探討兒童配戴角膜塑型片後眼睛高階像差及角膜形狀與厚度的改變

The Change of Ocular Aberration and Corneal Shape in Children after Wearing Overnight Orthokeratology Lenses

林芮宇(Jui-Yu Lin)

指導教授 ： 蕭清仁

中山醫學大學/醫學科技學院/生物醫學科學學系碩士班/碩士(2016年)

摘要

研究背景：在台灣近視的比例高達九成以上，近視控制的方法有許多種。角膜塑型片(Orthokeratology, Ortho-K) 屬非侵入性治療的視力矯正方法之一，於夜晚睡眠時配戴，鏡片的特殊設計可使角膜重新塑型以達到降低近視度數的作用，也因為角膜重新塑型會造成角膜中央和周邊的形狀厚度改變，以及眼睛像差的改變，藉此來探討配戴前後眼睛高階像差與角膜中央及周邊形狀厚度的改變以及像差與角膜形狀厚度的相關性。
研究方法：本研究為回溯型研究。病人在術前皆接受完整的眼睛檢查，包含術前眼睛屈光度、最佳矯正視力、角膜弧度測量、角膜地圖儀分析以及眼睛的高階像差。病人在驗配角膜塑型片前和配戴後第1週及第1個月，皆接受完整的角膜塑型片驗配評估，包含角膜弧度、鏡片定位、鏡片造成之效果，眼睛表面螢光染色評估角膜是否破皮或其它損傷。每次的檢查包含裸視視力、最佳矯正視力、前導波像差評估眼睛高階像差的的變化，以及利用OrB-scan量測角膜形狀改變及厚度的變化。
結果：19位受試者共37支眼列入分析( 12位女生，7位男生，平均年齡為11.31 ± 2.27 歲)，平均等價球面度數為 -3.27 ± 1.62 D。受試者在配戴角膜塑型片後7天角膜中央屈光度就有明顯變平 ( p < 0.05)；角膜鼻側1 mm屈光度、角膜顳側1 mm和2 mm屈光度、角膜上方1 mm屈光度、角膜下方1 mm屈光度在配戴7天後皆開始顯著變平( p < 0.05)；角膜下方2 mm屈光度在第30天後才有顯著變平( p < 0.05)；但角膜厚度在配戴角膜塑型片後30天皆無顯著差異。眼睛高階像差在配戴7天後就有顯著增加 (p < 0.05)；離焦像差在配戴角膜塑型片後30天才有顯著下降 (p < 0.05)；彗星像差和球面像差在配戴後7天皆明顯增加 (p < 0.05)，且球面像差在配戴後皆往正的方向增加。比較配戴角膜塑型片後角膜塑型片Target Power、角膜屈光度以及像差之間的關係，證實配戴角膜塑型片後”球面像差的改變”與”角膜塑型片的Target Power”、”角膜中央屈光度的改變”以及”角膜周邊和中央屈光度差的改變”有顯著關係 (p < 0.05)；配戴角膜塑型片後”彗星像差的改變”與角膜不對稱性也就是”角膜顳側3 mm (T3) 和角膜鼻側3 mm (N3) 的屈光度差”有顯著關係 (p < 0.05)。
結論：本篇研究結果證實眼睛的高階像差會因配戴角膜塑型片後角膜屈光度改變而增加，尤其是球面像差以及彗星像差。發現球面像差的變化與角膜塑型片的Target Power有正相關性；彗星像差的變化與角膜屈光度的不對稱性相關，越往角膜顳側偏彗星像差的變化越大。

關鍵字

角膜厚度 ； 高階像差 ； 角膜塑型片

並列摘要

Background: According to the statistics, the prevalence level of myopia has reached over 90% of the population in Taiwan. The methods of control myopia include Atropine, multifocal spectacle, and overnight orthokeratology. Orthokeratology is a temporally non-surgical correction of refractive errors. The special design of orthokeratology lens can offset the patient’s refractive error when patient sleep. Due to the lens design, cornea is reshaped and thickness changed. Cornea reshaping causes the thickness changes in central and peripheral region and thus inducing high order aberration.

Purpose: In this study, we will investigate the change of corneal central and peripheral thickness and ocular high order aberration associate with overnight orthokeratology.

Methods: This analysis is a retrospective study of patients with myopia who had undergone Ortho-K treatment. Before the treatment, patients would receive a comprehensive ocular-visual examination; it includes the refractive errors, best visual acuity, corneal curvature, corneal eccentricity, topography and Wavefront aberration. Patients were examined before OK treatment,7 days and 30 days post lens wearing. Each examination include slit lamp examination, corneal curvature, lens fitting assessment, fluorescein pattern , refractive errors, best visual acuity, corneal eccentricity, Wavefront aberration, topography and pachymetry.

Results: There are 19 subjects, 37 eyes (12 females, 7 males, mean age 11.31 ± 2.27 year-old). Mean spherical equivalent power (SER) is -3.27 ± 1.62 D. Corneal Apex refractive power has significant changed after wearing Ortho-K lens (p < 0.05). Corneal refractive power of nasal 1 mm (N1), temporal 1mm (T1), temporal 2 mm (T2), superior 1 mm (S1) and inferior 1 mm (I1) become significantly flatter after Ortho-K treatment (all p < 0.05). But there are no significant differences in corneal thickness change (p > 0.05). High order aberrations have significantly increased after treatment, especially Spherical aberration (all p < 0.05) and Coma aberration (all p < 0.05). Defocus aberration has significantly decreased after 30 days Ortho-K treatment. The change of Spherical aberration is positively correlated with OK Target Power (p < 0.05), the change of corneal apex refractive power (p < 0.05) and the change of the difference of corneal apex and mid-periphery refractive power (p < 0.05). The change of Coma aberration is significantly correlated with corneal asymmetry (p < 0.05).

Conclusion: In this study, it proves ocular high order aberrations will be increased by the corneal reshaping after wearing Ortho-K lens, especially Spherical aberration and Coma aberration. In conclusions, there is a positive correlation between Target Power of orthokeratology and Spherical aberration. Coma aberration is correlated with corneal asymmetry. The more temporal decentration, the more Coma aberration.

並列關鍵字

Corneal Thickness ； High Order Aberrations ； Orthokeratology

參考文獻

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