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Orthokeratology contact lenses cause permanent vision loss in children
Main Category: Public Health
Article Date: 01 Mar 2004 - 0:00 PDT
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SAN FRANCISCO--Children who wore contact lenses overnight as part of their orthokeratology regime developed corneal ulcers, resulting in corneal scarring and vision loss.
According to a case study from China, appearing in the March issue of the American Academy of Ophthalmology's clinical, peer-reviewed journal, Ophthalmology, six children, nine to 14 years of age, were treated for bacterial eye infections after wearing the contact lenses eight to 12 hours each night.
Orthokeratology is a controversial, nonsurgical option for correcting the refractive error myopia, or nearsightedness. According to the study from the Department of Ophthalmology and Visual Sciences at the Chinese University of Hong Kong, myopia is one of the most common ocular conditions in humans.
It affects 25 percent of the United States population between the ages of 12 and 54 years of age, and is thought to affect up to 71 percent of the adult Chinese population in Hong Kong.
Orthokeratology was first developed by optometrists during the 1960s. The procedure consists of fitting a series of rigid gas-permeable lenses (OKLs) to modify the shape of the cornea, resulting in a temporary reduction, modification or elimination of the refractive error.
Although not widely used in the United States, this procedure is gaining popularity, especially in countries such as China. However, the study states the role of orthokeratology in arresting or slowing the progression of refractive errors in children, and its long-term effects, are not clear.
The study authors said they could not determine whether or not the contact lenses worn by the patients were designed for orthokeratology.
They also did not know if the lenses were made of materials designed for high oxygen transmission or whether the lenses had been properly fitted for the patients. Factors that may have contributed to the increased risk of corneal ulcers and infection included:
Overnight wearing of the OKLs that may have deprived the corneas of oxygen,
The OKLs are designed to improve centralization and stability while being worn. However, the design may have caused the compressive forces to be exerted on the epithelium, the outermost layer of the cornea, resulting in local trauma and thinning.
This may have increased the risk of abrasion or further infection.
The OKLs tend to cause the ocular surface to swell, which may render the corneal surface more susceptible to the formation of ulcers.
According to the study, other problems with OKLs are:
The cost, which is approximately 10 times that of a pair of traditional gas-permeable lenses.
Children often have low motivation for contact lens wear, and depend on their parents for lens care and maintenance.
Children, as a group, are more prone to eye trauma.
'Parents certainly want the best for their children,' said Academy spokesperson Thomas L. Steinemann, of the MetroHealth Medical Center Eye Clinic in Cleveland and associate professor of ophthalmology at Case Western Reserve University's Department of Ophthalmology.
'However they need to consider this option carefully. Corrections to the refractive error may be only temporary. However, the contact lenses can cause some discomfort at the very least, and possibly lead to infections and permanent vision loss.'
Currently, the U.S. Food and Drug Administration has approved only one OKL, made with material that allows oxygen transmission to the cornea, for nighttime wear.
Study author Dennis S.C. Lam, FRCS, FRCOphth, chairman and professor Department of Ophthalmology and Visual Sciences at the Chinese University of Hong Kong, said, 'The general public must be aware that overnight OKL wear is non physiological. It may be associated with very serious and visually significant complications.'
'The safety of orthokeratology needs to be carefully evaluated, especially in children,' the study states in its conclusion.
'The issues of hygiene, risks of corneal trauma, infection and long-term effects of contact lenses on endothelial functions need to be further assessed.'
The study went on to say, 'Parents and children must be educated on the symptoms of contact lens-related infections and the need for immediate ophthalmic consultation.'
The American Academy of Ophthalmology is the world's largest association of eye physicians and surgeons--Eye M.D.s--with more than 27,000 members. For more information about eye health care, visit the Academy's partner Web site at www.medem.com/eyemd. To find an Eye M.D. in your area, visit the Academy's Web site at http://www.aao.org.
Contact: Media Relations media@aao.org
415-561-8534
American Academy of Ophthalmology. 作者: 多多 时间: 2009-12-25 20:25
文中提到:无论如何,该研究就角膜塑型镜在控制儿童近视发展的角色(作用机理)及远期效果方面,还是不清晰的。这句话可以理解为对儿童近视的控制是有效的,但是不明白为什么有效。
(However, the study states the role of orthokeratology in arresting or slowing the progression of refractive errors in children, and its long-term effects, are not clear.
)
文中也承认了一个事实就是美国FDA批准了用透气性材料(RGP)加工成的过夜配戴的角膜塑型镜。
(Currently, the U.S. Food and Drug Administration has approved only one OKL, made with material that allows oxygen transmission to the cornea, for nighttime wear.)
文中提到,该研究的作者说,他们无法确认这些(角膜感染、溃疡)的病人是否戴的是角膜塑型镜。在这里,不知道他们是想说角膜塑型镜导致角膜感染及溃疡,还是想说,隐形眼镜(角膜接触镜)导致角膜感染及角膜溃疡。作者还是很诚实地说明了问题。
(The study authors said they could not determine whether or not the contact lenses worn by the patients were designed for orthokeratology)
文中提到,角膜塑型镜发端于上世纪的六十年代的视光师。这里值得一提的是,在美国和香港,如果眼科医生没有验光师的专业资格,是不能进行验光配镜的,包括在国内被定义为第三类医疗器械的隐形眼镜。在这里,也就不难理解,为什么该论文中要特别强调他们不知道这些角膜感染及溃疡的病人戴的是不是角膜塑型镜了,估计作者无法用肉眼区分硬性隐形眼镜和角膜塑型镜。
(Orthokeratology was first developed by optometrists during the 1960s.)
文中最有价值的一句话就是:该研究继续指出,父母和孩子必须被告知,如果出现隐形眼镜相关的感染症状时,必须立即和眼科医生联系。对于戴隐形眼镜的人来说,这是防止严重的感染的必要措施。不过,很多人很容易被误导了,看完这段文字,以为隐形眼镜一定会导致角膜感染。但是如果我们把这段文字中的“隐形眼镜相关的”去掉,并不影响整段文字的含义。就是说,任何人如果出现眼部感染症状时,都应立即联系医生而不应该有任何延误。并不因为只是戴了隐形眼镜,包括角膜塑型镜。
(The study went on to say, 'Parents and children must be educated on the symptoms of contact lens-related infections and the need for immediate ophthalmic consultation.)