• Fri
  • Dec 26, 2014
  • Updated: 1:46am

Artist puts focus back on her work

PUBLISHED : Tuesday, 10 April, 2012, 12:00am
UPDATED : Tuesday, 10 April, 2012, 12:00am

As an artist, Jessica Liu relied on her perfect vision to capture her creativity on canvas. But with age, she found that she had to lean back farther and farther from her paintings to see them clearly as she worked.

By her 50th birthday, she had to wear reading glasses with a 200-degree power to paint. Presbyopia, or what people jokingly call the mark of middle age, had set in.

Dr John Chang So-min, a specialist in opthalmology and director of the Guy Hugh Chan Refractive Surgery Centre at the Hong Kong Sanatorium and Hospital, explains that the eye's lens - which focuses images on the retina to enable clear vision - is naturally springy and elastic. It is suspended in the middle of the eye by thousands of 'strings', which are attached to a circular muscle that surrounds the lens.

When the eye looks into the distance, the circular muscle relaxes away from the lens, pulling on those suspension strings which then stretch and flatten the lens. When the eye looks at something close, the muscles contract to allow the lens to thicken and increase its refractive power so that the image is 'brought forward' to rest on the retina. 'This is our autofocus mechanism,' says Chang.

Age and continual exposure to ultraviolet light harden the lens, which can no longer thicken sufficiently for clear, close vision. Reading glasses are then needed to help bend the light.

Liu (name has been changed for patient confidentiality reasons) hated her glasses. Fed up with the inconvenience she now had to suffer, she consulted Chang for glasses-free options.

Chang gave her a choice: Lasik eye surgery or lens exchange surgery.

Lasik is a well-established procedure that gives almost instant results. Liu had perfect distance vision so Chang could use Lasik to correct the presbyopia by making her non-dominant eye nearsighted by 200 degrees. She would have monovision: her dominant eye would be used to see distant objects, and the other would let her see close-up objects clearly.

Chang explains that most of us have one eye that is naturally dominant, meaning the brain 'prefers' the vision from that eye and registers it more prominently. Hence, if Chang blurs the vision in the non-dominant eye, the brain will not perceive it as much.

But monovision has drawbacks. Liu would lose stereopsis, or the ability to see with both eyes clearly. This can cause problems with gauging distance, making activities such as going down stairs or parking a car a challenge. In Chang's studies, he also found that nearly five out of 1,000 patients are unable to tolerate monovision and would feel dizzy and nauseated.

Using Lasik to correct for farsightedness is also less stable than correcting for nearsightedness. About 30 per cent of patients will slowly become farsighted again. Moreover, Liu's presbyopia could continue to worsen. This would entail more corrective procedures in the future.

With lens exchange surgery, Chang would make a 2.2mm micro-incision in Liu's eye, remove the gelatinous content of the lens and replace it with an artificial multifocal lens that could fully correct the maximum range of presbyopia, yet give her perfect distance vision.

This surgery is advantageous because it's a permanent solution: Liu gets to keep stereopsis and her chances of needing glasses again were very low. In Chang's experience, more than 90 per cent of patients become spectacles-free.

But it also carries risks and side effects. First, there is a 1-in-2,000 risk of retinal detachment. This however was far lower than the 1-in-56 risk for shortsighted patients, because people such as Liu with perfect vision or farsightedness have slightly shorter eyeballs, which means the retina is not stretched as thin.

Second, there was a 1-in-10,000 risk of eye infection that could result in permanent loss of vision.

Third, Liu will also likely suffer from halos in dim light, and glare and sparkles with bright lights. Chang says wearing sunglasses in bright light would reduce the glare and after some time, the halos might diminish. But 60 per cent of patients suffer permanent halos.

Chang warned that Liu's perception of colour might also change after the surgery. The eye's natural lens not only hardens with age but also yellows. However, the artificial lens is completely clear, so colours will appear brighter.

As with Lasik, some lens exchange surgery patients might still need glasses to use a computer.

Utterly frustrated with having to wear reading glasses, Liu opted to take care of the problem once and for all with the lens exchange surgery. She chose to operate on both eyes at the same time - the odds of a simultaneous infection being one in two million.

After the surgery, Liu jokingly told Chang she was enjoying her 'free laser show' and the pretty 'Christmas trees' and sparkles. Six months later the sparkles were gone.

Although she still saw halos at night, the initial multiple rings around each light source had reduced to a single, well-defined halo. But she was not fazed. To her, it was a small price to pay for a glasses-free existence.

More importantly, she was thrilled that the world around her looked brighter and more colourful with the new lenses, and Liu could take to her art with new vision.

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