Measurement of in vivo lens shapes using IOLMaster 700 B-scan images: Comparison with phakometry.

Purpose: This study compared in vivo crystalline lens shape measurements using B-scan images from the IOLMaster 700 with phakometry.

Methods: Twenty-four young adult participants underwent IOLMaster 700 and phakometry measurements under cycloplegia (1% cyclopentolate). The IOLMaster 700 generated B-scan images along six meridians in 30° increments, which were analysed using custom MATLAB software to determine lens surface radii of curvature. Phakometry measurements were obtained using Purkinje images reflected from the lens surfaces.

Results: The IOLMaster 700 image analysis method yielded a lower mean anterior lens surface spherical equivalent power (+6.20 D) than phakometry (+7.55 D); however, the two measurements were strongly correlated (R₍₂₁₎ = 0.97, p < 0.0001). The astigmatic power vectors (J₀ and J₄₅) for the anterior lens surface were significantly higher for the IOLMaster 700 measurements, with only J₀ showing a significant moderate positive correlation (R₍₂₁₎ = 0.57, p = 0.005). For the posterior lens surface, the IOLMaster 700 measurements had a higher mean spherical power (+14.28 D) compared to phakometry (+13.70 D); however, a strong positive correlation (R₍₂₁₎ = 0.90, p < 0.0001) was observed. No significant correlations were noted for posterior lens surface astigmatic vectors (J₀ and J₄₅). The IOLMaster 700 estimates for the equivalent lens mean spherical power were slightly lower than those for phakometry, with a mean difference of -0.72 D, and both methods were positively correlated (R₍₂₁₎ = 0.94, p < 0.0001).

Conclusions: The findings demonstrate that IOLMaster 700 B-scan image analysis technique provides similar estimates of lens surface powers to phakometry. These results highlight the potential of the IOLMaster 700 to provide measurements of lens shape, informing future research and clinical use.