SINGAPORE – A record 620 corneal transplants were carried out in Singapore in 2023 on patients, from toddlers to seniors in their 90s, to improve or restore their eyesight.

Four in five of them were able to see, or see better, thanks to almost 500 corneas brought in from the US in 2023, as there were only 129 local donations that year.

In comparison, 444 to 571 corneal transplants were carried out each year between 2018 and 2022, with the exception of 2020, when the number hit a low of 261 due to the Covid-19 pandemic.

Singaporeans and permanent resident recipients accounted for 80 per cent of the 620 corneal transplants in 2023.

The Singapore National Eye Centre (SNEC) does 60 per cent of all corneal transplants in Singapore. The rest are performed at other hospitals.

Despite the record number of transplants in 2023, 99 people were still waiting for a cornea to be available at the end of 2023.

Associate Professor Marcus Ang, a senior consultant at the SNEC, said the waiting time for a cornea in Singapore – averaging 5.3 months – is shorter than in most countries. He added that the global shortage of donated corneas means that only one in 90 people worldwide who needs a cornea gets the transplant.

He added: "The Singapore Eye Bank enjoys a good working relationship with our counterparts in the US and they have been reliable in making up for the shortfall in our local cornea supply."

The US is the Republic's only foreign source of cornea supply. The number of local donations remains low. Between 2018 and 2023, the number of corneas donated here ranged from 75 to 173 a year.

"But we have to also work on building our own supply pool – support for cornea donation needs to increase in Singapore for us to bring the local supply up," said Prof Ang.  "This is why we constantly work on raising awareness of cornea donation, in hopes that we break any taboos behind the topic and change the attitudes and perceptions of potential donors and their family, or help them to understand how their actions can touch another person's life."

Corneal blindness – the loss of sight due to damage to the cornea – is the fourth leading cause of blindness globally.

If cataract, which is the leading cause, is included, corneal blindness becomes the fifth leading cause of blindness.

Cataract blindness is rare in Singapore as cataract surgery is readily available here. The other top causes are glaucoma, age-related macular degeneration and diabetic retinopathy.

Over the past decade, the demand for corneal transplants has gone up, and is expected to remain high as the population ages.

Technological improvements in the procedure have resulted in a far higher level of success.

A decade ago, a corneal transplant involved replacing the entire cornea. This is major surgery and has to be done under general anaesthesia, which may pose a health risk to older patients.

This method is still used here for a small number of patients who need the entire cornea replaced.

Based on international literature, the success rate is 54.6 per cent.

The method most commonly used now, called Descemet membrane endothelial keratoplasty (DMEK), has a success rate of 94 per cent. Prof Ang said this method uses just one of the five layers that make up the cornea. 

It involves transplanting just the endothelial layer of the cornea, which is only 10 to 15 microns thick. One micron is one-thousandth of a millimetre.

The Singapore Eye Bank extracts this layer and prepares it, so the actual surgery is much faster.

DMEK is done through a keyhole incision, under local anaesthesia. The whole procedure, which can be completed in 30 minutes, is safer with fewer complications, he said.

The rejection rate ranges from 5 per cent to 10 per cent when the entire cornea is transplanted. This is reduced to 1 per cent to 2 per cent with DMEK.

Prof Ang said: "Patients have the possibility of attaining '6 / 6' (normal vision) within a few weeks after surgery."

The majority of people needing such a transplant are seniors, as corneal degeneration increases with age. Three in four corneal transplant patients are aged 50 and older.

In 2023, the oldest person who had a corneal transplant was 98, though the bulk – 28 per cent – went to people aged 60 to 69.

Madam Yau Li Heong, 65, a retired teacher, had trouble seeing with her left eye in 2023. Her vision was blurred due to problems with her cornea.

She initially did not want to consider getting a corneal transplant as her right eye was still good, and she thought she could live with one good eye.

In the past, her left eye had been problematic. The lens inserted during a cataract operation some years back shifted and had to be removed. This involved breaking up the lens while it was still in her eye, so it could be removed in small pieces.

Then her left eye had glaucoma, which occurs when the optic nerve is damaged, causing a build-up of fluid. The excess fluid, which puts pressure on the eye, had to be drained through a tiny tube implant.

She changed her mind about getting a transplant after finding out about the high success rate of DMEK and how quickly the procedure can be done.

On top of that, she found driving at night dangerous as lights made "everything hazy".

Following the transplant on Nov 30, 2023, she had to lie flat as much as possible over the following four days to allow the endothelial cells to adhere to her cornea.

On the third day after surgery, everything changed.

"Oh I can see," she recalled. Her vision was clear and sharp and she could admire the birds and flowers in her garden.

"I was so happy," she said. "I could drive again and continue with normal life."

Prof Ang said having good vision in one eye compared with in both eyes does affect a person's quality of life, as two working eyes give a person depth of vision.

"They can judge distance more accurately with binocular vision, thereby preventing accidents and falls."