While the primary constraint – that the usability of the solution must not be wholly dependent upon its visual elements – is obvious given the target user group, the research phase revealed a number of important possible additional constraints to take into consideration. Firstly, games are played in different environments; in the home, in a pub or café, even outside. If the key feature of the solution, that is, the aspect of the system which facilitates access to the game for the visually impaired user, is entirely dependent on a constant, stable wifi connection, it would become unusable in some locations in which games are played. This problem was flagged by David during our pre-game chat, and under certain circumstances, wifi is even used by sighted players to retrieve more recent rules related information. This is particularly common among players of customisable card games, which receive rules errata and addenda where necessary as each new set of cards is published. Additionally, old cards are often reprinted with updated versions of their text to reflect current conventions, or functionally altered in light of changes made to the game or ambiguous wording, leading to players interpreting it in an unintended manner.
Secondly, diabetic retinopathy is the leading cause of sight loss among working age adults in the UK. This is a complication of diabetes, a condition which also causes sensory neuropathy: a loss of sensation which usually presents in the feet but can also affect the hands and arms of a diabetic, rendering them unable to read Braille. Relying upon haptics to inform the user of the game or system state could therefore result in the exclusion of a significant proportion of potential users.
Thirdly, three quarters of visually impaired or blind people of working age are unemployed. While they are eligible for benefits they also incur costs which sighted people do not – some of which are one off, for instance to buy specialist equipment, and some of which are recurring, for example to pay for taxis to participate in social activities or attend appointments. The solution must not rely on very expensive technology to function.