43.角膜地形圖的指標中,下列何者最不適合用於評估潛在的圓錐角膜?(A)下-上值(inferior-superior value, I-S value)(B)表面不對稱指標(surface asymmetry index, SAI)(C)視力潛能(potential visual acuity, PVA)(D)視軸偏角(angle kappa)