Our study aims to evaluate the relationship between KP enzyme activities and key ocular phenotypes by correlating KAT and KMO activities measured indirectly via KYNA/KYN and 3-HK/KYN ratios with nuclear cataract severity as graded by SPONCS and determining how these activities differ in patients with diabetes, glaucoma, and PEXS. The gene discussed is NPPA; the disease is diabetes mellitus.