Purpose To determine the relationships between lens thickness (LT), lens density and anterior segment parameters in patients with mild to moderate cataracts. Setting Oftalmosalud Instituto de Ojos, Lima, Perú. Design Prospective, single-centre, cross-sectional study. Methods 169 eyes with age-related mild to moderate cataracts had lens density assessed using the Lens Opacification Classification System III, the built-in Pentacam HR Nucleus Staging software and ImageJ software. LT and axial length (AL) were measured with the IOLMaster 700, and angle parameters were measured using anterior segment optical coherence tomography. Pearson correlation coefficients and Kruskal-Wallis tests were used for statistical analyses. Results Nuclear colour score was the only clinical parameter with a weak significant correlation with LT (r=0.24, p=0.003) after accounting for age, AL, gender and anterior chamber depth (ACD). The maximum value of average lens density and the mean nuclear density were significantly correlated with LT (r=0.24, p=0.003 and -0.17, p=0.03, respectively) after controlling for the same factors. Central LT greater than 4.48 mm was present in 54.5% of the eyes with a nuclear opalescence grade 1. Conclusions LT is independent of lens density in mild to moderate cataracts after accounting for age, AL, ACD and gender contrary to previous studies.