Purpose: To determine the mechanism of nerve fiber damage in glaucoma by studying the structure of human optic nerve lamina cribrosa (LC) in different regions.
Methods: 15 human eyes of 10 cases were studied. The specimens were prepared for scanning electron microscopy, and numbers and areas of pores in LC were measured by electron image analysis system. Draw a frequency distribution map with each curve represents the tendency of pores distribution in a particular part. The proportion of the connective tissue in respective quadrant can also be calculated. The specimens were also prepared for histological examination.
Results: There are many pores of various magnitude and shapes on the surface of LC. There are significantly more large pores (> or = 3000 micron2) in the superior and inferior than those in the nasal and temporal quadrants, especially in the peripheral regions. In terms of area, the percentages of connective tissue in the nasal and temporal quadrants are the highest. Collageous fibers, various in diameter, are arranged in bundles and tangentially around each pore.
Conclusion: In normal persons, the percentage of large pores in the superior and inferior peripheral parts is the highest, the density of the connective tissue is the lowest. So, the force received by unit area of the superior and inferior parts is bigger than that of the nasal and temporal sides, therefore, it is susceptible to the impact of high intraocular pressure at the early stage and causing corresponding visual defect. Our study may suggest the mechanism of optic nerve damage of glaucoma.