Contributes to the transparency and refractive index of the lens. May act as a chaperone, preventing aggregation of various proteins under a wide range of stress conditions. Heteropolymer composed of three CRYAA and one CRYAB subunits (By similarity). Inter-subunit bridging via zinc ions enhances stability, which is crucial as there is no protein turn over in the lens. Can also form homodimers and homotetramers (dimers of dimers) which serve as the building blocks of homooligomers (By similarity). Within homooligomers, the zinc-binding motif is created from residues of 3 different molecules. His-100 and Glu-102 from one molecule are ligands of the zinc ion, and His-107 and His-154 residues from additional molecules complete the site with tetrahedral coordination geometry (By similarity). Translocates to the nucleus during heat shock. Belongs to the small heat shock protein (HSP20) family.