What is the name of the concave depression in the central retina for gathering light?

Fovea is the name of the concave depression in the central retina for gathering light.
Retina is the thin, transparent tissues that lie adjacent to the choroid, contains rods and cones. Retina senses light and send images to the brain. A healthy, intact retina is a key to clear vision. Fovea is responsible for sharp central vision.

Alinear relationship would look like a straight line on the graph. it could have a positive negative or 0 slope. so it could be a line potentially going in any direction but it must be perfectly straight.