As we age, the eye's ability to see decreases. The result is that older viewers need more illuminance, larger size print and more contrast to see tasks. Let's discuss what happens to the eye as we age and how it affects our vision.

The lens yellows as we age. This affects color vision. Especially in individuals over 50 years old, blues look less blue and they may confuse blue and green. The lens also gets thicker and less transparent. This results in light scattering within the eye itself making the person more sensitive to glare. Finally, the eye's lens (along with other parts of the body) may lose its elasticity, and therefore be unable to focus on close objects. This is why most people need reading glasses.

The pupil of the eye gets smaller as we age. This, of course, reduces the amount of light that enters the eye and reaches the retina. Therefore, we need higher luminances to see a task. This is why IES includes age in their recommended illuminance tables. Less light falling on the retina translates to less stimulus of the rods and cones. This mean visual processing and adaptation time to differing light levels increase.