各種2.4mmスリットナイフの評価

Comparison of 2.4 mm slit knives for cataract surgery

要約　目的：白内障手術時に使用するスリットナイフの評価をした。

対象と方法：2.4mmスリットナイフ9種（シングルベベル6種，ダブルベベル3種）を対象とし，ナイフ先端部の最大幅，最大幅位置，先端角度，先端強化部角度，刃付角度，板厚を測定した。また豚眼強角膜片を人工前房装置に固定し，眼圧を一定にした状態で角膜1面切開創を作製する際の刺通抵抗値を測定した。作製した切開創はトリパンブルーで染色し，デジタル顕微鏡で撮影しその大きさを測定し比較した。

結果：最大幅は2.35〜2.49mm，最大幅位置は2.02〜3.58mm，先端角度は36〜60°，先端強化部角度は42〜67°，刃付角度は4〜20°，板厚は0.09〜0.18mmとナイフ先端部の形状はそれぞれ大きく異なっていた。刺通抵抗値は132.5〜387.9mNと差が生じ，切れ味の違いがあった。切開創の大きさは内側で2.40〜2.55mm，外側で2.22〜2.41mmと内側のほうが創口が大きく，ばらつきも異なった。

結論：市販されている2.4mmスリットナイフはそれぞれ異なる形状をし，切れ味と作製される切開創の大きさも異なる。白内障手術の小切開化に伴い，スリットナイフの特徴が術後成績に関連する可能性が考えられた。

Abstract　Purpose：Evaluation of the sharpness of 2.4 mm slit knives used in cataract surgery.

Subject and Method：Six kinds of single-bevel 2.4 mm wide slit knives and three kinds of double bevel 2.4 mm wide slit knives were tested in the study. The maximum width at the tip of each knife, position of the maximum widths, angle of tips, angle of tip strengthening section, blade angle, and blade thickness were measured. To assess knife sharpness, an incision was made into the cornea of a pig eye, and the resistance value to each knife was measured. We used porcine sclerocorneal graft and artificial chamber system to measure resistance value. The incisions were stained with blue paint and their sizes were measured for comparison.

Result：The maximum slit knife width ranged from 2.35 to 2.49 mm. The position of maximum widths ranged from 2.02 to 3.58 mm. The angle of tips ranged from 36 to 60 degree. The angle of tip strengthening section ranged 42 to 67 degree. The blade angle ranged 4 to 20 degree, and blade thickness ranged 0.09 to 0.18 mm. The resistance values at penetrating to the grafts were different as 132.5 to 387.9 mN among the slit knives. The size of the inner incision ranged from 2.40 to 2.55 mm, and that of the outer incision ranged from 2.22 to 2.41 mm.

Conclusion：The nine commercially available slit knives showed differences in size and shape when examined by scanning electron microscope. Corneal incisions in porcine cornea showed differences regarding resistance to incision and regarding the inner and outer size of incised corneal wound.