The agency will focus on High Five, an initiative to raise £5m over three years for the charity, which operates in the North.
The campaign will use what the agency described as 'heart-warming and inspiring' case studies of visually impaired people helped by the charity.
It is also launching a regular news digest to regional media covering Henshaws' work.
AllBigFish is planning a number of summer and autumn activities with an as yet unnamed media partner.
It beat 18-month incumbent Cicada PR, Spin Media and Stormhouse in the pitch for the account.
AllBigFish chief executive Denise Mullen leads the account with director Sue Souter. They report to Henshaws PR and comms manager Vicky Delderfield.