Older patients may be missing out on sight-saving treatment because the NHS has seriously under-estimated the prevalence and cost of elderly eye disease, claim specialists.

New research indicates tens of thousands more people suffer from a condition called Wet Age-related Macular Degeneration (AMD) than official estimates suggest.

Up to 40,000 people develop the condition each year, according to the study published in the British Journal of Ophthalmology – way more than the 26,000 estimated by the NHS and National Institute for Clinical Excellence (NICE).

The difference has meant a big shortfall in investment with commissioners taken by surprise at demand for a drug to treat Wet AMD, according to the Macular Disease Society, which funded the research.

“What we’re hearing is that eye clinics across the country are struggling to cope with demand,” said Cathy Yelf, the society’s head of external relations.

“Very often they’re reporting PCTs haven’t planned for this adequately and they simply don’t have enough resources. It is absolutely essential that care planners and commissioners understand the extent of this issue.”

Some hospitals have laid on extra clinics but Ms Yelf said the overwhelming demand meant delays in follow-up care.

The study also suggests a further 44,000 people per year are diagnosed with an untreatable form of AMD – Dry AMD.

“This work suggests far more might benefit from treatment or are in need of advice about coping with the condition,” said study lead Dr Christopher Owen, senior lecturer in epidemiology at St George’s University of London.

The cost of treating Wet AMD – about £1,000 per injection with some patients needing eight injections per year - already accounts for more than one per cent of the NHS budget and this looks set to rise with an ageing population – despite a Patient Access Scheme that means trusts are only charged for the first 15 injections.

The study estimates there are currently more than half a million people in the UK with advanced AMD, many registered partially-sighted or blind, which will increase to 650,000 by 2020.