Recommendations

Guidance

1.1 Case-finding
1.2 Diagnosis
1.3 Standard practice for all assessments
1.4 Treatment
1.5 Reassessment
1.6 Organisation of care
1.7 Providing information
Terms used in this guideline

Recommendations

People have the right to be involved in discussions and make informed decisions about their care, as described in NICE's information on making decisions about your care.

Making decisions using NICE guidelines explains how we use words to show the strength (or certainty) of our recommendations and has information about prescribing medicines (including off-label use), professional guidelines, standards and laws (including on consent and mental capacity), and safeguarding.

1.1 Case-finding

The recommendations on case-finding are for primary eye care professionals before referral for diagnosis of chronic open angle glaucoma (COAG) and related conditions and are separate from a sight test.

1.1.1

Before referral for further investigation and diagnosis of COAG and related conditions, offer all of the following tests:

central visual field assessment using standard automated perimetry (full threshold or supra-threshold)
optic nerve assessment and fundus examination using stereoscopic slit lamp biomicroscopy (with pupil dilatation if necessary), and optical coherence tomography (OCT) or optic nerve head image if available
intraocular pressure (IOP) measurement using Goldmann‑type applanation tonometry
peripheral anterior chamber configuration and depth assessments using gonioscopy or, if not available or the person prefers, the van Herick test or OCT. [2017]

1.1.2

Do not base a decision to refer solely on IOP measurement using non-contact tonometry. [2017]

1.1.3

Do not refer people who have previously been discharged from hospital eye services after assessment for COAG and related conditions unless clinical circumstances have changed and a new referral is needed. [2017]

1.1.4

Before deciding to refer, consider repeating visual field assessment and IOP measurement on another occasion to confirm a visual field defect or IOP of 24 mmHg or more, unless clinical circumstances indicate urgent or emergency referral is needed. [2017]

1.1.5

Refer for further investigation and diagnosis of COAG and related conditions, after considering repeat measures as in recommendation 1.1.4, if:

there is optic nerve head damage on stereoscopic slit lamp biomicroscopy or
there is a visual field defect consistent with glaucoma or
IOP is 24 mmHg or more using Goldmann‑type applanation tonometry. [2017]

1.1.6

Provide results of all examinations and tests with the referral. [2017]

1.1.7

Advise people with IOP below 24 mmHg to continue regular visits to their primary eye care professional. [2017]

The following recommendations are for people planning and providing eye care services before referral.

1.1.8

People planning and providing eye care services should use a service model that includes Goldmann‑type applanation tonometry before referral for diagnosis of COAG and related conditions. [2017]

1.1.9

People planning eye care services should consider commissioning referral filtering services (for example, repeat measures, enhanced case-finding, or referral refinement) for COAG and related conditions. [2017]

1.2 Diagnosis

1.2.1

To diagnose COAG and related conditions, offer all of the following tests:

visual field assessment using standard automated perimetry (central thresholding test), repeated if necessary to establish severity at diagnosis
optic nerve assessment and fundus examination using stereoscopic slit lamp biomicroscopy, with pupil dilatation
IOP measurement using Goldmann applanation tonometry (slit lamp mounted)
peripheral anterior chamber configuration and depth assessments using gonioscopy
central corneal thickness (CCT) measurement. [2017]

1.2.2

Adopt professional or Department of Health and Social Care guidance to reduce the risk of transmitting infective agents via contact tonometry or gonioscopy.

See the Royal College of Ophthalmologists' ophthalmic services guidance and the Department of Health and Social Care's guidance on minimising transmission risk of CJD and vCJD in healthcare settings. [2009]

1.2.3

Use the van Herick peripheral anterior chamber depth assessment if clinical circumstances rule out gonioscopy (for example, when people with physical or learning disabilities are unable to participate in the examination). [2009]

1.2.4

Obtain an optic nerve head image at diagnosis for baseline documentation (for example, a stereoscopic optic nerve head image or OCT). [2009, amended 2017]

1.2.5

After referral, consider an early assessment appointment if there is clinical concern based on the information provided. [2017]

1.2.6

At the time of diagnosis of ocular hypertension (OHT), assess the risk of future visual impairment, taking into account risk factors such as:

level of IOP
CCT
family history
life expectancy. [2017]

1.3 Standard practice for all assessments

1.3.1

Ensure that all of the following are available at each clinical episode to all healthcare professionals involved in a person's care:

records of all previous tests and images relevant to COAG and OHT assessment
records of past medical history that could affect medicine choice
current systemic and topical medication
glaucoma medication record
drug allergies and intolerances. [2009]

1.3.2

Use alternative methods of assessment if clinical circumstances rule out standard methods (for example, when people with physical or learning disabilities are unable to participate in the examination). [2009]

1.3.3

Ensure that all machines and measurement instruments are calibrated regularly according to the manufacturers' instructions. [2009]

1.4 Treatment

1.4.1

Take into account any cognitive and physical impairments when making decisions about management and treatment. [2017]

1.4.2

Check that there are no relevant comorbidities or potential drug interactions before offering pharmacological treatment. [2009]

Treatment for people with OHT

1.4.3

Do not offer treatment to people with OHT who are not at risk of visual impairment within their lifetime. Advise people to continue regular visits to their primary eye care professional, at clinically appropriate intervals. [2017]

Initial treatment for people with OHT

1.4.4

Offer 360° selective laser trabeculoplasty (SLT) to people with newly diagnosed OHT with IOP of 24 mmHg or more (excluding cases associated with pigment dispersion syndrome) if they are at risk of visual impairment within their lifetime (see the recommendation on taking account of risk factors in the section on diagnosis). To help inform their decision, tell people:

that having 360° SLT can delay the need for eye drops and can reduce but does not remove the chance they will be needed at all
how long it may take for their IOP to improve after the procedure
about 360° SLT‑specific side effects and complications and how long they are likely to last
that a second 360° SLT procedure may be needed at a later date. [2022]

1.4.5

Consider a second 360° SLT for people with OHT if the effect of an initial successful SLT has subsequently reduced over time. [2022]

For a short explanation of why the committee made these recommendations and how they might affect practice, see the rationale and impact section on selective laser trabeculoplasty for people with ocular hypertension or chronic open angle glaucoma.

Full details of the evidence and the committee's discussion are in evidence review A: selective laser trabeculoplasty in ocular hypertension or chronic open-angle glaucoma adult patients.

1.4.6

Offer a generic prostaglandin analogue (PGA) to people with OHT with IOP of 24 mmHg or more if they are at risk of visual impairment within their lifetime (see the recommendation on taking account of risk factors in the section on diagnosis) and:

they choose not to have 360° SLT or
360° SLT is not suitable (for example, because they have pigment dispersion syndrome) or
they are waiting for 360° SLT and need an interim treatment or
they have had 360° SLT but need additional treatment to reduce their IOP sufficiently to prevent the risk of visual impairment.

Demonstrate correct eye drop installation technique and observe the person using the correct technique when eye drops are first prescribed. [2022]

See the recommendations on when to reassess for advice on when the next appointment should take place to assess the impact of any new treatments started.

For a short explanation of why the committee made this recommendation and how it might affect practice, see the rationale and impact section on generic PGAs for people with OHT or COAG.

Full details of the evidence and the committee's discussion are in evidence review A: selective laser trabeculoplasty in ocular hypertension or chronic open-angle glaucoma adult patients.

Ongoing treatment for people with OHT

1.4.7

Offer another pharmacological treatment to people with an IOP of 24 mmHg or more who cannot tolerate their current treatment. The first choice should be an alternative generic PGA, and if this is not tolerated, offer a beta‑blocker. If neither of these options is tolerated, offer a non-generic PGA, carbonic anhydrase inhibitor, sympathomimetic, miotic or a combination of treatments. [2017, amended 2022]

1.4.8

Offer a medicine from another therapeutic class (beta-blocker, carbonic anhydrase inhibitor or sympathomimetic) to people with an IOP of 24 mmHg or more whose current treatment is not reducing IOP sufficiently to prevent the risk of progression to sight loss. Topical medicines from different therapeutic classes may be needed at the same time to control IOP. [2009, amended 2017]

1.4.9

Refer people to a consultant ophthalmologist to discuss other options if their IOP cannot be reduced sufficiently with 360° SLT or pharmacological treatment or both to prevent the risk of progression to sight loss. [2009, amended 2022]

1.4.10

Offer preservative-free eye drops to people who have an allergy to preservatives or people with clinically significant and symptomatic ocular surface disease, but only if they are at high risk of conversion to COAG. [2009, amended 2017]

Treatment for people with suspected COAG

1.4.11

Do not offer treatment to people with suspected COAG and IOP less than 24 mmHg unless they are at risk of visual impairment within their lifetime. Advise people to continue regular visits to their primary eye care professional, at clinically appropriate intervals. [2017, amended 2022]

Stopping treatment for people with OHT or suspected COAG

1.4.12

Discuss the benefits and risks of stopping treatment with people with OHT or suspected COAG who have both:

a low risk of developing visual impairment within their lifetime and
an acceptable IOP.

If a person decides to stop treatment after this discussion, offer to assess their IOP in 1 month to 4 months with further reassessment if clinically indicated. [2009]

Treatment for people with COAG

In January 2022 the use of mitomycin-C (MMC) in recommendations 1.4.13 and 1.4.20 to 1.4.22 was off label. See NICE's information on prescribing medicines.

Treatment for people with advanced COAG

1.4.13

Offer people with advanced COAG, glaucoma surgery with pharmacological augmentation (MMC) as indicated. Give them information on the risks and benefits of surgery. [2009, amended 2022]

1.4.14

Offer people who present with advanced COAG and who are listed for glaucoma surgery, interim treatment with a generic PGA. [2009, amended 2022]

Full details of the evidence and the committee's discussion are in evidence review A: selective laser trabeculoplasty in ocular hypertension or chronic open-angle glaucoma adult patients.

Initial treatment for people with COAG

1.4.15

Offer 360° SLT to people with newly diagnosed COAG (excluding cases associated with pigment dispersion syndrome). For people with advanced COAG see the section on treatment for people with advanced COAG and recommendation 1.4.24. To help inform their decision, tell people:

that having 360° SLT can delay the need for eye drops and can reduce but does not remove the chance they will be needed at all
how long it may take for their IOP to improve after the procedure
about 360° SLT‑specific side effects and complications and how long they are likely to last
that a second 360° SLT procedure may be needed at a later date. [2022]

1.4.16

Consider a second 360° SLT for people with COAG if the effect of an initial successful SLT has subsequently reduced over time. [2022]

Full details of the evidence and the committee's discussion are in evidence review A: selective laser trabeculoplasty in ocular hypertension or chronic open-angle glaucoma adult patients.

1.4.17

Offer a generic PGA to people with COAG if:

they choose not to have 360° SLT or
360° SLT is not suitable (for example because they have pigment dispersion syndrome) or
they are waiting for an 360° SLT and need an interim treatment or
they have previously had 360° SLT but need additional treatment to reduce their IOP sufficiently to prevent the risk of visual impairment.

Demonstrate correct eye drop installation technique and observe the patient using the technique when eye drops are first prescribed. [2022]

See recommendations on when to reassess for advice on when the next appointment should take place to assess the impact of any new treatments started.

For a short explanation of why the committee made this recommendation and how it might affect practice, see the rationale and impact section on generic PGAs for people with OHT or COAG.

Full details of the evidence and the committee's discussion are in evidence review A: selective laser trabeculoplasty in ocular hypertension or chronic open-angle glaucoma adult patients.

Ongoing treatment for people with COAG

1.4.18

Encourage people to continue with the same pharmacological treatment unless:

their IOP cannot be reduced sufficiently to prevent the risk of progression to sight loss
there is progression of optic nerve head damage
there is progression of visual field defect
they cannot tolerate the medicine. [2009]

1.4.19

Ask about adherence to treatment and check the eye drop instillation technique in people with COAG whose IOP has not been reduced sufficiently to prevent the risk of progression to sight loss, despite pharmacological treatment with a generic PGA. [2009, amended 2022]

1.4.20

Offer 1 of the following to people with satisfactory adherence to treatment and eye drop instillation technique whose IOP has not been reduced sufficiently to prevent the risk of progression to sight loss:

a medicine from another therapeutic class (a beta-blocker, carbonic anhydrase inhibitor or sympathomimetic); topical medicines from different therapeutic classes may be needed at the same time to control IOP or
360° SLT or
glaucoma surgery with pharmacological augmentation (MMC) as indicated. [2009, amended 2022]

1.4.21

Consider 360° SLT or glaucoma surgery with pharmacological augmentation (MMC) as indicated for people with COAG who are at risk of progressing to sight loss despite treatment with medicines from 2 therapeutic classes. Give them information on the risks and benefits of surgery. [2009, amended 2022]

1.4.22

Consider 1 of the following for people with COAG who cannot tolerate a pharmacological treatment:

a medicine from another therapeutic class (a beta-blocker, carbonic anhydrase inhibitor or sympathomimetic) or
preservative-free eye drops if there is evidence that the person is allergic to the preservative or has clinically significant and symptomatic ocular surface disease.

After treatment with medicines from 2 therapeutic classes, consider 360° SLT or glaucoma surgery with pharmacological augmentation (MMC) as indicated. [2009, amended 2022]

1.4.23

Offer 1 of the following to people with COAG whose IOP has not been reduced sufficiently to prevent the risk of progression to sight loss after glaucoma surgery:

pharmacological treatment; topical medicines from different therapeutic classes may be needed at the same time to control IOP or
further glaucoma surgery or
360° SLT or
cyclodiode laser treatment. [2009, amended 2022]

1.4.24

Offer 1 of the following to people with COAG (including advanced COAG) who prefer not to have glaucoma surgery or for whom glaucoma surgery is not suitable:

pharmacological treatment; topical medicines from different therapeutic classes may be needed at the same time to control IOP or
360° SLT (for example in people with systemic comorbidities) or
cyclodiode laser treatment. [2009, amended 2022]

1.5 Reassessment

Reassessment tests

1.5.1

At each assessment, offer the following tests to people with COAG, people with suspected COAG and people with OHT:

Goldmann applanation tonometry (slit lamp mounted)
anterior segment slit lamp examination with van Herick peripheral anterior chamber depth assessment when clinically indicated. [2017]

1.5.2

When clinically indicated, repeat gonioscopy, for example, if a previous examination has been inconclusive or there is suspicion of a change in clinical status of the anterior chamber angle. [2017]

1.5.3

When clinically indicated, repeat visual field testing using standard automated perimetry (central thresholding test) for people with COAG and those with suspected visual field defects who are being investigated for possible COAG (see table 2 and table 3 for recommended reassessment intervals). [2009, amended 2017]

1.5.4

When clinically indicated, repeat visual field testing using either a central thresholding test or a supra-threshold test for people with OHT and those with suspected COAG whose visual fields have previously been documented by standard threshold automated perimetry (central thresholding test) as being normal (see table 1 and table 2 for recommended reassessment intervals). [2009, amended 2017]

1.5.5

When a visual field defect has previously been detected, use the same measurement strategy for each visual field assessment. [2009]

1.5.6

When clinically indicated, repeat assessment of the optic nerve head (for example, stereoscopic slit lamp biomicroscopy or imaging). [2017]

1.5.7

When a change in optic nerve head status is detected by stereoscopic slit lamp biomicroscopy, obtain a new optic nerve head image for the person's records to provide a fresh benchmark for future assessments. [2009]

1.5.8

When an adequate view of the optic nerve head and surrounding area is unavailable at reassessment, people should have their pupils dilated before stereoscopic slit lamp biomicroscopy or optic nerve head imaging is repeated. [2009]

When to reassess

People with COAG, suspected COAG and OHT

1.5.9

At each assessment, re-evaluate the risk of conversion to COAG and the risk of sight loss to set time to next assessment. [2017]

1.5.10

At each assessment, ask about general health and, if appropriate, factors affecting adherence to treatment, including cognitive impairment and any treatment side effects. [2017]

People with treated OHT (baseline IOP 24 mmHg or more) and a normal optic nerve head and visual field at most recent assessment

1.5.11

For people with treated OHT (baseline IOP of 24 mmHg or more) and a normal optic head and visual field at the most recent assessment:

use clinical judgement to assess control of IOP and the risk of conversion to COAG, and
reassess according to table 1. [2017]

**Table 1 Time to next assessment for people being treated for OHT**
Conversion from ocular hypertension to chronic open angle glaucoma	Control of intraocular pressure	Time to next assessment
Not detected or uncertain conversion	No	Review management plan and reassess between 1 month and 4 months
Uncertain conversion	Yes	Reassess between 6 months and 12 months
No conversion detected	Yes	Reassess between 18 months and 24 months
Conversion	No or yes	See recommendations on diagnosis and reassessment of chronic open angle glaucoma

Use clinical judgement to decide when the next appointment should take place within the recommended interval, including the need to assess the impact of any new treatments started.

Uncertain conversion includes having insufficient accurate information (perhaps because the person was unable to participate in the assessment).

People with suspected COAG

1.5.12

For people with suspected COAG:

use clinical judgement to assess control of IOP and risk of conversion to COAG (optic nerve head damage and visual field defect), and
reassess according to table 2. [2017]

**Table 2 Time to next assessment for people with suspected COAG**
Conversion to chronic open angle glaucoma	Control of intraocular pressure	Time to next assessment
Not detected or uncertain conversion	No	Review management plan and reassess between 1 month and 4 months
Uncertain conversion	Yes	Reassess between 6 months and 12 months
No conversion detected	Yes	Reassess between 12 months and 18 months
Conversion	No or yes	See recommendations on diagnosis and reassessment of chronic open angle glaucoma

Use clinical judgement to decide when the next appointment should take place within the recommended interval, including the need to assess the impact of any new treatments started.

Uncertain conversion includes having insufficient accurate information (perhaps because the person was unable to participate in the assessment).

People with COAG

1.5.13

For people with COAG:

use clinical judgement to assess risk of COAG progression to sight loss, and
reassess according to table 3. [2017]

**Table 3 Time to next assessment for people with COAG**
Progression of chronic open angle glaucoma	Control of intraocular pressure	Time to next assessment
Not detected	No	Review treatment plan and reassess between 1 month and 4 months
Uncertain progression or progression	No	Review treatment plan and reassess between 1 month and 2 months
No progression detected and low clinical risk	Yes	Reassess between 12 months and 18 months
No progression detected and high clinical risk	Yes	Reassess between 6 months and 12 months
Uncertain progression or progression	Yes	Review treatment plan and reassess between 2 months and 6 months

Use clinical judgement to decide when the next appointment should take place within the recommended interval, including the need to assess the impact of any new treatments started.

Uncertain conversion includes having insufficient accurate information (perhaps because the person was unable to participate in the assessment).

Discharge back to primary care

1.5.14

Discharge people back to primary eye care services if:

they were referred for OHT but do not need treatment
they were referred for suspected COAG but this is no longer suspected.

Advise people that they should continue with regular visits to their primary eye care professional, at clinically appropriate intervals. [2017]

1.5.15

Give a discharge summary to people who have been assessed and discharged to primary care. Send a copy to their GP and, with patient consent, copy the relevant information to the primary eye care professional nominated by the patient. Advise people to take their discharge summary with them when attending future sight tests. [2017]

1.6 Organisation of care

1.6.1

Refer people to a consultant ophthalmologist for consideration of a definitive diagnosis and formulation of a management plan if:

they have suspected optic nerve damage or repeatable visual field defect, or both, or
SLT treatment is suitable (see recommendation 1.4.4 and recommendation 1.4.15 for people with newly diagnosed OHT and COAG). [2009, amended 2022]

1.6.2

Diagnosis of OHT and suspected COAG and formulation of a management plan should be made by a suitably trained healthcare professional with:

a specialist qualification and
relevant experience. [2009, amended 2017]

1.6.3

Be aware that holding an independent or non-medical prescribing qualification alone (without a specialist qualification relevant to the case complexity of glaucoma being managed) is insufficient for managing glaucoma and related conditions. [2017]

1.6.4

Healthcare professionals involved in the diagnosis of OHT and COAG suspect status, and preliminary identification of COAG, should be trained in case detection and referral refinement and be able to identify abnormalities based on relevant clinical tests and assessments. They should understand the principles of diagnosis of OHT and COAG and be able to perform and interpret all of the following:

medical and ocular history
differential diagnosis
Goldmann applanation tonometry (slit lamp mounted)
standard automated perimetry (central thresholding test)
central supra-threshold perimetry
stereoscopic slit lamp biomicroscopic examination of anterior segment
examination of the posterior segment using slit lamp binocular indirect ophthalmoscopy
gonioscopy
van Herick peripheral anterior chamber depth assessment
CCT measurement. [2009]

1.6.5

People with OHT, suspected COAG or COAG should have monitoring and treatment from a trained healthcare professional who has all of the following:

a specialist qualification
relevant experience
ability to detect a change in clinical status. [2009, amended 2017]

1.6.6

Healthcare professionals involved in monitoring and treating OHT, suspected COAG and established COAG should be trained to make management decisions on:

risk factors for conversion to COAG
coexisting pathology
risk of sight loss
monitoring and detecting a change in clinical status (for example, visual field changes and stereoscopic slit lamp biomicroscopic examination of anterior segment and posterior segment)
pharmacology of IOP‑lowering medicines
eligibility for 360° SLT
treatment changes for COAG, suspected COAG and OHT (with consideration given to relevant contraindications and interactions). [2009, amended 2022]

1.6.7

Healthcare professionals should discuss with the responsible consultant ophthalmologist the decision to offer 360° SLT and how it will be performed. Healthcare professionals undertaking 360° SLT should be given support by the responsible consultant ophthalmologist. Training should include:

the suitability of the procedure
laser safety and procedures
benefits and risks of 360° SLT, and how to discuss these with patients and their family members or carers (as appropriate)
patient consent. [2022]

For a short explanation of why the committee made these recommendations and how they might affect practice, see the rationale and impact section on organisation of care.

Full details of the evidence and the committee's discussion are in evidence review A: selective laser trabeculoplasty in ocular hypertension or chronic open-angle glaucoma adult patients.

1.6.8

People with a confirmed diagnosis of OHT or suspected COAG and who have an established management plan may have monitoring (but not treatment) from a suitably trained healthcare professional with knowledge of OHT and COAG, relevant experience and the ability to detect a change in clinical status. The healthcare professional should be able to perform and interpret all of the following:

Goldmann applanation tonometry (slit lamp mounted)
standard automated perimetry (central thresholding test)
central supra-threshold perimetry (this visual field strategy may be used for monitoring OHT or suspected COAG when the visual field is normal)
stereoscopic slit lamp biomicroscopic examination of the anterior segment
van Herick peripheral anterior chamber depth assessment
examination of the posterior segment using slit lamp binocular indirect ophthalmoscopy. [2009]

1.6.9

Healthcare professionals who diagnose, treat or monitor independently of consultant ophthalmologist supervision should take full responsibility for the care they provide. [2009]

1.7 Providing information

1.7.1

Ensure that people are offered the opportunity to discuss their diagnosis, referral, prognosis, treatment and discharge so they can take an active part in decision making (see NICE's guideline on shared decision making). Provide them with relevant information in an accessible format at initial and subsequent visits. This should include telling them:

about their specific condition (OHT, suspected COAG and COAG), its life-long implications and their prognosis for retention of sight
that COAG in the early stages and OHT and suspected COAG are symptomless
that most people having treatment for COAG will have good quality of life and not go blind
that once lost, sight cannot be recovered
the different types of treatment options, including mode of action, frequency and severity of side effects, and risks and benefits of treatment
that glaucoma can run in families and that family members may wish to be tested for the condition
the importance of their role in their own treatment – for example, the ongoing regular application of eye drops to preserve sight. [2009, amended 2017]

1.7.2

Ensure that people are given practical information and advice on:

how to apply eye drops, including technique (punctal occlusion and devices) and hygiene (storage)
the need for regular monitoring as specified by the healthcare professional
methods of investigation during assessment
how long each appointment is likely to take and whether the person will need any help to attend (for example, driving soon after pupil dilatation would be inadvisable)
how to contact the eye clinic liaison officer (ECLO) and what information and assistance they can provide
support organisations and support groups
compliance aids (such as dispensers) available from their GP or community pharmacist
Letter of Vision Impairment (LVI), Referral of Vision Impairment (RVI) and Certificate of Vision Impairment (CVI), registration
Driver and Vehicle Licensing Agency (DVLA) regulations. [2009, amended 2017]

Terms used in this guideline

Enhanced case-finding

Enhanced community case-finding services use slit lamp mounted Goldmann-type applanation tonometry, dilated slit lamp indirect biomicroscopy and other tests deemed necessary by the healthcare professional.

MMC

Mitomycin‑C is an antimetabolite used during the initial stages of trabeculectomy to prevent excessive postoperative scarring and therefore reduce the risk of failure.

Primary eye care professionals

These include optometrists, GPs with a special interest in ophthalmology and community orthoptists.

Referral filtering

A general term for any type of accuracy checking before referral to hospital eye services. Referral filtering may take the form of 'repeat measures', 'enhanced case-finding', 'referral refinement', 'hospital-based triage' or 'administrative paper-based triage'.

Repeat measures

The repeated measurement of parameters related to the diagnosis of glaucoma. A simple repeat measures scheme may involve repeat measurement of IOP only. Other repeat measures schemes may also include repeated measurement of visual fields and other relevant ocular parameters when clinically necessary.

Sight loss

Sight loss in glaucoma is visual damage that manifests as blind spots in the field of vision. Early on these are mostly asymptomatic with many people being unaware of a problem. Sight loss may progress to visual impairment and eventually become symptomatic.

Sight test

A sight test determines whether or not a person has a sight defect, and if so, what is needed to correct, remedy or relieve it. An optometrist performing a sight test must conduct the examinations specified in the Sight Testing (Examination and Prescription) (No 2) Regulations 1989. These include an internal and external examination of the eyes and any other examinations needed to detect signs of injury, disease or abnormality in the eye or elsewhere.

Visual impairment

A severe reduction in vision that cannot be corrected with standard glasses or contact lenses and reduces a person's ability to function in a visual environment.