Is the crystalline lens refractive?

The crystalline lens of the eye is indeed a refractive structure, meaning it bends light as it passes through. Its primary function is to help focus light onto the retina, thereby aiding in clear vision. The lens's refractive nature allows it to adjust its shape for near and distant vision through a process known as accommodation, which is facilitated by the ciliary muscles.

In this context, while the lens is a dynamic and adjustable component of the eye's optics, it is fundamentally refractive at all times. This inherent property allows it to contribute to our ability to see clearly. Therefore, stating that it is not refractive does not align with the physiological and optical roles the lens plays in vision. The other choices suggest varying degrees or conditions under which the lens might bend light, but the accepted scientific understanding confirms that the crystalline lens is always refractive in nature.