May contribute to the transparency and refractive index of the lens. Has chaperone-like activity, preventing aggregation of various proteins under a wide range of stress conditions. In lens epithelial cells, stabilizes the ATP6V1A protein, preventing its degradation by the proteasome (By similarity). Heteromer composed of three CRYAA and one CRYAB subunits. Aggregates with homologous proteins, including the small heat shock protein HSPB1, to form large heteromeric complexes. Inter-subunit bridging via zinc ions enhances stability, which is crucial as there is no protein turn over in the lens. Interacts with HSPBAP1 and TTN/titin. Interacts with TMEM109. Interacts with DES; binds rapidly during early stages of DES filament assembly and a reduced binding seen in the later stages. Interacts with ATP6V1A and with MTOR, forming a ternary complex (By similarity). Translocates to the nucleus during heat shock and resides in sub-nuclear structures known as SC35 speckles or nuclear splicing speckles. Localizes at the Z-bands and the intercalated disk in cardiomyocytes. Belongs to the small heat shock protein (HSP20) family.