The thirteenth-century encyclopaedist, Bartholomaeus Anglicus, whose work was later translated into the vernacular by John Trevisa, included excessive alcohol consumption in his list of the possible causes of blindness; individuals who constantly deluged their body with unhealthy liquids would inevitably damage their eyesight. Bartholomaeus’ statement underscores the medieval theological and medical belief that most sufferers were responsible, at least in part, for their misfortunes. Classical Greek authorities had stressed that it was essential to keep the four humours – blood, phlegm, black and yellow bile – in balance by carefully following a regulated lifestyle appropriate to one's age, gender and environment. These ideas were readily adopted and fostered by the medieval Church as they accorded perfectly with the Christian belief that individuals should be personally responsible for following a regimen that was geared to restraint and moderation. For example, the Apocryphal Book of Sirach warned that too much wine would make even the wisest of men go astray. However, as Bartholomaeus’ entry shows, there were many different causes of eye complaints; in addition to failing to maintain one's humoral balance, an act as simple as staring at the sun or lengthy exposure to a cold wind could upset the eye's delicate equilibrium.

Because theologians often (but not always) equated disability with sin, some surveys of the disabled in the period before industrialisation take it as read that those with sensory impairments, such as blindness, must have been pushed to the margins of society or even completely excluded, and were forced to beg or join troops of wandering minstrels in order to earn a living. Family members suffering from physical and sensory disabilities have been described as burdens, reliant upon their kin to support them and unable to contribute to the household economy in return.