Ruth Perrott travelled to Tanzania as part of a group from the York Ainsty Rotary Club.
An estimated 350,000 people live on Ukerewe, with many living there on an income of about £1 a day.
On previous visits to the island, members of York Ainsty Rotary Club have helped to update parts of a hospital in Nansio to include a maternity waiting hostel, as well as helping to provide running water and filters.
In addition to testing the sight of local people, during this visit the team, who were supported by two Swedish Rotarians, replaced old local hospital mattresses with new ones and distributed water filters to 38 local schools.
The group hosted six clinics during their trip, testing 759 people and dispensing spectacles to 569 people.
During the testing Ms Perrott was supported by local ophthalmic nurse, Celine, whom she taught refraction during the clinics. Before leaving Ms Perrott donated her pocket retinoscope and optical flippers to the nurse so she could continue to test. Commenting on this, Ms Perrott told OT: “It is so deeply satisfying to teach myself out of a job.”