Corneal Disease Flashcards
What does the typical corneal involvement of herpes simplex virus infection present? And what are some consequences?
Corneal dendritic ulceration.
Ulcers may be multiple. If infection confined to corneal epithelium, healing occurs without scarring. But, if stromal involvement, there is always some degree of scarring and there may also be anterior uveitis.
What is astigmatism?
Irregular curvature of the cornea.
HSV may undergo latency in which ganglion?
Trigeminal ganglion.
A reactivation would then see the virus travelling along CNV to the eye.
Topical steroids applied to a herpetic corneal ulcer will result in what?
An amoeboid ulcer, which is slow to heal and very hard to treat.
Stromal disease and anterior uveitis require careful topical steroid use, after healing of any epithelial disease (for the above reason). It is also usual to administer aciclovir ointment and corneal scrape from ulcer edge to confirm dx.
What are the differences in ocular consequences between primary (chicken pox) and secondary (reactivated/shingles) VZV infection?
Primary VZV may cause a conjunctivitis, and rarely, a dendritic ulcer.
Secondary (reactivated) VZV may affect any ocular or adnexal structure (as was latent in trigeminal ganglion) -
eg. conjunctivitis, keratitis (principally affecting stroma, though dendritic & non-dendritic ulceration may occur), anterior uveitis with secondary glaucoma, scleritis, episcleritis.
Which division of the trigeminal nerve can be affected by VZV?
Any of the three, but V1 (ophthalmic) most common -> herpes zoster ophthalmicus.
Skin rash involves forehead to occiput and upper lid, tending to spare lower lid but usually affecting side of the nose (which is supplied by nerve fibres that course through the orbit).
What are the two most disabling sequelae of herpes zoster (VZV/shingles) ophthalmicus?
- Recurrent keratitis with scarring
- Post-herpetic neuralgia
Conjunctivitis and iritis may continue for many months but are less disabling than the above.
Treatment of ophthalmic shingles (herpes zoster ophthalmicus)?
Systemic aciclovir reduces duration and severity of acute disease as well as post-herpetic neuralgia.
Topical steroids significant in suppressing inflammation, but may lead to ‘dependence’ (inflammation returns as soon as steroids stopped).
What are three features of bacterial keratitis?
- Purulent conjunctivitis
- Corneal ulcer
- Corneal opacity
Vision is reduced.
What can bacterial keratitis (corneal infection) progress to?
Intraocular infection (endophthalmitis), leading to blindness. This is suggested by presence of a hypopyon (presence of white cells in the anterior chamber).
Name four common organisms causing bacterial corneal infection/keratitis.
- Staph epidermidis
- Strep pneumoniae
- Enterobacter (coliforms, proteus, klebsiella)
- Pseudomonas aeruginosa (this can cause particularly aggressive infection).
The contact lens wearer with redness and discomfort should carefully be examined for what?
The presence of corneal infection.
Should be referred for further assessment by ophthalmologist.
How is bacterial corneal infection managed?
Urgent Ix (conjunctival and corneal samples for M&C) and admission for intensive treatment.
Broad-spec ABx every 15 mins, 24 hrs per day, until response.
Sometimes, subconjunctival and systemic ABx prescribed.
Topical steroids used only when resolution of infective element is thought to have occurred.
Name a protozoan which causes corneal infection.
Acanthamoeba.
Ubiquitous organism, present even in tap water.
What are the features of acanthamoebic corneal infection?
- Pain disproportionate to ocular signs
- Stromal keratitis without ulceration. Keratitis is usually severe and unrelenting, and does not respond to standard ABx treatment.
- Particularly associated with contact lens use.
Where does thinning (melting) of the cornea occur, and what does progressive thinning lead to?
Occurs adjacent to and usually parallel to the limbus, may proceed centrally and circumferentially.
May occur with or without epithelial loss (ulceration) and with or without inflammation.
Progressive thinning can lead to corneal perforation and intraocular infection, or to severe astigmatism (irregular corneal shape).
What is the long term prognosis for patients with a corneal melt associated with a systemic disease?
Poor.
Name 3 non-autoimmune causes of peripheral corneal thinning (melt).
- Marginal keratitis (usually a sterile hypersensitivity reaction to bacterial toxins. Blepharitis +/- acne rosacea = common cause of marginal corneal ulceration).
- Infection (Ix corneal scrapes)
- Dellen (a localised swelling of the conjunctiva, such as post-surgical inflammation or a pterygium, which prevents normal transit of tears across the adjacent cornea, which becomes thinned as a result).
