Quantitative evaluation of choroidal thickness and vascularity in subclinical keratoconus: a cross-sectional EDI-OCT study.

PURPOSE: To assess choroidal thickness (CT) and choroidal vascularity index (CVI) in a subclinical keratoconus (SK) population.

METHODS

A prospective, cross-sectional analysis was performed on 42 participants of unilateral keratoconus (KC), defined by clinical keratoconus (CK) in one eye and SK in the contralateral eye along with 42 age- and sex-matched healthy control participants. CT measurements were obtained at the subfoveal, nasal 750 µm (N750), and temporal 750 µm (T750) locations. Measurements of CVI, luminal area (LA), stromal area (SA), and total choroidal area (TCA) were calculated from enhanced depth imaging optical coherence tomography (EDI-OCT) images. Generalized estimating equations were used to account for the inter-eye correlation between CK and SK eyes.

RESULTS

CT values at all three measured points differed significantly among the study groups (all p < 0.001). Both the CK and SK groups exhibited significantly greater CT than the control group at all measured locations. CK eyes also demonstrated significantly greater subfoveal CT than SK eyes (adjusted p = 0.003), whereas nasal and temporal CT did not differ significantly between the CK and SK groups. The CK group exhibited a significantly larger TCA than both the SK (adjusted p = 0.019) and control groups (adjusted p = 0.005). No significant differences were observed in LA (p = 0.173) or CVI (p = 0.104) among the groups, while SA demonstrated a significant overall group difference (p = 0.011), which was attributable only to the comparison between the CK and control groups (adjusted p = 0.016).

CONCLUSION

The findings demonstrate increased CT in both CK and SK, whereas most quantitative choroidal vascularity parameters remained unchanged. These observations suggest that choroidal thickening may represent an early structural alteration in the keratoconus spectrum. However, these findings represent associations only, and the underlying biological mechanisms and their prognostic significance cannot be determined from this cross-sectional design.