- Blindness: Visual acuity <3/60 in the better eye
- Vision Impairment: Moderate & Severe Visual Impairment with visual acuity <6/18 to ≥3/60
- Vision Impairment: Mild with visual acuity <6/12 to ≥6/18
- Prevalence: The prevalence is the percentage of a population that is affected with vision impairment or blindness. The data are age-standardized for comparability
- Population Affected: Calculated based upon the total population and the crude prevalence rate
How to use the maps
The GVD dataset provides several data-points to access. Our new map designs let you toggle between the following aspects:
Selecting either ‘Blind’, ‘MSVI’ or ‘Mild’ on the navigation panel (to the right) toggles between these three conditions. At the bottom of the navigation panel is a key matching the intensity of colour with prevalence of the condition (lighter is lower, darker is higher prevalence). This gives us a global perspective on prevalence. Running your mouse over each country, or tapping on a touchscreen, will give you the name of the country, the prevalence rate, the country’s population and the population affected – as at the date for the year you select at the top; as the GVD dataset has been prepared for different years (1990-2015 with projections to 2020), the mouseover or tap shows you the year under consideration. The percentage given is the age-standardised prevalence which accounts for the difference in age structure between populations.
The ‘population affected’ figure represents the number of people according to the condition, sex, age, and year that you selected. This figure multiplies the ‘crude prevalence’ (not age-standardised) by number of population, to give the number of population affected by vision impairment or blindness.
NB: One of the key aspects of the GVD dataset is the ability to compare prevalence of changes over time. You will note that, by default, the data is set to ‘2015’. You can run the time-lapse feature or toggle the years by clicking the year at the top to take you back in time.
Once you have chosen the condition, you can now choose to look at prevalence in men, women or both sexes combined. This is also a powerful aspect, hitherto unavailable with existing datasets. We now know, for example, that women represent 55% of blindness and vision impairment. Again, you get country-wise information by running your mouse over, or tapping, each country.
NB: Again, note the time aspect as you toggle through these options.
The GVD dataset allows us to look at two separate age categories – all ages and those aged 50 years and older. This becomes helpful because older populations account for a higher proportion of vision impairment and blindness. By running the mouse over, or tapping on, each country these variations stand out.
NB: The ‘population’ figure on mouseover/tap refers to the total population by age category. For example, the total population of France for 2015 is 64.39 million (all ages) and 24.63 million (adults aged 50 years and older).
The prevalence of blindness, MSVI and Mild have been in decline over the past 25 years. The timelapse option, from 1990-2015, (click the play button at the top left) makes this evident in a powerful and graphical manner.
An exciting develoment for World Sight Day 2017, the addition of Causes maps enable you to see the breakdown by GBD Region for the seven commonest causes broken down by year, age, prevalence type, and condition.
These maps are fully interactive, with live updates so you can hover/tap, for example on Eastern Europe (for 2015, All Ages, Crude Prevalence, Blind) and see that the crude prevalence for all causes combined is 0.41%, affecting 857,494 people. Select 2020 and hover over the same region and you will see that the crude prevalence is predicted to fall to 0.39%, affecting 804,214 people.
Now click the region, and you will see how the 0.39% Crude Prevalence breaks down by specific cause – hover over or tap on one of the pie chart segmants and you will see the breakdown of that cause (AMD, for example, has a crude prevalence prediction of 0.07%, predicted to affect approx 150,000 people by 2020). Remember this is still for 2020, All Ages, Crude Prevalence, Blind. But now select Severe/Moderate and the pie chart will instantly update showing the change in ‘real time’.
Also new for World Sight Day 2017, the Near-Vision Loss tab allows you to see the population affected. Near-Vision Loss figures were introduced using 2015 numbers, with 2020 estimates also shown when you hover over or tap any of the 21 GBD regions.