- Established and important risk factors for primary open-angle glaucoma (POAG) include age, race/ethnicity, level of intraocular pressure (IOP), family history of glaucoma, low ocular perfusion pressure, type 2 diabetes mellitus, myopia, and thin central cornea.
- POAG with consistently normal IOP is common, especially in certain populations. Lowering pressure in these patients can be beneficial.
- Characteristic clinical features of POAG include an open angle on gonioscopy, and glaucomatous optic nerve head (ONH) and retinal nerve fiber layer (RNFL) changes that usually are associated with typical glaucomatous visual field defects.
- Computer-based imaging and stereoscopic photography provide different and complementary information about optic nerve status and are useful adjuncts to a good clinical examination.
- Adjusting computerized visual field programs (24°, 30°, 10°) and varying stimulus size for patients with advanced glaucoma aid in detecting and monitoring progressive visual field loss.
- Clinical trials have shown that lowering IOP reduces the risk of developing POAG and slows the progression of POAG, including normal-tension open angle glaucoma (OAG).
- Effective medical, laser, and incisional surgical approaches exist for lowering IOP.
- A reasonable initial treatment in a POAG patient is to reduce IOP 20%–30% below baseline and to adjust up or down as indicated by disease course and severity.
Table 1. Recommendation Grading
|I||High-quality meta-analyses, systematic reviews of randomized controlled trials (RCTs), or RCTs with a very low risk of bias|
|I||Well-conducted meta-analyses, systematic reviews of RCTs, or RCTs with a low risk of bias|
|I-||Meta-analyses, systematic reviews of RCTs, or RCTs with a high risk of bias|
|II||High-quality systematic reviews of case-control or cohort studies High-quality case-control or cohort studies with a very low risk of confounding or bias and a high probability that the relationship is causal|
|II||Well-conducted case-control or cohort studies with a low risk of confounding or bias and a moderate probability that the relationship is causal|
|II-||Case-control or cohort studies with a high risk of confounding or bias and a significant risk that the relationship is not causal|
|III||Nonanalytic studies (e.g., case reports, case series)|
|G - Good quality||Further research is very unlikely to change our confidence in the estimate of effect|
|M - Moderate quality||Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate|
|In - Insufficient quality||Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate Any estimate of effect is very uncertain|
|S - Strong recommendation||Used when the desirable effects of an intervention clearly outweigh the undesirable effects or clearly do not|
|D - Discretionary recommendation||Used when the trade-offs are less certain—either because of low-quality evidence or because evidence suggests that desirable and undesirable effects are closely balanced|
- To rate individual studies, a scale based on Scottish Intercollegiate Guideline Network (SIGN) is used.
- The body of evidence quality ratings is defined by Grading of Recommendations Assessment, Development and Evaluation (GRADE). GRADE is a systematic approach to grading the strength of the total body of evidence that is available to support recommendations on a specific clinical management issue.
- Key recommendations for care are defined by GRADE.
- POAG is a chronic ocular disease process that is progressive, generally bilateral, but often asymmetric.
- POAG represents a spectrum of disease in adults in which the susceptibility of the optic nerve to damage varies among patients. Although many patients with POAG present with elevated IOP, nearly 40% of those with otherwise characteristic POAG may not have elevated IOP measurements.
- Population-based studies indicate that a variable proportion of patients with IOP >21 mmHg have glaucomatous optic nerve damage (See Figure 1). This suggests that an IOP level of >21 mmHg is an arbitrarily defined level and highlights the poor predictive value of utilizing a specific IOP cutoff as a measure for screening or diagnosis of POAG.
- The vast majority of patients with POAG have disc changes or disc and visual field changes, but there are rare cases where there may be early visual field changes before there are detectable changes to the optic nerve.
- The optic nerve should be carefully examined for the above signs of glaucoma damage, and its appearance should be serially documented. (I+, M, S)
- Eye care providers can view the optic disc and RNFL using magnified stereoscopic visualization with the slit-lamp biomicroscope and through a dilated pupil. (I+, M, S)
- Eye care providers evaluate the visual field using standard automated perimetry (SAP) with white-on-white stimuli. It is the gold standard test for comparing other types of visual field testing. (II, G, S)
- Although they are distinctly different methodologies, stereoscopic disc photographs and computerized images of the nerve are complementary with regard to the information they provide the clinician who must manage the patient. In the absence of these methodologies, a nonstereoscopic photograph or a drawing of the ONH should be recorded, but this is a less desirable alternative to stereophotography or computer-based imaging. (III, In, S)
- Because some patients show visual field loss without corresponding optic nerve progression, both structural and functional assessments remain integral to patient care. Even though quantitative imaging technology is approved as an adjunct to aid in glaucoma diagnosis, the clinician should include all perimetric and other structural information when formulating patient management decisions. (III, In, S)
- Routine genetic testing for glaucoma risk alleles is NOT recommended for patients with POAG at this time. (III, G, S)
Clinical Findings Characteristic of POAG
|Evidence of optic nerve damage from either, or both, of the following:|
|Optic disc or RNFL structural abnormalities|
|Reliable and reproducible visual field abnormality — considered a valid representation of the subject's functional status|
|Open anterior chamber angles|
|Absence of other known explanations (i.e., secondary glaucoma) for progressive glaucomatous optic nerve change (e.g., pigment dispersion, pseudoexfoliation [exfoliation syndrome], uveitis, trauma, and corticosteroid use)|
Definite optic disc or RNFL abnormalities consistent with glaucoma can be associated with the following severities:
|Mild||a normal visual field as tested with SAP|
|Moderate||visual field abnormalities in one hemifield that are not within|
5º of fixation as tested with SAP
|Severe||visual field abnormalities in both hemifields and/or loss within|
5º of fixation in at least one hemifield as tested with SAP
|Indeterminate||inability of patient to perform visual field testing, unreliable/uninterpretable visual field test results, or visual fields not performed yet|
- Ocular history (e.g., refractive error, trauma, prior ocular surgery)
- A history of prior glaucoma laser or incisional surgical procedures should be elicited. (G, S)
- Family history. The severity and outcome of glaucoma in family members, including a history of visual loss from glaucoma, should be obtained during initial evaluation.
- Systemic history (e.g., asthma/chronic obstructive pulmonary disease, migraine headache, vasospasm, diabetes, cardiovascular disease)
- Review of pertinent records, with particular reference to the past IOP levels, status of the optic nerve, and visual field
- Current ocular, topical, oral, injected, or inhaled medications (e.g., corticosteroids) and known local or systemic intolerance to ocular or nonocular medications
- Ocular surgery