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Keratitis

  • Keratitis means inflammation of the cornea, although most commonly it refers to corneal infections

  • Can be:

  1. Bacterial 

  2. Viral - e.g. herpes simplex

  3. Amoeboid - ancanthamoeba

  4. Fungal

  5. Autoimmune e.g. in association with rheumatoid arthritis, SLE, GPA​

  • The former three causes will be discussed in more detail below. 

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  • Bacterial keratitis

    • most common organism= Pseudomonas aeruginosa (also Staph. aureus, Streptococcus) 

    • Appearance:

      • white infiltrate in the centre of the cornea

      • surrounding haze

      • hypopyon (when inflammatory cells and molecules collect in the inferior angle of the anterior chamber)

      • red conjunctiva, red & swollen eyelids

    • Symptoms

      • gritty, painful eye

      • photosensitivity

      • blurred vision​

    • Associated with contact lens wear and improper hygiene (e.g. sleeping with lenses, non-adherence to hand hygiene, washing in tap water rather than lens solution)

    • this is because contact lenses can trap microorganisms on the surface of the eye, causing infection to develop

      • usually the tear film protects the eye from these organisms but this is lost when a contact lens is in place.​

    • Treatment

      • admission (sometimes)

      • stop wearing contact lenses

      • corneal scrape, send for culture & sensitivity

        • a corneal scrape involves taking a sample of corneal tissue at the site of an ulcer, to test for the causative microorganism (culture) and which antibiotic it is sensitive to (sensitivity).​

      • topical antibiotic (eyedrops) e.g. ciprofloxacin, initially hourly (including overnight)

      • may be given ocular hypotensives and cycloplegic drops

      • topical steroid eyedrops later in healing phase

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  • Viral keratitis - herpes simplex keratitis

    • Herpes simplex virus can lie dormant in trigeminal ganglia and traverse ophthalmic branch, causing a characteristic dendritic (branching) ulcer on the cornea

    • Less severe than bacterial keratitis​

    • Symptoms:

      • Gritty sensation

      • Moderate vision impairment

      • Watery discharge

      • Red conjunctiva

      • Reduced corneal sensation

    • Investigations:

      • when ocular surface stained with fluorescein - characteristic branching pattern with terminal bulbs at ends of branches – dendritic ulcer

    • Treatment:

      • antiviral ointment e.g. aciclovir, mydriatic drops

      • Steroids must be avoided due to presence of ulceration - slow down resolution and healing

    • Complications:

      • corneal scarring

      • corneal ulcer / perforation

      • secondary bacterial infection 

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  • Acanthamoeba keratitis

    • ​Strongly associated with contact lens use

    • Symptoms out of proportion compared with clinical signs/appearance - intense pain, photophobia

    • MUST exclude in all contact lens wearers with painful red eye

    • Difficult to treat - requires long course, treated with a biguanide (e.g. chlorhexidine) and diamine

    • Complications:

      • chronic inflammation, recurrent infection, corneal ulcer​​​​​

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References

  • James, B., Bron, A. J. and Parulekar, M. V. (2016) Lecture Notes Ophthalmology. 12th edn. Nashville, TN: John Wiley & Sons (Lecture Notes)

  • Salmon, J. F. (2019) Kanski’s clinical ophthalmology. 9th edn. London, England: Elsevier Health Sciences.

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