对很多人来说，眼睛的颜色从生下来那一天开始就确定了，或黑或绿或褐，而且一辈子不变。但对另外一些人来说，却不是这样。究竟是什么原因会导致眼睛变色呢?下面，就请进入今天的新托福阅读材料：他的眼睛会变色。

It can bend light,bring the world into focus,and next to the human brain may be our most complicated organ. But for many people the most intriguing feature of the human eye is simply its color.

In most people,the answer is no. Eye color fully matures in infancy and remains the same for life. But in a small percentage of adults, eye color can naturally become either noticeably darkerorlighter with age.

What determines eye color is the pigment melanin. Eyes that have a lot of it in the connective tissue at the front of the iris, called the stroma, are darker, while those that have less tend to be lighter.

The levels of melanin generally remain the same throughout life, but a few things can change them permanently.

The first is a handful of ocular diseases like pigmentary glaucoma. Another is a condition called heterochromia, ormulticolored eyes, which affects about 1 percent of the population and is often caused by traumatic injuries. An example of this can be seen in the rock star David Bowie, who attributes his contrasting eye colors, hazel and light blue,to a blow to the face as a child.

The third cause appears to be genetics. A study in 1997, for example, looked at thousands of twins and found that 10 percent to 15 percent of the subjects had gradual changes in eye color throughout adolescence and adulthood, which occurred at nearly identical rates in identical twins.

The bottom lines Eyes can change color in some people because of geneticsorinjury.

以上就是今天的托福阅读材料，大家可以积累其中的高分词汇及句型，并且练习提升阅读速度，迅速找到托福阅读的主题句和出题点。