Ophthalmology
Question 6 of 97
A 23 year old tradesman presents to the Emergency Department complaining of pain to the right eye. He was using an electric saw to cut wood and thinks he may have gotten some debris in the eye. You are concerned about the risk of corneal defect. What is the best method of testing for corneal defects?
Answer:
Fluorescein examination:- Fluorescein stains basement membrane which is exposed in the area of the epithelial defect
- The stained abrasion appears yellow with the naked eye
- Visualisation is enhanced by the use of a cobalt blue filter on an opthalmoscope or slit lamp, whereby the fluorescein fluoresces bright green
- Vertical linear scratches on cornea suggest subtarsal foreign body due to repeated scratching with blinking
Corneal Abrasion
Ophthalmology
Last Updated: 12th February 2021
Corneal abrasions are defects in the epithelial surface of the cornea. The cornea is susceptible to injury as it is the most anterior part of the eye. Relatively minor superficial injuries can cause significant pain as the cornea is densely innervated with sensory fibres from the ophthalmic branch of the trigeminal nerve.
Causes
- Mechanical trauma from external objects
- Foreign bodies (lodged under the eyelid or on the corneal surface)
- Chemical, radiation or flash burns
- Contact lens use during insertion or removal
- Recurrent erosions - spontaneous abrasions which can develop in people with structural defects of the corneal epithelium due to a previous injury
Clinical features
- History of precipitating event (e.g. object striking eye, foreign body entering eye, difficult contacts lens removal)
Sudden onset of eye pain on blinking- Foreign body sensation (may be described as 'gritty' or 'scratching')
- Lacrimation
- Photophobia
- Decreased or blurred vision due to epithelial disruption and stromal oedema
- Conjunctival injection
- Blepharospasm (abnormal contraction of eyelid)
Assessment
- The eye should be carefully examined
- A topical anaesthetic may ease examination
- Inspect for conjunctival or corneal foreign body (eversion of the eyelid may reveal a subtarsal foreign body)
- Visual acuity should be tested and documented
- Fluorescein examination
- Fluorescein stains basement membrane which is exposed in the area of the epithelial defect
- The stained abrasion appears yellow with the naked eye
- Visualisation is enhanced by the use of a cobalt blue filter on an opthalmoscope or slit lamp, whereby the fluorescein fluoresces bright green
- Vertical linear scratches on cornea suggest subtarsal foreign body due to repeated scratching with blinking
Management
- Exclude retained foreign body
- Consider analgesia (oral paracetamol, ocular lubricants)
- Prescribe topical antibiotics (e.g. chloramphenicol)
- Prognosis
- Most uncomplicated small corneal abrasions will heal rapidly within 1–2 days without visual impairment
- Larger defects, or those associated with contact lens use, should have ophthalmological follow-up in 1 to 2 days to ensure healing
Referral
Refer the person immediately to the emergency eye service if:
- A suspected penetrating eye injury has occurred or an intraocular foreign body is suspected — all high-velocity injuries (such as from drilling, lawn mowing or hammering) or injuries caused by sharp objects (such as glass, knives, pencils or thorns) should be treated as penetrating injuries until proven otherwise
- Significant orbital or periocular trauma has occurred
- A chemical injury has occurred
- A retained foreign body that cannot be removed safely is present
- Infection or corneal ulcer is suspected
- Any of the following red flag clinical features are present:
- Severe pain
- Irregular, dilated or non-reactive pupils
- Significant reduction in visual acuity
- Hyphaema (blood in the anterior chamber) or hypopyon (pus in the anterior chamber)
- Large or deep abrasions
- Corneal opacity
Complications
- Corneal ulceration
- Infective keratitis
- Iritis
- Recurrent erosion syndrome
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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 |
