A 55-year-old patient complains of decreased distance vision. However, now he does not require his near glasses for near work. The most likely cause is –

This is a typical example of second-sight. When a nuclear cataract develops, it can bring about a temporary improvement in near vision, called 'second sight'. Now, the question arises, why does this occur? Normally, the aging process brings about hypermetropic changes (hyperopic shift) in the lens. However, nuclear changes induce a modification of the refractive index of the lens and produce a myopic change (myopic shift). It is possible to predict that an aging process who had hypermetropia previously, can now read with no correction (without glasses), i.e. improvement in near vision, called 'second-sight'.