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Quantitative studies of elastin in the optic nerve heads of persons with primary open-angle glaucoma
E N Quigley1, H A Quigley, M E Pease
1Glaucoma Service, Wilmer Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Purpose:
To compare quantitative and qualitative differences in elastin content in the optic nerve heads of glaucomatous and control human eyes.
Methods:
Transmission electron microscopy and quantitative histomorphometry on ten control and ten glaucomatous eyes.
Results:
Elastin fiber complexes in the control lamina cribrosa were smaller and more numerous than in the insertion zone of the sclera immediately surrounding the lamina. Although the density of elastin fibers in the normal lamina was twice that of the insertion zone (P = 0.004), the percent area of the connective tissue matrix occupied by elastin was the same for both zones (P > 0.4). There was no difference between control and glaucomatous eyes in the quantified parameters of elastin content or in the ultrastructure of elastin between control and glaucomatous eyes.
Conclusions:
The authors demonstrated for the first time that elastin in the normal lamina consists of fibers of smaller diameter than in the adjacent sclera, although the total amount of elastin is similar in both locations. This may provide maximum viscoelasticity within the limited connective tissue beam area of the lamina. Despite using a large number of specimens, the authors again found no differences between normal and glaucomatous eyes in the number or ultrastructural appearance of elastin fibers.