The Sandman?

I have to admit that I'm not sure I completely understand the meaning and context of the story "The Sandman".  Is Nathanel's comical yet tragic experience with Olimpia supposed to be an indication of the importance of determining to what degree our senses can be deceived?  In this case, the story would seem to emphasize our ability to approximate such a determination through the science of optics.  I suppose that this is why philosophers such as Descartes must have been so interested in the science of optics.  It makes sense that Descartes, who begins his Meditations by disregarding all of his a posteriori knowledge and doubts his senses, would want to determine precisely how and with what degree of accuracy these senses perceive the material world.