The primary outcome is improvement in visual acuity from baseline to the two-year examination or retention of baseline visual acuity through the two-year examination. Secondary outcomes include change in quality of life from baseline to the 2- and 4-year examinations, change in visual acuity over 4 years, large losses of visual acuity, and adverse ocular outcomes (e.g., those requiring additional treatment such as cataract, retinal detachment, or recurrent CNV).