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Title: | 準分子雷射近視手術術後的角膜表面高階像差變化以及其影響因子的研究 Higher-Order Aberration Changes of Corneal Surface after Laser Refractive Surgery and the Affecting Factors |
Authors: | Yi-Ting Hsieh 謝易庭 |
Advisor: | 胡芳蓉 |
Keyword: | 雷射近視手術,角膜表面像差,電腦角膜地形分析圖, laser in situ keratomileusis,LASIK,photorefractive keratectomy,PRK,corneal surface aberration,computerized videokeratography, |
Publication Year : | 2006 |
Degree: | 碩士 |
Abstract: | 雷射近視手術是利用氬氟準分子雷射(Ar-F excimer laser),將角膜組織的分子間鍵結打斷而對角膜進行削切;利用此方法來改變角膜的弧度,以達到改變角膜屈光能力的效果。不過雷射近視手術在治療近視以及散光的同時,也會因為傷口癒合以及雷射本身的因素,造成角膜表面的不規則變化而導致高階像差的增加。
隨著雷射近視手術的進步,手術方法從早期所使用的雷射屈光角膜切除術(photorefractive keratectomy,PRK),到目前常用的雷射原位層狀角膜塑型術(laser in situ keratomileusis,LASIK)。雷射光束也從早期的大光斑(broad beam),到飛點式小光斑(flying spot),以及混合型光斑。由於雷射近視手術本身即會造成角膜表面高階像差的增加,而這些不同手術方法以及不同原理的雷射機器各有其優點和缺點,也會對高階像差有不同的影響。 本研究是利用電腦角膜地形儀及電腦分析軟體,來分析病人接受雷射近視手術之後角膜表面高階像差的變化,並分析各種不同種類的雷射機器程式和手術方法對角膜表面高階像差變化的影響;並分析其他的各種可能影響因子,包括矯正的近視度數多寡,矯正散光度數多寡,年齡,治療區域大小等等。另外,以問卷調查的方式取得資料,來分析病人的視力品質與術後的滿意度和角膜表面高階像差變化的關係。 研究結果發現,在接受各種不同的雷射機器和手術方法術後,所有的高階角膜像差都明顯地增加。LASIK比起PRK在手術後會引起更多較細微的高階像差(第五、六階)。矯正近視的球鏡當量度數多寡,和手術引起的高階像差變化呈高度相關;矯正的度數越多,術後像差增加也越多。年齡越大,手術引起的高階像差變化越少。治療區域越大(包括光學區及過渡區),手術引起的高階像差變化也越少。有些小光斑雷射比起大光斑雷射在術後會引起較少的彗星像差,不過在球面像差及總高階像差方面並沒有明顯的差別。病人術後的視力品質和滿意度,與球面像差的關聯性最強,其次是總高階像差,再其次是彗星像差。 未來,可以根據這些研究的結果,來改進手術的方法以及機器的準確度,以期使病人擁有更好更完美的視力! Laser refractive surgery is performed by using Ar-F excimer laser to disrupt the inter-molecular bonding of corneal tissue and ablate the cornea, thereby changing the curvature and refractive power of anterior corneal surface. However, as soon as the spherical and cylindrical refractive errors are corrected by laser, higher-order aberrations of anterior corneal surface also result. This is due to the irregular change of anterior corneal surface by wound healing process or the laser treatment itself. The surgical and mechanical techniques of laser refractive surgery have been processing during the past decade. Photorefractive keratectomy (PRK) was preformed in the past, whereas laser in situ keratomileusis (LASIK) is used most often at present time. The laser beams also evolve from broad beams to flying spots and mixed spots. Since the laser refractive surgery itself induces the higher order aberrations of anterior corneal surface, these different surgical techniques and machines attribute differently to the higher-order aberration (HOA). In this study, we calculate the HOAs of anterior corneal surface by computerized corneal topography and calculating software. We then analyze the affecting factors of HOA changes after surgery, including surgical techniques (PRK vs. LASIK), laser machines (Summit Apex Plus, Allegretto Wave, Bausch & Lomb Technolas 217z, and VISX S4), age, attempted sphere correction, attempted cylinder correction, optic zone size, and transitional zone size. Besides, we use questionnaires to evaluate the visual quality and the extent of satisfaction of patients, and analyze the relationships with corneal surface HOA changes. As the result shows, all HOAs increased significantly after surgery by various techniques and machines. LASIK induced more trivial HOAs (the 5th and 6th orders) after surgery than PRK did. The diopters of spherical equivalent corrected were highly correlated with surgical-induced HOA changes. Patients with older ages had less HOA changes. The larger the treatment zone sizes (including optic zones and transitional zones), the less the surgical-induced HOA changes. Some flying-spot machines induced less coma-like aberrations, while no obvious differences of spherical-like aberrations and total HOAs between broad-beam machines and flying-spot ones were noted. The visual quality and the extent of satisfaction of patients correlated most strongly with spherical-like aberrations, then with total HOAs, and then with coma-like aberrations. In the future, we can try to improve the surgical techniques and the preciseness of laser machines according to these results. We hope our efforts can contribute to more perfect visions of future patients! |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/32222 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 臨床醫學研究所 |
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