Table 1. Relative circadian photoreception vs age*.

	10 years	15 years	25 years	35 years	45 years	55 years	65 years	75 years	85 years	95 years
10 years	1.0	0.9	0.8	0.6	0.5	0.4	0.3	0.2	0.1	0.1
15 years	1.1	1.0	0.9	0.7	0.5	0.4	0.3	0.2	0.1	0.1
25 years	1.2	1.1	1.0	0.8	0.6	0.4	0.3	0.2	0.1	0.1
35 years	1.6	1.5	1.3	1.0	0.8	0.6	0.4	0.3	0.2	0.2
45 years	2.0	1.8	1.6	1.3	1.0	0.7	0.5	0.3	0.2	0.2
55 years	2.8	2.5	2.3	1.8	1.4	1.0	0.7	0.5	0.3	0.3
65 years	3.8	3.5	3.2	2.4	1.9	1.4	1.0	0.6	0.5	0.4
75 years	6.1	5.6	5.0	3.9	3.0	2.2	1.6	1.0	0.7	0.6
85 years	8.2	7.6	6.7	5.2	4.1	3.0	2.1	1.4	1.0	0.8
95 years	10.0	9.2	8.2	6.4	5.0	3.6	2.6	1.6	1.2	1.0

*Circadian photoreception declines with ageing due to pupillary miosis and decreased crystalline lens transmission. This table presents circadian performance for an age in the top row relative to that of an age in the left column. For example, a person aged 45 has photoreception roughly half that of a 15-year-old and twice that of a 65-year-old. The table can also be used to estimate the light requirements for an age in the left column relative to that of an age in top row. For example, a person aged 65 needs roughly three times the illuminance of a 25-year-old and half that of a 85-year-old for equivalent circadian photoreception performance.