A model of the incidence and consequences of choroidal neovascularization secondary to age-related macular degeneration. Comparative effects of current treatment and potential prophylaxis on visual outcomes in high-risk patients.

OBJECTIVE

To describe the comparative impact of current and preventive treatments on incidence of choroidal neovascularization (CNV) and severe vision loss in patients with bilateral soft drusen (BSD).

DESIGN

Stochastic model.

SETTING

US population.

PATIENTS

Prevalence cohort of white patients 43 years or older with BSD.

INTERVENTIONS

Application of prophylaxis of 10% to 50% efficacy to 1 or both eyes of patients with BSD, application of laser photocoagulation to eligible CNV lesions, or both.

MAIN OUTCOME MEASURES

Proportion of patients with BSD after 10 years with unilateral and bilateral CNV and resultant unilateral and bilateral vision loss to visual acuity of 20/200 or worse.

RESULTS

The natural history of patients with BSD generated by the model shows that 12.40% of these patients develop either unilateral or bilateral CNV within 10 years of their entry into the BSD prevalence cohort. Bilateral disease occurs in 3.86% of patients with BSD within 10 years. The proportion of patients with BSD becoming legally blind from CNV within 10 years is 2.54% if no treatment is performed. Current laser treatment for CNV decreases the proportion with legal blindness within 10 years to 2.24%. The addition of a preventive treatment of 10% efficacy applied bilaterally to the current laser treatment regimen decreases the proportion with legal blindness to 1.86%; a 25% effective preventive treatment decreases it to 1.34%. Comparatively, preventive treatment of 10% and 25% efficacy given to the fellow eye only after the first eye has developed CNV decreases the proportion of legally blind patients at 10 years only to 2.06% and 1.77%, respectively. All outcomes vary with sex and age at entry into the BSD cohort.

CONCLUSIONS

Patients with BSD face a 12.40% risk of developing CNV within 10 years. The addition of even a modest (10% effective) bilateral preventive treatment to the current regimen for CNV would more than double the prevention of legal blindness in the BSD population relative to current laser treatment; a preventive treatment of 33% efficacy more than halves the rate of legal blindness caused by CNV. Preventive treatment given to the fellow eye only after the first develops CNV has substantially less impact.