Carbon quantum materials for ocular nanotheranostics: Dimensionality-guided design for barrier transport, drug delivery, and therapeutic function

Ocular drug administration faces significant challenges since anatomical barriers, rapid precorneal clearance, and the blood-retinal barrier collectively restricts drug penetration and reduces ocular bioavailability to less than 5%. Although polymeric, lipid-based, and inorganic nanocarriers have advanced the research. Persistent inflammation, poor biodegradability, metal ion-mediated toxicity, and inadequate multifunctionality impede clinical translation Carbon quantum materials (CQMs), which include zero-dimensional carbon quantum dots (CQDs), one-dimensional carbon nanotubes (CNTs), and two-dimensional graphene derivatives, have emerged as a structurally programmable and therapeutically adaptable platform to solve these constraints. This article provides a unified design approach in which material dimensionality serves as an important framework for relating CQM structure to ocular therapeutic function, while final performance also depends on size, surface chemistry, defect structure, and functionalization. Depending on material properties, surface functionalization, and administration route, CQDs can support corneal transport, antioxidant activity, and fluorescence-based imaging; CNTs can support scaffold-assisted delivery and ocular neural interfacing; and graphene derivatives can provide large-area and electroactive interfaces for biosensing, responsive drug release, and implantable devices. This review examines how atomic-level structural factors relate to ocular barrier trafficking and therapeutic function across eye segments, as well as the efficacy of CQM platforms for diverse disorders.