Eye screening linked to fall in sight loss in people with diabetes

July 27, 2017 420

"The proportion of diabetics who go blind or suffer sight loss has almost halved since a new national retinopathy screening programme started in 2007," BBC News reports. The screening programme was in fact launched in 2003 but rolled out to all diabetic people over the age of 12 by 2007.

The main risk to vision for people with diabetes is diabetic retinopathy, a condition where high blood sugar levels damage the retina, leading to sight loss and even blindness.

Because of this, an NHS screening programme for people with diabetes in England and Wales was launched in 2003.

This latest study looked at patient data from Wales to assess whether the programme had been successful in preventing cases of sight loss arising from diabetic retinopathy.

Results suggest that it has been. The number and rate of people with diabetes who went on to have a Certificate of Visual Impairment decreased from 2008 to 2014.

This shows the potential of screening for diabetic retinopathy to prevent future sight loss, but detailed interpretation of the results is difficult without data from before the screening programme. The reduction could also be down to other factors, such as general increased awareness of diabetes and improvements in care.

If you have diabetes, whether type 1 or type 2, it’s important to get your eyes checked once a year. If you haven’t received a letter inviting you to a screening appointment in the past year, contact your GP.

Where did the story come from?

The study was carried out by researchers from Swansea University, Cardiff University, Cardiff and Vale University Health Board, Moorfields Eye Hospital and King’s College London, all in the UK. The authors did not declare any competing interests.

It was funded by the Wales School of Primary Care Research and the Diabetes Research Unit Cymru.

The study was published in the peer-reviewed BMJ Open on an open-access basis, meaning it’s freely available to read online.

The BBC reporting of the story was generally accurate, although the headline declaring "Diabetic sight loss cut by screening" is not necessarily correct, as there are a number of potential reasons for the reduction in sight loss in people with diabetes.

What kind of research was this?

This was a retrospective analysis of data. This means the researchers looked back at data on the number of new certifications for visual impairment and blindness over a period of eight years to examine any trends – in this case, related to diabetic retinopathy.

This type of research is good at identifying possible associations. However, it cannot determine cause and effect, and therefore cannot prove that the implementation of screening directly caused a reduction in the number of people with visual impairment from diabetic retinopathy.

Diabetic retinopathy is related to type 1 and type 2 diabetes, as having high blood sugar levels damages the retina. It can lead to sight impairment (SI) and severe sight impairment (SSI) if not detected and treated early, and is therefore high on the public health agenda.

Diabetic retinopathy is one of the most common causes of sight loss among people of working age.

What did the research involve?

This was a retrospective analysis of data on the number of new certifications of SI and SSI where the main cause was diabetic retinopathy or maculopathy (diabetic eye disease affecting the central part of the retina). The data came from Wales, for the period 2007 to 2015.

The screening programme for diabetic retinopathy was launched in Wales in 2003 and, by the end of 2006, all people over the age of 12 in Wales known to have diabetes were offered an appointment for screening. This study aimed to see if earlier detection through screening was associated with a fall in cases of SI and SSI.

The level of sight impairment was assessed by looking at the clarity of vision (visual acuity) as well as the field of vision (for example, was there tunnel vision).

Researchers also looked at the population in Wales and the number of people with diabetes as recorded by relevant health statistics.

What were the basic results?

In Wales in 2014-15, there were 339 fewer new certifications for SI and SSI from any cause than there were in 2007-8. Specifically:

The rate of SI and SSI combined reduced from 3.6 (95% confidence interval [CI] 3.0 to 4.3) per 100,000 in 2007-8 to 2.8 (95% CI 2.2 to 3.4) per 100,000 people in 2014-15.
The rate of SI alone reduced from 2.1 (95% CI 1.7 to 2.7) per 100,000 in 2007-8 to 1.6 (95% CI 1.3 to 2.2) per 100,000 people in 2014-15.
The rate of SSI alone reduced from 1.4 (95% CI 1.0 to 1.8) per 100,000 in 2007-8 to 0.9 (95% CI 0.7 to 1.2) per 100,000 people in 2014-15.

Overall, the number of sight loss certifications due to diabetic retinopathy fell by 22 over this period, after an initial increase in 2008.

In detail:

The number of new certifications for SI and SSI combined caused by diabetic retinopathy increased from 108 in 2007-8 to 140 in 2008-9.
The number then fell year on year from 2008-9 to 2014-15 to a total of 86, a 20.4% reduction from the original number of 108.
During the same eight-year period (2007-8 to 2014-15), the number of people with diabetes increased by 52,229, from 131,119 to 183,348.

How did the researchers interpret the results?

The researchers concluded: "Findings from this analysis provide positive and useful epidemiological information to assist in the future monitoring of diabetic eye disease in order to provide the basis for assessing the benefit or otherwise of changes in the management of diabetes and diabetic retinopathy/maculopathy."

They added that the analysis "highlights the positive benefits of introducing a community-based screening programme for the early detection of sight-threatening diabetic retinopathy".

Conclusion

The results indicate that since the introduction of the screening programme for diabetic retinopathy in Wales, the total number and rate of new certifications of sight impairment and severe sight impairment have decreased. This is despite an increase in the number of people diagnosed with diabetes.

The study shows a promising trend and highlights the possible benefit of such screening. However, there are some important considerations:

Reporting of visual loss currently requires a consultant ophthalmologist to complete a Certificate of Vision Impairment, and this isn’t compulsory.
Patients may be reluctant to be registered as visually impaired/blind, so true numbers and rates might be underestimated.
Screening isn’t the only thing that could have led to the decrease in certifications. It may also have been due to increased awareness of diabetes, improved referrals to specialists and better overall diabetes management, rather than the screening.

Everyone with diabetes aged 12 or over should be invited to have their eyes screened once a year.

You should receive a letter from your local Diabetic Eye Screening Service inviting you to attend an appointment. The letter will include a leaflet about diabetic eye screening.

Contact your local screening service or your GP if you haven’t received a letter and your appointment is overdue.