Myopia Epidemic in Hong Kong and South East Asia

Shortsightedness or myopia has assumed epidemic proportions in South East Asia over the past few decades. It is the most prevalent refractive error in Hong Kong. The average prevalence of myopia in Hong Kong people born before 1950 is about 30 % whereas it is about 70% people born between 1950 and 1980. Hong Kong Chinese students have a higher prevalence of myopia regardless of whether they attend in local or international schools when compared with other ethnic groups.

The severity of myopia is also escalating and it is common to find young adults with over 5D of myopia in Hong Kong. Similar figures have been reported in other Asian regions including Singapore, Taiwan and Southern China. Alarmingly, more than 80% of the entire adult population will be myopic within the next 30 years. In addition to the cost of myopic refractive correction, there are myopia-related ocular complications which have raised significant health concerns. High myopia is frequently associated with retinal degeneration, peripheral retinal breaks and glaucoma. These conditions may lead to permanent visual loss and blindness.

There is no clinically accepted method in controlling myopic growth at present. The goal of our myopia research is to find ways to retard and, one day, can cure myopia.

Myopia Research in PolyU

The scale of the myopia problem in Hong Kong was revealed by a number of early epidemiological studies by our research team in the late 1980s and early 1990s. In 1997, the PolyU created the Centre for Myopia Research as one of the Areas of Strategic Development (ASD). With ASD funding, the scope of work has greatly expanded from epidemiological studies to in-depth inquiry into the basic biological mechanisms of myopia. Our Centre is now conducting clinical, genomic and proteomic research using a multi-disciplinary approach, pulling in expertise from all areas of clinical and basic science. In 2007, the Centre for Myopia Research was designated as an Area of Strength of the PolyU.

Orthokeratology (Ortho-k) in Hong Kong

Overnight ortho-k is a treatment for correcting myopia by altering the corneal shape with specially designed, high oxygen permeability rigid gas permeable contact lenses. Patients wear the lenses when they go to sleep and remove them in the morning. When the treatment is completed and stabilized, they will be able to see clearly without the use of any other optical aids in the daytime. The effect is temporary and requires lens wear usually on a nightly basis. In Hong Kong, the majority of ortho-k patients are children wearing their lenses to slow the progression of myopia.

In 2000, our research team conducted a pilot study on ortho-k for myopic control - the LORIC study. The results of the LORIC have attracted extensive attention worldwide as it is the first study reporting the potential use of ortho-k in slowing the progression of myopia in children. Our objective is to promote a safe and effective alternative to the general public, especially to children, for correcting refractive errors and slowing the increase in myopia. The ultimate goal is to prevent the development of high myopia in the population thereby reducing vision loss in our community.

Our current research studies address the factors governing the success of ortho-k and the corneal responses to these specially designed contact lenses. We also want to identify the characteristics of good candidates for ortho-k and to follow the long-term refractive and ocular changes of these patients.

Orthokeratology (Ortho-K) Continuing Education Programme

Proteomic Analysis of Myopia Development in the Animal Model

Proteomics is the study of cellular proteins in a high-throughput manner where thousands of proteins can be profiled, quantified and identified very quickly. The procedure involves a sensitive separation technique that can resolve many cellular proteins simultaneously. It also makes use of the accuracy of mass spectrometry (MS) in quantifying the mass of ionized peptides after a protein is fragmented. Unknown proteins can even be fragmented in such a way that de novo protein sequencing can be carried out. One of the major aims in proteomic research is to understand the biochemical signals that drive myopic growth using animal models. We have studied chick retina and profiled a comprehensive-proteome. Since myopia is believed to be a local process that involves signal transduction within the eye, i.e. from the retina to the sclera, we have attempted to trace these signals during myopia development.

Differential expression of myopic retinal proteins

Differential in gel electrophoresis (DIGE) of chick retinal proteins

Chick (gallus gallus) retinal 2D proteome map

Myopia Genomics Study

The myopia genomics study aims to identify human genes that may predispose people to myopia. In turn, this helps to delineate the molecular mechanisms underlying myopia development, and devise new strategies to delay the onset or even prevent the development of myopia in susceptible individuals.

Our research team employs a variety of strategies to identify myopia genes. In terms of study subjects, we recruit families with severely myopic children, and unrelated individuals who are either severely myopic or without myopia. In terms of the study approach, we study individual candidate genes selected based on putative biological functions and related information, and also systematically screen the whole human genome with high-throughput genotyping technologies. We have already identified a number of myopia genes and will continue our efforts to identify more myopia genes and delineate the molecular mechanisms underlying myopia.

Pathophysiology of Myopia Development

It has been demonstrated that retinal neurons are able to differentiate between different types of optical defocus, and thereby initiating compensatory changes in ocular growth. In response to the artificially-induced dioptric blur, it has been shown that ocular growth is regulated by local growth signals or mediators generated in the retina. Subsequently, these signals transfer from the neural retina across the retinal pigment epithelium (RPE) to the targets including choroid and sclera. Recent evidence has shown that myopic and hyperopic defocuses induce thinning and thickening of choroid, respectively. The change in choroidal thickness is one approach to study the major focus of studying the development of refractive errors and myopia. However, the underlying mechanism of this phenomenon is unclear and it may be mediated by the change in fluid transport across the RPE. We have been focused on the contribution of ion and fluid secretion across the RPE in lens deprived eyes using chick as a model.

Astigmatism

In addition to myopia, astigmatism is also a very common refractive error that affects visual quality at all ages. Although it is frequently associated with short- and long-sightednesses, ageing eyes, and eye diseases, the cause of astigmatism is not fully understood. The main research interest is to study the mechanism underlying astigmatism in response to the changes in the visual environment. It is hoped that these studies will shed light on the clinical management of astigmatic errors.