SAN FRANCISCO, CA The August issue of Ophthalmology, the journal of the American Academy of Ophthalmology, includes surprising findings on Asian ethnicity and macular degeneration and on nearsightedness in school children, as well as a study of successful treatments for ocular surface cancer.
Age-Related Macular Degeneration (AMD) in an Asian Population
AMD erodes and can eventually destroy the central vision needed for reading, driving, and other daily tasks. When AMD risk levels among racial and ethnic groups are compared, Caucasians are usually identified as at highest risk. Asians in particular have been assumed to have lower risk. Recently Ryo Kawasaki, MD, and colleagues compared the prevalence of early and late AMD in approximately 4,000 residents of Funagata, Japan, to the rate in white participants in the Australian Blue Mountains Eye Study (BMES); diagnostic definitions were identical in the two studies and age standardization enhanced data comparability. Importantly, the Funagata study is the first in a Japanese population to confirm a link between smoking and AMD prevalence.
The overall AMD prevalence rate in right eyes was 4.1 percent for the Funagata study, very close to the BMES rate of 4.4.percent. Prevalence of late AMD in men was also comparable for the two groups, 1.1 percent for Funagata participants and 1.2 percent for BMES, but was markedly different for the two groups of women: 0.3 percent and 2.1 percent, respectively. The authors note that these findings need to be confirmed by larger studies in Asian populations. Two earlier studies also found a higher prevalence of late AMD in Asian men, in contrast with most studies in Caucasians where rates are higher for women. The authors think a key reason may be that 36.8 percent of the Funagata men smoked, but only 2.8 percent of the women. In the BMES study, 14.4 percent of women were smokers. While many Asian men smoke, the habit is less socially acceptable for women. "As smoking is a well-recognized, modifiable AMD risk factor, smoking cessation is an important public health measure to reduce AMD, particularly among Japanese men," Dr. Kawasaki says.
Outdoor Activity and Nearsightedness in Children
A growing number of the world's children are mildly to severely nearsighted (myopic), with rates especially high among urbanized East Asians. In addition to coping with poor distance vision, children with severe myopia are more prone to visual impairment and blindness later in life. Although genetic inheritance plays a role, the rapid rise of myopia suggests that environmental factors are driving the trend. Myopia usually begins and progresses during children's school years, but research on the role of intensive reading or other "near work" has determined that this is a minor factor. A new study led by Kathryn A. Rose, MD, used data from the Sydney Myopia Study of more than 4,000 Australian school children to assess whether outdoor activity might be significant in controlling myopia.
Parents and their children, at age 6 or 12, reported on the children's daily activities, which were classified as indoor or outdoor, and as near, medium or distance. Myopic refractive error, if any, was diagnosed for parents and children, and the children's ethnicity was recorded. A key finding was that the lowest myopia rates in 12-year-olds were associated with high outdoor activity, independent of the level of near work activity. In 12-year-old students myopia was most strongly associated with high levels of near work and low levels of outdoor activity. The findings suggest that it is the time spent outdoors rather than engagement in sports that is critical; the association between increased outdoor hours and lower myopia was found even if an outdoor sport was not included, while time spent on indoor sports, such as playing basketball in a gym, had no effect.
The researchers think the intensity of outdoor light may be an important factor. Myopic eyes are longer, measured front-to-back, than normal eyes; in response to intense light, the retina releases dopamine, a neurotransmitter that inhibits eye growth and may thus influence the development of myopia. Also, the pupils of the eyes constrict in intense outdoor light, which increases the visual depth of field, the distance at which objects can be clearly seen. The researchers recommend further study to prove conclusively whether certain levels of time spent outdoors can control myopia and to define the mechanisms involved. The higher exposure to intense outdoor light may explain the lower prevalence of myopia in children in Australia, compared with ethnically matched peers in other countries, Dr. Rose says. She adds that "this protective effect suggests that a public health measure aimed at preventing development of myopia could be based on increasing the engagement of children in outdoor activity," including family and school activities and sports.
Interferon or Surgery for Eye Surface Cancer Which is Best?
James Chodosh, MD, and colleagues evaluated 29 patients who were treated within a 10-year period for ocular surface squamous neoplasia (OSSN), a type of cancer, either by surgical removal of the tumor or with topical interferon (alfa-2b). There were no statistically significant differences in age, gender-affected eye and tumor size between patients in the two groups. Risk factors for this form of cancer include advanced age, light skin, extensive UV-light exposure, smoking, and exposure on the job to petroleum products. HPV (human papilloma virus) and HIV have also been associated with higher rates of OSSN.
Fourteen of the study patients opted for surgical excision; in all cases an aggressive removal of the tumor, with wide and deep margins around the tumor site, was followed by cryotherapy. The aggressive approach was used because more conservative excisions had been associated with high OSSN recurrence rates in other patients. This is the first report on results of this aggressive approach. Eight study patients received simultaneous reconstruction of the ocular surface using amniotic membrane. Fifteen study patients were treated with interferon; two of these did not respond to treatment and were treated surgically. All patients in both treatment groups eventually experienced complete resolution of their OSSN without recurrence, and with no significant side effects of treatment in either group. Dr. Chodosh says these results suggest that "topical interferon alfa-2 b and aggressive surgical excision can both be considered effective treatments for OSSN."
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American Academy of Ophthalmology