What role does schlemms canal play in glaucoma?

Crucial role: Shclemm's canal is the little canal that acts as the outflow channel for the fluid to leave from inside the eye. This fluid brings nourishment to the eye from the nutrients in the blood and the schlemm's canal is the exit for this fluid. Any blockage to the exit of this fluid will cause the eye pressure to increase. In open angle glaucoma it is believed that the fluid has difficulty leaving the ey.

Relevant: Part of the drain of the eye. Secondary glaucomas cause blockage of this region. Even when schlemm's canal appears ok on gonioscopy, there is probably some downstream resistance, especially at the microscopic level leading to decreased outflow when the pressure is elevated.