Offering financial incentives to make diabetic eye screenings more attractive may backfire, according to a study published in the British Journal of Ophthalmology.

In a three-armed randomized control trial conducted in London, more than 1,000 people who did not attend eye screening appointments for two years or more were sent either an invitation letter (control group), an offer of £10 cash ($13.34) for attending a screening (fixed incentive group) or a one-in-100 chance of winning £1000 ($1,334.75, lottery incentive group) if they attended.

Researchers found those who received incentive offerings were significantly less likely to attend their appointment compared with the control group. Individuals who only received the invitation letter had the best attendance results—7.8% of controls—followed by the group who was offered cash to attend, 5.5%. The lottery incentive group had the lowest response rate of 3.3%.

“Financial incentives, particularly lottery-based incentives, attract fewer patients to diabetic eye screening than standard invites in this population. Financial incentives should not be used to promote screening unless tested in context, as they may negatively affect attendance rates,” researchers said.