Ординатура / Офтальмология / Английские материалы / Clinical Pathways in Glaucoma_Zimmerman, Kooner_2001

Is There Glaucomatous Cupping?

The changes on the optic nerve head should be carefully evaluated and compared with the other eye. If the optic disc changes are asymmetrical then there should be a very high suspicion for glaucoma. Occasionally, the disc features may suggest glaucomatous damage but still appear symmetrical. In such a situation visual fields and other risk factors would help to rule out physiologic cupping or congenital deformity of the optic nerve disc.

Are There Glaucomatous Field Defects?

In most patients visual field examination is most crucial. If the fields are normal in both eyes, then the patient may have any of the three diagnoses depending on the IOP, optic nerve head, and risk factor: glaucoma suspect (ocular hypertensive), physiologically large cups, or congenital deformity of the optic nerve head. When there are typical glaucomatous field defects in one or both eyes, then the glaucoma diagnosis is more likely as long as the IOP and optic nerve head features support the clinical impression. All efforts should be made to rule out conditions that may mimic glaucomatous field defects as discussed previously.

(2) How Is a Patient with Increased Cupping and Optic Atrophy Evaluated?

The features of glaucomatous optic nerve damage have been discussed before, and all other conditions that may simulate glaucomatous damage should be ruled out. A patient may show signs of damage in only one eye and this should alert the clinician to exclude secondary causes of unilateral nerve damage such as congenital deformity, trauma, inflammation, space-occupying lesions, and past or present use of topical corticosteroids (see Fig. 2–2).

Is the IOP Normal or High?

Careful measurement of IOP may reveal normal, low, or raised pressure in one or both eyes. A single pressure reading is noncontributory and may have to be repeated at different times of the day. Elevated IOP aids in the diagnosis but a normal or low pressure does not exclude glaucoma.

What Does Gonioscopy Reveal?

Gonioscopy is an essential step in the evaluation of patients manifesting suspicious optic disc changes. A closed angle may suggest primary or secondary angle-closure glaucoma and the management is discussed in Chapter 5. A patient exhibiting signs of narrow angle may be harboring combined mechanism glaucoma or impending angle-closure glaucoma, or may be a glaucoma suspect. If the iridocorneal angle is open, then the list of differential diagnosis is long. This individual may have POAG, low-tension or normal-tension glaucoma, ocular hypertension, secondary glaucoma, physiologic cupping, or congenital optic nerve deformity. The next step is evaluation of the visual fields.

mal pressures may harbor normalor low-tension glaucoma. On the other hand, a patient with typical glaucomatous field defects in one or both eyes and high IOP needs to be carefully evaluated for secondary causes of elevated pressure before a diagnosis of POAG is established.

(3) How Is a Patient Who Presents with Glaucomatous Visual Field Defects Evaluated?

It is not uncommon that a diagnosis of glaucoma is initially entertained when a patient shows suspicious field defects during the course of some other ocular investigations. If in doubt, the visual fields may be repeated to rule out shortterm or long-term fluctuations in patient responses. The glaucomatous field defects may be unilateral or bilateral and one should rule out other causes of glaucoma-like field changes (Table 2–2). The next step is to check ocular tensions (Fig. 2–3).

How Are the Ocular Pressures?

The IOP may be elevated in one or both eyes and a record of past pressures would be very helpful to better understand the range of IOP fluctuations. In any case, knowledge of the status of the iridocorneal angle would be very helpful.

What Does Gonioscopy Reveal?

The iridocorneal angle may be open, narrow, or closed. The last condition should point to both primary and secondary types of angle-closure glaucoma. Similarly, an open-angle should suggest either POAG or other varieties of secondary open-angle glaucomas. A patient with narrow angles may present some difficulty in categorizing and usually needs careful follow-up and evaluation. Finally, fundus examination should help us to narrow in on the ultimate diagnosis.

What Does the Fundus Examination Show?

A thorough evaluation of the optic nerve head includes looking for signs of glaucomatous changes and any differences in the extent of damage between the two eyes. Though asymmetrical cupping is quiet common in POAG, symmetrical damage does not rule out the diagnosis. The final diagnosis should be made taking all pieces of information together.

Treatment and Management

The treatment and management of a patient with POAG poses a great challenge for the physician. Like many other chronic diseases, POAG may cause havoc to the mental, physical, economical, and social well-being of the patient. It is essential, therefore, to mentally prepare the patient while the investigations are progressing. After the diagnosis is confirmed and the initial status of

44 Primary Open-Angle Glaucoma

Patient with history of glaucomatous VF defects

•Confirm diagnosis

•Disc photos

Figure 2–3. Management of a patient who presents with history of glaucomatous visual field defects.

the optic nerve structure and function is documented, it is time to break the news to the patient. Many physicians find it helpful if a family member is also present at the discussions. The physician should emphasize the lifelong commitment to therapy and follow-up. Different therapies, including topical and

systemic medications, lasers, and mechanical surgeries, should be explained. An estimate of the target pressure should also be a top priority as the therapy is begun, and henceforth all efforts are focused to maintain IOP at that level or below. The beneficial effect of reduced IOP on progression of glaucomatous damage is well documented.137,138

What Is the Initial Therapy of POAG?

This depends on multiple factors such as the height of IOP, extent of disease damage, age, local and systemic contraindications to therapy, social support, and mental status of the patient. If the IOP is very high (e.g., >35 mm Hg) it may be appropriate to begin with more than one medication. Otherwise, it is best to add one medication at a time. In this way, not only the response of therapy but also the dosage and side effects of each drug can be evaluated. To minimize diurnal effects on the IOP, many clinicians advocate monotherapy when considering additional topical therapy.

What Is the Definitive Treatment for POAG?

It may take months before the most appropriate combination of drugs is found. Chapter 18 provides a detailed description of individual drugs used to treat glaucoma, and Chapter 19 discusses various surgical procedures employed in managing the disease. The first agent of choice for most clinicians is still a beta-blocker. Both selective and nonselective agents are available. The chief contraindications are restrictive airway disease, bradycardia, and cardiovascular compromise. For the second position agent, one may choose between a prostaglandin analogue and an α-agonist. Latanoprost is the only prostaglandin analogue available and is very effective in reducing IOP, presumably by increasing uveoscleral outflow. The long-term side effects are still not known. Alphaclonidine and brimonidine are the two α-agonists currently available in the United States, and their long-term use is marred by a high degree of associated allergic conjunctivitis. If two different agents are unable to control IOP, some clinicians may consider argon laser trabeculoplasty next over adding another drug. The main considerations are noncompliance by the patient and the inability to bear the higher cost of medical therapy. For the third-agent spot, there is a choice between a topical and an oral carbonic anhydrase inhibitor (CAI). The two topical CAIs are dorzolamide and brinzolamide. Local allergies for both the agents are a concern for long-term use. Systemic CAIs are acetazolamide and methazolamide; the former also has a parenteral form. Oral therapy is associated with untoward systemic effects such as nausea, weakness, dizziness, insomnia, renal stones and skin rashes. The remaining antiglaucoma drugs are the miotics and epinephrine or its derivatives. Miotics are inexpensive but are associated with side effects such as miosis, ciliary spasm, myopia, and cataract formation, and noncompliance is a problem. Epinephrine-type drugs may cause annoying local irritation, headaches, elevated blood pressure, and cystoid macular edema in aphakes.

Argon laser trabeculoplasty is an effective way of reducing IOP. The advantages include its effectiveness and that it is performed in the office under topical anesthesia only. The availability of apraclonidine has reduced the chances

46 Primary Open-Angle Glaucoma

of transient postoperative pressure spikes. The disadvantages are a lack of long-term control and ineffectiveness in young adults.

A number of other surgical procedures are employed for uncontrolled glaucoma, namely trabeculectomy with or without antimetabolites, setons, and various cyclodestructive procedures (see Chapter 19).

What Is a Target Pressure?

Target pressure refers to an arbitrary range of pressure that a treating physician may feel is unlikely to cause further damage to the optic nerve.139 As is obvious from the definition the pressure may vary from patient to patient and even in the same patient over the course of the disease. The minimal pressure that a clinician may try to achieve initially is reduction by 25 to 30%. Later the target pressure depends on variables such as age, race, degree of glaucomatous damage, compliance, and associated systemic ailments. The target pressure therefore, is an ever-changing number that the physician and patient both try to achieve with reasonable means. As a rule of thumb, the greater the damage, the lower the initial target pressure. It is always important to remember that there are factors other than pressure alone that may be responsible for glaucomatous damage.

How Common Is Noncompliance in Patients with Glaucoma?

Patient compliance with medications is an important challenge faced by all physicians. The close relationship between poor patient compliance to either medical or surgical therapy and progressive glaucomatous visual loss is well established.68,140 It is such a complex problem that new noncompliance reasons are being confronted every day. In glaucoma patients some of the well-known reasons for noncompliance are lack of awareness of the severity of the disease, cost of medications, side effects of therapy, and helplessness under deteriorating visual status. Various helpful techniques that may help compliance include patient education, tailor-made topical therapy, family involvement in the management of the disease, support groups, and constant encouragement. The time spent in confronting noncompliance is well spent, as studies have shown that one-third or more patients do not take their medications as prescribed.141,142

What Is the Follow-Up Schedule for Patients with POAG?

The follow-up schedule should be tailor-made for individual patients. Apart from the level of control and severity of glaucomatous damage, other factors that may influence a patient’s follow-up visits include noncompliance and degree of family/social support. It is essential to inquire about side effects of therapy, measure visual acuity, check IOP, and examine the optic nerve at each visit. Visual field evaluation and gonioscopy should also be done periodically. A patient with uncontrolled IOP and/or deteriorating optic nerve may have to be seen every day or weekly until the condition is stabilized. After adequate control, the visits may be increased to every 1 to 4 months. A compliant, stable patient may need to

be seen only two to three times a year. A visual field examination and optic nerve photography/imaging may be performed one to two times yearly.

What Is the Cost of Glaucoma Medications?

Whenever initiating medical therapy or changing medications, it is worthwhile to consider the cost of drugs. This is all the more important because most patients with glaucoma are elderly, on fixed income, and may be taking several other drugs concurrently. Several studies have looked at the question of the cost of glaucoma medications.143,144 In 1999, Fiscella and coworkers145 calculated daily patients cost of glaucoma medications. The costs per day for various drugs were beta-blockers $0.30 to $0.81, brimonidine $0.90, and latanoprost $0.92, respectively.

Is There Any Information Available Regarding

Characteristics of Office Visits by Glaucoma Patients?

The data collected by the NAMCS have provided useful sampling information on various aspects of office visits by glaucoma patients.60 In the most recent 2- year survey report of 1991–92, there were 17.5 million visits made by patients who were listed with the principal diagnosis of glaucoma. This translated to an average of 8.7 million visits per year or 3.5 visits per 100 persons per year. The visit rate for persons 75 years of age and over was considerably higher, being 26.8 visits per 100 persons. Moreover, during the same period 3.2 million more visits were by patients with glaucoma as their secondary or tertiary diagnosis. As would be expected, 92.8% of glaucoma visits were made by individuals at least 45 years of age, but over 61.3% of all patients were female. The average visit rate for females was 4.2 visits per 100, whereas for males the rate was 2.8 per 100 persons. Visit rates increased by age in both sexes, but no significant difference was observed for age-specific rates by sex in any age group. Nearly 88% of all visits were made by white patients. The average visit rate for white individuals was 3.7 visits per 100 persons, whereas it was 3.0 visits per 100 black persons. The findings from the NAMCS in 1992 showed that black patients accounted for about 36% of the glaucoma-related visits to the hospital outpatient departments compared to approximately 61% by the white patients. There were some geographical differences in the office visit rates. In the South the visit rate was 4.3 visits per 100 persons compared to 2.1 visits per 100 persons in the West.

General ophthalmologists saw about 76% of glaucoma patients, and the rest were taken care of by glaucoma specialists. Although 68.1% of all new patients were referred by other physicians, only 6.8% of glaucoma patients had such a referral. Even the referral rate for patients with diagnoses other than glaucoma was better—31.6%. Patients making return visits composed 90%, of the total, whereas 10% of visits were by new patients. Approximately 17% of all visits made by subjects in age group of 45 to 64 years were for new problems compared to 9% of those 65 years of age and older. The mean physician–patient contact time during glaucoma visits was 21.7 minutes compared to 17.3 minutes for other office visits.

48 Primary Open-Angle Glaucoma

What Are the Sources of Payments for Office Visits?

For the period 1991–92, payment sources for patient visits were Medicare (61.9%), private insurance (36.6%), self-payment (18.8%), Medicaid (8.0%), Health Maintenance Organization/prepaid (7.1%), other government (4.7%), other (2.9%), no charge (1.2%), and unknown (0.8%).

What Are the Reasons for Patient Visits?

The NAMCS provides detailed information on the reasons for office visits by glaucoma patients during 1991–92. The various reasons, in descending order of frequency, were diagnosis of glaucoma (46.9%), diagnostic screening and preventive measures (27.2%), treatment (9.7%), symptoms (9.4%), other (5.8%), and test results (1.0%). Among patients returning for diagnostic tests, about onethird had one diagnostic test, and approximately half had two diagnostic tests.

Are There Any Resource Centers for Glaucoma

Information?

There are several national and international organizations concerned with the problems associated with glaucoma. Table 2–6 lists Internet Web sites providing a wide range of information concerning glaucoma.

Are There Public Awareness Programs for Glaucoma?

The largest public-awareness program is the glaucoma portion of National Eye Health Education Program (NEHEP), funded by the National Eye Institute in 1991. The National Society to Prevent Blindness (NSPB) has a very active ongoing program schedule such as Glaucoma High-Risk Alert, National Glaucoma Awareness Week, an Eye-Saving Sabbath, a National Center for Sight information clearinghouse, Fight For Sight research awards, an industry safety program, a patient brochure series, implementation of a screening pilot study, and formation of a coalition of African-American organizations. The chief aim of all the programs is to make the public fully aware of the importance of periodic ophthalmologic examinations especially among high-risk groups.

What Type of Counseling Is Required in POAG?

As eyesight is so essential for social and economical health, many glaucoma patients fall into depression, often feeling desperate and helpless. The treating physician should be aware of the signs and symptoms of depression and be willing to provide information and support. The family members can be a great source of information regarding the extent of the problem. Drug-related psychiatric side effects might be resolved by altering medications. The most common offenders are CAIs and beta-blockers. Employers may need letters from the physician explaining the extent of visual disability and other handicaps. For example, the patient may not be able to return to jobs requiring the use of heavy machinery or night shifts. Some patients may benefit from currently available low visual aids. Others may require referrals to glaucoma resource centers, social agencies, and psychiatrists.