Glaucoma is a group of eye diseases that are characterized by progressive damage to the optic nerve resulting in impaired vision and sometimes blindness if left untreated (1)
The disease is charcterised by:
- visual field loss - arcuate scotomas, nasal steps, altitudinal scotomas, focal defects e.g. paracentral scotomas (2)
- optic disc changes - localised or generalised thinning of the neuroretinal rim, enlargement of the optic cup and increased cup to disc ratio (1)
- nerve fiber layer defects (3)
Although in most cases there is an increase in intraocular pressure (IOP) which is sufficient to cause damage to the optic nerve head and changes in the visual field, the disease may be seen even in patients with normal IOP (4)
- the mean value for intraocular pressure is 15-16 mm Hg with a standard deviation of +/- 2.5. The upper limit of normal is considered to be 21 mm Hg.
- about 2% of adults have an intraocular pressure over 21 mmHg with no evidence of glaucoma (5)
Glaucoma can be described according to the:
- cause – as primary (without an underlying cause) or secondary (due to another eye or systemic condition, trauma, or by certain medication)
- anatomy of the anterior chamber angle of the eye – as either open angle glaucoma or angle closure glaucoma (3).
- (1) Burr JM et al. The clinical effectiveness and cost-effectiveness of screening for open angle glaucoma: a systematic review and economic evaluation. Health Technol Assess. 2007;11(41):iii-iv, ix-x, 1-190
- (2) National Instittue for Health and Clinical Excellence (NICE) 2009. Glaucoma. Diagnosis and management of chronic open angle glaucoma and ocular hypertension
- (3) Americal Optometric Association (AAO) 2010. Optometric clinical practice guideline. Care of the patient with open angle glaucoma
- (4) Liesegang TJ. Glaucoma: changing concepts and future directions. Mayo Clin Proc. 1996;71(7):689-94
- (5) GP magazine (August 2nd 2004):33-4s