幼年時期的近視問題可以經由藥物控制


  May 8, 2003 - 在視力和眼科學研究學會年會(5月4~8日)上報告的兩項研究結果指出,pirenzepine具有減輕幼年時期近視進展的潛在好處。第三項研究是到目前為止最大規模的隨機臨床試驗,研究中指出局部阿托品的作用。研究人員表示,這些研究結果可以提供強有力的證據顯示,近視是可以被藥物所控制的。
  
  Dean A. McGee眼科研究所(Oklahoma City)的R. Siatkowski寫到,Pirenzepine (PIR)是一種相對選擇性M1-muscarinic(毒菌鹼)拮抗劑,通過縮短動物模型眼軸長度減輕形覺剝奪性近視(form-deprivation myopia)。研究中讓受試者在幼年時期使用2%眼藥凝膠,且每日兩次共28天,結果顯示是安全的。
  
  多中心隨機對照試驗的研究對象是174名近視兒童,年齡為8至12歲,並以2:1的比例基礎接受PIR 2% gel 或者安慰劑,研究給予這些兒童每日兩次並且持續整整一年。一開始時,這些受試者的平均屈光偏差(refractive error)分別是,PIR組是 -2.10 D,安慰劑組是 -1.93 D (P = .221)。
  
  使用PIR或安慰劑12個月左右,再次測量他們的平均近視已經進展成為,PIR 組是 -0.26,安危機組是 -0.53 D (P < .001)。其中PIR組只有2%的受試者近視進展超過1D,相較之下,安慰劑組有20% (P < .001)。而出現副作用方面,治療組的頻率是98%,安慰劑組93% (P = .091)。
  
  因為副作用而退出此次實驗的兒童比例,治療組為11%,安慰劑組0%。最常見的副作用是凝膠殘留在眼瞼、近視力模糊以及無症狀結膜反應。
  
  作者寫到,中等程度近視在兒童時期使用PIR 2% gel每日兩次持續一年,與對照組比較減緩近視進展比例達到50% (0.26 D),其安全性是可以接受的。為了更了解PIR對近視的作用,Phase 3 研究將在更大年齡範圍檢測不同劑量PIR的效果,以便了解PIR是否為乙種新的有效的藥物治療近視的方法。
  
  第二項研究是為期一年的雙盲安慰劑對照平行組研究,分別在亞洲的七個地方進行。研究對象是353名年齡6-12歲的兒童,按照2:2:1的比例隨機分配,施以PIR 2% 每日兩次一組、安慰劑組以及晚上使用2% PIR一組,或者安慰劑每日兩次。
  
  基線平均值是 -2.3 to -2.4D,PIR治療組的效果在三個月的時候顯現。一年後,PIR 每日兩次組的平均近視進展為 -0.47D (P < .001 vs. PIR 每日一次 and vs. 安慰劑), PIR 每日一次組為-0.70D,每日兩次安慰劑組為 -0.84D。
  
  作者寫到,PIR b.i.d.和安慰劑組之間的差別表示,治療組近視進展可減少大約50%。雖然出現瞳孔放大和適應效應等副作用,但是相對比較輕微。然而與劑量相關的濾泡和乳突等情形常常是沒有症狀的。所有研究作者與Valley Forge Pharmaceuticals都有商業往來。
  
  第三項研究名為阿托品治療近視 (ATOM),試驗包括400名合格的兒童,年齡6-12歲,近視程度 -1 D to -6 D。研究將這些受試者以雙盲方式隨機分配,每人的其中一只眼睛接受1% atropine滴劑或者Isoptotears,每晚一次。
  
  359名(90%)受試者完成一年的隨訪追蹤,331名(83%)完成兩年的研究。在69名未完成研究的受試者中,安慰劑組有21名,阿托品組有48名。
  
  一年的時候,安慰劑組平均近視進展為 -0.76 D ± 0.44 D,阿托品治療組復原+0.3 D ± 0.50 D (P < .0001),而且眼軸長度減少 -0.14 mm ± 0.28 mm,相較之下,安慰劑組平均眼軸長度卻增加了 +0.20 mm ± 0.30 mm (P < .0001)。
  
  二年左右,安慰劑組平均近視進展為和眼軸長度增加分別是-1.20 D ± 0.69 D和 +0.38 mm ± 0.38 mm。阿托品治療組,近視進展為 -0.25 D ± 0.92 D,眼軸長度基本維持不變 (-0.02 mm ± 0.35 mm; P < .0001 )。
  
  新加坡眼科研究所的W. H. Chua和同事寫到,ATOM是到目前為止最大規模的隨機對照試驗,研究結果提供強有力證據顯示幼年時期近視進展和眼軸長度增加可以經由藥物方法,例如局部阿托品治療,獲得控制。

Myopia May Be Pharmacologicall

By Laurie Barclay, MD
Medscape Medical News

May 8, 2003 — Two studies presented at the Association for Research in Vision and Ophthalmology annual meeting from May 4 through May 8 show the potential benefit of pirenzepine in reducing progression of myopia in children. A third study, the largest randomized trial of its kind to date, shows the benefits of topical atropine. The investigators suggest that these findings provide strong evidence that myopia can be pharmacologically controlled.

"Pirenzepine (PIR), a relatively selective M1-muscarinic antagonist, reduces form-deprivation myopia in animal models by attenuating axial length," write R. Siatkowski, from Dean A. McGee Eye Institute, in Oklahoma City. "A 2% ophthalmic gel has been shown to be safe in children when used twice daily for 28 days."

This multicenter, controlled U.S. trial randomized 174 myopic children, aged 8 to 12 years, on a 2:1 basis to receive either PIR 2% gel or placebo twice daily for one year. At baseline, mean refractive error was -2.10 D in the PIR group and -1.93 D in the placebo group (P = .221).

At 12 months, mean myopic progression was -0.26 D in the PIR group and -0.53 D in the placebo group (P < .001). Only 2% of PIR subjects had more than 1D of myopic progression compared with 20% of the placebo group (P < .001). Frequency of adverse events was 98% in the PIR group and 93% in the placebo group (P = .091).

Dropout rate due to adverse events was 11% in the PIR group and 0% in the placebo group. The most common adverse events were gel residue on the eyelids, blurred near vision, and asymptomatic conjunctival reactions.

"PIR 2% gel used twice daily in moderately myopic children reduced the rate of myopic progression at one year by 50% (0.26 D) compared to placebo. Safety profile was acceptable," the authors write. "Phase 3 studies will examine varying doses of PIR used over a broader age range. PIR is an exciting, novel, and effective approach to the pharmacologic treatment of myopia."

The second study was a one-year, double-masked, placebo-controlled, parallel group study conducted at seven sites in Asia. D. T. Tan and colleagues from the Asian Pirenzepine Study Group randomized 353 children aged 6 to 12 years at a ratio of 2:2:1 to treatment with PIR 2% twice daily, placebo in the morning and 2% PIR in the evening, or placebo twice daily.

From a mean baseline of -2.3 to -2.4D, differences favoring PIR began at three months. After one year, the mean progression in myopia was -0.47D with PIR twice daily (P < .001 vs. PIR once daily and vs. placebo), -0.70D with PIR once daily, and -0.84D with placebo twice daily.

"The difference between PIR b.i.d. and placebo represents approximately a 50% reduction in progression," the authors write. "Mydriatric and accommodative effects were present, but relatively mild, as were adverse events. However, there was a dosing-related incidence of follicles and papillae that were often asymptomatic."

All of the authors of each of these studies have a commercial relationship with Valley Forge Pharmaceuticals.

In a third study, the Atropine in the Treatment Of Myopia (ATOM) trial enrolled 400 eligible children aged 6 to 12 years, with myopia of -1 D to -6 D. Subjects were randomized in double-masked fashion to receive in one eye either 1% atropine eye drops or Isoptotears once nightly.

Of 359 subjects (90%) who returned for one-year follow-up, 331 (83%) also completed the two-year study. Of the 69 subjects who did not complete the study, 21 were from the placebo group and 48 were from the atropine group.

At one year, mean myopia progression in eyes treated with placebo was -0.76 D ± 0.44 D. In the atropine-treated eyes, myopia regressed by +0.3 D ± 0.50 D (P < .0001), and there was a reduction in axial length by -0.14 mm ± 0.28 mm, compared with a mean axial elongation in the placebo-treated eyes of +0.20 mm ± 0.30 mm (P < .0001).

After two years, the mean myopia progression and axial elongation in the placebo-treated eyes were -1.20 D ± 0.69 D and +0.38 mm ± 0.38 mm, respectively. In the atropine-treated eyes, myopia progression was -0.25 D ± 0.92 D, and the axial length remained essentially unchanged compared with baseline (-0.02 mm ± 0.35 mm; P < .0001 for both comparisons).

"The ATOM study is the largest randomized controlled trial of its kind to date, and the results provide strong evidence that childhood myopia progression and axial elongation can be controlled through pharmacological means such as topical atropine," write W. H. Chua, from the Singapore Eye Research Institute, and colleagues.

None of this study's authors disclosed any significant financial interests.

ARVO 2003 Annual Meeting: Abstracts 44778/B437, 801/B776, 3119. Presented May 4-8, 2003.

Reviewed by Gary D. Vogin, MD

    
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