The plasticity-first hypothesis offers an explanation for the rapid evolution of convergent traits. It suggests that adaptation to new environments relies on the plastic appearance of phenotypic traits that become genetically assimilated through the rewiring of existing developmental and homeostatic networks. However, how the initial plastic responses, especially maladaptive, influence derived phenotypes over evolutionary time remains elusive. Here, we will use the Mexican tetra, Astyanax mexicanus, as a model system to address this question. This species is comprised of ancestral surface fish that independently colonized caves and evolved into cavefish. Cavefish exhibit novel traits, such as eye loss, depigmentation, sensory system expansions, and metabolic changes, which evolved within a remarkably short evolutionary timespan. Our previous study revealed that surface fish raised in complete darkness express many cavefish-like traits within a single generation, while cavefish traits are robust to environmental perturbation. Surprisingly, the eyes of dark-reared Astyanax surface fish and also in a cave population of the unrelated fish Telestes karsticus showed a maladaptive plastic response: increased thickness of the retinal layers. This suggests that convergent mechanisms underlie eye development in surface fish exposed to darkness and that eye degeneration in cavefish involves compensatory processes to overcome and reverse this initial maladaptive plasticity. We aim to investigate eye traits in ancestral Astyanax surface fish, multiple generations of dark-raised surface fish, and evolved cavefish, to understand the developmental, cellular, molecular, and epigenetic processes driving plasticity, compensatory mechanisms against maladaptive plasticity, and the transition to trait robustness in cavefish. Our findings will illuminate the mechanisms of rapid evolution and convergence, shedding new light on fundamental processes driving phenotypic diversity in nature.