Experience with cardiovascular risk model offers useful lessons for glaucoma

Dr. Liebmann, clinical professor of ophthalmology, New York University School of Medicine and director, glaucoma services, Manhattan Eye, Ear & Throat Hospital and New York University Medical Center, New York, explained there are many parallels between glaucoma and coronary heart disease (CHD) that enabled glaucoma experts to draw from the experience of their cardiology colleagues.

Both glaucoma and CHD are chronic disorders that can be depicted on a progression continuum from disease that is first undetectable, then asymptomatic, and ultimately results in functional impairment. In addition, there is risk-factor information available from clinical trials for both diseases (glaucoma: Ocular Hypertension Treatment Study; CHD: Framingham Heart Study), and each is associated with a modifiable causal risk factor (IOP and serum cholesterol) that when effectively treated results in reduced progression risk. Both diseases are also prime targets for developing global risk assessment models because of their high burdens in terms of prevalence, functional impact, and direct and indirect costs.

"Risk of CHD increases incrementally in relation to serum cholesterol values, but there is a continuous graded increment extending into the purported normal range," Dr. Liebmann said. "Similarly, glaucoma risk increases in relation to IOP in a continuous graded fashion but extends down into what is regarded as the normal range. Optimal levels have not been determined for either cholesterol or IOP."

Both multifactorial diseases

Like CHD, glaucoma is a multifactorial disease, and so global risk assessment involves integration of multiple variables.

"Assessing risk for glaucoma is more complex than just measuring IOP, but rather it should involve the assessment of overall risk based on multiple factors, and ideally it should be based on evidence gathered in well-controlled clinical trials and help drive decision-making for optimal clinical care just as guidelines for cholesterol-lowering treatment have been developed for CHD," said Dr. Liebmann.

As ophthalmologists begin to apply the new risk calculator for glaucoma to their patients with ocular hypertension, there are also lessons to be learned from the challenges faced in cardiovascular medicine with respect to risk assessment implementation by physicians and patient adherence to treatment recommendations. Results of various patient- and physician-based surveys indicate not all physicians are using the risk calculator, less than half of eligible patients undertake treatment for elevated cholesterol, and those who do often adhere poorly to their prescribed treatment plan.

"Only 20% to 25% of patients in the United States with cardiovascular disease are reported to be receiving treatment, which is similar to the situation we see in glaucoma, and only one-third of those treated with medication for dyslipidemia are reaching target LDL-cholesterol levels," Dr. Liebmann said.

Yet, it is encouraging to note that despite those difficulties, the application of risk assessment in cardiovascular medicine has had a tremendous positive impact on cardiovascular-related mortality in the United States and consequently on life expectancy.

"Considering those outcomes, we can anticipate that development of the risk calculator and guidelines for intervention should help us in improving the management of glaucoma. However, lifetime risk data need lifelong studies, and because certain assumptions must be made early in the process of developing risk assessment models, it is likely that the risk calculator will evolve as more evidence accumulates," Dr. Liebmann said.

Glaucoma 2005 was a continuing medical education symposium jointly sponsored by The University of Medicine and Dentistry of New Jersey-Center for Continuing and Outreach Education and Ophthalmology Times. It was made possible by an unrestricted educational grant from Pfizer Ophthalmics.