Quantifying retinal size and shape distortion in different ultra-widefield imaging systems.

Objective: To quantitatively investigate the retinal size and shape distortion in different ultra-widefield (UWF) imaging systems.

Methods and analysis: We imaged the posterior segments of model eyes using Daytona, Mirante, CLARUS 500, VG2001, BMizar and TRC-NW8. We measured the scale bars of each grid and the compactness of each ring to quantify the size and shape distortion. The relationship between the relative size with eccentricity and axial length was analysed. The size and shape distortion were compared among different UWF systems.

Results: The size is positively associated with eccentricity (β=0.202-0.482; p<0.001) and negatively associated with axial length (β=-0.787 to -0.890; p<0.001) in all UWF systems. There is a significant difference in slopes across devices. The size distortion of Mirante is lower than the other UWF systems (p=0.0083-0.0472) except for TRC-NW8. Multivariate linear regression analysis found the adjusted R²=0.809-0.948, which was improved to more than 0.960 with a quadratic polynomial equation. Only Daytona showed shape distortion, and the compactness of Daytona is smaller than the others (p<0.0001).

Conclusion: Quantitative measurements identified different relationships between size distortion with axial length and eccentricity in different UWF systems, which can serve as a reference for correcting size distortion. Shape distortion only occurs in Daytona.