Disclosed are a processed starch powder in which the amount of water soluble component is greater than 2 wt % but less than 10 wt %, the water retention amount is greater than 600% and 1500% or less, and which comprises nonbirefringent particles, and a manufacturing method thereof. These tools and methods allow a user to select and maintain different guidewire stiffness characteristics such that a single guidewire can address a range of access capabilities. A woven PVC layer is laminated by heat and pressure to the underlying second PVC layer. In this manner the laser radiation propagated in the direction of the retina in further incisions are scattered and partially reflected such that the influence impinging upon the retina is reduced.