Background

Bacterial keratitis is also known as corneal ulcer. It is corneal tissue infection. It is caused by various bacterial species. The infection can be acute, chronic or transient. It affects the different parts of the cornea. It can cause vision-threatening keratitis and have permanent visual consequences. Bacterial keratitis increases nowadays because of the increasing the uses of contact lenses. It is necessary to treat this disease to reduce the permanent vision loss. 

Epidemiology

Bacterial keratitis is a severe eye disease. Cases of these disease vary globally. The greater cases are found in tropical and subtropical areas. It is most common in undeveloped areas because of the limited access to healthcare, agriculture methods and economic status. The cases increase as the season change. As per the study, younger populations are more affected by this disease. prevalence, possibly due to higher contact lens use. 

Anatomy

Pathophysiology

In this condition, bacteria penetrate the corneal epithelial barrier. This led to connection of bacteria to the corneal stroma. This facilitates bacterial adhesins and host cell receptors. The bacteria begin the immune response and release the cytokines and chemokines. Bacterial toxins and enzymes cause the tissue damage. This led to corneal ulcer. Some bacteria produce collagenase. It can degrade the collagen fibers in corneal stroma. This can lead to tissue breakdown and loss of corneal substance. If infection is not controlled or treated, then there is a risk of corneal perforation and cornea become transparent. Recovering may lead to damage of acuity and corneal transparency. 

Etiology

Microbial Agents  

Bacterial keratitis is caused by the pathogenic bacteria which affect the cornea. Gram positive bacteria like Staphylococcus aureus and Streptococcus pneumoniae and gram negative bacteria like Pseudomonas aeruginosa can cause bacterial keratitis. 

Other bacteria like Haemophilus influenzae and Moraxella species also contribute to infections.  

Trauma  

The main risk factor for the bacterial keratitis is corneal trauma. Injuries like corneal abrasions, scratches, or foreign body penetration lead to the gap in  the corneal epithelium. This can allow the bacteria to enter.  

Agricultural Practices  

In the rural areas where there has been agricultural activity is happening may have this disease. The main cause is the contact with plant debris and soil that can cause the corneal trauma. This facilitates to allow the bacteria to cornea. 

Environmental Factors  

Area without sanitation, exposure to contaminated water and other sources can lead to infection of this bacteria. 

Poor Hygiene   

The main reason for bacterial keratitis is to use the contact lens by longer period of time and poor cleaning techniques. Improper handwash and poor contact lens hygiene lead to poor ocular hygiene. The lens surface may contain the bacteria. This lens when contacted with cornea lead to epithelial disruption. 

Genetics

Prognostic Factors

Factors that affect the prognosis of bacterial keratitis are like superficial corneal ulcers, compliance by patients, presence of the sclera or endophthalmitis, adherence to follow-up appointments, and appropriate counseling. 

Positive result may lead to ulcer. It affects the superficial layers of the cornea and goes up to the anterior one-third of the stroma. Ulcers with more than two-thirds of the  

Clinical History

Bacterial keratitis is identified by severe eye pain, conjunctival redness, and generalized eye redness. It may lead to excessive tearing, watery eyes, blurred vision, purulent discharge, foreign body sensations, and corneal infiltrates or ulcers. The symptoms of this disease may appear after the infection. It may vary in duration. Early diagnosis and prognosis are necessary to treat the disease. It is not treated, patients with chronic condition may have the symptoms for very long time.  

The hypopyon corneal ulcer associated with pneumococci is known as ulcus serpens. The chronic dacryocystitis is the most common form of infection. The virulence of bacteria and resistance to the host tissue lead to the formation of hypopyon bacterial ulcers. This condition is most common in people who are elder and weak and malnourhsied or history of drinking. Whie blood cells enter into the blood vessels and develop the hypopyon in cases of iritis.  

Physical Examination

Corneal Infiltrate/Opacity 

A symptom of bacterial keratitis is a visible white or yellowish filtration on the cornea. It can be local or widespread. The severity depends on the size and shape of the infection. 

Epithelial Defects 

Bacterial keratitis can cause damage to the corneal epithelium. This can lead to the formation of epithelial defects or ulcers. These can be seen by a examination. It is associated with the pain, tearing and photophobia. 

Tearing and Discharge 

Affected eyes can cause excessive crying and discharge with pus. Bacterial infections produce a yellow or green discharge. This may help to identify the main organism. 

Corneal Hypopyon

The hypopyon can develop in severe cases. This can be seen as a horizontal fluid level within the anterior chamber during a slit-lamp examination.  

Decreased Visual Acuity 

Visual activity is decreased as the infection progresses. The extension of the visual defect depends on the location and size of the corneal infiltrate and the treatment.  

Age group

Associated comorbidity

Associated activity

Acuity of presentation

Differential Diagnoses

• Fungal keratitis  
• Exposure keratopathy  
• Marginal keratitis  
• Interstitial keratitis  
• Viral keratitis  
• Rosacea keratitis  
• Mooren’s Ulcer 

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

Bacterial keratitis is a fatal or deadly disease of corneal infection. It requires immediate and urgent treatment. To start the antibiotic therapy, it is necessary to know the bacteria by corneal culture or scraping. External antibiotics like fluoroquinolones or cephalosporins is used. In extreme condition or situation, there need to be hospitalization to treat the patient with intravenous antibiotics.  

Adjunctive therapy like cycloplegics and lubricating eye drops is also used. Close observation is needed for the reaction of patient is necessary. It is also crucial to connect with ophthalmologists and specialists in infectious disease. 

by Stage

by Modality

Chemotherapy

Radiation Therapy

Surgical Interventions

Hormone Therapy

Immunotherapy

Hyperthermia

Photodynamic Therapy

Stem Cell Transplant

Targeted Therapy

Palliative Care

Role of <a class="wpil_keyword_link" href="https://medtigo.com/drug/thrombin-topical" title="Topical" data-wpil-keyword-link="linked" data-wpil-monitor-id="2206">Topical</a> Antibiotics

Cephalosporins 

Cephalosporins is effective against Staphylococcus aureus and Streptococcus pneumoniae. Before any microorganism identify, topical cephalosporins is used a part of the treatment. Topical cephalosporins is used with the antimicrobial agents like aminoglycosides or fluoroquinolones in some cases. It increases the resistance and scope of coverage. 

Topical cefazolin 5% is the most common drug which is used. The type of cephalosporin depends on severity of infection, pattern of resistance and symptoms of patient. Cephalosporins are widely used because of the ability to penetrate the corneal tissue. This can allow it to go to the site of infection successfully.

Aminoglycosides 

Aminoglycosides like gentamicin and tobramycin is used to treat the disease. They are very effective against the gram positive and gram negative bacteria. It is used with the antimicrobial agents like beta-lactams cephalosporins or fluoroquinolones. It increases the resistance and scope of coverage. Aminoglycosides can be used in topical ophthalmic formulations. The treatment depends on the clinical examination and microbial culture result. 

Role of Systemic Antibiotics

Systemic antibiotics is used to treat the endophthalmitis, scleritis or bacterial ulcers. The drug dosage includes ciprofloxacin 750 mg twice a day. It is also used in a combination with an aminoglycoside and cephalosporin.   

Role of Antiglaucoma medications

Timolol 

Antiglaucoma drugs are used to treat the intraocular pressure. It opens the trabecular meshwork and drainage channels. It helps in hypopyon drainage. This will decrease the intraocular pressure. These drugs also help to control the trabeculitis which is caused by inflammatory response. The dosage is 0.5% timolol twice a day. 

Role of Systemic Anti-inflammatory drugs

These drugs are used to reduce the pain and inflammation. It is used in the combination of the diclofenac, serratiopeptidase and ibuprofen. The dosage is 50 mg diclofenac with 10 mg serratiopeptidase twice a day and 200 mg ibuprofen twice aday. 

Role of Lubricating agents

Carboxymethylcellulose 

Carboxymethylcellulose is used to provide lubrication and corneal healing. This ocular lubrication reduces the dryness and discomfort. It maintains the moist environment near the ocular surface. It helps to prevent the irritation and heal by natural process. It is used in the form of topical 0.5% carboxymethylcellulose. 

Hydroxypropyl methylcellulose 

Hydroxypropyl methylcellulose is an ophthalmic lubricant and artificial tear substitute. It is used to reduce the dryness and discomfort. It forms a protective layer over the cornea. It reduces the friction and irritation. It provides the corneal healing. This treatment involves the antimicrobial agents. Discussion with an eye care specialist is crucial to diagnose and treat the disease. 

Surgical Care

Gunderson Flap   

The Gunderson flap is a crucial procedure. It treats a ruptured corneal ulcer without a donor cornea. It involves dissecting the upper conjunctiva, creating a thin flap, and placing it over the cornea. It is secured with sutures to cornea to provide metabolic support.

Therapeutic Penetrating Keratoplasty  

Therapeutic Penetrating Keratoplasty (TPK) is an important surgical intervention. It is used in cases where the treatment failed or the corneal ulcer is not healing. It eliminates the infection. It replaces the damage cornea with a healthy corneal donor. It is preferred for those who do not show any improvement for 2 weeks.  

intervention-with-penetrating-keratoplasty

Penetrating keratoplasty (PKP) is used to remove the infected tissue and replace it with a health cornea. It is performed when cornea became thin and ruptured. This surgery helps to seal the rupture and maintain the integrity of the cornea. It also prevent the complications. 

Medication

Future Trends

Media Gallary

References

Bacterial Keratitis – StatPearls – NCBI Bookshelf (nih.gov)