['The main objective of the present study was the investigation of possible influence of lens opacification on macular pigment optical density (MPOD) measurements.', 'Eighty-six eyes of 64 patients (mean age 73.4 ± 8.3 years) were included in the study. MPOD was prospectively measured using the one-wavelength reflection method (Visucam500, Carl Zeiss Meditec AG) before and after cataract extraction, with implantation of a blue-light filtering intraocular lens (AlconSN60WF). The median of the maximum optical density (MaxOD) and the median of the mean optical density (MeanOD) measurements of macular pigment across the subject group were evaluated.', 'Statistically significant differences were noticed between pre-operative and post-operative measurements, the absolute values were generally lower after cataract extraction. The following median (lower/upper quartile) differences across the group were determined: MaxOD -33.8 % (-46.2 to -19.1 %), MeanOD -44.0 % (-54.6 to -26.6 %). Larger changes were observed in elderly patients [<70 years of age (n\u2009=\u200925 eyes): MaxOD -13.4 % (-20.5 to 3.6 %), MeanOD -23.6 % (-30.5 to -15.3 %) versus patients ≥70 years (n\u2009=\u200961 eyes) MaxOD -40.5 % (-53.2 to -30.1 %), MeanOD -47.2 % (-57.8 to -40.1 %)] and in patients with progressed stage of cataract. MaxOD for lens opacification grade 1 (n\u2009=\u20099 eyes): -27.4 % (-42.1 to -19.6 %), grade 2 (n\u2009=\u200926 eyes): -35.0 % (-44.2 to -25.3 %), grade 3 (n\u2009=\u200921 eyes): -34.4 % (-45.4 to -11.4 %), grade 4 (n\u2009=\u200925 eyes): -32.6 % (-53.2 to -6.4 %), and grade 5 (n\u2009=\u20095 eyes): -53.5 % (-61.7 to -38.7 %) and MeanOD for cataract stage 1 (n\u2009=\u20099 eyes): -42.6 % (-46.0 to -26.0 %), stage 2 (n\u2009=\u200926 eyes): -44.1 % (-51.8 to -26.2 %), stage 3 (n\u2009=\u200921 eyes): -45.7 % (-54.7 to -24.7 %), stage 4 (n\u2009=\u200925 eyes): -39.5 % (-59.4 to -26.1 %), and stage 5 (n\u2009=\u20095 eyes): -57.0 % (-66.1 to -51.4 %).'] Does macular pigment optical density measurements by one-wavelength reflection photometry -- influence of cataract surgery on the measurement result?