What is the fine-grained topic of the following text: RESULTS: As IOP increased from 0 to 49 mm Hg, mean cross-sectional cup area increased (28% ± 3%, P < 0.001), lamina cribrosa area decreased (18% ± 2%, P < 0.001), and prelaminar tissue area decreased (5.5% ± 0.5%, P < 0.001). Only return the topic.
Impact of intraocular pressure on eye structure changes