Keratitis

Question 1

What is keratitis?

Answer 1

Infectious or non-infectious inflammation of the cornea.
-Ocular emergency

Question 2

Anatomy of the cornea

Answer 2

-Epithelium → densely innervated, maintained by limbal stem cells (pain, photophobia)

-Stroma → responsible for 75% light refraction of the eye (blurred vision)

-Endothelium → controls hydration and transparency (oedema)

Question 3

Risk factors for keratitis

Answer 3

-Compromised corneal epithelium (trauma, contact lens wear, severe dry eyes, immunocompromised, autoimmune Hx, blepharitis)

-Bacterial: previous eye surgery, poor lid function (1)- staph aureus, pseudo aeruginosa

-Viral: topical steroids, previous HSV (2)/VZV

-Fungal: topical steroids, ocular trauma with plant matter

-Protozoal: contaminated water exposure, contact lens wear

Question 4

Symptoms and signs of keratitis

Answer 4

-Redness (particularly around the limbus), pain, increased lacrimation, lid oedema, discharge, decreased VA, photophobia, foreign body, gritty sensation, high IOP

-Bacterial: corneal ulcers, hypopyon (pus in anterior chamber), focal white staining opacity
-Viral: HSV (dendritic ulcer- stains with fluorescein, increased IOP), VZV (dermatomal rash)
-Fungal: satellite lesions
-Protozoal: prominent nerves, ring abscess (Acanthamoeba), pain out of proportion to findings

Question 5

Investigations of keratitis

Answer 5

URGENT REFERRAL
-Corneal scraping for microscopy and culture
-FBC (?systemic infection)
-HIV test (?immunosuppression)
-VA
-Slit-lamp with fluorescein dye- HSV
-IOP
-Fundoscopy

Question 6

Management of keratitis

Answer 6

-Analgesia (cyclopentolate), remove contact lenses, eye shield (if corneal thinning), atropine drops (if anterior chamber inflammation and photophobia)

-Bacterial: topical gentamicin if high risk- 5% cefuroxime and 1.5% gentamicin drops hourly (quinolones first line)
-Viral: PO and TOP acyclovir x5 a day (higher dose if VZV)
-Fungal: antifungals
-Proto: TOP Chlorhexidine, polyhexanide and propamidine for 6 months

Question 7

Complications of keratitis

Answer 7

-Corneal scarring
-Perforation
-Endophthalmitis
-Visual loss

Question 8

Non-infectious keratitis types

Answer 8

-Exposure (incomplete eye closure)
-Photo keratitis (snow blindness/ UV keratitis)
-Allergic (vernal keratoconjunctivitis)
-Autoimmune (RA, SLE, PAN)
-Post-LASIK (inflammation under flap)