角膜塑型鏡片對兒童可能的傷害

資料來源:台灣展鑫醫療器材有限公司  展鑫觀點

作者：Laurie Barclay, MD
審閱：Gary D. Vogin, MD
      　March 3, 2004 -

      整晚戴著角膜塑型隱形鏡片(OKL) 矯正近視可能對兒童有害，這項對六個病例的研究發表在三月份的Ophthalmology。研究人員建議與患者和家長討論可能的危險時要參考這個資訊。
      香港中文大學的Dennis S. C. Lam FRCS FRCOphth在新聞稿中表示，一般的民眾必須意識到整晚戴著角膜塑型隱形鏡片是不符合生理學的，這與非常嚴重的視覺上明顯的併發症有關。
      角膜塑型術是一項具爭議性的非手術治療近視方法，首次在1960年代使用，目前在中國等地方廣泛使用。它包含適應一系列的硬式隱形眼鏡壓迫眼球表面把角膜壓扁，達到把角膜變成凹透鏡的效果，從而將光線的聚焦回復正常至視網膜上。但是，有效性和長期效果還不清楚。
       從1999年3月到2001年6月，研究人員評估了六例角膜塑型隱形鏡片相關角膜潰瘍兒童患者，其中有五個女孩、一個男孩，年齡介於9至14歲，平均年齡為12歲。所有的孩子出現單側潰瘍，開始角膜塑型隱形鏡片治療後發生感染的時間3至36個月不等，平均為16.6個月，每晚配戴時間8至12小時，所有的患者喪失最佳視力敏銳度，五個患者檢體培養出陽性Pseudomonas aeruginosa。
      研究的侷限性，包括缺少是否配戴被設計為角膜塑型術的隱形眼鏡、是否鏡片材質的設計為高氧穿透性、配戴是否恰當。
      潛在導致角膜潰瘍和感染危險增加的因素，包括整晚配戴使得角膜不能接觸到氧氣，對角膜上皮的強迫外力造成擦傷、變薄、水腫等。研究人員強調，其它角膜塑型隱形鏡片相關問題，包括高費用，大約是傳統氣體穿透性鏡片的十倍，配戴的動機低、眼外傷的危險增加。英國角膜塑型學會報告角膜塑型隱形鏡片的其他可能併發症，包括散光、角膜疤痕、角膜感染。
      美國角膜塑型學會的發言人Thomas L. Steinemann表示，家長需要仔細考慮這種治療，矯正屈光的偏差可能僅是暫時性的。但是，隱形眼睛會造成不適，可能導致感染和永久的視力喪失。
      美國FDA僅核準了一個夜晚配戴的角膜塑型隱形鏡片，是由fluorosilicone acrylate為材料的、有高透氧性。研究人員希望對兒童角膜塑型的安全性、衛生、角膜創傷和感染的危險，以及隱形鏡片對內皮功能的影響等作進一步研究。
      必須教育家長和孩子有關隱形鏡片相關感染的症狀，以及即時尋求眼科檢查和治療，對角膜塑型術併發症警覺性的提昇和正式的大規模公共衛生研究是探討這個議題最安全和有效的方式。

Orthokeratology Lenses May Be Harmful to Children
By Laurie Barclay, MD Medscape Medical News
March 3, 2004 —

    Overnight wearing of orthokeratology contact lenses (OKL) to correct myopia may be harmful to children, according to a series of six cases published in the March issue of Ophthalmology. The investigators recommend including this information when discussing risks with patients and parents.
   "The general public must be aware that overnight OKL wear is nonphysiological," senior author Dennis S. C. Lam, FRCS, FRCOphth, from the Chinese University of Hong Kong, says in a news release. "It may be associated with very serious and visually significant complications."
    Orthokeratology is a controversial, nonsurgical treatment for myopia first developed during the 1960s and currently gaining popularity in countries such as China. It consists of fitting a series of rigid gas-permeable lenses to modify the shape of the cornea and temporarily reduce, modify, or eliminate the refractive error. However, the efficacy and long-term effects are still unclear.
    From March 1999 to June 2001, the investigators evaluated six consecutive cases of OKL-related corneal ulcers in children who presented to a tertiary referral center. There were five girls and one boy, mean age of 12 years (range, 9-14 years). All children had unilateral ulcers, with onset of infection 3 to 36 months (mean, 16.6 months) after beginning treatment with OKL, wearing them for 8 to 12 hours nightly. All had a resultant loss in best corrected visual acuity, and five of the six children had positive cultures for Pseudomonas aeruginosa.
    Limitations of this case series include lack of data concerning whether the contact lenses worn by the children were designed for orthokeratology, whether the lenses were made of materials designed for high-oxygen transmission, and whether they fit properly.
    Factors potentially contributing to increased risk of corneal ulcers and infection may include oxygen deprivation of the corneas from overnight wear, and compressive forces on the corneal epithelium resulting in abrasion, thinning, and edema, according to the authors. They also note other problems with OKLs, including high cost (approximately 10-fold that of traditional gas-permeable lenses), low motivation in children for contact lens wear, and increased risk of eye trauma in children. The British Orthokeratology Society reports that other possible complications from OKL include astigmatism, corneal scar, and corneal infection.
    "[Parents] need to consider this option carefully," says American Academy of Ophthalmology spokesperson Thomas L. Steinemann, from Case Western Reserve University in Cleveland, Ohio.
    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."
    The U.S. Food and Drug Administration has approved only one OKL for overnight wear, one made of fluorosilicone acrylate, which is reported to have high oxygen permeability. The authors mandate further research on the safety of orthokeratology in children, and on proper hygiene, risks of corneal trauma and infection, and long-term effects of contact lenses on endothelial function.
    "Parents and children must be educated on the symptoms of contact lens–related infections and the need for immediate ophthalmic consultation," they write. "An increased vigilance for orthokeratology complications and formal large-scale public health studies may be the best way to address the safety and efficacy of such lenses."

Ophthalmology. 2004;111:590-595
Reviewed by Gary D. Vogin, MD



資料來源:台灣展鑫醫療器材有限公司  展鑫觀點