FEB 2014

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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Page 45 of 114

E W CATARACT 4 3 What cases of myopia and hyperopia may portend H aving a refractive error may mean more than simply needing correc- tion, according to Jie Jin Wang, PhD, Centre for Vision Research, Department of Ophthalmology, and Westmead Millennium Institute, University of Sydney, Australia. The type of m yopia a patient has may portend increased incidence of cataracts, a new study shows. Results published in the September 2013 issue of Clinical & Experimental Ophthalmol- ogy indicated that compared with emmetropia, high myopia was asso- ciated with increased incidence of nuclear cataract, as well as posterior subcapsular cataract. "High myopia (–6 D or worse) at baseline was associated with an in- creased (about three-fold higher) risk of developing nuclear cataract, and substantially increased risk of devel- oping posterior subcapsular cataract and of cataract surgery, over a 10- year period," Dr. Wang reported. Likewise, having myopia of any sort was associated with increased inci- dence of cataract surgery, she noted. Considering a possible connection Dr. Wang, who worked on the study in conjunction with Paul Mitchell, MD, PhD, director, Centre for Vision Research, and others, said that looking into the connection be- tween refractive error and incidence of cataract surgery was a decision that stemmed from several factors. "Age-related cataract is the most common condition leading to visual impairment in older people," Dr. Wang said, adding, "Although cataract surgery can restore vision in most patients, the healthcare cost to meet this demand is high." She also pointed out that causes and risk factors for age-related cataract are not yet fully understood. When it comes to nuclear cataract, this is also known to be associated with a secondary myopic shift in refraction due to an increase in refractive index of the lens that occurs with nuclear sclerosis, Dr. Wang explained. Still, unexplained questions lingered. "Whether eyes with baseline moderate or high m yopia have an increased risk of developing nuclear cataract remains unclear," she said. In addition, the association between myopia and posterior sub- capsular cataract had been based solely on clinical impressions. "Evi- dence from observational studies was inconsistent, likely due to rela- t ively low numbers of cases," Dr. Wang noted. The study launched here was an outgrowth of the Blue Mountains Eye Study that had involved a popu- lation-based sample of older Aus- tralians, who were residents of the Blue Mountains area west of Sydney. "They were aged 49 years or older at baseline (1992–94) and were fol- lowed up for 15 years (2007–2010)," she explained. For the study, investigators took lens photographs of each eye of the participants at each visit and per- formed lens photographic grading following the Wisconsin cataract grading system, according to Dr. Wang. "We also measured refractive errors using standard protocols," she said. Studying outcomes Investigators determined that high myopes in particular were vulnera- ble to cataracts. "High myopia of –6 D or worse at baseline was associated with an increased risk of developing nuclear cataract that was about three-fold higher and substantially increased risk of developing poste- rior subcapsular cataract and of cataract surgery, over a 10-year pe- riod," Dr. Wang noted, adding that, "These findings are consistent with what we expected and what cross- sectional data from our and other studies had shown previously." At work here underlying the as- sociations observed could be multi- ple mechanisms and pathways, Dr. Wang thinks. "As our study is an ob- servational one, we are not in a posi- tion to provide evidence relevant to potential causes," she said. However, she speculates that oxidative damage may be involved. One unexpected finding was an association between moderate hy- peropia and increased risk of nuclear cataracts. However, Dr. Wang re- mains cautious about these findings. "Given that it was observed for per- sons with moderate hyperopia only, we cannot exclude the possibility of chance finding of this association," she said. "Future conformation of this association is needed." Still, the take-home message here is clear, she thinks. "Myopia and high myopia are strong risk fac- tors of nuclear cataract and posterior subcapsular cataract," Dr. Wang said. She views the results as poten- tially having a powerful, multifac- eted outcome down the road. "From a clinical perspective, my- opia, particularly high myopia, leads to an increased demand for cataract surgery and eye healthcare provision later in life," she observed, adding, "From a public health perspective, preventing myopia development and progression to high myopia dur- ing school ages could be an impor- tant public health strategy to reduce healthcare burden and costs." Going forward, Dr. Wang hopes that there will be experimental stud- ies to investigate mechanisms of the associations between myopia and both nuclear and posterior subcap- sular cataracts. Also, eventually she would like to see the development and implementation of effective strategies to prevent myopia devel- opment and/or progression in chil- dren of early school ages, as well as in teenagers. "This will be challeng- ing," Dr. Wang admitted, but she remains hopeful. EW Editors' note: Dr. Wang has no finan- cial interests related to this article. Contact information Wang: jiejin.wang@sydney.edu.au by Maxine Lipner EyeWorld Senior Contributing Writer Honing in on refractive error and long-term incidence of cataract For those with high myopia there's about a three-fold increased risk of developing a nuclear cataract. Source: Jie Jin Wang, PhD February 2014 38-45 Cataract_EW February 2014-DL2_Layout 1 1/30/14 10:18 AM Page 43

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