The authors evaluated the shapes of the largest clinically visible pores on the surface of the lamina cribrosa in 87 eyes of 52 glaucoma patients and found an apparent progression in pore shape as a function of the extent of glaucomatous optic nerve head damage. Small, round pores predominated in eyes with mild field loss, oval pores were more common in eyes with moderate field loss, and striate or slit-shaped pores were most frequent in eyes with advanced field loss. If the pores of the lamina cribrosa elongate as a function of increasing glaucomatous optic atrophy, and if large pore size is associated with an increased risk for pressure-related axonal damage, then the threshold for ganglion cell atrophy may drop as the damage to the optic nerve progresses.