Dickens describes Pip's first impressions, or visions, of Estella and Miss Havisham in order to convey to his reading public that not only the poor, but also the rich are imprisoned, although in a different manner.
Estella leads Pip through the corridors as one who is superior to him; with a name that denotes "star," she lights the way for him and speaks as though she has authority. But, before this they pass by the iron bars on the windows of the house that has a gate with chains across it, much as a prison does. Inside in a shadowed room, Pip meets the prisoner of her own house, Miss Havisham, a woman lost in time and the "strangest woman [he] had ever seen."
One of the motifs of Great Expectations is that society is a prison, meaning that there was no upward mobility for the lower classes, and sometimes no happiness for the wealthy. So, just as the convict that Pip meets has been imprisoned, so, too, are Miss Havisham and Estella imprisoned in the Manor House, ironically named Satis House, a name suggesting that the occupants inside have everything for which they could ever want. As Pip has observed, the house is barred, it is dark and dusty. There is "no glimpse of daylight...to be seen."