Contributes to the transparency and refractive index of the lens (PubMed:18302245). In its oxidized form (absence of intramolecular disulfide bond), acts as a chaperone, preventing aggregation of various proteins under a wide range of stress conditions (PubMed:18199971, PubMed:19595763, PubMed:22120592, PubMed:31792453). Required for the correct formation of lens intermediate filaments as part of a complex composed of BFSP1, BFSP2 and CRYAA (PubMed:28935373). {ECO:0000269|PubMed:18199971, ECO:0000269|PubMed:19595763, ECO:0000269|PubMed:22120592, ECO:0000269|PubMed:28935373, ECO:0000269|PubMed:31792453, ECO:0000303|PubMed:18302245}. This is the function of ENSG00000160202 (CRYAA, crystallin alpha A).