Retinal Neurovascular Assessment And Choroidal Vascularity Index In Patients With Keratoconus

Keratoconus is a bilateral asymmetric disorder marked by progressive corneal thinning and steepening. Its prevalence varies due to factors like race, age, and lifestyle. While the pathogenesis remains unclear, risk factors such as eye rubbing, family history, atopy, and genetic predisposition have been suggested. Recent studies highlight the role of inflammation, with collagen disorder being a key mechanism in KC. This study investigates the impact of collagen changes on retinal and optic nerve neurovasculature in KC patients, using OCTA, and compares them with healthy emmetropes and myopic-astigmatic controls.

This cross-sectional study, approved by Mashhad University of Medical Sciences, was conducted at Khatam-Al-Anbia Eye Hospital between 2022-2023. Participants (18-40 years) were categorized into emmetropes (E), myopic-astigmatic (MA), and keratoconus (KC) groups. Inclusion criteria for KC patients included specific indices like Skewed Radial Axis (SRAX) and Keratoconus Index (KCI). Exclusion criteria included recent contact lens use, systemic diseases, or prior eye surgeries.

In this study, various imaging techniques were used to evaluate corneal, retinal, and choroidal features in subjects. The axial length was measured with the Tomey optical biometer, and corneal parameters were assessed using TMS-4 and Pentacam AXL. OCT and OCT-A imaging were employed to evaluate macular and optic nerve head (ONH) vascular profiles. Additionally, choroidal thickness and vascularity were measured using EDI-OCT and the Choroidal Vascularity Index (CVI). Statistical analysis was performed using ANOVA and Tukey post hoc tests, with a significance level set at p<0.05.

This study included 143 participants: 50 KCN, 46 emmetropes (E), and 47 myopic-astigmatic (MA). Significant differences in corneal parameters were observed between the KCN and control groups. KCN patients had lower whole image SVD, AVD, and RPC vessel density. Macular vascular parameters (SCP and DCP) were significantly lower in KCN. Choroidal vascularity index (CVI) and choroidal luminal area (CLA) were higher in KCN compared to controls. Correlation analyses showed no significant links between corneal parameters and vascular profiles. Subgroup analysis revealed no differences in vascular or choroidal parameters based on disease severity.

In conclusion, this study highlights significant differences in the macular and optic nerve head vessel densities and an elevated choroidal vascularity index (CVI) in keratoconus (KC) patients compared to control groups. These changes are likely due to oxidative stress, inflammation, and compensatory mechanisms in KC. Although astigmatism may influence OCT-A measurements, the findings emphasize the need for further research to understand better the systemic effects of KC on vascular health, particularly in microcirculation. Future studies with larger sample sizes and more accurate methods are needed to clarify the clinical implications.