CUHK is the First in the World to Identify a New Relationship betweenSilent Cerebral Infarct and Deterioration of Normal Tension Glaucoma
It was estimated that by 2010, over 60 million people in the world will be suffering from glaucoma. Among them, over 15 million will be in China. About 1 in 38 of those aged over 40 will be affected by glaucoma. Glaucoma remains the number one cause of permanent blindness in Hong Kong, accounting for about 1 in 4 cases. Traditionally, glaucoma is thought to be caused by raised eye pressure, which leads to damage to the optic nerve. As a result, patients will suffer from a gradual loss of visual field and vision, potentially leading to blindness.
‘However, the world comes to realize an important fact that, as many as 50% of patients with glaucoma have their eye pressures at a “normal” or even low range. Raised eye pressure is a risk factor, but not the only cause of glaucoma. A raised eye pressure is no longer part of the definition of glaucoma,’ said Professor Clement Chee-yung Tham, Professor, Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong (CUHK). Apart from raised eye pressure, other factors which may cause glaucoma are not known yet.
‘With advancing diagnostic imaging tools, more patients are nowadays diagnosed to have glaucoma at an earlier phase of their disease. This shall mean earlier treatment and better outcomes,’ said Professor Christopher Kai-shun Leung, Associate Professor, Department of Ophthalmology & Visual Sciences, CUHK. Various newer investigation modalities, such as Optical Coherence Tomography (OCT), detect structural defects before functional loss in patients with glaucoma.
‘The concept of target eye pressure revolutionized the treatment of glaucoma. In the past, the aim of glaucoma treatment was to return the eye pressure to a “normal” range (6-21mmHg). Many patients still develop significant worsening of their visual function despite their pressures are well within the normal range. So the normal range may not be safe or that “normal”. Nowadays, the target treatment pressure is individualized for each patient, depending on many factors such as age, the type of glaucoma, the stage of the disease, the rate of worsening, and other coexisting risk factors for deterioration. The target treatment pressure could be lower that 10mmHg. These are paradigm shifts,’ said Professor Dennis Shun-chiu Lam, Chairman, Department of Ophthalmology & Visual Sciences, CUHK.
‘In a prospective 3-year study of 286 patients with Normal Tension Glaucoma (NTG), we demonstrated that patients with Silent Cerebral Infarcts (SCI), an asymptomatic stroke-precursor condition, were 61% more likely to have their NTG worsened than those without,’ said Dr. Dexter Yu-lung Leung, Clinical Assistant Professor (honorary), Department of Ophthalmology and Visual Sciences, CUHK and Associate Consultant of Hong Kong Eye Hospital. ‘Our study is consistent with a growing body of evidence that a number of vascular factors are likely to be involved in normal tension glaucoma. This study gives more evidence to challenge the old belief that glaucoma is a disease due only to high eye pressures,’ said Dr. Leung, who was also the principal investigator of the study.
The results of this study were published in Ophthalmology, the official journal of the American Academy of Ophthalmology (AAO), which is considered as the leading authority in the field of ophthalmology. The study has been cited by AAO and has stirred up much discussion across the globe.
Remarks: The Faculty of Medicine, CUHK is pleased to announce that a surgical video produced by Professor Dennis Shun-chiu Lam has received 2 international awards recently as follows:
1. Winning Award (1st prize) in the “Glaucoma Surgery” Section of the Annual Congress of American Society of Cataract and Refractive Surgery, April 3-8, 2009, San Francisco, USA;
2. Winning Award (1st prize) of the Film Festival of the 3rd World Glaucoma Congress, July 8-11, 2009, Boston, USA.
The video is about how to use the ‘Needling’ technique in treating failed trabeculectomy, the most commonly performed glaucoma operation.
For those who are interested in the video (8-minute long), please refer to: www.cuhk.edu.hk/medint/ovs/dovs