Ratings of importance to the care process (A-C) and ratings of strength of evidence (I-III) are defined at the end of the "Major Recommendations" field.
Diagnosis
The comprehensive initial glaucoma suspect evaluation (history and physical examination) includes all components of the comprehensive adult eye evaluation (Practice Patterns Committee, "Comprehensive adult medical eye evaluation," 2005) in addition to and with special attention to those factors that specifically bear upon the diagnosis, course, and treatment of glaucoma suspects. Completion of the evaluation may require more than one visit; the patient may need to return for further evaluation, including additional intraocular pressure (IOP) measurements, central corneal thickness determination, visual field assessment, and optic nerve head and nerve fiber layer evaluation and documentation.
History
The comprehensive initial evaluation for a glaucoma suspect includes a review of ocular, [A:III] family (Dielemans et al., 1994), [A:II] and systemic history. [A:III] It also includes an assessment of the impact of visual function on daily living and activities; [A:III] review of pertinent records [A:III] with particular reference to the status of the optic nerve, visual field, and IOP; [A:III] ocular surgery; [A:III] the use of ocular and systemic medications; [A:III] known local or systemic intolerance to ocular or systemic medications; [A:III] and the severity and outcome of glaucoma in family members, including history of visual loss from glaucoma (Tielsch et al., 1994; Wolfs et al., 1998). [B:III]
Physical Examination
In completing the elements in the comprehensive adult medical eye evaluation, the physical examination specifically focuses on the following eight elements:
Pupil
The pupils are examined for reactivity and an afferent pupillary defect (Kohn, Moss, & Podos, 1979; Brown et al., 1987). [B:II]
Anterior Segment
A slit-lamp biomicroscopic examination of the anterior segment can provide evidence of physical findings associated with narrow angles, corneal pathology, or a secondary mechanism for elevated IOP such as pseudoexfoliation, pigment dispersion, iris and angle neovascularization, or inflammation (Practice Patterns Committee, "Comprehensive adult medical eye evaluation," 2005). [A:III]
Intraocular Pressure
Intraocular pressure is measured in each eye, [A:III] preferably using a contact applanation method (typically a Goldmann tonometer) before gonioscopy or dilation of the pupil (Whitacre & Stein, 1993). [A:III] Time of day should be recorded because of diurnal variation (Whitacre & Stein, 1993). [C:III] The assessment may benefit from determining diurnal IOP fluctuations, either on the same day or on different days.
Central Corneal Thickness
Measurement of central corneal thickness (pachymetry) aids the interpretation of IOP measurement results and stratification of patient risk (Gordon et al., 2002; Medeiros et al., 2003; Agudelo, Molina, & Alvarez, 2002). [A:II] Measurement methods include ultrasonic and optical pachymetry.
Gonioscopy
The diagnosis of primary open-angle glaucoma (POAG) suspect requires careful evaluation of the anterior-chamber angle to exclude angle closure or secondary causes of IOP elevation such as angle recession, pigment dispersion, peripheral anterior synechiae, angle neovascularization, and trabecular precipitates (Tasman, 2004). [A:III]
Optic Nerve Head and Retinal Nerve Fiber Layer
The preferred technique for optic nerve head and retinal nerve fiber layer evaluation involves magnified stereoscopic visualization (as with the slit-lamp biomicroscope), preferably through a dilated pupil. [A:III] Direct ophthalmoscopy is useful in some cases to complement magnified stereoscopic visualization; it is capable of higher magnification and can provide more comprehensive information of optic nerve detail. Red-free illumination may aid in evaluating the retinal nerve fiber layer. Inability to dilate (or the reason not to dilate) the pupil should be documented. [B:III]
Color stereophotography or computer-based image analysis of the optic nerve head and retinal nerve fiber layer are the best currently available methods of documenting optic disc morphology and should be performed (Caprioli, Prum, & Zeyen, 1996; Uchida, Brigatti, & Caprioli, 1996; Anton et al., 1997; Schuman et al., 1995; American Academy of Ophthalmology, 1999; Kamal, Bunce, & Hitchings, 2000; Chauhan et al., 2001; Poinoosawmy et al., 2000; Zangwill et al., "The confocal scanning laser," 2004; Zangwill et al., "Racial differences," 2004; Zeyen et al., 2003). [A:II] In the absence of these technologies, a nonstereoscopic photograph or a detailed drawing of the optic nerve head should be recorded, but these are less desirable alternatives to stereophotography or computer-based imaging (Shaffer et al., 1975). [A:III]
Fundus
Examination of the fundus, through a dilated pupil whenever feasible, includes a search for other abnormalities that might account for visual field defects if present (e.g., optic nerve pallor, tilted disc, disc drusen, optic nerve pits, optic nerve hypoplasia, neurological disease, macular degeneration, and other retinal disease). [A:III]
Visual Field
The preferred technique for evaluating the visual field is automated static threshold perimetry using either white-on-white standard automated perimetry or short-wavelength automated perimetry (SWAP, blue-on-yellow). [A:III] Careful manual combined kinetic and static threshold testing is an acceptable alternative when patients cannot perform automated perimetry reliably or if it is not available. [A:III] Causes of visual field loss other than glaucomatous optic neuropathy should be sought and assessed during the history review and physical examination (Anderson, 1989). [A:III] A repeat, confirmatory examination for field test results that are unreliable or show a possible new glaucomatous defect should be considered. [A:III] It is important to use a consistent examination strategy when visual field testing is repeated. [A:III]
Management
Intraocular pressure is the only risk factor known to be amenable to treatment in glaucoma and glaucoma suspects. The decision to begin treatment to lower IOP in the glaucoma suspect is complex and depends on ocular, systemic, medical, and psychosocial factors. The determination is based on the ophthalmologist's analysis of the examination results and evaluation of the patient and the patient's preferences. The number and severity of risk factors, prognosis, management plan, and likelihood that therapy, once started, will be long-term should be discussed, involving the patient and family in the decision process. [A:III] Whether or not a patient is treated, long-term monitoring for the development of glaucoma is essential [A:III]
The patient who is a POAG suspect has a chronic, asymptomatic condition that when treated may require frequent use of one or more expensive medications that may cause significant side effects. When treatment is appropriate, an effective regimen requires attention to its effect on IOP (potential impact on the condition) and toxicity (the drug-induced side effects), and the degree to which efficacy is reduced by nonadherence due to visual, physical, social, economic, or psychologic factors. The ophthalmologist should consider these issues in choosing a regimen of maximal effectiveness and tolerance to achieve the desired therapeutic response for each patient. [A:III]
Target Intraocular Pressure
In managing the glaucoma suspect for whom treatment is indicated, the ophthalmologist strives to achieve a stable range of measured IOPs deemed likely to protect against optic nerve damage. The estimated upper limit of that range is considered the "target pressure." The target pressure will vary among patients, and in the same patient it may vary during the clinical course. For glaucoma suspects not being treated, the target pressure can be viewed as that pressure over which treatment would be recommended (i.e., the threshold for the initiation of treatment).
If therapy is initiated, the ophthalmologist assumes that the measured pretreatment pressure range is that which places the optic nerve at risk for damage. The Ocular Hypertension Treatment Study (which limited enrollment to patients with an IOP of 32 mmHg or below) used a target pressure 20% lower than the mean of several baseline IOP measurements and 24 mmHg or below. This seems an appropriate initial goal. [A:I] At present, there is no a priori way to determine the pressure below which optic nerve damage will be prevented in any particular patient. The initial target pressure is an estimate and a means toward the ultimate goal of protecting the optic nerve. Current IOP and its relationship to the target IOP should be evaluated at each visit. [A:III]
Failure to achieve and maintain a target pressure should trigger a reassessment of the treatment regimen in light of the potential risks and benefits of additional or alternative treatment. [A:III] In a glaucoma suspect, a definite deterioration in optic nerve structure or visual field (i.e., conversion from glaucoma suspect to glaucoma patient) indicates that the target pressure should be reduced [A:I] and the patient managed as described in the Primary Open-Angle Glaucoma Preferred Practice Pattern. [A:III]
Therapeutic Choices
If the decision to begin treatment is made, the choice of initial therapy depends on numerous considerations, and discussion of treatment with the patient should include appropriate options. [A:III] In most instances, topical medications constitute effective initial therapy. The prostaglandin analogs and the beta adrenergic antagonists are the most frequently used eye drops for lowering IOP in patients with glaucoma. Agents less frequently used include alpha2 adrenergic agonists, topical and oral carbonic anhydrase inhibitors, and parasympathomimetics.
If a drug fails to reduce IOP, it should be replaced with an alternate agent until effective medical treatment is established. [A:III] If a single medication is effective in lowering IOP but the target pressure is not reached, combination therapy or switching to an alternative therapy may be appropriate.
The ophthalmologist should discuss the benefits and risks of medical treatment with the patient. [B:III] The ophthalmologist should assess the patient who is being treated with IOP-lowering medication for local and systemic side effects, toxicity, and possible interactions with other medications. [A:III] The ophthalmologist must be prepared to recognize potential life-threatening adverse reactions. [A:III] To reduce systemic absorption, patients should be educated about eyelid closure or nasolacrimal occlusion when applying topical medications. [B:II]
At each examination, medication dosage and frequency of use should be recorded. [A:III] Adherence to the regimen and the patient's response to recommendations for therapeutic alternatives or diagnostic procedures should be discussed. [A:III]
Laser and filtering surgery are rarely indicated in the treatment of glaucoma suspects.
Follow-up Evaluation
Guidelines for follow-up frequency are specified in Table 2 in the original guideline document. These guidelines represent the consensus of an expert panel in the absence of conclusive scientific evidence in the literature. The interaction between patient and disease is unique for every patient, and management for each patient must be individualized with this in mind. [A:III]
History
The following interval history should be elicited during follow-up visits for POAG suspect patients:
- Interval ocular history [A:III]
- Interval systemic medical history and any change of systemic medications [B:III]
- Side effects of ocular medications if patient is being treated (Stamper et al., 1999) [A:III]
- Frequency and time of last IOP-lowering medications, and review of medication use if the patient is being treated [B:III]
Physical Examination
The following components of the physical examination should be performed during follow-up visits for POAG suspect patients:
- Visual acuity [A:III]
- Slit-lamp biomicroscopy [A:III]
- IOP and time of day of measurement [A:III]
Optic nerve head evaluation and documentation (Caprioli, Prum, & Zeyen, 1996; Shaffer et al., 1975; Lichter, 1976; Airaksinen, Tuulonen, & Alanko, 1992) and visual field evaluation (Smith, Katz, & Quigley, 1996; Katz et al., 1995; Heijl & Asman, 1989) should be performed at least at the recommended intervals listed in Table 2 of the original guideline document. Gonioscopy is indicated when there is a suspicion of an angle-closure component, anterior-chamber shallowing, anterior-chamber angle abnormalities, or if there is an unexplained change in IOP. [A:III] Gonioscopy should be performed periodically (i.e., 1 to 5 years). [A:III]
Adjustment of Therapy
The indications for adjusting therapy are as follows: [A:III]
- Target IOP is not achieved.
- IOP is consistently below target, or visual field and optic discs remain stable for years. In this situation, a carefully monitored attempt to reduce the medical regimen is appropriate.
- Patient is intolerant of the prescribed medical regimen.
- Patient does not adhere to the prescribed medical regimen.
- Contraindications to individual medicines develop.
Conversion from POAG Suspect to POAG
Any patient who shows evidence of optic nerve deterioration based on optic nerve head appearance, increased optic disc cupping, retinal nerve fiber layer loss, or visual field changes consistent with glaucomatous damage should be diagnosed as having developed POAG and treated as described in the Primary Open-Angle Glaucoma Preferred Practice Pattern (Glaucoma Panel, Preferred Practice Patterns Committee, "Primary open-angle glaucoma," 2005). [A:III]
Provider and Setting
The performance of certain diagnostic procedures (e.g., tonometry, pachymetry, perimetry, fundus imaging, and photography) may be delegated to appropriately trained and supervised personnel. However, the interpretations of results and the medical and surgical management of disease require the medical training, clinical judgment, and the experience of an ophthalmologist.
Counseling/Referral
- Patients should be educated about the disease process, the rationale and goals of intervention, the status of their condition, and the relative benefits and risks of alternative interventions so that they can participate meaningfully in developing an appropriate plan of action. [A:III]
- Patients should be encouraged to alert their ophthalmologists to physical or emotional changes that occur when taking glaucoma medications, if prescribed. [A:III] The ophthalmologist should be sensitive to these problems and provide support and encouragement.
Definitions:
Ratings of Importance to Care Process:
Level A, most important
Level B, moderately important
Level C, relevant, but not critical
Ratings of Strength of Evidence:
- Level I provides strong evidence in support of the statement. The design of the study allowed the issue to be addressed, and the study was performed in the population of interest, executed in such a manner as to produce accurate and reliable data, and analyzed using appropriate statistical methods. The study produced either statistically significant results or showed no difference in results despite a design specified to have high statistical power and/or narrow confidence limits on the parameters of interest.
- Level II provides substantial evidence in support of the statement. Although the study has many of the attributes of one that provides Level I support, it lacks one or more of the components of Level I.
- Level III provides a consensus of expert opinion in the absence of evidence that meets Levels I and II.
