Importance of macular degeneration declining in England and Wales

Macular degeneration and diabetes appear to be playing smaller roles in sight impairment in England and Wales, according to the National Institutes for Health Research (NIHR).

In a tally of certificates of visual impairment from April 2012 to March 2013, degeneration of the macula and posterior pole accounted for 50% of applications for certificates of visual impairment (CVIs) for blindness, down from 54% five years earlier.

“This is most likely attributable to increasing availability of anti-VEGF drugs which have represented a steep change in the management of neovascular AMD,” wrote the NIHR researchers in the journal Eye.

Reports on the causes of blindness and low vision in England and Wales date to 1950. Since 2005 in England and 2007 in Wales, people seeking public assistance for sight impairment have had to fill out a CVI.

Before the current report, the last time anyone analysed the certificates to produce a report on causes of blindness was for the period from 1 April 2007 to 31 March 2008.

For the new analysis, the researchers analyzed the 24,009 forms of which 10,410 were for blind people and 13,129 were for people with partial visual impairment. Another 470 did not state which of these conditions applied (a decline from 755 in the tally from five years earlier). England accounted for 11,647 of the forms and Wales for 1362.

After macular degeneration (most of which was age-related), the next most common cause of blindness was glaucoma. It accounted for 11% of cases, up from 8.4% five years earlier.

Hereditary retinal disorders accounted for 8.2% of the blindness certificates, up from 5.5% in 2007 to 2008.

The proportional increase in hereditary retinal disorders made them the third leading cause of blindness, demoting diabetes, which dropped into fourth place as its share declined from 8.2% to 5.4%.

The other most common causes of blindness, in order of importance, were optic atrophy (4.9%), cerebrovascular disease (2.7%), disorders of the visual cortex (2.6%), congenital anomalies (2.1%) and retinal vascular occlusions (2%).

The causes of partial sight impairment followed a similar pattern with degeneration of the macula and posterior pole accounting for 52.5%, down from 57.2% in 2007-2008.

Glaucoma followed at 7.6% (up slightly from 7.4%). The third leading cause of partial visual impairment was cerebrovascular disease, which accounted for 6.4%, up from 4.9%.

Next came hereditary retinal disorders (5%), disorders of the visual cortex (3.9%), optic atrophy (3.5%) and retinal vascular occlusion (1.7%).

In 14% of the CVIs, multiple causes accounted for sight impairment, down from 16.6% in 2008. More adults (14.8%) than children (11%) suffered from multiple causes of visual impairment. And multiple causes accounted for 16% of blindness, compared to 13.4% of partial visual impairment.

On most of the CVIs that included macular degeneration, it appeared as the sole cause of the impairment. By contrast glaucoma appeared almost as often as a contributory cause as it did as a sole cause.

Keratitis, corneal opacities and other disorders of the cornea more often appeared as contributory causes than as sole causes of visual impairment.

Improved treatments explain the shift in relative importance of the causes of visual impairment, the researchers wrote. In addition to neovascular age-related macular degeneration “[d]iabetes has also shown decreases as a proportional comparison and this is likely to reflect both better treatments and screening.”

The main purpose of the CVIs, the authors pointed out, is not to measure relative causes of visual impairment but to get help for those who need it. Previous research suggests that this help substantially improved the lives of the recipients, they wrote.

They acknowledged some uncertainty about the accuracy of the CVIs as a measurement of the actual burden of sight loss.

A future analysis will look at changes in incidence rather than proportionate changes, and will include an exploration of diagnosis with age, the researchers said.