Glaucoma

H40.0-6/H40.8-9

DESCRIPTION

Glaucoma is characterised by damage to the optic nerve with associated visual field loss, for which raised intra-ocular pressure (IOP) is a primary risk factor.
Glaucoma is classified as open-angle or angle-closure. Glaucoma may occur as a primary condition or secondary to other ocular conditions. The condition is usually bilateral, but may be unilateral or asymmetrical (especially with secondary causes).

Clinical features

Open-angle glaucoma:

  • Mostly asymptomatic.
  • History of gradual loss of vision in the affected eye or loss of visual field.
  • Often suspected after seeing cupping of optic disc on routine fundoscopy or finding elevated intra-ocular pressure on screening.

Acute closed-angle glaucoma:

  • Usually presents acutely with sudden onset of severe eye pain and redness, associated with nausea, vomiting and hemicranial headache.
  • Loss of vision in the affected eye.
  • Coloured haloes or bright rings around lights.
  • Hazy-looking cornea.
  • Fixed, semi-dilated pupil.
  • Shallow anterior chamber.
  • Severely elevated intra-ocular pressure. When measured with finger palpation, the affected eye feels hard, compared to the other eye.
  • If IOP rises more slowly, patients may be asymptomatic with gradual loss of vision.

GENERAL MEASURES

Treatment options for glaucoma include medication (topical or systemic), laser and surgery.
Choice of treatment modality depends on: intraocular pressure at diagnosis, optic nerve damage at diagnosis, type of glaucoma, age of the patient, rate of progression, target intraocular pressure, co-morbidities and adherence issues and adverse drug reactions.
First line laser treatment or surgery may be indicated.

LoEIII [5]

MEDICINE TREATMENT

Refer all patients with suspected glaucoma to an ophthalmology unit for diagnosis and initiation of treatment.

Open-angle glaucoma

Refer to an ophthalmology unit for diagnosis and initiation of treatment.

First line

ß-blocker

  • Non-selective ß-blocker, e.g.:
    • Timolol 0.25%, ophthalmic drops, instil 1 drop 12 hourly.

LoEII [6]

OR

Selective ß-blocker:

  • Betaxolol 0.25–0.5%, ophthalmic drops, instil 1 drop 12 hourly.

Poor response despite adequate adherence:

ADD

  • Prostaglandin analogues, e.g.:

LoEII [7]

  • Bimatoprost 0.01%, ophthalmic drops, instil 1 drop daily.
    • First line if patient has contra-indication to ß-blocker.
    • In place of ß-blocker if patient has intolerable side effects or there is no significant reduction in IOP with other medicines.
    • In combination with ß-blocker if there is no significant reduction in IOP with ß-blocker.

LoEI [8]

Intolerance to prostaglandin analogue, or no response:

LoEII [9]

  • Alpha-agonist, e.g.:
    • Brimonidine 0.15–0.2%, ophthalmic drops, instil 1 drop 12 hourly.
      • Second line if patient has allergic reaction to prostaglandin analogue.
      • In place of prostaglandin analogue if there is no significant further reduction in IOP when adding prostaglandin analogue to ß-blocker.
      • In combination with ß-blocker and prostaglandin analogue if there is significant reduction in IOP with ß-blocker and prostaglandin analogue, but patient still has progression of disease or target IOP is not reached.

Failure to respond:

Alternatives in consultation with a specialist:

Parasympathomimetic agent:

  • Pilocarpine 1%, ophthalmic drops, instil 1 drop 6 hourly.

LoEIII

In severe cases, as a temporary measure before ocular surgery in consultation with a specialist:

Carbonic anhydrase inhibitors:

  • Acetazolamide, oral, 250 mg 6 hourly.

LoEII [10]

Note: Fixed combination therapy, when available, is preferred to two separate instillations of agents. This improves patient adherence and decreases excess exposure to preservatives (minimising ocular discomfort).

LoEII [11]

Angle closure glaucoma (acute) H40.1

Institute initial therapy and then refer to an ophthalmology unit.

Try to achieve immediate reduction in IOP :

  • Acetazolamide, oral, 500 mg immediately as a single dose.
    • Followed by 250 mg 6 hourly.

AND

  • Timolol 0.25–0.5%, ophthalmic drops, instil 1 drop 12 hourly.

Also treat patient for associated pain and nausea. See Anaesthesiology, pain and intensive care .

Where those measures fail, for short-term use only:

  • Mannitol, IV, 1.5–2 g/kg as a 20% solution over 30–60 minutes.

OR

  • Glycerol, oral, 1 g/kg of 50% solution as a single dose immediately.

REFERRAL

All to an ophthalmology unit.