Madam Achara started having trouble with her vision in her early 60s. Her once-clear eyesight started misting and blurring.
A consultation with an ophthalmologist showed that she had senile cataract in both eyes - in other words, age was causing the lenses in her eyes to become progressively thicker and more opaque. The lens focuses light on the retina and gives sight. Without a clear and healthy lens, light could not penetrate to the back of the eye.
Cataracts are a common eye problem. In Hong Kong in 2009, there were more than 54,000 people waiting for cataract surgery at Hospital Authority hospitals alone, and more than 42,000 were over 71 years old. But cataracts are developing at a younger age: a 2007 survey by University of Hong Kong found that about 14 per cent of people between the ages 36 and 45 have cataracts.
According to Prevent Blindness America, a volunteer eye health and safety organisation, an estimated 24 million Americans over the age of 40 suffer cataracts.
Untreated, cataracts will rob sufferers completely of their vision. The remedy is fairly simple - a quick surgery to replace the cloudy lenses with artificial ones.
However, Achara (whose name has been changed for reasons of patient confidentiality) was nervous about surgery. She agreed only to an operation on the right eye first.
The most common form of cataract surgery is called phacoemulsification, where an ultrasound probe is used to emit ultrasonic vibrations to dissolve the clouded lens. The lens fragments are then removed and an artificial lens is inserted into the eye.
This usually takes less than 30 minutes with local anaesthesia and minimal sedation. Hence, the patient is often conscious during the procedure and exposed to the sounds in the operating room. Achara's anxiety over the surgery was amplified by the experience of hearing the strange surgical noises and conversations. The surgery seemed to drag on endlessly.
Despite the fact that her cataract surgery was a success, Achara was so traumatised by the experience that she refused to have surgery performed on her left eye.
Five years later at age 67, Achara was finally persuaded. This time, however, she agreed to be part of a new study on reducing cataract patients' anxiety during surgery led by Dr Pornpattana Vichitvejpaisal of Chiang Mai University in Thailand.
Pornpattana was studying if binaural beat audio therapy had an effect on patient anxiety. The therapy uses two tones that are pitched at a specific, slightly different frequency. Each tone is delivered to one ear via headphones. For example, 300 hertz may be played in one ear while 310 hertz is played in the other ear. The 10 hertz difference will give the effect of a pulsating sound.
At a frequency of 10 hertz, binaural beats stimulate alpha-frequency brainwaves, linked to relaxation and reduced perception of fear and pain.
In Pornpattana's study, 141 patients were placed into three groups, matched for age, gender, cataract type and other health factors. The first group listened to binaural beats mixed with soothing music and nature sounds before, during and after the surgery. The second group was exposed only to the soothing music and nature sounds. The last group did not receive any sound therapy.
All patients were assessed for anxiety, heart rate and blood pressure before and after surgery.
Achara was randomly selected to be part of the group that received binaural beat audio therapy. When she arrived at the hospital, her systolic blood pressure was in the normal range of 130 millimetres of mercury (mmHg), with a heart rate of 68 beats per minute.
While waiting for surgery, her systolic blood pressure shot up to 150mmHg - considered high - and her heart rate rose to 72 bpm. She scored 40 on the State-Trait Anxiety scale, a standard measurement of anxiety with scores ranging from 20 to 80. The higher the score, the greater the state of anxiety.
Achara was given headphones that piped in the binaural beat and music mix. Five minutes into the procedure, her systolic blood pressure dropped to 136mmHg and her heart rate slowed to 69 bpm.
Twenty minutes after the surgery, Achara's systolic blood pressure was 128mmHg with a heart rate of 63 bpm. Her anxiety score also dropped to 25. She happily reported that she felt very little anxiety during the surgery, which seemed to conclude in a flash.
Achara's experience was not an isolated one. Pornpattana's study found that the patients in the group that received binaural beat audio therapy reported less anxiety and had lower heart rates than those in the control group.