Table 3. Within-supplement group analysis of letter contrast sensitivity by intervention groups.

Intervention	N	Baseline, mean±SD	36 Months, mean±SD	% Δ	Sig.	Baseline, mean±SD	12 Months, mean±SD	% Δ	Sig.	12 Months, mean±SD	24 Months, mean±SD	%Δ	Sig.	24 Months, mean±SD	36 Months, mean±SD	% Δ	Sig.
Letter CS 1.2cpd
Group 1	12	1.87±0.25	1.89±0.16	1	0.817	1.87±0.25	1.96±0.23	5	0.222	1.96±0.23	1.76±0.22	−10	0.000	1.76±0.22	1.89±0.16	7	0.059
Group 2	15	1.71±0.24	1.86±0.18	9	0.012	1.71±0.24	1.93±0.29	13	0.004	1.93±0.29	1.85±0.25	−4	0.207	1.85±0.25	1.86±0.18	1	0.861
Group 3	13	1.75±0.31	1.82±0.20	4	0.432	1.75±0.31	1.89±0.27	8	0.069	1.89±0.27	1.86±0.24	−2	0.602	1.86±0.24	1.82±0.20	−2	0.494
Letter CS 2.4cpd
Group 1	12	1.76±0.30	1.87±0.17	6	0.227	1.76±0.30	1.89±0.33	7	0.077	1.89±0.33	1.70±0.25	−10	0.011	1.70±0.25	1.87±0.17	10	0.065
Group 2	15	1.68±0.31	1.81±0.21	8	0.087	1.68±0.31	1.86±0.31	11	0.000	1.86±0.31	1.78±0.26	−4	0.221	1.78±0.26	1.81±0.21	2	0.657
Group 3	13	1.63±0.31	1.78±0.21	9	0.083	1.63±0.31	1.85±0.29	13	0.005	1.85±0.29	1.77±0.22	−4	0.225	1.77±0.22	1.78±0.21	1	0.947
Letter CS 6cpd
Group 1	12	1.42±0.30	1.60±0.15	13	0.112	1.42±0.30	1.49±0.41	5	0.224	1.49±0.41	1.39±0.26	−7	0.200	1.39±0.26	1.60±0.15	15	0.037
Group 2	15	1.37±0.24	1.52±0.25	11	0.040	1.37±0.24	1.44±0.30	5	0.079	1.44±0.30	1.39±0.34	−3	0.357	1.39±0.34	1.52±0.25	9	0.164
Group 3	13	1.23±0.44	1.52±0.27	24	0.034	1.23±0.44	1.55±0.29	26	0.005	1.55±0.29	1.48±0.20	−5	0.357	1.48±0.20	1.52±0.27	3	0.547
Letter CS 9.6cpd
Group 1	12	1.14±0.31	1.35±0.16	18	0.043	1.14±0.31	1.14±0.32	0	0.959	1.14±0.32	1.14±0.28	0	1.000	1.14±0.28	1.35±0.16	18	0.031
Group 2	15	1.06±0.27	1.27±0.34	20	0.024	1.06±0.27	1.17±0.39	10	0.072	1.17±0.39	1.06±0.37	−9	0.115	1.06±0.37	1.27±0.34	20	0.025
Group 3	13	0.94±0.48	1.30±0.22	38	0.020	0.94±0.48	1.17±0.44	24	0.031	1.17±0.44	1.23±0.27	5	0.503	1.23±0.27	1.30±0.22	6	0.201
Letter CS 15.15cpd
Group 1	12	0.75±0.32	1.02±0.23	36	0.033	0.75±0.32	0.83±0.31	11	0.055	0.83±0.31	0.79±0.29	−5	0.509	0.79±0.29	1.02±0.23	29	0.011
Group 2	15	0.70±0.37	0.91±0.38	30	0.083	0.70±0.37	0.78±0.44	11	0.278	0.78±0.44	0.60±0.47	−23	0.013	0.60±0.47	0.91±0.38	52	0.029
Group 3	13	0.61±0.48	0.97±0.25	59	0.019	0.61±0.48	0.81±0.38	33	0.028	0.81±0.38	0.93±0.35	15	0.169	0.93±0.35	0.97±0.25	4	0.555

Abbreviations: CS, contrast sensitivity; cpd, cycles per degree; N, number of subjects; SD, standard deviation; Sig., level of significance set at P<0.05; %Δ, percentage change.

Letter contrast sensitivity was assessed using Thompson Test Chart PRO and recorded in the logarithm of contrast sensitivity (Log CS) units. Statistical significance was tested using paired t-test. The calculated percentage change from baseline to 36 months, calculated as the 36-month value minus baseline value divided by baseline value, multiplied by 100 (−, negative change; +, positive change); the calculated percentage change from baseline to 12 months, calculated as the 12-month value minus baseline value divided by baseline value, multiplied by 100 (−, negative change; +, positive change); the calculated percentage change from 12 to 24 months, calculated as the 24-month value minus the 12-month value divided by the 12-month value, multiplied by 100 (−, negative change; +, positive change); the calculated percentage change from 24 to 36 months, calculated as the 36-month value minus the 24-month value divided by the 24-month value, multiplied by 100 (−, negative change; +, positive change).

Group 1: 20 mg lutein and 0.86 mg zeaxanthin; Group 2: 10 mg meso-zeaxanthin, 10 mg lutein, and 2 mg zeaxanthin; Group 3: 17 mg meso-zeaxanthin, 3 mg lutein, and 2 mg zeaxanthin.