PROBLEMS WITH THE CORNEA Flashcards
What proportion of the refractive power is done by the cornea?
2/3rds
What are the most likely bacteria to cause infective keratitis (infection of the cornea) in an uncompromised patient?
Streptococcus
Pseudomonas
Moraxella
This is actually very rare if they are not wearing contact lenses
What are the most likely bacteria to cause infective keratitis (infection of the cornea) in a patient who wears contact lenses?
Pseudomonas
Staphylcoccus
Streptococcus
What are the most likely bacteria to cause infective keratitis (infection of the cornea) in an immunocompromised patient?
Pseudomonas
Staphylococcus
Enterobacter
What bacteria would you be suspecting in a patient with bacterial keratitis who had ringed ulcers?
Pseudomonas
Streptococcus
What bacteria would you be suspecting in a patient with bacterial keratitis who had localized ulcers?
Staphylococcus
What bacteria would you be suspecting in a patient with bacterial keratitis who had purulent ulcers?
Pseudomonas
How would you manage a patient who presented with suspected bacterial keratitis?
Do a corneal scrape to work out cultures
Start topical broad spectrum antibiotics - usually quinolone such as ofloxacin. Intensive treatment is continued (hourly drops) and clinical response is assessed.
Steroids may then be needed to reduce stromal scarring.
What is the protozoan associated with keratitis?
Acanthamoeba infection
What are the risk factors for corneal acanthamoeba infection?
Soft contact lens wear and poor lens hygiene (particularly use of tap water)
What are the clinical features of corneal acanthamoeba infection?
Red eye associated with intense pain which is out of proportion to the other clinical signs
Ring ulcer with stromal immune rings (Wessely rings)
Perineural infiltrate
How do you treat a corneal acanthamoeba infection?
Propamidine (Brolene)
Polyhexamethylene biguanide
Ketoconazole
What are the main viruses to cause infective keratitis?
Herpes simplex
Herpes zoster
How do you treat all types of non-microbial keratitis?
Topical steroids
Topical antibiotics
And occasionally systemic steroids
What are the main two types of ocular disease that might lead to non-microbial keratitis?
Marginal keratitis - associated with staphylococcal blepharitis
Vernal keratoconjunctivitis - superiorly located ulcer found in patients with allergic eye disease as a result of giant papillae under the lid
What are the stystemic diseases that can lead to peripheral necrotizing keratitis?
Rheumatoid arthritis
SLE
Wegener’s granulomatosis
Relapsing polychondritis (very rare)
What is Fuch’s endothelial corneal dystrophy?
A reasonably common dystrophy which presents in the 5th to 8th decade with blurring of vision, which is initially worse in the morning.
How do you treat Fuch’s endothelial corneal dystrophy?
Hypertonic saline drops (5%) to aid corneal drying and corneal graft. Patients also told to use a hairdryer to accelerate drying of the cornea and the blisters.
What is keratoconus?
A degenerative disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than the more normal gradual curve.
What are the clinical signs of keratoconus?
Conical cornea
Corneal thinning and scarring
Vogt’s striae - fine lines on posterior corneal surface
Fleischer’s ring - iron line on corneal epithelium at base of cone
Munson’s sign - bulging of lower lid on down gaze
Scissor reflex on retinoscopy
What are the systemic diseases associated with keratoconus?
Atopic diseases (asthma, allergies, eczema) Down syndrome Marfan's Osteogenesis imperfecta Turner's syndrome
How do you treat keratoconus?
Initially refractive - glasses/lens (need to be rigid lens due to astigmatism
Corneal graft - very successful
What are the indications for corneal transplant?
Keratoconus Bullous keratopathy Corneal dystrophies Herpetic disease Microbial keratitis Corneal melt Trauma Alkaline burn
What is recurrent erosion syndrome (RES)?
Some patients with previous traumatic abrasions will experience symptoms of pain due to the scarring sticking to the eyelid during sleep.
What are the long term treatments for someone with recurrent erosion syndrome?
Bland eye cream (eg lacrilube ointment) to be used at night or if eyes start to feel dry.
If still problematic you consider following in this order: Debridement Bandage contact lens Anterior stromal puncture Phototherapeutic keratoplasty (PTK)
How do you treat an alkaline burn to the cornea?
Heavy irrigation
Sweep fornices with cotton swab
Topical antibiotic and cycloplegic
Oral analgesia
Monitor IOP and treat with steroids if necessary
Sodium citrate - reduces risk of corneal melt
if melting occurs use collagenase inhibitor - acetylcysteine
Bandage contact lens
