Landmark study on PACG

by | September 4, 2012

Singapore scientists are now able to understand the disease better and focus their screenings.


BY: Eleanor Yap


Singapore scientists have identified three new genes associated with Primary Angle Closure Glaucoma (PACG), a leading cause of blindness in Chinese people.  Worldwide, 60 million people had glaucoma in 2010 and that figure is slated to increase to 80 million by 2020. Furthermore, 8.4 million people were blind from glaucoma in 2010, with an estimated increase of 11.2 million people in 2020.

PACG is more common in Asia with Asians representing 87 percent of angle closure glaucoma. Glaucoma, which usually occurs after age 60, is a disease of the optic nerve and those with the condition gradually lose peripheral field like looking through a toilet roll and this later leads to blindness.


A collaborative effort

The discovery, which was published in the scientific journal, “Nature Genetics”, was conducted collaboratively by scientists from the Singapore Eye Research Institute (SERI)/Singapore National Eye Centre (SNEC), Genome Institute of Singapore (GIS), National University of Singapore (NUS), National University Hospital’s (NUH) Department of Ophthalmology and Tan Tock Seng Hospital (TTSH). The genome-wide association study was conducted over a three-year period and had 1,854 PACG cases and 9,608 controls of over five sample collections in Asia. The Singapore patients in the study were mostly from SNEC with some from NUH and TTSH, and mostly Chinese.

The scientists also performed validation experiments in another 1,917 PACG cases and 8,943 controls collected from a further six sample collections from around the world. The study was funded by a S$1-million grant from the National Research Foundation.

The scientists found that each of the three gene variants had an increased risk from 20 percent to 50 percent of getting PACG, while someone with all three genes would have three times greater risk. “The next step for the scientists is to do further research to find out how the genes cause PACG,” said Professor Aung Tin, the lead principal investigator of this project who is a senior consultant and head of Glaucoma Service at SNEC, deputy executive director at SERI and professor of ophthalmology at NUS. At SNEC, 10,000 to 20,000 glaucoma patients are seen each year.

He added that through their study, they may be able to identify people who are at risk better and earlier, and preventive measures like laser iridotomy can be done. The laser iridotomy uses a focused beam of light to create a hole on the outer edge of the iris and allows fluid to flow better. This opening may decrease pressure in the eye and usually prevents sudden buildup of pressure within the eye, which occurs during an episode of angle closure glaucoma.


Focused screenings

Said Prof Wong Tien Yin, executive director at SERI and Provost’s Chair Prof and head, Department of Ophthalmology, NUHS: “The study puts Singapore on the map. This study cannot be done in Western countries [as most cases are in Asia].” He added that the study also allows them to have more focused screenings. “In the future, there may be no need to screen or treat everyone as a result and a reduced need for mass approach in care,” he said, therefore making the screenings more cost-effective.

Added Dr Eranga Vithana, associate director, Basic and Experimental Sciences, SERI: “PACG is not often studied and now we can [through the findings] understand the disease better.”



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