Yes, frequent and continious heat can be quite harmful for the eyes because there is large amount of thermal radiation and infrared rays in the heat, which will make the eyes feel very dry, the injury in the optic organism, and so on. People whose eyes are usually in the environment of heat possess higher rate of getting optic lenticular opacity and serious vitreous opacity which can develop into cataracts. Therefore, if you are in a heat environment, you had better wear protective eyewear. As to black eyes, heat can indeed to some extent make the black eyes even worse. To reduce the black eyes, you should first of all make sure that you get adequate amount of sleep at night, do not usually stay up late at night. Second, you can apply some eye scream on the skin under your eyes and massage the skin for a minute or two, do it every day, two or three times a day. Also you can put sliced cucumber, apple or potato on the surface of your closed eyes, for about ten munites each time. Besides, do not stay at front of the computer or the TV for too long.