A woman has become blind after her monthly eye injections were delayed for four months during lockdown.
Helen Jeremy, 73, said everything she enjoyed doing has “gone out of the window” after losing her eyesight.
Thousands more people in Wales are at risk of “irreversible sight loss” because of treatment delays, RNIB Cymru warns.
The Welsh Government said health boards are working to increase services.
Mrs Jeremy, from Bridgend, has glaucoma and was diagnosed with age-related macular degeneration four years ago.
Monthly injections controlled the condition and meant she could still drive and play the piano.
However, her appointments were cancelled when the pandemic struck and her eyesight deteriorated.
“I was panicking. It was terrifying. Because I’m a widow I’m on my own and it was awful,” she said.
“Suddenly my eyesight was basically gone. By the time of my next appointment I was told there was no point in going on with these injections because the damage had been done to the back of my eye.
“Everything I loved doing has gone out of the window and my life’s changed totally.”
Cardiff and Vale University Health Board said priority at the time was based on patient risk.
“We are sorry that Mrs Jeremy sadly experienced deterioration in her eyesight a few weeks following her last treatment in July,” a spokesperson said.
“Sadly, some eye conditions can become worse over time despite ongoing treatment.”
However, a Freedom of Information request by BBC Wales to all health boards in Wales found more than 33,000 people at risk of sight loss were waiting too long for treatment.
Health boards are expected to meet the target to see 95% of the most serious cases on time.
The average was 66% for all health boards in March – and that figure fell to just 53% in October.
The number of people waiting more than nine months for cataract surgery has also quadrupled in the last year, from 1,096 in October last year to 5,693 this October.
Consultant ophthalmologist Gwyn Williams, who specialises in cataract surgery at Singleton Hospital, said the number of people waiting had “ballooned almost exponentially”.
“It is simply impossible to bring forward the appointment of everybody that asks because our capacity has been cut so severely,” he said.
“There is a visual price being by the people of our country for the coronavirus restrictions in the name of a greater good of controlling the spread of this virus.”
RNIB Cymru described the delays are “extremely worrying” and said it has helped other people who believe they have lost vision because of cancelled appointment during the coronavirus pandemic.
Director Ansley Workman said that while she recognises the impact of Covid on the NHS, “that doesn’t take away from the fact that there are thousands of people in Wales who are at risk of irreversible sight loss”.
She called on the Welsh Government to commit to putting in the “investment and resources to make sure that people are seen in a timely manner and that sight is saved.”
“Before Covid came along there were already people waiting far too long for the treatment they needed to make sure they didn’t lose their sight unnecessarily,” she added.
The Welsh Government said optometric practices and hospital eye care departments across Wales have been open for essential and urgent eye care during the pandemic.
“As with all planned care specialities, ophthalmology has been impacted by the pandemic and performance has been effected,” a spokesperson said.
“Health Boards are working to increase ophthalmology activities and are prioritising patients based on clinical risk.
“They are doing all they can to keep Covid and non-Covid patients separate and have been changing the care environment with the creation of ‘green zones’.”