Final answer:
A cortical cataract affects one layer of the crystalline lens and is surrounded by clear areas.
Step-by-step explanation:
The type of cataract that affects one layer of the crystalline lens and is surrounded by clear areas is called a cortical cataract. Cortical cataracts form in the outer layer of the lens, causing the lens fibers to break down and form wedge-shaped opacities. As the cataract progresses, the clear areas appear as spokes or lines extending from the outer edge towards the center of the lens.