Healio
Healio
ByBrian J. Jacobs, MD
ByDeepak Edward, MD
March 18, 2011
9 min read
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To Treat or Not To Treat?

ByBrian J. Jacobs, MD
ByDeepak Edward, MD

To treat or not to treat? A subject of controversy within ophthalmology, that is the question that continually plagues ophthalmologists when dealing with patients who are suspected to have or to develop glaucoma. Both those in favor of treatment and those who favor postponing treatment to observe raise valid points, and it is important to understand both arguments.

Observation

A variety of reasons to observe the patient over time rather than to initiate treatment exist. First, glaucoma is a slowly progressive disorder that primarily affects elderly individuals. Most patients afflicted with glaucoma die before developing blindness. Quigley and researchers found that it takes 13 years for whites and 16 years for blacks to go blind from glaucoma.1 In cross-sectional data using the Baltimore Eye Study,2 the Beaver Dam Eye Study,3 and the Framingham Eye Study,4 only 4% of whites and 8% of blacks with glaucoma were legally blind from the disease.5 In addition, studies indicate that until moderate damage from glaucoma occurs, the health-related quality of life is unaffected.6 Because glaucoma affects the peripheral vision first, it may take several years before a patient develops functional visual loss. Thus, of the nearly 2.5 million people in the United States with glaucoma, only half of them are actually aware that they have the disease. The decision to initiate treatment in patients who are asymptomatic is often difficult for the patient to understand and may lead to difficulties in the patient’s adherence to the treatment regimen.

Obstacles To Treatment

Compliance is a common obstacle in treating asymptomatic patients. Patients may not follow advice for treatment for various reasons; for example, the treatment of glaucoma has many potential side effects and could create symptoms in a previously asymptomatic patient. Jampel and colleagues found that medical therapy can alter and potentially diminish quality of life.7 The Collaborative Initial Glaucoma Treatment Study found that the average number of symptoms reported by patients treated medically and surgically at baseline was 7.7 and 8.1, respectively.8 In addition, approximately half of the patients reported some worry or concern about going blind.9 Furthermore the cost of therapy can be substantial, and many patients will require a lifetime of medicines once treatment is initiated.

Incidence

On the other hand, glaucoma affects more than 60 million people worldwide, causing visual impairment in nearly half of all people affected and resulting in bilateral blindness in 6.7 million of these people.10-12 Glaucoma is the second leading cause of blindness in the United States and the most common cause of blindness among black Americans.

The Barbados Eye Study (BES) found a 4-year incidence of 2.2% in blacks.13 The BES data suggest that both black and mixed (black and white) populations have higher IOP values than white populations. The study also found a high proportion of blindness due to glaucoma (28%) in persons of African origin.14

A retrospective population-based study in Olmstead County estimated an incidence rate of 0.145 per 1000 person-years in a predominantly white population.10 In this study, 10% of patients were blind in at least one eye at the time of diagnosis. Subsequent analysis of this patient population found the cumulative probability of blindness in at least one eye to be 27% at 20 years and the cumulative probability of blindness in both eyes to be 9% at 20 years. Several other studies with predominately white participants found the rate of blindness to be generally less than 1% and the rate of visual impairment to be approximately 3% to 6%, whereas the prevalence of both conditions is higher in black populations.14

Even though the incidence of glaucoma varies with race, there is general agreement that it increases with age. In the Rotterdam Study, the incidence of bilateral open-angle glaucoma in persons 75 years of age and older was five-fold higher than in those aged 55 to 75 years.15 In addition, only one third of the patients with glaucoma were treated by an ophthalmologist. Similarly, prevalence rises steeply with age from 0.2% to 2.7% at age 50 to 59 years to 1.6% to 12.8% after age 80 years.3,16-26 Thus, regardless of race, glaucoma is a prominent public health issue and its economic implications are substantial. The National Eye Institute reports that blindness as a result of glaucoma costs the US government more than $1.5 billion annually in Social Security benefits, lost income tax revenues, and health care expenditures.

Reduced IOP/Reduced Vision Loss

Even though glaucoma can result in permanent vision loss including blindness, several large, prospective studies including the Ocular Hypertensive Treatment Study, the Early Manifest Glaucoma Treatment Study, the Collaborative Normal Tension Glaucoma Study, the Advanced Glaucoma Intervention Study, and the Collaborative Initial Glaucoma Study have provided evidence that reduction of IOP reduces the rate of disease progression.27-31

The Ocular Hypertension Treatment Study (OHTS) showed that topical ocular hypotensive medication is effective in delaying or preventing POAG in eyes with ocular hypertension. The results showed that by reducing IOP by at least 20% the risk of developing glaucoma was reduced by more than half over a 5-year period (9.5% in the observation group vs. 4.4% in the medication group).27

The Early Manifest Glaucoma Trial (EMGT) showed that the treatment of early glaucoma reduced the risk of progression by half. Treatment reduced the IOP on average 5.1 mm Hg (25%). Each 1-mm Hg decrease in IOP from baseline to the first follow-up visit (3 months) reduced the risk of progression by approximately 10%.28

The Collaborative Normal-Tension Glaucoma Study (CNTGS) found that, by reducing the IOP by greater than 30%, the rate of visual field progression decreased from 35% to 12%. However, in 65% of patients, disease did not progress over the length of the study, despite having no treatment at all.29,30

The Advanced Glaucoma Intervention Study: 7 (AGIS 7) evaluated the effects of argon laser trabeculoplasty (ALT) vs. trabeculectomy as the initial surgery in patients with advanced open-angle glaucoma not controlled by medical treatment. AGIS 7 showed that lower IOP was associated with less visual field loss.31 Eyes with average IOP of 14 mm Hg or less over the first 18 months, or eyes with IOP of 18 mm Hg or less at all visits throughout the study, had significantly less visual field loss.

To Treat or Not To Treat?

Clinical trials have provided prospective studies of sufficient sample size and duration to help aid in the detection and management of glaucoma. It is the responsibility of the ophthalmologist to use the guidelines from these trials sensibly and in a cost-effective manner.

However, it is important to only initiate therapy in appropriate patients. There is individual variability in susceptibility to damage of the optic nerve, and therefore a need for continued vigilance to monitor progression. Thus, when determining which patients should undergo therapy, one must consider not only IOP but also the appearance of the optic nerve and visual fields. The presence of various risk factors should also be considered.

OHTS identified risk factors for developing POAG including baseline IOP, age, cup: disc ratio, and central corneal thickness (CCT).32 The EMGT identified risk factors for progression including higher baseline IOP, exfoliation, bilateral disease, older age, and frequent disc hemorrhages.33 Other possible risk factors include diabetes, myopia, hypertension, and migraines.

Estimating Risk

Recently, a predictive model to estimate the risk of conversion from ocular hypertension to glaucoma was developed.34 The scoring tool for assessing risk (STAR) stratifies six risk factors including age, baseline IOP, CCT, pattern standard deviation, vertical cup: disc ratio, and diabetes. The approach allows one to estimate the degree of risk an individual patient has for progressing from ocular hypertension to glaucoma within 5 years. Such risk assessment models, which are used commonly in other fields of medicine, are an important step forward in trying to determine risk of developing glaucoma and can further facilitate decisions regarding initiating therapy.34

In addition to these risk factors, the pressure at the time of diagnosis, the amount of optic nerve damage present, the rate of damage from prior records, and the patient’s symptoms and life expectancy should also be considered.

Kass also recommends treatment if certain features exist in the patient’s personality or medical condition that favor treatment, for example, a monocular patient, an unreliable patient, a patient who is unable to do reliable visual fields or in whom the optic disc cannot be visualized, a patient who prefers to be treated, and a patient who is at risk for a retinal vascular occlusion.35,36

Conclusion

Deciding to initiate treatment in patients with glaucoma can be a difficult decision. Many factors must be considered, including visual, physical, medical, psychologic, and social circumstances. It is essential to individualize the decision to commence treatment and to include the patient in the decision process. As the American Academy of Ophthalmologists Preferred Practice Patterns recommends, a risk-benefit analysis should be done, and the likelihood of development of glaucomatous optic nerve damage and visual impairment should be carefully weighed against the risks of treatment.

References

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