In a statistical experiment, a treatment is the factor or the independent variable which is under the control of experimenter. Experimenter can change the conditions of this factor according to his will and according to needs of experiment.
In the given example, the experimenter make 10 people wear sunglasses and check their eyesight after 10 weeks. To another group he does not give sunglasses and check their eyesight after 10 weeks.
So, sunglasses are such a factor which are under the control of experimenter. So the treatment in this case is sunglasses.
Hence 1st option is the correct answer.