使用Scheimpflug imaging評估白內障手術後人工水晶體偏位之研究

Abstract

白內障手術是現代常見的手術之一，從早期的囊外摘除術到今天的超音波水晶體乳化術都使得手術傷口越來越小，術後造成的散光也較少，然而白內障術後仍可能因水晶體偏位而影響視力表現及視覺品質。因此本研究使用Scheimpflug imaging搭配影像處理程式來量化水晶體的位置，並分析可能導致術後人工水晶體偏位的原因及術後人工水晶體偏位對視力表現造成的影響。 本研究分別量測白內障術後人工水晶體及自然水晶體的位置，人工水晶體受試者共30人，平均年齡67±10歲; 自然水晶體受試者共13人，平均年齡53±23歲。所有受試者在研究前皆詳細告知研究內容，並簽署受試者同意書，首先使用自動驗光儀Topcon KR 8900量測其散光及軸度，並使用眼前節成像儀器Pentacam HR拍攝眼前節影像，每隻眼收取角膜前後有效資料大於95%之影像一組，一組共25張，最後使用Matlab撰寫之影像處理程式量化水晶體位置，以得到水晶體最大傾斜角度及偏心值的影像及與之裂隙燈角度夾90度角的影像所測得之偏心值及傾斜角度，兩張影像所量得的水晶體偏心值(傾斜角度)合成最後的結果，當作受試者該次量測的水晶體偏心值及傾斜角度，並以Alpin的向量分析方式計算受試者之水晶體散光值，最後將水晶體偏心值、傾斜角度和年齡、最佳矯正視力(BCVA)、眼軸長、水晶體散光值做相關分析。 量測結果人工水晶體組平均偏心值0.20±0.07 (0.08至0.33)mm，平均傾斜角度2.24±0.93 (0.65至3.93)度，平均晶體散光值-0.50±0.34 (0至-1.33)D，人工水晶體有向上偏心的趨勢(左眼71%、右眼63%)，傾斜方向上則是向顳側傾斜(左眼100%、右眼94%); 自然水晶體組平均偏心值0.081±0.034 (0.032至0.17)mm，平均傾斜角度1.76±0.49 (0.80至3.08)度，平均晶體散光值-1.00 0.50 (0至-1.87)D。結果發現，受試者年齡與人工水晶體偏心值有顯著正相關(r=0.552, p=0.002)，與人工水晶體傾斜角度則無顯著相關(r=0.033, p=0.863)，眼軸長和年齡雖有顯著負相關(r=-0.515, p=0.008)，但和人工水晶體偏心值(r=0.122, p=0.570)及傾斜角度(r=0.066, p=0.758)皆無顯著相關。在人工水晶體偏位造成的影響方面，研究結果發現，最佳矯正視力(BCVA)與人工水晶體偏心值(r=-0.157, p=0.434)及傾斜角度(r=-0.333, p=0.089)皆無顯著相關; 水晶體散光值和人工水晶體偏心值及傾斜角度皆無顯著相關(r=0.138, p=0.483)、(r=-0.182, p=0.354)。 結果顯示，年齡可能是影響人工水晶體偏位的重要因素，老化過程使得水晶體厚度隨著年齡逐漸增加而變厚，睫狀肌的力量變小，水晶體懸韌帶及後囊袋的機械強度變弱，這皆是老年人可能產生較大的水晶體偏心值原因。本研究所開發之水晶體位置量化工具搭配眼前節成像儀器，可用來幫助醫師更加了解病患水晶體位置，未來更希望水晶體位置能成為醫師治療診斷及術前評估的一個重要參數。

Modern cataract surgery is the one of the commonly surgery in this era, it small wound size cause little astigmatism after surgery, but the decentration of intraocular lens (IOL) also can impair the visual outcomes, so the position of the IOL has become the most important issue in ophthalmology. This study try to quantify the IOL position with scheimpflug imaging and try to find the factor that cause the IOL decentration and tilt after surgery. The influence of IOL decentration and tilt on visual outcomes also discuss in this paper. We enrolled 30 eyes of 30 patients who underwent cataract surgery with IOL insertion and 23 eyes of 13 patients has crystalline lens at Far Eastern Memorial Hospital in this study. The patients averaged were 67±10, 53±23 years old respectively. All of the patients provided informed consent before this study. Corneal curvatures were measured by Topcon KR 8900 auto-refractor and capture the anterior segment image by Pentacam HR. Each eye has 25 scheimpflug image and the quality of image have to over than 95% valid data of cornea. The code written by Matlab use to measure the position of the lens. Lenticualr astigmatism was calculated by Alpin’s vector analysis method. Correlations were analyzed between IOL decentration, IOL tilt, age, axial length, BCVA, lenticular astigmatism. The mean decentration of IOL group is 0.20±0.07 (0.08 to 0.33)mm, mean tilt of IOL group is 2.24±0.93 (0.65 to 3.93)degree, mean lenticular astigmatism of IOL group is -0.50±0.34 (0 to -1.33)D. The mean decentration of crystalline lens group is 0.081±0.034 (0.032 to 0.17)mm, mean tilt of crystalline lens group is 1.76±0.49 (0.08 to 3.08), mean lenticular astigmatism of crystalline lens group is -1.00±0.50 (0 to -1.78)D. The correlation between IOL decentration and patient’s age was significant (r=0.552, p=0.002), but there was no correlation between IOL tilt and patient’s age(r=0.033, p=0.863). The correlation between axial length and patient’s age was significant (r=-0.515, p=0.008), but there was no correlation between axial length and IOL tilt (r=0.066, p=0.758) and decentration (r=0.122, p=0.570). The correlation between IOL decentration and the BCVA and lenticular astigmatism was not significant (p>0.05), nor was the correlation between IOL tilt and BCVA and lenticular astigmatism (p>0.05). The aging process may play an important role in IOL decentration. Major changes that occur in the lens with age, such as changes in the lens thickness, weakening of the zonular and capsular bag also cause the IOL decentration to increase with age. The tools used to quantify the IOL position present by this research and Pentacam HR can measure the IOL position easily and quickly, and hope the IOL position can be an important parameters to help the doctor in clinically.