Complications of Age-Related Macular Degeneration Prevention Trial (CAPT)

To determine whether application of low-intensity laser treatment of eyes with drusen in the macula can prevent later complications of age-related macular degeneration and thereby preserve visual function.

Complications of age-related macular degeneration (AMD) are the leading cause of severe vision loss among people aged 65 and over in the United States and many Western countries. Most, (approximately 90 percent), of this vision loss is due to the neovascular (or wet) form of AMD. The word neovascular describes the development of new, abnormal blood vessels in the back of the eye. Unfortunately, the majority of these new vessels are not amenable to currently available treatments.

The first sign that an eye may develop AMD is the presence of drusen, yellowish deposits under the retina. Current data suggests that eyes with large drusen are at increased risk for developing the vision threatening complications of AMD. Since the 1970s investigators have reported consistently that laser photocoagulation causes a reduction in large drusen. However, results of the effects of laser treatment on preventing later complications of AMD have been less consistent and based on relatively small numbers of patients.

Further study into the ability of a treatment to prevent vision loss from the advanced forms of AMD would have profound public health implications. A treatment that could reduce the risk of developing neovascularization by 30 percent might reduce the risk of blindness from AMD by one half. The Complications of Age-related Macular Degeneration Prevention Trial (CAPT) will assess whether treating drusen by laser photocoagulation reduces the risk of loss of visual acuity.

The CAPT is a multi-center, prospective, randomized clinical trial designed to assess the safety and effectiveness of low-intensity laser treatment in preventing vision loss among patients with large drusen in both eyes. Eligible patients had one eye randomly assigned to laser treatment performed by a CAPT-certified ophthalmologist. The other eye was not treated. Both eyes were observed carefully for any changes for a period of five years. The effectiveness of the treatment was assessed using the following criteria:

• Change in visual acuity (primary outcome measure of the study)
• Incidence of complications of AMD such as neovascularization, serous detachment of the pigment epithelium, and geographic atrophy
• Changes in contrast threshold and critical print size for reading

Patients eligible for CAPT can be either male or female and meet the following criteria:

• Age at least 50 years old
• Vision in each eye must measure 20/40 or better.
• At least 10 large drusen in each eye
• Available for follow-up examinations for 5 years after enrollment

No longer recruiting. Comments: Completed. A total of 1,052 were enrolled at 22 clinical centers across the United States. Recruitment began on May 1, 1999 and ended on March 31, 2001. Participants were followed for a minimum of 5 years.

Completed, with results published. Comments:

Follow-up of patients was excellent; less than 3% of visual acuity examinations were missed. At 5 years, 188 (20.5%) treated eyes and 188 (20.5%) observed eyes had visual acuity scores 3 or more lines worse than at the initial visit (p= 1.00). The cumulative 5-year incidence rates for treated and observed eyes for CNV were 13.3% and 13.3% (p=0.95), respectively; and for GA were 7.4% and 7.8% (p=0.64), respectively. The contrast threshold doubled in 23.9% of treated eyes and in 20.5% of observed eyes (p=0.40). The critical print size doubled in 29.6% of treated eyes and in 28.4% of observed eyes (p=0.70). Seven (0.7%) treated eyes and 14 (1.3%) observed eyes had an adverse event of a 6 or more line loss in visual acuity in the absence of late age-related macular degeneration or cataract. As applied in CAPT, low intensity laser treatment did not demonstrate a clinically significant benefit on vision in eyes of people with bilateral large drusen.