There is new data in the Sight Loss Data Tool on the incidence of sight loss. This article explains what that term means, where the data has come from and how it might be useful for you.
Incidence
Incidence is the number of people who have started to live with sight loss in the last 12 months. This is different from prevalence, which is the total number of people living with sight loss at any one point of time.
Think of prevalence as a snapshot whole picture, and incidence as the new pieces being added over a specific period of time.
Data
In 2017, RNIB commissioned Deloitte Access Economics to estimate incidence and lifetime risk of sight loss. This report developed a model that considered prevalence, risk of mortality, life expectancy and demographic changes.
We regularly use the key message that “250 people a day start to lose their sight”, which comes from this project.
The report also provided underlying incidence rates by age band and sex. We can apply these rates to official population projections to generate new estimates for local areas in the UK. This is the same approach we use to generate prevalence estimates.
To be included in the incidence estimates, someone must have experienced permanent and irreversible sight loss as a result of eye conditions such as age-related macular degeneration, glaucoma and diabetic retinopathy.
Usage
The intention of including the incidence estimates in the Sight Loss Data Tool is to provide another way to express demand and the potential need for support services in your area. Like any modelled estimate, there are local factors that will also influence demand, and expert local knowledge will help with the interpretation.
The incidence estimates can be seen as supporting prevalence estimates. Just think of one being the snapshot of the whole picture, and the other the new, and permanent, pieces being added.
Finally, it’s important to consider the relationship between the new incidence estimates and Certification of Vision Impairments (CVIs),
Incidence estimates are higher than the number of CVIs issued each year. Therefore, they reflect the wider potential need for practical and emotional support. It’s important to remember each CVI is issued to an actual individual, whereas the incidence data is a modelled estimate.
CVIs still provide a useful indicator of new referrals from health to social care, particularly the variation between different local authorities. However, they don’t capture everyone starting to live with sight loss each year – and this is the gap that that new incidence data can start to address.