Eye Muscle

When you approach middle age, your eye muscles tend to lose their ability to finely focus the lens.

EYES : The muscles tend to lose their ability to finely focus the lens as one approaches middle age. Eyesight that was 6/4 [ability to read at 6 metres what most people read at 4 metres] [20/15 feet] at 30 drops to 6/6 [20/20] at 50. Slight magnifying glasses might be needed for reading. At 60, people tend to become shotsighted when the inner part of the lens hardens and refracts rays to a focus just before the retina. Vision drops to 6/12 [20/40] and the retina's fine discrimination of colours is dulled, particularly with greens and pinks. Ophthalmologists like to point to Renoir's pink stage as an example. By 70 almost everyone has signs of cataracts, an opacity in the lens. The older, harder, clouded lenses scatter light haphazardly and glase becomes a problem.