<p>Around 12 million people globally are estimated to be blind with age-related cataract and numerous studies have sought to evaluate the causes of this lens opacification, many of these complicated by the difficulty of determining the impacts of varying aetiological factors from daylight through diet, diabetes and many more. While various experimental investigations on laboratory animals have sought to unpick these influences on lens transparency to date none has sought to evaluate age-related cataract across different animal species kept as companion animals. Here we look at a number of studies on companion dogs, cats and horses to determine the effects of daylight, diet, diabetes, dehydration, drugs, genetics (DNA to continue the D alliteration) and trauma (Damage again as a final D).</p>