In Europe we live in an increasingly ageing society and solutions that help that ageing society to self care in context are a major goal for the EU and UK governments. Given this climate coupled with the fact that more than 80% of people aged 35-54 own a mobile phone (National Statistics, 2003) we believe that developing an easy to use application for self diagnosis may be of great use to this age group as they grow older. In our paper we present how we designed one such mobile application, targeted to 40-55 years olds with declining eyesight. Our system enables users to undertake self diagnosis via their mobile phone. This article reports our findings on the challenges of interface design for this particular age group.