Clinical features

Both sexes are affected, men slightly more than women. The incidence rises sharply after the age of 60. The early stages are asymptomatic.

Clinically, suspect chronic open angle glaucoma ifthere is:

• chronic rise in intra-ocular pressure - no pain, no redness, no discomfort
  
  
• gradual deterioration in visual fields -
• visual field loss may not be evident until loss of around 50% of nerve fibres have occurred (1)
• initially, there are patches of variable sensitivity in a zone 10-20 degrees from fixation. These develop into arcuate scotomas which approach or join the blind spot. In glaucoma arcuate scotomas above and below the horizontal often do not coincide at the 180 degree meridian and result in a step in the defect nasally - nasal step. Peripheral sensitivity is gradually reduced and central vision is affected late - tunnel vision.
• changes in the optic disc -
• cupping
  • optic disc is enlarged - cupped - pale and atrophic
  • generalised thinning, focal narrowing or notching of the neuroretinal rim (2)
  • increased cup to disc ratio of 0.5 or greater
  • cup to disc ratio difference between the discs of the two eyes of 0.2 or more (3)
• disc margin haemorrhages (2)

Note that glaucoma may occasionally occur in patients with normal intraocular pressures (in around 15 – 25% of patients) (2).

Reference:

• (1) Khaw PT, Shah P, Elkington AR. Glaucoma--1: diagnosis. BMJ. 2004;328(7431):97-9
• (2) The College of Optometrists 2009. Glaucoma (primary open angle) (POAG).
• (3) Distelhorst JS, Hughes GM. Open-angle glaucoma. Am Fam Physician. 2003;67(9):1937-44