Two intermediate filaments specific to the lens, beaded filament structural protein 1 (BFSP1; also called filensin) and beaded filament structural protein 2 (BFSP2; also called 49 kDa Cytoskeletal Protein (CP49) or phakinin), function to maintain cellular structure and are vital for lens transparency, with mutations of either protein leading to cataracts [33]. The gene discussed is BFSP1; the disease is cataract.