Posterior segment alterations in keratoconus patients: an updated comprehensive review

Keratoconus (KC) has traditionally been classified as a progressive anterior segment disorder, primarily affecting the cornea. However, emerging evidence from advanced imaging modalities-such as optical coherence tomography (OCT), OCT angiography, and enhanced depth imaging (EDI-OCT)-has revealed a broader spectrum of ocular involvement, including significant alterations in the posterior segment. This narrative review explores the structural and vascular changes observed in the retina, choroid, macula, and optic nerve head in KC patients, drawing on findings from more than 40 peer-reviewed studies. Retinal thickening, particularly in the central and parafoveal regions, has been consistently reported, with some studies suggesting a correlation between retinal morphology and disease severity. Vascular density reductions, especially in the superficial capillary plexus and radial peripapillary capillaries, have also been documented, suggesting microvascular compromise potentially associated with KC progression. Choroidal thickness appears to be increased in both pediatric and adult populations, with some evidence linking these changes to disease stage and systemic factors such as atopy. Although findings on macular thickness are more variable, patterns of thickening in early disease and thinning in advanced stages have been observed. Alterations in optic nerve head morphology and retinal nerve fiber layer parameters have also been noted, particularly in advanced or post-surgical cases. Taken together, these posterior segment changes challenge the traditional anterior-centric view of KC and suggest a more systemic ocular remodeling process. Understanding these alterations may enhance disease staging, prognostication, and personalized management strategies. While current evidence supports the clinical relevance of posterior segment evaluation in KC, further longitudinal studies with standardized imaging protocols are needed to clarify causality, functional implications, and potential therapeutic targets.