The macular microvasculature evaluated by OCTA in various stages of keratoconus compared to healthy controls: A cross-sectional study

OBJECTIVE: To investigate the macular microvasculature and thickness in keratoconus (KCN) cases with various stagings and compare them with healthy controls. DESIGN: Cross-sectional METHODS: 110 eyes of 57 KCN cases (35 males and 22 females) and 150 eyes of 75 controls (25 males and 50 females) entered this cross-sectional study. After a thorough ophthalmic examination and corneal tomography with Pentacam, KCN cases were staged using the Amsler-Krumeich classification. All included eyes underwent macular OCTA using the RTVue XR Avanti system, evaluating vessel density in the superficial and deep capillary plexus (SCP and DCP) in various macular segments, the foveal avascular zone (FAZ) area, and the foveal flow area. Linear mixed-effect models were used to compare parameters between groups, adjusted for age and sex, while accounting for inter-eye correlation. RESULTS: In the KCN group, the majority of eyes were in stages 2 and 4 of KCN, 34 eyes (30.9%) in each stage. 22 eyes (20%) were in stage 1, and 20 eyes (18.2%) were in stage 3. The macular vessel density (VD) adjusted for age and gender was significantly lower in KCN cases compared to the controls in all areas in both superficial and deep capillary plexus, except the parafoveal DCP VD, which showed no significant difference. However, macular thickness did not differ significantly between KCN cases and controls. The macular VD in most areas was also significantly lower in stage 4 cases than in stage 1 cases. CONCLUSION: This finding supports the concept that keratoconus may involve posterior segment microvascular alterations in addition to corneal ectasia. Future prospective studies applying standardized OCTA protocols and longitudinal follow-up are needed to determine whether these changes have prognostic value or demonstrate a broader systemic phenotype.