The evolution of visual systems is guided by visual requirements imposed by the environment, the size of the animal's eyes, and physical limitations imposed by the resolution-sensitivity trade-off. Given a particular eye surface area, resolution and sensitivity cannot be simultaneously maximized: gains in resolution, the ability of the eye to detect detail, will come at the cost of sensitivity, the ability to capture photons, and vice versa, without an increase to eye size. How this constraint interacts with ecology and whether it allows the fine-tuning of the visual system to smaller scale habitat heterogeneity remains an understudied question in visual ecology. Here, we use closely-related species of damselflies in the Hawaiian genus Megalagrion which differ in ecology to test whether variation in the resolution-sensitivity trade-off is the evolutionary result of scaling or differences in microhabitat use. We use regression analyses and phylogenetic comparative methods to examine the effects of size and microhabitat use on traits related to light sensitivity and visual resolution. We find that eye size is tightly associated with body size in these damselflies, but other visual morphology traits related to light sensitivity and resolution are associated with microhabitat type. Furthermore, size and morphology relationships vary across microhabitats, and performance related to resolution tends to be more conserved than to variation in light sensitivity. Additionally, smaller species in visually challenging microhabitats have more regionalized eyes than species with larger eyes in open, well-lit areas. Thus, regionalization of the eye allows a decoupling of size and morphology/performance so that even small insect species can exploit visually challenging habitats. These results suggest that variation in visual performance results from changes in eye geometry as well as size. These morphological changes are likely adaptive to differences in microhabitat, indicating that variation in microhabitat use, even at small scales, can play an important role in the evolution of visual systems.