So clear and yet so far

PUBLISHED : Tuesday, 13 March, 2012, 12:00am
UPDATED : Tuesday, 13 March, 2012, 12:00am


Kitty Wu, 42, has worn glasses for most of her life. By the age of five or six, her myopia was already at minus six dioptres, meaning she needed lenses with a corrective power of 600 degrees.

The young Wu (name changed for patient confidentiality reasons) wore thick glasses that were heavy on her face, and she couldn't play as freely as her friends.

By the time she hit her teens, her nearsightedness had reached 2,400 degrees, and she suffered 300 degrees of astigmatism. She was unable to see things a short distance away, and the astigmatism blurred all the fine details up close or far away. Her glasses severely restricted her field of vision, and she could see clearly only when looking straight ahead.

When Wu started work, she had to wear both contact lenses and glasses to correct her vision.

She longed to play sports and travel, but her severe myopia made it difficult. She had to rush home after work each day to switch from contact lenses to goggle-like glasses, because her eyes were getting too dry.

Last year, she had to stop using contact lenses, as they made her eyes unbearably dry. Several of her friends had raved about the liberating results of Lasik eye surgery and implantable contact lenses (ICL), and Wu decided to explore those options.

She sought the help of Dr John Chang So-min, a specialist in ophthalmology and director of the Guy Hugh Chan Refractive Surgery Centre at the Hong Kong Sanatorium and Hospital.

After assessing Wu's condition, Chang said neither Lasik nor ICL was a good option for her.

With Lasik, the cornea of the eye is reshaped to correct up to 1,200 degrees of myopia. In ICL, a special type of contact lens is inserted into the eye in front of its natural lens to correct up to 1,800 degrees of myopia and 600 degrees of astigmatism.

Another option was a procedure called bioptics, which combines the two techniques. But Chang considered that Wu was 42, the age at which presbyopia (long-sightedness) usually kicks in. Once it does, it will climb slowly to a maximum of 300 degrees.

In some patients who already had presbyopia, Chang had fully corrected the vision in one eye and under-corrected it in the other to enable monovision. That's where one eye is used for distance vision and the other for things up close.

But Wu did not yet have reading problems, so monovision was not an option. The difference in vision between the two eyes would leave her dizzy. If he fully corrected both eyes now, her options for correcting the eventual presbyopia would be limited and unsatisfactory.

Chang offered a third option - a lens exchange surgery known as clear lens extraction.

'The lens of the eye is like a grape,' Chang says. 'We make an opening in the front of the grape skin, suck out the pulp and put in an artificial lens.'

A new artificial lens, called a multifocal toric lens, had arrived in Hong Kong a few months earlier. It can correct up to 3,000 degrees of myopia, 1,200 degrees of astigmatism and all 300 degrees of presbyopia, making it an ideal solution for Wu's condition.

The genius of the lens lies in its multiple rings, which bend light into two zones, near and far. This creates two images in the eye.

When the patient wishes to see something in the distance, the images in the 'far zone' will dominate, and the brain will not notice that the 'near zone' images are present. When the patient looks at something close, the reverse will happen. The brain adroitly adapts to this process, which is transparent to the patient.

But in low light, the patient will notice the double images in the form of halos around light sources.

Chang says 60 per cent of patients will see halos at night. But in Wu's case, halos and glare were already a permanent part of her world, so she would barely notice the post-surgical side effects.

The results are not perfect. About 20 per cent of patients might need to wear glasses of 125 degrees for reading or when using a computer, Chang says.

Also, the surgery is not without risks. There is a one-in-10,000 chance of developing a bacterial infection in the eye, which risks permanent loss of vision from 10 per cent to more.

There is also a one-in-500,000 chance of being blinded. Patients under the age of 50 risk a nine-in-500 chance of retinal detachment, in which the light-sensitive membrane at the back of the eye tears away from its supporting layers, causing vision problems. But Chang says with advances in micro-incision surgical techniques, the success rate for retinal detachment surgery is high.

There is also a slight chance of needing Lasik surgery to touch up the vision after the clear lens extraction procedure.

Wu mulled over her options and risks for three months. Finally, she decided to go ahead with the surgery. Chang operated on one eye at a time, at an interval of two weeks. The procedures were a resounding success: Wu was left with only 75 degrees myopia.

Breaking free from the frames that had cramped her existence, Wu promptly quit her job and set out to travel the world.