratch), prior corneal surgery (like refractive surgery or corneal grafts), or pre-existing ocular surface diseases. Conditions like severe dry eye syndrome, chronic eyelid inflammation (blepharitis), and neurotrophic keratopathy (loss of corneal sensation) all compromise the integrity and health of the corneal epithelium, paving the way for bacterial invasion.

What To Remember About Getting Keratitis

The cause of bacterial keratitis is the invasion of the corneal tissue by bacteria, which occurs almost always after the protective epithelial barrier has been disrupted by injury or pre-existing disease.

The single largest risk factor in industrialized nations is improper contact lens hygiene, creating a mechanism for bacteria like Pseudomonas aeruginosa to gain access to the compromised corneal surface.

References

(Note: The original document did not include references. Standard medical references for this topic would include:)

American Academy of Ophthalmology (AAO). "Bacterial Keratitis."

StatPearls. "Bacterial Keratitis."

Centers for Disease Control and Prevention (CDC). "Contact Lens Health."

National Eye Institute (NIH). "Corneal Conditions."

PubMed. "Microbial Keratitis: Risk Factors and Prevention."Retry