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Questions Answered: 300

Final Score 76%

229
71

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Ophthalmology

Question 234 of 300

A 43 year old woman presents to the Emergency Department with right eye pain and excessive lacrimation. On fluorescein staining you note a corneal ulcer with a delicate linear branching pattern. What is the most likely infective cause for this patient's symptoms?

Answer:

The description is of a dendritic corneal ulcer in keeping with herpes simplex keratitis.

Infective Keratitis

Ophthalmology

Last Updated: 10th January 2023

Bacteria, fungi, protozoa, and viruses can penetrate the body's defence mechanisms and invade the cornea. A key underlying predisposing factor for bacterial, fungal, Acanthamoeba, and viral keratitis is a compromised corneal epithelium.

Risk Factors

  • Corneal trauma
  • Contact lens wear
  • Corneal abrasion/erosion
  • Corneal exposure from poor lid function
  • Foreign body (particularly vegetable matter)
  • Previous eye surgery
  • Severe dry eyes
  • Trichiasis
  • Hereditary corneal dystrophies
  • Blepharitis and conjunctivitis
  • Immunosuppression

Causes

  • Bacteria
    • Pseudomonas aeruginosa
    • Staphylococcus aureus
    • Staphylococcus epidermidis
    • Streptococcus pneumoniae
    • Haemophilus influenzae
    • Moraxella catarrhalis
  • Viruses
    • Herpes simplex
    • Varicella/Herpes zoster
  • Fungi
    • Aspergillus and Fusarium species
    • Candida albicans
  • Protozoa
    • Acanthamoeba species

Clinical Features

  • Symptoms
    • Eye pain
    • Redness
    • Photophobia
    • Lacrimation
    • Discharge
    • Lid oedema
    • Reduced visual acuity
  • Signs
    • Corneal infiltrate (presence of pathogens and inflammatory cells in the corneal stroma causes oedema and opacification of the normally transparent cornea)
    • Corneal ulcer (a corneal infiltrate with an overlying epithelial defect is termed a corneal ulcer)
    • Corneal vesicles (may be seen in herpetic keratitis)
    • Dendritic ulcer (in HSV epithelial keratitis)
      • This classic herpetic lesion consists of a linear branching corneal ulcer

Management

  • Refer urgently to ophthalmology
  • Corneal scrapings should be sent for cultures and sensitivity prior to initiating treatment
  • General management
    • Contact lens use should be discontinued while the eye is inflamed
    • Oral analgesics and other pain medicine should be given as needed
    • A topical cycloplegic (pupil-dilating agent) should be used in the presence of an anterior chamber reaction and photophobia
    • An eye shield should be placed over eyes when considerable corneal thinning is present
  • Bacterial infection
    • Unless specific historical or clinical evidence suggests otherwise, microbial keratitis should be assumed to be bacterial; empiric treatment consists of topical antibacterials
    • Topical corticosteroids should usually be added as soon as the epithelial defect closes and the infiltrate appears to be responding well to the antibiotic treatment.
    • Even in non-bacterial infectious keratitis, epithelial defects should prompt the use of broad-spectrum topical antibacterials for prophylaxis
  • Herpetic infection
    • Topical antiviral drug treatment for epithelial keratitis
    • Oral antiviral and topical corticosteroid drug treatment for stromal keratitis

Complications

  • Corneal perforation
  • Endophthalmitis
  • Corneal scarring
  • Cataract
  • Glaucoma
  • Secondary infection
  • Permanent visual impairment

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  • Biochemistry
  • Blood Gases
  • Haematology
Biochemistry Normal Value
Sodium 135 – 145 mmol/l
Potassium 3.0 – 4.5 mmol/l
Urea 2.5 – 7.5 mmol/l
Glucose 3.5 – 5.0 mmol/l
Creatinine 35 – 135 μmol/l
Alanine Aminotransferase (ALT) 5 – 35 U/l
Gamma-glutamyl Transferase (GGT) < 65 U/l
Alkaline Phosphatase (ALP) 30 – 135 U/l
Aspartate Aminotransferase (AST) < 40 U/l
Total Protein 60 – 80 g/l
Albumin 35 – 50 g/l
Globulin 2.4 – 3.5 g/dl
Amylase < 70 U/l
Total Bilirubin 3 – 17 μmol/l
Calcium 2.1 – 2.5 mmol/l
Chloride 95 – 105 mmol/l
Phosphate 0.8 – 1.4 mmol/l
Haematology Normal Value
Haemoglobin 11.5 – 16.6 g/dl
White Blood Cells 4.0 – 11.0 x 109/l
Platelets 150 – 450 x 109/l
MCV 80 – 96 fl
MCHC 32 – 36 g/dl
Neutrophils 2.0 – 7.5 x 109/l
Lymphocytes 1.5 – 4.0 x 109/l
Monocytes 0.3 – 1.0 x 109/l
Eosinophils 0.1 – 0.5 x 109/l
Basophils < 0.2 x 109/l
Reticulocytes < 2%
Haematocrit 0.35 – 0.49
Red Cell Distribution Width 11 – 15%
Blood Gases Normal Value
pH 7.35 – 7.45
pO2 11 – 14 kPa
pCO2 4.5 – 6.0 kPa
Base Excess -2 – +2 mmol/l
Bicarbonate 24 – 30 mmol/l
Lactate < 2 mmol/l
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