to work to achieve the goal, the realities of adherence expectations for that invidual, and what potential side effects, complications, and cost that particular regimen might entail.The target pressure is then continually reassessed and reset based on the clinical course.

The less the initial pretreatment IOP, the more advanced the optic nerve damage, and the older the patient, the lower the target pressure should be set. The presence of a vasculopathy such as diabetes or arteriosclerotic cardiovascular disease should also lower the target pressure. A young person with glaucoma secondary to trauma with a pretreatment IOP of 32 mmHg and a 0.5 cup-to- disc ratio with early visual field loss may do quite well with an initial target IOP in the low 20s.An elderly patient with a pretreatment IOP of 22 mmHg, a cup-to-disc ratio of 0.9, and advanced visual field loss may require a target pressure of 15 mmHg or lower.

The currently available approaches to lower IOP include medical therapy, laser trabeculoplasty, filtering surgery, and cyclodestructive procedures – each of these has its own risk:benefit ratios.Whichever method is chosen, it should ideally be predictable, safe, and easy for the patient to use. Unfortunately, there is no ideal treatment for glaucoma. Because the risk:benefit ratio for medical therapy seems to be lowest, both historical and current practice has been to attempt medical treatment before resorting to other alternatives. However, this approach has been called into question in recent years.15

Medical therapy

Advantages

Medical therapy has been the mainstay of initial glaucoma treatment for over a century.The vast majority of patients respond to a simple regimen with a desirable reduction in IOP. Side effects are usually few and tolerable. When they do occur, side effects are often easily reversible by stopping the medication. Only rarely are visionor life-threatening side effects seen. Medical therapy is less costly over the short term, and because many glaucoma patients are elderly, the cost of medical treatment may never exceed that of surgery. Finally, most patients expect a trial of medical therapy first and are likely to be somewhat suspicious of a too rapid suggestion for surgery.

Disadvantages

Over the last decade, the disadvantages of medical therapy have been increasingly highlighted. Several prospective studies have pointed to medical therapy as less effective in lowering IOP and perhaps in preventing further visual field loss than either laser trabeculoplasty or filtering surgery.16–18 However, some of the differences between the medically and surgically treated groups in these studies may be the result of not setting the target IOP low enough in the medically treated group (the surgically treated groups had pressures ‘automatically’ set at low levels). The Glaucoma Laser Trial showed that after 2 years, only 30% of patients initially treated with medications were still being controlled with a single topical -blocker.19 The Collaborative Glaucoma Initial Therapy Trial at the end of 5 years showed no difference in the progression of visual field loss with either medication as initial therapy in glaucoma or trabeculectomy.20 While quality of life issues were similar in both groups, the medication group had more local eye symptoms and those in the surgery group were more likely to develop cataract and reduced visual acuity early. However,

by 5–8 years, cataract incidence and severity was again even in the two treatment groups.

Medically treated eyes may not have as good a success rate from subsequent filtering surgery compared with eyes treated with surgery from the outset.21 This may be due to an increased number of inflammatory cells and a decreased number of goblet cells in the conjunctiva of medically treated eyes compared with eyes treated initially with surgery.22,23 Medical treatment has the potential for significant and serious side effects, not all of which may be obvious to the patient or physician. During an 8-year period (1978–1985) in the United States, 32 deaths (of about 2 million glaucoma patients) were attributed to complications arising from the use of topical timolol maleate.24 Carbonic anhydrase inhibitors also can produce rare fatal reactions.25

Less dramatic side effects of topical medications include allergic reactions, toxic corneal changes, induced refractive errors, cataract formation, asthma, tachycardia, bradycardia, orthostatic hypotension, gastrointestinal symptoms, decreased libido, impotence, mood changes, possible memory loss, and alopecia. Systemic carbonic anhydrase inhibitors are notorious for significant side effects such as lethargy, depression, diarrhea, and loss of appetite. All of these may have subtle or profound effects on the patient’s quality of life.

In addition, many older patients are also taking a number of other medications, which may add to the potential for crossreaction and confusing side effects. Patients and their primary care physicians often do not associate systemic side effects with topical eye medications, and the ophthalmologist may fail to ask about systemic symptoms; in these cases, the cause of a systemic problem induced by antiglaucoma medications may go undetected.

A further complication of antiglaucoma medications is their high cost. Retail prices for any one type of topical eyedrop may run as high as $80 for a month’s supply. If the patient is using multiple glaucoma medications, the cost of antiglaucoma therapy could well be over $120 per month.26 For someone whose only source of income is a modest pension or social security, this may mean choosing between eating and taking needed medication. Because glaucoma is a chronic, lifetime condition, the cost of medications over the long term may be astronomic, both personally and from a public health/medical economics point of view.This is a major factor in nations with limited resources and can be a significant factor even in the most wealthy countries.

Finally, the issue of compliance must be addressed. It is probably unrealistic to think that a typical elderly patient who is taking medications for hypertension, diabetes, arthritis, and hiatal hernia is going to be able to accurately stick to a regimen that includes two or three topical medications and a carbonic anhydrase inhibitor. Kass and co-workers have shown that compliance is surprisingly poor, even with just one medication used four times a day.27 Similar studies more recently have shown surprisingly low persistence rates even with once a day medication (prostaglandin or similar), although once daily dosing seems significantly better from a persistence point of view than medications requiring more frequent dosing during the day.28,29

Surgical therapy

Advantages

As noted previously, surgical treatment (either laser trabeculoplasty or a filtering operation) is more likely than is medical treatment to