A fluorescein pattern that has a black area over the corneal apex and a diffuse green area in the periphery normally indicates:

When examining a fluorescein pattern, a black area over the corneal apex accompanied by a diffuse green area in the periphery typically suggests that the contact lens is fitting flat on the cornea. This occurs because a flat fitting lens does not adequately conform to the curvature of the cornea, leading to an area of lack of fluorescein (appearing black) at the center where the lens is not touching the cornea, while the periphery still shows green staining due to the fluorescein pooling in the space created by the lens edge.

In a normal scenario, you would expect to see a more evenly spread green area indicating that the lens is properly aligned with the curvature of the cornea, allowing for adequate tear film exchange beneath the lens. The presence of a steep fit would generally manifest as more central pooling and less peripheral staining, as the lens would align closely to the cornea's shape. A tight fit would show very little to no pooling of fluorescein, indicating that the lens is too snug on the eye. The distinctive pattern of having a black zone centrally and diffuse green at the edges specifically supports the flat fit characterization.