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Yu Qiang Soh, Shakil Rehman, C. J. R. Sheppard, Roger W. Beuerman; Multi-photon Microscopic Evaluation of Lamina Cribrosa Pore Deformation. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3958.
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To investigate if changes in intra-ocular-pressure (IOP) are associated with mechanical deformations in lamina cribrosa (LC) pores, and the differences in susceptibilities to such deformations among pores located in different regions of the LC.
Ten freshly enucleated porcine eyes were dissected to reveal their LCs from the retinal aspect. Each sample was stretched apart circumferentially to simulate two IOPs: a) original IOP and b) 19.2 - 31.4mmHg above that. Second-harmonic-generation (SHG) microscopic images of the retinal-aspect of each LC were taken at each IOP, allowing for visualization and morphometric measurements of LC pores, the LC surface and central vascular bundle (CVB). The location of each pore within the LC was defined by: a) the 45-degree sector it was located in (8 sectors in an LC) and b) distance away from the centre of the LC (radial distance). Multivariate linear regression was carried out to determine if simulated IOP rises were associated with changes in pore dimensions, controlling for the factors of pore location, LC and CVB dimensions. ANCOVA was then carried out to identify the sectors associated with significantly greater IOP-related LC pore deformations.
Stepwise regression models revealed that simulated rises in IOP brought about the following changes in LC pore dimensions: a) increases in minimum feret (calliper) diameter, circularity (1(max) = perfect circle) and area, and b) decrease in aspect ratio. ANCOVA indicated the following trends in susceptibilities to pore deformation: a) pores located in superior-inferior axis sectors, in particular the inferior sectors, were most susceptible to deformations (minimum feret diameter, circularity and area); b) where differences in susceptibilities may exist in the nasal-temporal axis (pore circularity), temporal pores were more susceptible than nasal pores, c) the least susceptible sector was located superior-nasally in the LC. (p<0.05 for all trends mentioned)
When IOP was raised, LC pores experienced circular expansion and deformation. Sectors most susceptible to deformation were located in the inferior and temporal LC, corresponding to the prevalence of arcuate scotomas in the superior-nasal visual field in early glaucoma. This suggests a role of mechanical LC pore deformation in the pathogenesis of visual field losses.
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