Sweet poison for the eyes: High-Fructose diets as drivers of metabolic disruption and ocular diseases - Insights and therapeutic horizons.

Excess consumption of added sugars, commonly delivered through sucrose and high-fructose corn syrup, has increased in parallel with obesity, metabolic syndrome, and type 2 diabetes. These systemic metabolic disturbances are consistently associated with a range of ocular conditions. However, whether high-fructose intake exerts independent and fructose-specific effects on ocular tissues remains uncertain, because most human evidence is indirect, often mediated through metabolic syndrome phenotypes, and frequently confounded by mixed dietary exposures and total energy intake. This review synthesizes mechanistic pathways that are plausibly enriched by fructose biology, including hepatic fructose metabolism with ATP depletion and uric acid generation, oxidative and inflammatory signaling, altered lipid handling, and gut barrier and microbiome perturbations. We evaluate how these systemic changes may intersect with ocular surface homeostasis, retinal neurovascular integrity, intraocular pressure regulation, and choroidal and macular vulnerability. Across dry eye disease, diabetic retinopathy, glaucoma-related outcomes, age-related macular degeneration and choroidal neovascular responses, and cataract, we distinguish fructose-specific exposure studies from metabolic syndrome only and mixed diet reports, and we emphasize limitations related to exposure definition, replication, and translation to humans. Overall, current evidence supports the view that excess fructose may amplify ocular susceptibility in metabolically stressed states, but direct causal links in humans remain preliminary. We conclude by outlining methodological priorities and testable study designs needed to clarify fructose-specific contributions to ocular disease risk. Some experimental findings, particularly those related to ocular-surface responses, originate from single research groups and require independent replication, underscoring that current evidence remains preliminary and hypothesis-generating.