Structural alterations in the retina and choroid of keratoconus patients detected by optical coherence tomography: A systematic review and meta-analysis.

Keratoconus (KC) is a progressive corneal disorder that typically manifests during adolescence characterized by corneal thinning and irregularity. Recent studies have revealed that pathoanatomical abnormalities may not be limited to the anterior segment. Posterior segment alterations may also occur in KC patients. We provide a comprehensive review of the posterior segment changes in KC and assess the role of optical coherence tomography (OCT) in detecting these alterations. An initial systematic search of PubMed, EMBASE, and Web of Science was conducted on November 28, 2024. To identify any newly published literature, the search was updated on September 1, 2025. Random-effects models were employed to calculate pooled effect estimates. A total of 38 studies involving 4584 eyes were reviewed, and 26 studies (3124 eyes) met our eligibility criteria for meta-analysis. The remaining 12 studies, although not included in the quantitative synthesis, were reviewed and their findings integrated. Our systematic analysis revealed significant reductions in several macular measurements, including average and temporal parafoveal (inner ring) thickness as well as temporal and superior perifoveal (outer ring) thickness. Peripapillary parameters also showed notable decreases, specifically in lamina cribrosa thickness, average retinal nerve fiber layer (RNFL) thickness, and RNFL thickness in the superior, temporal, and inferior quadrants. By contrast, subfoveal choroidal thickness was significantly increased in KC patients. Additionally, optic nerve head parameters, including cup area and cup volume, showed significantly greater values. When comparing different stages of the disease, patients with moderate KC exhibited significantly higher superotemporal RNFL thickness than those with severe disease. This meta-analysis underscores the concept that keratoconus, primarily a corneal disease, is associated with retinal and choroidal structural abnormalities. Changes in the posterior segment were similar across mild and advanced stages of the corneal disease. OCT monitoring in KC patients can facilitate detection of these alterations.