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 evaluation (history and physical examination) includes all components of the comprehensive adult eye evaluation (Preferred Practice Patterns Committee, 2005) in the addition to and with special attention to those factors that specifically bear upon the diagnosis, course, and treatment of primary open-angle glaucoma (POAG). Completion of the evaluation may require more than one visit. For instance, an individual might be identified as having glaucoma on one visit but may return for further evaluation, including additional intraocular pressure (IOP) measurements, central corneal thickness determination, visual field assessment, and optic nerve head evaluation and documentation.
History
The comprehensive initial glaucoma evaluation includes a review of ocular, [A:III] family (Dielmans 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 (Gutierrez et al., 1997; Lee et al., 1998; Parrish et al., 1997; Sherwood et al., 1998; Wilson et al., 1998); [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 glaucoma medications; [A:III] adherence to the treatment regimen and time of last use of glaucoma medications; [B:III] and 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
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 (Preferred Practice Patterns Committee, 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). [B:III] The assessment may benefit from determining diurnal IOP fluctuations, either on the same day or on different days, which may be indicated when disc damage exceeds the amount expected based on a single IOP measurement.
Central Corneal Thickness
Measurement of central corneal thickness (pachymetry) aids the interpretation of IOP measurement results and stratification of patient risk (Herndon, Weizer, & Stinnett, 2004; Gordon et al., 2002; Kass et al., 2002; Agudelo, Molina, & Alvarez, 2002). [A:II] Measurement methods include ultrasonic and optical pachymetry.
Gonioscopy
The diagnosis of POAG 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
There is evidence that glaucomatous changes detected with optic disc and retinal nerve fiber layer analysis may precede changes detected by standard automated perimetry.
Evaluation
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, providing more comprehensive information of optic nerve detail due to the greater magnification of the direct ophthalmoscope. 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]
Documentation
Color stereophotography or computer-based image analysis of the optic nerve head and retinal nerve fiber layer are the best currently available methods to document 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 confolcal 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 (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
Automated static threshold perimetry is the preferred technique for evaluating the visual field. [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] Visual field testing based on short wavelength automated perimetry and frequency doubling technology may detect defects earlier than conventional white-on-white perimetry. It is important to use a consistent examination strategy when visual field testing is repeated. [A:III]
Management
Target Intraocular Pressure
In managing the glaucoma patient, the ophthalmologist strives to achieve a stable range of measured IOPs deemed likely to retard further optic nerve damage. The estimated upper limit of that range is considered the "target pressure." At present, there is no a priori way to determine the pressure below which further 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. The target pressure will vary among patients, and in the same patient it may need adjustment during the course of the disease.
When initiating therapy, the ophthalmologist assumes that the measured pretreatment pressure range contributed to optic nerve damage and is likely to cause additional damage in the future. The initial target pressure selected should be at least 20% lower than the pretreatment IOP, depending upon the clinical findings. [A:III] Further reduction of the target IOP is often also justified by the severity of existing optic nerve damage, the level of the measured pretreatment IOP, the rapidity with which the damage occurred, and other risk factors. In general, the more advanced the damage, the lower the initial target pressure should be. [A:III]
There are two clinically useful empirical observations about POAG:
- Past damage predicts future damage, unless the IOP is lowered.
- Damage in one eye is associated with a significantly increased risk of future damage in the other eye.
The severity of glaucoma damage can be estimated using the following scale:
- Mild: characteristic optic nerve abnormalities consistent with glaucoma and a normal visual field as tested with standard automated perimetry
- Moderate: characteristic optic nerve abnormalities consistent with glaucoma and visual field abnormalities in one hemifield and not within 5 degrees of fixation
- Severe: characteristic optic nerve abnormalities consistent with glaucoma and visual field abnormalities in both hemifields and loss within 5 degrees of fixation in at least one hemifield
The adequacy and validity of the target pressure are periodically reassessed by comparing optic nerve status (by optic disc appearance, quantitative assessments of the disc and nerve fiber layer, and visual field tests) with previous examinations. If progression occurs at the target pressure, the target IOP should be lowered. [A:III] Failure to achieve and maintain a target pressure should trigger a reassessment of the treatment regimen in light of potential risks and benefits of additional or alternative treatment. [A:III]
Therapeutic Choices
The IOP can be lowered by medical treatment, or by laser, filtering, or cyclodestructive surgery (alone or in combination). The choice of initial therapy depends on numerous considerations, and discussion of treatment with the patient should include appropriate options. [A:III]
In many instances, topical medications constitute effective initial therapy. Laser trabeculoplasty is an appropriate initial therapeutic alternative. [A:I] Filtering surgery is effective at lowering IOP and may sometimes be an appropriate initial therapeutic alternative instead of medications or laser trabeculoplasty. [A:I]
Medical Treatment
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 glaucoma 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 (Zimmerman et al., 1984). [B:II]
At each examination, medication dosage and frequency of use should be recorded. [A:III] Adherence to the therapeutic regimen and the patient's response to recommendations for therapeutic alternatives or diagnostic procedures should be discussed. [A:III]
Laser Trabeculoplasty
Laser trabeculectomy is an alternative for patients who cannot or will not use medications reliably due to cost, memory problems, difficulty with instillation, or intolerance to the medication.
The ophthalmologist who performs the surgery must ensure that the patient receives adequate postoperative care. [A:III] The plan for care prior to and after laser trabeculoplasty should include the following elements:
- At least one preoperative evaluation and IOP measurement by the surgeon [A:III]
- Informed consent prior to surgery [A:III]
- At least one IOP check within 30 to 120 minutes of surgery [A:I]
- A follow-up examination within 6 weeks of surgery or sooner if there is concern about IOP-related damage to the optic nerve during this time [A:III]
Filtering Surgery
Filtering surgery provides an alternative path for the escape of aqueous humor, and it often reduces IOP and the need for medical treatment.
Patients who require filtration surgery and who also have cataract may benefit from simultaneous cataract and glaucoma surgery, as may glaucoma patients with a visually significant cataract and severe, but well-controlled, glaucoma. Generally, combined cataract and glaucoma surgery is not as effective as glaucoma surgery alone in lowering intraocular pressure, so patients who require filtration surgery who also have mild cataract may be better served by filtration surgery alone and cataract surgery later.[B:III]
The plan for care before filtering surgery should include the following elements:
- At least one preoperative evaluation by the surgeon [A:III]
- Informed consent prior to surgery [A:III]
The ophthalmologist who performs the surgery must ensure that the patient receives adequate postoperative care, which includes the following: [A:III]
- Use of topical corticosteroids in the postoperative period, unless contraindicated [A:II]
- Follow-up evaluation on the first postoperative day (12 to 36 hours after surgery) by the surgeon and at least once from the second to the tenth postoperative day to evaluate visual acuity, IOP, and status of the anterior segment [A:II]
- In the absence of complications, additional postoperative visits during a 6-week period to evaluate visual acuity, IOP, and status of the anterior segment [A:III]
- More frequent follow-up visits, as necessary, for patients with postoperative complications such as a flat or shallow anterior chamber or evidence of early bleb failure, increased inflammation, or Tenon's cyst formation [A:III]
- Additional treatments as necessary, including surgical procedures to correct a flat anterior chamber, repair bleb leaks, perform bleb massage, perform suture lysis, or perform bleb needling or other surgical revisions of the bleb to maximize the chances for a successful long-term result [A:III]
- A discussion between the surgeon and the patient to explain that filtration surgery places the eye at risk for endophthalmitis for the duration of the patient's life, and that the patient must regard the symptoms of pain and decreased vision and the signs of redness and discharge as a medical emergency that requires medical attention [A:III]
Cyclodestructive Surgery
Cyclodestructive procedures reduce the rate of aqueous production. In recent years, cyclodestructive procedures are more commonly performed using a transscleral laser delivery system but they can also be performed endoscopically. Because cyclodestructive procedures have been associated with subsequent decrease of visual acuity, and, rarely, cases of sympathetic ophthalmia, they are often reserved for eyes with reduced visual acuity and patients who are poor candidates for incisional surgery. The advantages and disadvantages of a cyclodestructive procedure compared with a filtration operation or a tube shunt procedure should be discussed with patients who are poor surgical candidates, have limited visual potential, or have undergone multiple previous glaucoma operations. [A:III]
Follow-up Evaluation
Patients with POAG should receive follow-up evaluations and care to monitor and treat their disease according to the guidelines summarized in Table 2 in the original guideline document. These recommendations apply to ongoing glaucoma management and not to visit for other purposes.
History
The following interval history should be elicited at POAG follow-up visits
- Interval ocular history [A:III]
- Interval systemic medical history [B:III]
- Side effects of ocular medications [A:III]
- Frequency and time of last intraocular pressure (IOP)-lowering medications, and review of use of medications [B:III]
Physical Examination
The following components of the physical examination should be performed at POAG follow-up visits:
- Visual acuity [A:III]
- Slit-lamp biomicroscopy [A:III]
- IOP and time of day of measurement [A:III]
Optic nerve head evaluation and documentation by imaging, photography, or drawing (Caprioli, Prum, & Zeyen, 1996; Shaffer et al., 1975; Zeyen & Caprioli, 1993; Airaksinen, Tuulonen, & Alanko, 1992) and visual field evaluation (Smith, Katz, & Quigley, 1996; Katz, Tielsch, & Quigley, 1995; Heijl & Asman, 1989; Jay & Murdoch, 1993) should be performed at the recommended intervals listed in Tables 3 and 4 of the original guideline document. Based on the understanding of the effect of central corneal thickness on IOP measurements (Herndon, Weizer, & Stinnett, 2004; Gordon et al., 2002; Kass et al., 2002), pachymetry should be repeated after any event (e.g., refractive surgery [Hjortdal et al., 2005]) that may alter central corneal thickness. [A:II]
Gonioscopy
Gonioscopy is indicated when there is a suspicion of an angle-closure component, anterior-chamber shallowing or anterior-chamber angle abnormalities, or if there is an unexplained change in IOP. [A:III] Gonioscopy should also be performed periodically (e.g., 1 to 5 years). [A:III]
Within each of the recommended intervals, factors that determine frequency of evaluations include the severity of damage (mild, moderate, severe), the stage of disease (more frequent evaluations for more severe disease), the rate of progression, the extent to which the IOP exceeds the target pressure, and the number and significance of other risk factors for damage to the optic nerve. [A:III] In certain cases, follow-up visual field testing may be required more or less frequently than the recommended intervals (e.g., a second test to establish a baseline for future comparisons, to clarify a suspicious test result, or to overcome an apparent testing artefact).
Adjustment of Therapy
The indications for adjusting therapy are as follows: [A:III]
- Target IOP is not achieved.
- A patient has progressive optic nerve damage despite achieving the target IOP. The validity of the diagnosis and target pressure should be reassessed. [A:III] Additional evaluation may reveal conditions that are contributing to the progression of damage and serving as a justification to escalate therapy. These evaluations include obtaining diurnal IOP measurements, repeating the central corneal thickness measurement to verify a thin cornea or a change in corneal thickness after refractive surgery, or seeking evidence of unrecognized low ocular perfusion pressure. A neurologic evaluation also may be considered.
- Patient is intolerant of the prescribed medical regimen.
- Patient does not adhere to the prescribed medical regimen.
- Contraindications to individual medicines develop.
- Stable optic nerve status and low IOP occurs for a prolonged period in a patient on pressure-lowering medications. Under these circumstances, a carefully monitored attempt to reduce the medical regimen may be appropriate.
Downward adjustment of target pressure should be made in the face of progressive optic disc or visual field change. [A:III] Upward adjustment of target pressure should be considered if the patient has been stable and if the patient either requires (because of side effects) or desires less medication. [B:III] The ophthalmologist should plan a follow-up visit in 2 to 8 weeks to assess the response and side effects from washout of the old medication or onset of maximum effect of the new medication. [A:III]
Provider and Setting
The performance of certain diagnostic procedures (e.g., tonometry, pachymetry, perimetry, optic disc imaging and photography) may be delegated to appropriately trained and supervised personnel. However, the interpretation of results and medical and surgical management of disease require the medical training, clinical judgment, and experience of the ophthalmologist.
Counseling/Referral
- Patients should be encouraged to alert their ophthalmologists to physical or emotional changes that occur when taking glaucoma medications. [A:III]
- Patients with significant visual impairment or blindness should be referred for and encouraged to use appropriate vision rehabilitation and social services (American Academy of Ophthalmology [AAO], 2001). [A:III]
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.
