Final answer:
Christine is concerned about Leroy's eyesight as she comments on the possibility of eye strain due to poor lighting conditions while he works.
Step-by-step explanation:
In the dialogue, Christine expresses her concern about Leroy's eyesight. When she mentions that he is 'working in the dark' and that this might strain his eyes, it indicates her worry about the potential damage to his vision due to poor lighting conditions. This concern is evident as she notes he is straining his eyes while working, implying that insufficient lighting while working could lead to eye strain or deterioration of eyesight.