AbstractPurpose to study changes of a crystalline lens’s physical properties with the yearsMethods Patients at the age from 57 to 90. 73 crystalline lens’s nuclei with a cataract of the various maturities, received by a method of the extracapsular extraction were investigated. Before operation we determined relative acoustic density of a crystalline lens by an original technique, also we estimated color of a crystalline lens and weight of a lens’ nucleus.Results We revealed that brown color of a crystalline lens’s nucleus a little intensify with the years ‐ the correlation factor is equal 0.4 (р <0.05). Average value of relative acoustic density was 0.59 ± 0.01. Average weight of a lens’ nuclei was 98.3 ± 1.0 mg. The average density of a lens’ nuclei was 1312 ± 12 mg m2. It’s revealed that the mature cataract isn’t always rigid: the correlation factor is equal ‐0.4 (р <0.05). If density of a crystalline lens increases, a mechanical hardness increases too– the correlation factor is equal 0.4 (р <0.05). At the same time, a mechanical hardness of a crystalline lens’s nucleus reinforces with the years, factor of correlation is 0.74 (р <0.05). It’s revealed that the age isn't a determining factor in appearance and cataract progressing.Conclusion Mechanical properties of a crystalline lens depend on change of its chemical compound, at ageing there is a increasing of brown coloring of a crystalline lens and mechanical hardness of a crystalline lens’s nucleus, visual acuity thus can change slightly. Processes of maturing of a cataract and increase in hardness of a crystalline lens are chemically different and go not in parallel each other.