7
Freeman, Cataract Surgery and Age-Related Macular Degeneration
assessed as a cause of blindness. During the personal interview, information was collected on
age, race, sex, and smoking habits.
The definition of late AMD for this study was choroidal neovascularization, geographic
atrophy, or if AMD was diagnosed by an ophthalmologist as a cause of blindness (20/200 or
worse). Two definitions were used for early AMD-- definition 1 was drusen >=64 microns in
size, hyperpigmentation, or nongeographic atrophy. Early AMD definition 2 was drusen >=125
microns in size, hyperpigmentation, or nongeographic atrophy in the macular zone. Those who
had late AMD were excluded from analyses of early AMD. Presence of a severe cataract was
defined if visual impairment or blindness were attributed to cataract in the clinical exam.
Eyes excluded from the analyses were those whose photographs were not of gradable quality for
the specific outcome under study. Out of 8,792 eyes, there were 7,428 eyes that were gradable
for late AMD, 8,734 eyes for early AMD 1, and 8,717 eyes for early AMD 2.
Statistical Analysis
The general characteristics of the three study populations were examined and compared.
Next, the characteristics of those who had cataract surgery in at least 1 eye were compared to
those who did not for the three populations. Age and race-specific prevalence rates of having
late AMD in at least 1 eye were calculated. Next, regression analyses were performed for each
of the individual study populations and then for all the data sets combined together.
The primary outcome for this study was late AMD. However, associations with early AMD
were also assessed in SEE and BES. Indicator variables were created for the various cataract
exposures with neither cataract surgery nor severe cataract at the time of the clinical exam as the
reference level, presence of a severe cataract as the next level, and previous cataract surgery or
time since cataract surgery as the final level(s). Regression analyses were done at the eye level
