What is the main risk factor for bacterial keratitis in developed countries?

Contact lens wear Contact lens wear is the main risk factor in developed countries, and overnight lens wear is especially dangerous.

Which organism is common in bacterial keratitis among contact lens wearers?

Pseudomonas aeruginosa Pseudomonas aeruginosa is common in lens wearers, while Staphylococcus and Streptococcus species cause many other ulcers.

What is the typical slit-lamp appearance of bacterial keratitis?

Dendritic epithelial ulcer with terminal bulbs

Ring infiltrate under an intact epithelium

Diffuse stromal haze with keratic precipitates

Which bacterial keratitis ulcer should be scraped for microbiology before treatment?

A large, central or deep ulcer Large, central or deep ulcers are scraped, as are those with hypopyon or poor response; small peripheral lesions in lens wearers may be treated empirically.

A small peripheral infiltrate in a lens wearer

Any ulcer already improving on drops

Only ulcers in patients over 60

Corneal scrapings in bacterial keratitis are plated on which culture media?

Blood agar and chocolate agar Material is plated on blood and chocolate agar, with a Gram stain giving early guidance; lenses and cases are cultured when possible.

Sabouraud agar and non-nutrient agar

What is the standard empiric antibiotic regimen for most bacterial corneal ulcers?

Fluoroquinolone monotherapy, such as moxifloxacin Fluoroquinolone monotherapy is standard for most ulcers, with moxifloxacin and levofloxacin giving broad coverage; severe ulcers need fortified antibiotics.

Topical chloramphenicol ointment at night

Subconjunctival gentamicin alone

How are drops given at the start of treatment for severe bacterial keratitis?

Four times daily from the first day

Hourly by day only, stopping overnight

Once daily as a depot injection

What did the SCUT trial find about adjunctive corticosteroids in bacterial keratitis?

No overall benefit from adjunctive steroids SCUT found no overall benefit from adjunctive steroids, although patients with severe central ulcers may benefit, so the decision is individualised.

Higher perforation rates in all patients

Benefit only in small peripheral ulcers

How should an eye with bacterial keratitis be protected?

A shield, while avoiding any patching The eye is protected with a shield but never patched, alongside cycloplegic drops for pain and stopping contact lens wear.

A firm pressure patch for 24 hours

A bandage contact lens worn continuously

A temporary tarsorrhaphy in every case

What chiefly determines final visual outcome after bacterial keratitis?

The size and site of the corneal scar Vision depends on the size and site of the scar, and central scars limit vision more than peripheral ones.

The organism's Gram stain result

Bacterial Keratitis: Empiric Treatment Principles

Bacterial keratitis is an ophthalmic emergency that can scar the cornea within days.

Contact lens wear is the main risk factor in developed countries.

Prompt scraping and broad-spectrum drops give the best results.

Risk Factors for Bacterial Keratitis

Contact lenses, trauma and ocular surface disease all raise risk.

Overnight lens wear is especially dangerous.

Previous corneal surgery and steroid use also contribute.

Therefore, take a full lens history (see contact lens overwear syndrome).

Common Organisms

Pseudomonas aeruginosa is common in lens wearers.

Staphylococcus and Streptococcus species cause many other ulcers.

Resistance patterns vary by region.

So know your local data.

Test your knowledge 10 questions from this article

Clinical Features of Bacterial Keratitis

A focal white infiltrate with an overlying epithelial defect is typical.

Pain, redness and discharge are common.

A hypopyon signals severe inflammation.

However, small peripheral infiltrates may be sterile.

When to Scrape

Scrape ulcers that are large, central or deep.

Also scrape if there is hypopyon or poor response.

Small peripheral lesions in lens wearers may be treated empirically.

Therefore, use clinical judgment.

Laboratory Work-Up for Bacterial Keratitis

Plate material on blood and chocolate agar.

Use Gram stain for early guidance.

Culture contact lenses and cases when possible.

Also record the results for later review.

Bacterial Keratitis and Empiric Antibiotics

Monotherapy with a fluoroquinolone is standard for most ulcers.

Moxifloxacin and levofloxacin have broad coverage.

Severe ulcers need fortified antibiotics.

So match the choice to severity.

Dosing Schedule in Bacterial Keratitis

Give a loading dose every five minutes for the first half hour in severe cases.

Then continue hourly day and night for two days.

Taper according to response.

Also warn patients about sleep interruption.

Fortified Antibiotics

Combine fortified cefazolin and tobramycin or vancomycin when severe.

These drops need pharmacy preparation.

They can be toxic to the surface.

Therefore, use them for selected cases.

Role of Steroids

The SCUT trial found no overall benefit from adjunctive steroids.

Patients with severe central ulcers may benefit from earlier use.

Do not use steroids until the organism is controlled (see SCUT).

So individualize the decision.

Adjunctive Care

Use cycloplegic drops for pain.

Protect the eye with a shield but avoid patching.

Treat raised pressure when it develops.

Also stop contact lens wear.

Follow-Up

Review daily until the infiltrate shrinks.

Look for epithelial healing and less pain.

Consider cultures if the ulcer does not improve.

Therefore, change therapy when the course is poor.

Clinical image illustrating Bacterial Keratitis (figure 2)

Complications of Bacterial Keratitis

Perforation, scarring and endophthalmitis are possible.

Neovascularization can threaten graft success later.

Early treatment reduces these risks.

Also plan rehabilitation for scars.

Prevention of Bacterial Keratitis

Good lens hygiene prevents many cases.

Avoid sleeping in lenses.

Educate patients at every visit.

So prevention is the best treatment.

Pitfalls to Avoid

Do not start steroids before culture results
Never patch an infected cornea
Avoid tapering too early
Do not forget to culture lens cases

Bacterial Keratitis in Children

Children with bacterial keratitis often have a history of trauma.

Because they cannot cooperate easily, examination may need sedation.

Fluoroquinolone drops are usually first-line.

Therefore, treat promptly and monitor closely.

Bacterial Keratitis and Resistance

Resistance to fluoroquinolones has increased in some regions.

If an ulcer fails to improve, culture results guide changes.

Because local data matter, review your hospital antibiogram.

Then update your first-line choice when needed.

Bacterial Keratitis in Corneal Grafts

Graft infections spread fast and threaten the graft.

When a graft ulcer appears, culture and treat at once.

Because steroid drops are often in use, check the regimen.

Therefore, refer to the corneal surgeon quickly.

Bacterial Keratitis and Perforation

Thin, melting ulcers may perforate.

If the cornea is thin, avoid pressure on the globe.

Then arrange urgent surgical repair.

In addition, use a shield to protect the eye.

Bacterial Keratitis and Cross-Linking

Cross-linking has been tried as an adjunct for infection.

Results are mixed and the evidence is limited.

Therefore, it is not standard care.

However, trials are ongoing.

Bacterial Keratitis Prognosis

Vision depends on the size and site of the scar.

Central scars limit vision more than peripheral ones.

Because early care helps, tell patients to seek help fast.

Then plan rehabilitation, including contact lenses or transplant.

Bacterial Keratitis: Practical Summary

When a patient presents with a painful white infiltrate, scrape the ulcer if it is large or central.

Then start a broad-spectrum drop without delay.

Because the course can change, review the eye every day at first.

Finally, reinforce lens hygiene before wear resumes.

References

Ung L, Bispo PJM, Shanbhag SS, Gilmore MS, Chodosh J. The persistent dilemma of microbial keratitis: global burden, diagnosis, and antimicrobial resistance. Surv Ophthalmol. 2019;64:255-271.
Austin A, Lietman T, Rose-Nussbaumer J. Update on the management of infectious keratitis. Ophthalmology. 2017;124:1678-1689.
Srinivasan M, Mascarenhas J, Rajaraman R, et al. Corticosteroids for bacterial keratitis: the Steroids for Corneal Ulcers Trial (SCUT). Arch Ophthalmol. 2012;130:143-150.
Stapleton F, Carnt N. Contact lens-related microbial keratitis. Eye. 2012;26:185-193.

Test yourself

A few questions straight from this article.

1 / 10 0 correct

What is the main risk factor for bacterial keratitis in developed countries?
Contact lens wear is the main risk factor in developed countries, and overnight lens wear is especially dangerous.
Which organism is common in bacterial keratitis among contact lens wearers?
Pseudomonas aeruginosa is common in lens wearers, while Staphylococcus and Streptococcus species cause many other ulcers.
What is the typical slit-lamp appearance of bacterial keratitis?
A focal white infiltrate with an overlying epithelial defect is typical, with pain, redness and discharge; a hypopyon signals severe inflammation.
Which bacterial keratitis ulcer should be scraped for microbiology before treatment?
Large, central or deep ulcers are scraped, as are those with hypopyon or poor response; small peripheral lesions in lens wearers may be treated empirically.
Corneal scrapings in bacterial keratitis are plated on which culture media?
Material is plated on blood and chocolate agar, with a Gram stain giving early guidance; lenses and cases are cultured when possible.
What is the standard empiric antibiotic regimen for most bacterial corneal ulcers?
Fluoroquinolone monotherapy is standard for most ulcers, with moxifloxacin and levofloxacin giving broad coverage; severe ulcers need fortified antibiotics.
How are drops given at the start of treatment for severe bacterial keratitis?
Severe cases get a loading dose every five minutes for the first half hour, then hourly drops day and night for two days before tapering by response.
What did the SCUT trial find about adjunctive corticosteroids in bacterial keratitis?
SCUT found no overall benefit from adjunctive steroids, although patients with severe central ulcers may benefit, so the decision is individualised.
How should an eye with bacterial keratitis be protected?
The eye is protected with a shield but never patched, alongside cycloplegic drops for pain and stopping contact lens wear.
What chiefly determines final visual outcome after bacterial keratitis?
Vision depends on the size and site of the scar, and central scars limit vision more than peripheral ones.

Ahmed Ophthalmologist

Writes and reviews the clinical articles on Educate. Every post is checked against peer-reviewed sources before it goes live.