PROBLEMS WITH THE CORNEA

Question 1

What proportion of the refractive power is done by the cornea?

Answer 1

2/3rds

Question 2

What are the most likely bacteria to cause infective keratitis (infection of the cornea) in an uncompromised patient?

Answer 2

Streptococcus
Pseudomonas
Moraxella

This is actually very rare if they are not wearing contact lenses

Question 3

What are the most likely bacteria to cause infective keratitis (infection of the cornea) in a patient who wears contact lenses?

Answer 3

Pseudomonas
Staphylcoccus
Streptococcus

Question 4

What are the most likely bacteria to cause infective keratitis (infection of the cornea) in an immunocompromised patient?

Answer 4

Pseudomonas
Staphylococcus
Enterobacter

Question 5

What bacteria would you be suspecting in a patient with bacterial keratitis who had ringed ulcers?

Answer 5

Pseudomonas

Streptococcus

Question 6

What bacteria would you be suspecting in a patient with bacterial keratitis who had localized ulcers?

Answer 6

Staphylococcus

Question 7

What bacteria would you be suspecting in a patient with bacterial keratitis who had purulent ulcers?

Answer 7

Pseudomonas

Question 8

How would you manage a patient who presented with suspected bacterial keratitis?

Answer 8

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.

Question 9

What is the protozoan associated with keratitis?

Answer 9

Acanthamoeba infection

Question 10

What are the risk factors for corneal acanthamoeba infection?

Answer 10

Soft contact lens wear and poor lens hygiene (particularly use of tap water)

Question 11

What are the clinical features of corneal acanthamoeba infection?

Answer 11

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

Question 12

How do you treat a corneal acanthamoeba infection?

Answer 12

Propamidine (Brolene)
Polyhexamethylene biguanide
Ketoconazole

Question 13

What are the main viruses to cause infective keratitis?

Answer 13

Herpes simplex

Herpes zoster

Question 14

How do you treat all types of non-microbial keratitis?

Answer 14

Topical steroids
Topical antibiotics
And occasionally systemic steroids

Question 15

What are the main two types of ocular disease that might lead to non-microbial keratitis?

Answer 15

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

Question 16

What are the stystemic diseases that can lead to peripheral necrotizing keratitis?

Answer 16

Rheumatoid arthritis
SLE
Wegener’s granulomatosis
Relapsing polychondritis (very rare)

Question 17

What is Fuch’s endothelial corneal dystrophy?

Answer 17

A reasonably common dystrophy which presents in the 5th to 8th decade with blurring of vision, which is initially worse in the morning.

Question 18

How do you treat Fuch’s endothelial corneal dystrophy?

Answer 18

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.

Question 19

What is keratoconus?

Answer 19

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.

Question 20

What are the clinical signs of keratoconus?

Answer 20

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

Question 21

What are the systemic diseases associated with keratoconus?

Answer 21

Atopic diseases (asthma, allergies, eczema)
Down syndrome
Marfan's
Osteogenesis imperfecta
Turner's syndrome

Question 22

How do you treat keratoconus?

Answer 22

Initially refractive - glasses/lens (need to be rigid lens due to astigmatism

Corneal graft - very successful

Question 23

What are the indications for corneal transplant?

Answer 23

Keratoconus
Bullous keratopathy
Corneal dystrophies
Herpetic disease
Microbial keratitis
Corneal melt
Trauma
Alkaline burn

Question 24

What is recurrent erosion syndrome (RES)?

Answer 24

Some patients with previous traumatic abrasions will experience symptoms of pain due to the scarring sticking to the eyelid during sleep.

Question 25

What are the long term treatments for someone with recurrent erosion syndrome?

Answer 25

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)

Question 26

How do you treat an alkaline burn to the cornea?

Answer 26

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