More double vision cases with no known cause in Singapore, part of worldwide trend: SNEC

SINGAPORE - The number of cases of diplopia – which causes a person to see double – with no known cause seen at the Singapore National Eye Centre (SNEC) is rising, in line with the worldwide trend, said senior consultant Yvonne Ling.

Commonly known as double vision, diplopia can occur when one eye is covered (monocular diplopia) or only when both eyes are open (binocular diplopia).

A survey of binocular diplopia cases at SNEC conducted earlier in 2024 showed there were 234 patients between 2011 and 2020, up from 15 patients from 2001 to 2010. From 2021 to 2023, there were already 76 patients. These patients are mostly adults.

Binocular diplopia is when you see double with both eyes open, and it disappears upon closing either eye, said Dr Ling. It may be due to a neurological problem, or it may be due to too much screen time, especially on mobile phones, she said.

“If the ‘double vision’ happens with one eye alone, see your friendly optometrist first. All you may need is a change of glasses, or it may be early onset of cataract which is a non-urgent condition,” said Dr Ling, of monocular diplopia.

At her 2019 church wedding ceremony, Madam Jeviene Sim, 38, one of Dr Ling’s patients, had an episode of double vision, and saw two images of the candle that she was about to light. Her husband-to-be had to hold her hand and guide her to it.

When her double vision episodes first occurred occasionally earlier that year, they lasted around 10 to 15 minutes each time. The episodes gradually grew more frequent, reaching a point where it happened every other day, lasting up to an hour each time.

Madam Sim’s eye misalignment or binocular diplopia was diagnosed in 2020 when she went for a follow-up check at the SNEC for a contact lens-related complication.

The cause of her condition was non-typical, as scans had ruled out neurological causes.

Such cases of binocular diplopia with no known cause used to be few and far between at SNEC, but they have risen in recent years, possibly due to excessive and uninterrupted screen time use on mobile phones, said Dr Ling, whose speciality is adult strabismus and paediatric ophthalmology.

She said the rise could be due to excessive screen time, particularly time spent on mobile phones, as the small screen forces one to focus more and for prolonged periods.

Madam Sim used to spend many hours watching videos on her mobile phone. For nearly a decade, she would often spend weekends binge-watching drama serials on her phone for about 12 to 15 hours each time, continuing through mealtimes, she said. She would also binge-watch after work on weekdays.

Another SNEC patient, national serviceman Jariri Ishaq Jasseri, 22, said he started playing games on his parents’ mobile phones when he was in upper primary school, before he got his own phone when he started secondary school. He would watch videos and play games on it upon reaching home at 5pm, and that would be his main activity till he went to bed around 10pm.

His first episode of double vision happened in 2021 when he was doing a lot of physical activity but he thought it was due to tiredness. In September 2022, he experienced the same while he was doing exercises as part of his national service training. “I saw two versions of a person and didn’t know which was the real one,” he said.

His in-camp doctor referred him to the hospital, who then referred him to SNEC. Dr Ling advised him to do eye exercises, cut down on his screen time and take regular breaks when using screens. As he is in the early phase of the eye condition, good eye habits and adequate sleep can help, Dr Ling said.

Mr Jariri’s double vision has improved, and he rarely experiences it now, even though he is on the computer a lot at work.

In moderate cases of diplopia, stick-on prisms on glasses are prescribed to help correct the eye misalignment while squint surgery may be needed in severe cases.

Madam Sim underwent squint surgery in February 2024, to move the muscles that control eye movement so that the eyes align better.

She now uses bigger screens more and has tried to change her habits to cut down on screen time. “It’s not so intense (now), maybe like a few hours and not 12 hours straight,” she said.

She is also careful not to allow her toddler too much screen time, and makes the effort to take her to the park to play whenever she can. Screen time is generally not encouraged for babies below 18 months of age.

Nevertheless, she told The Straits Times that the double vision has come back intermittently.

“Surgery only moves muscles to try to align the eyes but the final control is by the fusion centre in the brain,” Dr Ling said.

“So if the brain is too tired (from) too much input from screen time, insufficient sleep and lack of distance vision eye breaks, eye alignment can break down again – although usually not to the same extent as before surgery.”

Good habits must be maintained, with or without surgery, for good in order to eliminate diplopia, Dr Ling stressed. Repeat surgery can be done but there is a limit as there are only so many muscles which can be operated on, she added.

Those who develop binocular diplopia may have been predisposed to the condition with weaker control of eye alignment at the outset, and the excessive screen time breaks the control more easily, said Dr Ling.

However, anyone who spends hours on the screen daily, especially mobile phones, is at risk of diplopia, regardless of age, she said.

“In our cohort, we note that the patients spent at least four hours a day on their mobile phones. Hence, our current advice is to limit mobile phone use to three hours daily on average, with breaks every five to 10 minutes, and transferring anything (that needs more time), such as videos, games or e-mailing to a larger screen with eye breaks every 20 to 30 minutes.”

Eye breaks mean looking into the far distance, for instance, at the clouds in the sky, to give the eyes’ focusing muscles a rest, she added.

Adequate restful sleep is also important, said Dr Ling.