I read both Jane Eyre and Wide Sargasso Sea while thinking about the Modern Lit class I took this summer, which focused on the effects of colonialism. So while it isn't an official critical lens, I'm going to look at them in that sense.
Much like with the triangle trade, you have the love triangle of Antoinette\Bertha, Edward Rochester and Jane Eyre. Antoinette\Bertha is basically used up and then discarded, as in the colonies. She suffers immensely, loses touch with reality and is renamed, all of which directly translates to the experiences of both the enslaved brought from Africa and the native peoples of the Americas. But I think Jean Rhys wants you to see all of that.
More interesting is the way that this applies to Jane Eyre, which was not written with the effects of colonialism in mind. Yet we still see the same themes in the live triangle, but this time the colonies are something foreign and wild, uncontrolled. The colonies are not prim and proper and disciplined like a proper Christian, an ideal human, should be. An interesting addition to this is how St. John is off to India, another British colony, to perform missionary work. Jane knows that he is off to seek his death, because India is another place that is wild and untamed, dangerous, wild and uncontrolled. And Jane is right - India does kill him. There seems to be a general mistrust of the colonies, as valued as they were for the material goods that they provided.
Both novels comment pretty deeply on what a huge impact colonialism had on both the colonized and the colonizer. It's far more obvious in Wide Sargasso Sea, but even Jane Eyre mentions it in two parts, which is significant, since Bronte could easily have left them out of the plot and had her characters that needed to be from/go to places far away go somewhere in Europe just as easily. But she doesn't - she chooses to focus on colonies as untamed places where madness, licentiousness and death endanger good Christians.