A decision to delay approval of a treatment for a common form of blindness could lead to thousands of people losing their sight, say campaigners.
AMD is a common cause of blindness
The National Institute for Clinical Excellence (NICE) has ruled the treatment should be made available to people who have the "wet" form of age-related macular degeneration (AMD).
However, the Department of Health has decided to delay implementation of the guidance.
AMD is the most common cause of loss of sight in the elderly. Wet AMD is the most aggressive form of the condition.
It is caused by the development of new blood vessels beneath the retina of the eye.
The treatment approved by NICE combines a technique called photodynamic therapy (PDT) with a drug called Visudyne.
Campaigners say the move could mean that patients who have already waited more than two years for the treatment will now have to wait for a further nine months before they get it.
NICE guidance is supposed to be implemented within three months, but NHS chiefs have received guidance telling them they will not have to fund PDT for another nine months.
The Department of Health says that too much work is required to meet the three-month deadline.
It says new PDT centres are needed, existing centres will have to be expanded and specialist staff will have to be recruited.
A spokesman told BBC News Online: "NICE told us that they were concerned that it would not be be possible implement this guidance within three months, and we concurred with their assessment.
"The capacity does not currently exist to meet demand, and we want to ensure that capacity is expanded in a planned way that ensures patient's needs are met."
Steve Winyard, head of public policy at the Royal National Institute for the Blind and chair of the AMD Alliance UK, said: "Every year 21,000 people in the UK develop wet AMD and NICE estimates that 7,500 of these will be suitable for PDT treatment.
"Therefore, for every week that implementation of new NICE guidance is delayed, another 150 people risk losing their sight."
NICE first announced it was to review PDT with Visudyne for wet AMD in July 2001 - making this one of the longest appraisals in NICE's four year history.
Even though PDT with Visudyne was approved in the UK in July 2000, it has not been widely available, as the NHS has been waiting for NICE guidance.
Tom Bremridge, chief executive of the Macular Disease Society, said: "Many people assume vision loss is a natural part of ageing and ignore the early warning signs of AMD.
"The most obvious symptoms of AMD are distortion and blurring in the centre of the vision and straight lines start to appear wavy.
"Anyone who thinks they have the symptoms of AMD should go to their optician straightaway for a thorough eye examination.
"PDT therapy has been proven to slow down or halt the disease process in some patients - therefore the quicker patients are seen, the more likely they are to benefit from treatment."