Glaucoma

Abstract

Primary open angle glaucoma is diagnosed principally on the basis of relevant visual field defects, typically supported by evidence of nerve fibre layer and optic nerve damage. An intraocular pressure above the normal range is an important risk factor but not a diagnostic requirement. Many cases are virtually `definite', but others can be assessed as only `probable'. Some `ocular hypertensives' also justify treatment and need to be included in any target for screening. The overall prevalence, including the treatable ocular hypertensives, is estimated at about 2% in people over 40 years of age. Various modes of screening have differing sensitivities and positive predictive values. The advantages are demonstrated of using not only ophthalmoscopy and tonometry routinely on patients over 40 years of age (as has been typical optometric practice), but also perimetry either routinely or at least on that fifth or so of patients in the recognised glaucoma high-risk categories. Raised intraocular pressure remains central to most referral decisions. Thus, electronic tonometers need to be calibrated regularly, and referral candidates should usually have a second test, preferably with a Goldmann or Perkins applanation tonometer. In addition, more formal reporting of a referred patient's glaucoma risk status can aid prioritisation and facilitate better organisation of the secondary examination of the many borderline cases. Collaboration between hospital clinics and referring optometrists is essential.