Originally marketed as 'Starlight Eyes' by a NovaPharma subsidiary in the early 2180s, this cosmetic modification replaces the tapetum lucidum's passive reflective function with active bioluminescence, causing the cat's eyes to emit a soft, sustained glow in low-light conditions. The product was intended for domestic cats and was commercially successful for approximately three years before the manufacturer discovered the modification was heritable — passing from modified cats to all offspring regardless of the other parent's modification status. By the time the product was discontinued, enough modified domestic cats had been abandoned or escaped to establish breeding populations throughout the Shelf. The feral cat population of the Circuit District now carries the modification at an estimated 90% prevalence. Three color variants exist: green (dominant, ~82%), amber (~15%), and blue (rare, ~3%). An unintended functional consequence: the modified tapetum has expanded feline visual sensitivity into near-ultraviolet wavelengths, making Circuit ferals significantly more capable predators in low-light and no-light conditions.