ソフトコンタクトレンズにおける周辺部厚の位相差顕微鏡による計測

Measurement of peripheral thickness of soft contact lenses using a phase-contrast microscope

要約　目的：ソフトコンタクトレンズ（SCL）の厚みについては中心厚の計測データが一般に添付文書に記載されている。しかしながら，周辺部の厚みも強度や装用感の観点から検討の必要がある。位相差顕微鏡は異なる屈折率をもつ物質を透過した際に生ずる位相差を応用した顕微鏡であり，透明な対象の観察のために一般に広く普及している。今回，SCLの周辺部を観察するため，位相差顕微鏡を用いて周辺部厚の計測を試みた。

対象と方法：径60mmのペトリ皿内の生理食塩液に周辺部が対物レンズ側になるようにSCLを浮かべ，対物レンズ10倍と2000万画素の顕微鏡カメラで周辺部が鮮明となるまで位相差顕微鏡により接写した。SCLには−3, −7.5, −12 diopterの1日，2週間用のSCL〔AQUALOX^®（AQ）：Bausch & Lomb, ACUVUE OASYS^®（OA）：Johnson & Johnson〕，ソフトウェアとして画像解析にはSigmaScan^®，統計学的解析にはSigmaStat^®を用いた。

結果：t検定，2元配置分散分析の結果，周辺部厚は度数，装用期間にかかわらずAQがOAより有意に薄く，2週間用OAでは多変量解析の結果，近視度数に従い，有意に薄くなる傾向があった。

結論：SCLの種類により周辺部厚にも相違があることが判明し，今後，装用感や耐久性についても検討を加える必要があると考えられた。

Abstract　Purpose：We have checked the central thickness on the pamphlet about soft contact lenses. In this study we measured the peripheral thickness using a phase contrast microscope and a 20- megapixel camera because the phase shifts were transformed into changes in amplitude, which can be observed as differences in image contrast.

Materials and Methods：We set up the upper side of SCL at the side of the objective lens to observe the edge of the peripheral SCL〔−3, −7.5, −12 diopter（D）〕of the wearable lenses for 1 day and 2 weeks〔AQUALOX^®（AQ）：Bausch & Lomb, ACUVUE OASYS^®（OA）：Johnson & Johnson〕as the specimens. SigmaScan^® was used for image analysis, and SigmaStat^® for statistical analysis as software. Linear regression analysis is commonly used to forecast values for a given variable（dependent variables）based on the values of other variables（independent variables）. The relative contributions of diopter（Diopter）and wearable time（Time）, i.e., independent variables, to the repression of thickness, i.e., the dependent variables for multiple linear regression. We added that（I_AQ）is an indicator for AQ both set equal to 1 in the case of AQ and to 0 for OA as the included terms for specific differences in thickness. The indicator of AQ was used with another variable, e.g.（I_AQ）（Diopter）and（I_AQ）（Time）to identify of significant AQ as specific differences in response to a specific factor, in this case, the response of Thickness influenced by AQ, Diopter, and Time.

Results：The significant positive coefficient value（Diopter）about OA was shown, and it meant that the peripheral thickness of OA was thinner according to diopter because diopter in myopia was negative. The significant negative coefficient value（I_AQ）, an indicator for AQ, showed that the peripheral thickness of AQ, which had nothing to do with diopter and wearable time was thinner than that of OA.

Conclusions：Soft contact lenses have different peripheral thickness；thus among the types of SCL, and we suggested that it was necessary to consider the comfortable quality of fitting and fragility must be considered.