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Marginal keratitis

Summary
Background
Clinical features
Diagnosis
Radiology in Focus
Optical Coherence Tomography (OCT)
Management
References
Author(s)

Summary

Marginal keratitis refers to inflammation of the peripheral cornea, thought to represent a type III hypersensitivity reaction to Staphylococcus aureus, classically associated with acne rosacea and blepharitis.

Background

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Marginal keratitis is thought to result from a hypersensitivity reaction to Staphylococcus aureus antigens, as opposed to being caused directly by the bacteria, differentiating it from other causes of microbial keratitis

A type III reaction is an immune complex-mediated reaction where the formation of antigen-antibody aggregates may precipitate in various tissues, activating the classical complement pathway. This triggers the recruitment of inflammatory cells, which release lysosomal enzymes, triggering tissue damage. In the case of marginal keratitis, this response leads to stromal infiltrates, which can later progress to marginal ulcers.

Although staphylococcus aureus blepharoconjunctivitis is classically linked to this, Haemophilus, Moraxella and Streptococcus species have also been known to trigger the inflammatory response.

Clinical features

Stromal infiltrates in the peripheral cornea, where the eyelid margin most likely comes into contact with the limbus (at 2, 4, 8 and 10 o clock positions). These infiltrates are usually located 1-2mm away from the limbus, with healthy cornea in between.
Prolonged inflammation results in the stromal infiltrated developing into an epithelial infiltrate and later a marginal ulcer
Features of blepharitis: redness and swelling of the eyelid margin, telangectasia, hard scales in the eyelashes
Features of acne rosacea

Marginal keratitis in the peripheral cornea in a 2 o clock position, showing a clear margin of around 1-2mm away from the limbus with healthy cornea in between. Image courtesy of Babu and Maralihalli.

Diagnosis

The diagnosis of marginal keratitis is made clinically. However if there are epithelial defects, corneal scrape cultures would be useful to differentiate between other forms of ulceration.

Radiology in Focus

Although the diagnosis of marginal keratitis is mainly clinical, imaging techniques can provide valuable insights into the degree of corneal involvement.

Optical Coherence Tomography (OCT)

OCT provides high-resolution cross-sectional images of the cornea, allowing for detailed assessment of the corneal layers and any associated changes. It can help visualise the depth and extent of the infiltrates and assess any corneal thinning or scarring.

OCT of Fuch’s superficial marginal keratitis, showing hyper-reflective infiltration along Bowman’s layer and mild peripheral stromal thinning. Image source.

Management

Stromal infiltrates without epithelial involvement: topical corticosteroids
Epithelial involvement: steroids + broad spectrum antibiotics
Blepharitis treatment: lid hygiene measures and topical antibiotics (progressing to oral antibiotics and steroids if severe).
Prevention of blepharitis is the most effective way to prevent marginal keratitis

References

Cornea, 2-Volume Set - 4th Edition. https://www.elsevier.com/books/cornea-2-volume-set/mannis/978-0-323-35757-9. Accessed 2 Oct. 2022.CloseDeleteEdit
Usman, Norina, and Pavan Annamaraju. ‘Type III Hypersensitivity Reaction’. StatPearls, StatPearls Publishing, 2022. PubMed, https://www.ncbi.nlm.nih.gov/books/NBK559122/
Babu, Kalpana, and Rashmi E. Y. Maralihalli. ‘Insect Wing Tarsal Foreign Body Causing Conjunctival Granuloma and Marginal Keratitis’. Indian Journal of Ophthalmology, vol. 57, no. 6, 2009, pp. 473–74. PubMed Central, https://doi.org/10.4103/0301-4738.57154.

Author(s)

Dr Sara Memon

Sara is the Co-Founder of Ophtnotes. She is a doctor who graduated from UCL Medical School in London. She won the Allen Goldsmith Prize in Ophthalmology. Sara is also the co-founder of PAMSA: an organisation linking doctors and medical students of Pakistani origin. She’s especially passionate about teaching and education, having presented a workshop she designed herself at the 2019 Annual GMC Conference.

Dr Abhiyan Bhandari

Abhiyan is the Co-Founder and Radiology & Imaging Lead of Ophtnotes. He is a doctor who graduated from UCL Medical School in London. He scored in the top 10% of candidates who sat the Duke Elder examination and runs ophthalmology and Duke Elder revision sessions aimed at medical students. He also runs a YouTube channel aimed at medical students, covering topics ranging from study tips, productivity and vlogs of his journey through medical school.

Published: 2/10/22

Last updated: 29/1/25