Ophthalmology
Question 27 of 52
A 67 year old woman presents to the Emergency Department complaining of right eye pain, headache and nausea. On examination you note a reduced visual acuity in the right eye and a cloudy cornea. Which of the following is NOT indicated in the management of this condition?
Answer:
This patient has acute angle closure glaucoma. First line drugs (all act to suppress aqueous humour production):- Systemic carbonic anhydrase inhibitor (e.g. 500 mg acetazolamide oral or IV)
- Topical beta-blocker (e.g. 0.5% timolol maleate)
- Topical alpha-2 agonist (e.g. 1% apraclonidine)
- Topical ophthalmic cholinergic agent (e.g. 2% pilocarpine)
- Causes pupil constriction with thinning of the iris and its pulling away from the inner eye wall and trabecular meshwork, thus opening the angle
- Hyperosmotic agents (e.g. mannitol)
- Produces transient reduction in IOP but should be administered under the guidance of an ophthalmologist, since angle-closure should be confirmed before treatment is started
Acute Angle Closure Glaucoma
Ophthalmology
Last Updated: 8th September 2021
Clinical anatomy
- Aqueous humour is the fluid produced from plasma by the ciliary epithelium of the ciliary body. The enzyme carbonic anhydrase plays a key role in its production.
- Aqueous humour is secreted into the posterior chamber before flowing through the pupil into the anterior chamber. Secretion of aqueous humour is increased by stimulation of beta-2 receptors and decreased by stimulation of alpha-2 receptors of the sympathetic nervous system which are located on cells of the ciliary body.
- Aqueous humour is drained out of the eye primarily through the trabecular meshwork at the apex of the anterior chamber angle (the angle between the iris and the cornea where they join the sclera towards the outside of the eye).
Intraocular pressure (IOP) keeps the eye in the shape of a globe and is maintained by the balance between production and outflow of aqueous humour. In angle closure glaucoma the angle between the iris and the cornea is at least partially closed and the peripheral iris comes into contact with the trabecular meshwork. This restricts the drainage of aqueous humour from the eye and as aqueous humour continues to be produced, IOP increases which can then lead to damage to optic nerve fibres.
Aqueous Humour Pathway. (Image modified by FRCEM Success. Original image by National Eye Institute, National Institutes of Health [CC BY 2.0])
Risk factors
- Advancing age (size of lens increases with age crowding the region of the anterior chamber angle)
- Female gender (women tend to have more shallow anterior chambers)
- Asian ethnicity
- Hyperopia
- Precipitating factors:
- Watching television in a darkened room
- Adopting a semi-prone position (e.g. reading)
- Use of an adrenergic drug e.g. phenylephrine
- Use of an antimuscarinic drug e.g. a tricyclic antidepressant
Clinical features
- Symptoms
- Severe eye pain associated with headache, nausea and vomiting
- Unilateral sudden onset red eye
- Impaired visual acuity
- Lights are seen surrounded by halos (caused by a hazy oedematous cornea)
- Signs
- Semi-dilated and fixed pupil (classically in a vertically oval shape)
- Corneal epithelial oedema
- Tender, hard eyeball (palpate very gently)
- Conjunctival injection
- Shallow anterior chamber
- Raised intraocular pressure measured by ophthalmologist/optometrist (IOP is generally 10 - 21 mmHg in healthy eyes; typically rises to >40 mmHg in acute attacks)
Management
- Urgent ophthalmology referral
- Encourage patient to lie flat with their face up and head not supported by pillows
- Analgesia +/- antiemetic as required
- First line drugs (all act to suppress aqueous humour production)
- Systemic carbonic anhydrase inhibitor (e.g. 500 mg acetazolamide oral or IV)
- Topical beta-blocker (e.g. 0.5% timolol maleate)
- Topical alpha-2 agonist (e.g. 1% apraclonidine)
- Adjunct drugs:
- Topical ophthalmic cholinergic agent (e.g. 2% pilocarpine)
- Causes pupil constriction with thinning of the iris and its pulling away from the inner eye wall and trabecular meshwork, thus opening the angle
- Hyperosmotic agents (e.g. mannitol)
- Produces transient reduction in IOP but should be administered under the guidance of an ophthalmologist, since angle-closure should be confirmed before treatment is started
- Topical ophthalmic cholinergic agent (e.g. 2% pilocarpine)
- Definitive treatment:
- Laser Iridotomy or Surgical Iridectomy
- Creates a hole in the iris which then allows aqueous humour to flow into the anterior chamber without having to go through the pupil; this reduces the pressure difference between the anterior and posterior chambers, permits the angle to open, and reduces IOP
- Laser Iridotomy or Surgical Iridectomy
Complications
- Irreversible loss of vision
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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 |
