"Old pearl yellow" is actually an abnormal phenomenon of eye metabolism. There is a thin transparent film on the surface of human eyeball, which is called conjunctiva. After being polluted by ultraviolet rays and dust for a long time, there will be adverse reactions of pigmentation. Pigments gather in the conjunctival layer to form a large area of macula. A slightly convex dark yellow substance appeared on the surface of the white eyeball, and the black eyeball became more turbid. Human beings have been stimulated by the external environment for a long time, and the elderly are more likely to produce conjunctival pigmentation, so there is a saying that "people are old and yellow." Modern medicine believes that there is a thin transparent film on the surface of human eyeball, which is called conjunctiva. After being polluted by ultraviolet rays and dust for a long time, there will be adverse reactions of pigmentation. Pigments gather in the conjunctival layer to form a large area of macula. A slightly convex dark yellow substance appeared on the surface of the white eyeball, and the black eyeball became more turbid. Human beings have been stimulated by the external environment for a long time, and the elderly are more likely to produce conjunctival pigmentation, so there is a saying that "people are old and yellow."