The College of Optometrists

Examining patients at risk from glaucoma

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Key points

  • You must carry out relevant tests when examining a patient who is in an at-risk group for glaucoma.
  • Those with a greater than average risk include certain ethnic groups, patients with first degree relatives with glaucoma and those over 40.
  • In England, patients whose IOP is 24mmHg or greater should be treated.
  • You should follow local protocols if you are participating in community services.

Principles of examining patients at risk from glaucoma

When examining a patient who is in an at-risk group for glaucoma you must carry out relevant tests.60 Guidance varies across the UK. 61, 62, 63 You should be familiar with this guidance and the relevant thresholds at which further tests should be undertaken. If local protocols apply you should comply with these.
Glaucoma can be difficult to detect in the early stages and you should keep up to date with current thinking on the pathophysiology, clinical signs and diagnostic techniques required to detect it. 

Identifying patients at risk from glaucoma

You will identify the majority of patients who are at risk from primary open angle glaucoma during a routine eye examination. They are principally patients with one or more of the following: 
  1. optic disc features suggestive of glaucoma
  2. loss of peripheral vision
  3. high IOP.
Even in the absence of the signs or symptoms in the paragraph above, patients at greater than average risk of primary open angle glaucoma include those:64
  1. in certain ethnic groups, for example African-Caribbean people
  2. with first degree relatives with glaucoma
  3. over the age of 40. The risk increases with every decade of life thereafter
  4. with thinner corneas
  5. with myopia >6D
  6. with diabetes
  7. with systemic hypertension, or
  8. taking topical or systemic steroids, as they may develop steroid-induced glaucoma.
The signs of asymptomatic primary angle closure glaucoma are almost identical to those of primary open angle glaucoma with the exception that the anterior chamber angle is capable of closure. 
The prevalence of angle closure glaucoma is greater than that of open angle glaucoma in people of South or East Asian descent. 

Diagnostic information

You should be familiar with signs and symptoms of primary open angle glaucoma including that around 40% of patients with glaucoma have IOP below 21mmHg.65

Assessment of the central visual field may provide useful diagnostic information and complement the examination of the optic nerve head. Visual field findings should fit with optic disc findings. For example, if examination shows an inferior optic disc notch, you would expect to see a superior field defect.

Visual field examination may sometimes produce anomalous results; however, you should not underestimate the usefulness of baseline measures and ongoing comparisons. 
Patients with raised IOP are at increased risk of developing glaucoma. Where pressures are borderline, you should repeat the test, noting the time of day of each test. NICE recommends66 that patients whose IOP by applanation tonometry is 24mmHg or higher should be:
  • formally diagnosed with ocular hypertension by a healthcare practitioner who has appropriate training or qualifications, and
  • treated, as they are at greater risk of developing glaucoma

    SIGN recommends that patients with IOP >25mmHg may be considered for referral to the HES.
You should be aware of the signs and symptoms of other forms of glaucoma, such as acute or sub-acute narrow angle glaucoma or secondary glaucoma, for example due to pseudoexfoliation syndrome or pigment dispersion syndrome.

Procedures to include in an examination in routine practice

In addition to the procedures for a routine eye examination, you should select additional ones according to the patient’s clinical need. You should normally: 
  1. assess the optic nerve head. This would include assessing the size of the disc, and
  2. measure the IOP. See para A158.
If a patient refuses to consent to tonometry, after you have explained the reason for this procedure, you should record the patient’s reason for refusal. You should use your professional judgement to decide how best to manage the patient.
The examination may also include an assessment of the central visual field using perimetry with threshold control. Where necessary, you should repeat visual field assessment to obtain a meaningful result.
If the patient is at risk from glaucoma you should assess the anterior eye and angle, for example by slit lamp – van Herick technique. You should also look for signs of pigment dispersion syndrome (PDS) and pseudoexfoliation (PEX). 

Use of non-contact tonometry (NCT)

It is good practice to follow up equivocal results from non-contact tonometry with contact applanation tonometry. If you are using non-contact tonometry, before considering referral you should take four readings per eye and use the mean as the result. In the absence of other signs of glaucoma, you should refer the patient for further assessment only when the mean is 24mmHg or above. You should advise people with IOP below 24mmHg to continue with their routine eye examinations.

Referral and organisation of care

In England, unless clinical circumstances indicate that urgent or emergency referral is indicated, patients should have referral filtering before they are referred to the HES. For these non-urgent patients, you should only refer without referral filtering if there are no such local arrangements. Referral filtering is where the patient has additional tests done. These may be repeat measures, referral refinement or enhanced case finding.66 In Scotland you should follow SIGN guidelines, which are different.

Community services

If you are participating in a community service you should follow local protocols where they differ from this guidance. 

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