Simplified model calculations:

(1) Multiplying: (census data)×(incidence/prevalence)×(life expectancy). This gives the annual surviving prevalence and incidence numbers. 
These numbers were then multiplied by: 
(Incremental AREDS visual acuity events figure)×(calculated utility figure). This gives annual incremental utilities, enabling quality adjusted life years (QALYs) to be calculated. 
(Incremental AREDS neovascular events figure)×(% of lesions applicable for treatment estimate)×(% actually treated estimate)×(unit cost). This gives the annual incremental laser or PDT cost saving associated with the reduced use of the relevant therapy. 
(2) The total number of people screened by optometrists was calculated from census and unit cost data and accrued to the treatment arm alone. 
(3) The cost of ongoing antioxidant and zinc treatment for all AREDS category 3 and 4 was calculated on an annual basis from screened survivors and accrued to the treatment arm alone. 
(4) Final cost utility output = relevant cost/QALY. 