- 學位論文
逆幾何角膜塑型鏡片與一般硬式隱形眼鏡之機械性質比較
Comparison of Mechanical Properties between Reverse Geometry Orthokeratology and Conventional Rigid Gas Permeable Contact Lenses
摘要
目的： 隱形眼鏡的機械性質對於鏡片的耐用性及配戴者的安全性而言都很重要。本研究的目的是要比較，相同的隱形眼鏡材質，逆幾何角膜塑型鏡片設計及一般球面鏡片設計其機械性質是否有所不同。 方法： 使用相同後光學區弧度、鏡片直徑、後頂點度數、中央厚度、邊緣厚度以及相同鏡片材質的角膜塑型逆幾何設計和一般球面設計的鏡片來比較其彎曲強度。用Instron 4301的測量儀器測量鏡片破裂時的彎曲強度、彎曲變形量及鏡片變形30%時的彎曲強度。 結果： 逆幾何角膜塑型鏡片抗破裂的彎曲強度為369±56 gf；一般球面鏡片破裂時的彎曲強度339±10 gf，角膜塑型鏡片的彎曲強度較一般硬式隱形眼鏡大，但此差異未達統計上的顯著差異，p值為0.465。逆幾何鏡片及一般球面鏡片破裂時的彎曲變形分別是72±5 %及73±2 %，也沒有顯著的差異，p值是0.602。然而，逆幾何鏡片變形30%時的彎曲強度為121±9 gf，明顯高於一般球面硬式隱形鏡變形30%時的彎曲強度77±3 gf，p值為0.009。 結論： 逆幾何角膜塑型鏡片設計在變形30%時的抗彎強度顯著高於一般球面鏡片的設計。這表示未破裂之前，逆幾何角膜塑型設計的鏡片在受壓迫的狀況下，較不易被改變其幾何參數。
並列摘要
Purpose. The ability of resistance to breakage is important for the durability of a contact lens and also the safety of wearer. The aim of this study is to understand the mechanical properties of reverse geometry orthokeratology (OK) lens design when compared with conventional standard (alignment fitted) lens design of the same gas permeable contact lens material. Methods. Reverse geometry orthokeratology and conventional alignment lenses designs with identical back optical zone radius, total diameter, back vertex power, center thickness, edge thickness and lens material were chosen for this comparison study. The flexural strength, flexural deformation at rupture and flexural strength at 30% deformation were measured using the Instron 4301 automated materials testing instrument. Results. The flexural strength at rupture of reverse geometry lenses (369±56 gf) and alignment lenses (339±10 gf) were not significantly different (p=0.465). The flexural deformation at rupture of reverse geometry lenses and alignment lenses were 72±5 % and 73±2 %, respectively, without significant differences as well (p=0.602). However, the flexural strength at 30 % deformation of reverse geometry lenses (121±9 gf) was significantly higher than that of conventional alignment rigid gas permeable lenses (77±3 gf)(p=0.009 ). Conclusions. Reverse geometry orthokeratology lens design showed higher flexural strength at 30 % deformation compared to conventional alignment lens design. This suggest that reverse geometry lens design have less tendency to change its geometric parameters during pressure.