Laser photocoagulation for choroidal neovascularisation in pathologic myopia

  • Review
  • Intervention

Authors


Abstract

Background

Pathologic myopia is usually defined as the need for a spectacle correction of -6 diopters or higher. Choroidal neovascularisation (CNV) is the most commonly occurring cause of visual loss in people with pathologic myopia. In myopic macular degeneration the occurrence of newly formed vessels in the macula often leads to a fibrotic pigmented scar causing a blind spot in the centre of the visual field.

Objectives

The primary objective of this review was to examine the effects of laser photocoagulation for CNV associated with pathologic myopia. A secondary objective was to compare the effects of different photocoagulation techniques.

Search methods

We searched the Cochrane Controlled Trials Register (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) in The Cochrane Library (Issue 1, 2007), MEDLINE (1966 to March 2007), EMBASE (1980 to March 2007), LILACS (March 2007) and reference lists of identified trial reports.

Selection criteria

We included randomised controlled trials comparing photocoagulation with observation or comparing different photocoagulation techniques in people with CNV associated with myopia of -6 diopters or higher.

Data collection and analysis

Two authors independently assessed the search results for eligibility.

Main results

Two studies were included that enrolled people with CNV located at 100 microns or more from the foveal centre. One study compared photocoagulation with observation. At the final examination, 16/35 participants randomised to photocoagulation versus 31/35 randomised to observation had visual acuity of 20/100 or worse after six to 48 months. The second study randomised 27 eyes (26 participants) to photocoagulation with three laser wavelengths (nine eyes per group). The number of eyes losing two or more lines was two (577 nm), three (590 nm) and three (620 nm) after three to 17 months. In both studies comparisons were made using outcomes assessed at the final examination. As the final examination took place at different follow-up times it was difficult to interpret the findings and it was impossible to extract data for further analyses.

Authors' conclusions

Despite its use over several years the effectiveness of laser photocoagulation for myopic CNV has not been established. Although there was a suggestion of short-term effectiveness in one small study on non-subfoveal CNV the results were potentially biased. Observational studies suggest that the enlargement of the atrophic laser scar after laser treatment of non-subfoveal CNV could be a potentially vision-threatening long-term complication, even in eyes free of CNV recurrence.

摘要

背景

雷射光凝固雷射用於病理性近視併發脈絡膜新生血管病患治療之研究

病理性近視通常被定義為需要六百度或以上之近視眼鏡矯正的近視。至於脈絡膜新生血管則是病理性近視病患視力喪失最常見的原因。近視造成的黃斑部退化,若在黃斑部出現新生血管,通常會造成纖維化色素性之結疤,並且造成視野中心的盲點。

目標

這篇研究初級目標主要是探討病理性近視併發脈絡膜新生血管使用雷射治療後的效果。而次級目標則比較不同雷射技術的效果。

搜尋策略

我們找了實證資料庫(Issue 1, 2007)中Cochrane對照試驗註冊資料庫 (CENTRAL) (其中包含了對Eyes 及Vision的試驗評論), 醫學文獻資料庫 (1966 to March 2007), 生物醫學與藥理學資料庫(1980 to March 2007), LILACS (March 2007) ,並所有試驗報告的參考文獻。

選擇標準

搜集的必須是隨機控制試驗,且在近視六百度或以上併發脈絡膜新生血管之患者使用雷射治療或純粹觀察,或是不同的雷射技術的比較。

資料收集與分析

共有兩位作者獨立地去評估符合準則的搜尋研究結果

主要結論

共有兩篇研究符合準則並紀錄了距離中央窩(foveal centre)100微米或以上的脈絡膜新生血管之病患。第一篇研究在比較雷射治療與僅接受觀察。在6個月到48個月後的檢查中,在35個隨機取樣使用雷射治療病患中有16個病人以及35個隨機取樣接受觀察的病患中有31個病人,最後視力都在20/100或甚至更差。第二篇研究中,隨機取樣27隻眼(26名參與者) 分成三組並分別使用三種不同的雷射波長(每組有9隻眼)。在3到17個月後,視力有明顯變差損失看不見兩行或以上者,在雷射波長577nm那組有2位,在590nm有3位,及在620nm有3位。以上兩篇研究都在最後的檢查中比較結果。因最後的檢查是在不同的追蹤時間所做,因此很難去解釋實驗的結果,且不太可能再做進一步分析。

作者結論

儘管此研究花了幾年的時間,雷射治療在近視所產生的脈絡膜新生血管之功效仍尚未能確立。雖然其中一個小研究中,雷射治療在非中央凹下(nonsubfoveal)的脈絡膜新生血管有短期的效果之建議,但其結果可能是有潛在性誤差;觀察性研究結果則建議對於非中央凹下的脈絡膜新生血管,如果使用雷射治療後會造成萎縮的雷射疤痕擴大,甚至可能會出現長期視力受損的併發症,即使在脈絡膜新生血管未復發的眼睛也可能發生。

翻譯人

本摘要由高雄榮民總醫院畢勇賢翻譯。

此翻譯計畫由臺灣國家衛生研究院(National Health Research Institutes, Taiwan)統籌。

總結

使用雷射光凝固術去治療高度近視所造成的靠近視網膜中央之脈絡膜新生血管。在高度近視(屈光異常達−6屈光度或更差)的病人在眼睛視網膜下方可能會形成新生血管(脈絡膜新生血管)。在過去數十年間雷射已被使用來破壞那些並非位於中央處的病灶。這次的回顧發現一個小型研究,共70個患有此類的疾病,參與者去比較接受雷射治療,或不接受治療而只有觀察的研究。雖然這個研究主張雷射在追蹤的前兩年是有顯著的益處,但其實這研究是不適當的報導及分析。另一個小型研究則是在病灶上不同的雷射波長效果的比較,實際上只有27個病患參與沒足夠的效度來顯現差異。因此,儘管雷射已普遍使用在此類患者中多年,究竟雷射所達到的效果及是否可維持多年的可能性仍是未知數。此外這些研究中也提到雷射疤痕的擴大在兩年後有可能造成長期視力受損的併發症,因為這類的視網膜進展性的萎縮會使得視野中心的盲點逐漸的產生。

Plain language summary

Laser photocoagulation for treating choroidal new vessels near the centre of the retina in people with high myopia

In people with high myopia (refractive error -6 diopters or worse) new blood vessels can grow under the retina of the eye (choroidal neovascularisation). For decades laser coagulation has been used to destroy lesions that are not central. This review found one small study, including 70 participants, which compared laser photocoagulation with no treatment for people with this disease. This study was inadequately reported and analysed, although it suggested a benefit with photocoagulation during the first two years of follow up. Another small study compared three laser wavelengths to achieve photocoagulation of the lesion, but actually had very little power to demonstrate a difference between them as only 27 participants were included. Therefore, despite its widespread use for many years, the amount of benefit achieved with photocoagulation and the possibility that it is maintained over the years remains unknown. Furthermore, these and other studies suggest that the enlargement of the laser scar could be a potentially vision-threatening long-term complication after two years, since it may cause the gradual occurrence of a blind spot in the centre of the visual field due to progressive atrophy of the retina.

Ancillary