How is symbolism used in "The Lady with the Pet Dog" to portray the theme of isolation?

The theme of isolation in “The Lady with the Pet Dog” is portrayed through darkness and silence that often obscures the characters from each other and through lonely images associated with travel. On the night that Anna and Dmitri first sleep together, they go to the harbor to watch a ship come in. The ship takes a long time to arrive, and by the time it docks it is “too dark to see people’s faces” (5). The wind dies away and the people from the ship depart so that it is still, silent, and pitch black when he suggests they go back to Anna’s room.
Later, when Anna goes home to take care of her sick husband, Dimitri stands on the train platform: “The train moved off rapidly, its lights soon vanished from sight, and a minute later there was no sound of it, as though everything had conspired together to end as quickly as possible that sweet delirium, that madness.” Again, there is a lone transport vehicle, silence, and darkness, separating the characters.
Even in the final scene when it seems they may finally find a way to be together, the blocking creates a sense of separation. Anna keeps her back to Dmitri so that he can’t see her face. When he goes to her at the window, he looks not at her, but at himself. He notices that he looks old and realizes that women never see him as he sees himself: “He always seemed to women different from what he was, and they loved in him not himself, but the man created by their imagination” (19).
http://www.shortstoryamerica.com/pdf_classics/chekhov_lady_withthe_pet_dog.pdf