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Editors Selection IGR 20-4
Anatomical Structures: Mechanic factors underlying axonal damage
Comment by Ki Ho Park on:
56036 Eye-specific IOP-induced displacements and deformations of human lamina cribrosa, Sigal IA; Grimm JL; Jan NJ et al., Investigative Ophthalmology and Visual Science, 2014; 55: 1-15
While there have been many reports on the change in the thickness or volume of optic nerve head tissue after intraocular pressure (IOP) change, the study by Sigal et al. is quite unique in that it performed high-resolution measurements of displacements and deformations induced within the human lamina cribrosa (LC) microstructure. After an acute increase in the IOP of six donor eyes, the microstructural change was analyzed in terms of displacement, stretch, shear, and compression. Based on second-harmonic-generated imaging, the microstructural displacement and deformation were determined two-dimensionally at IOP levels varying from 10 to 50 mmHg. The authors found that IOP elevation induced substantial levels of in-plane LC stretch and compression.
The regions of largest displacement, stretch, compression, and shear were not co-localized. The responses of the contralateral eyes to IOP were not always more similar than were those of the unrelated eyes. The study clearly showed the regions of different kinds of deformation in the LC, which might facilitate understanding of the pathogenesis of mechanical axonal damage in glaucoma.
The regions of largest displacement, stretch, compression, and shear were not co-localized
The finding that the regions of stretch and compression did not co-localize when analyzed two dimensionally is very interesting. However, it is possible that in the axis vertical to the plane of analysis (z-axis), the stretched region has a compressive z-axis component and the compressed region has a stretched z-axis component.
Even though there are some limitations, such as (1) the lack of blood flow in the system, which might have contributed to the IOP-induced structural LC change; and (2) the two-dimensional analysis, the study represents pioneering research on LC microstructural change induced by IOP elevation. I look forward to the authors' follow-up research based on 3-D analysis of LC change.
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