آﻗﺎي رﺿﺎ ﯾﻮﺳﻔﯽ(ENDOTHELIAL SPECULAR MICROSCOPY)

ENDOTHELIAL SPECULAR MICROSCOPY

Shahid Beheshti University of Medical Sciences, School of Rehabilitation

Abstract: Endothelium is the innermost layer of cornea - consisting of 350000-500000 cells. This layer has some vital functions. It provides water and nutrition for adjacent corneal layers and has a barrier function which controls in and out flow and hydration of cornea by inter-cellular tight junctions and active processes. Hexagonal cell shapes of this layer permits to take best use of each cell ( hexagone has largest surface in similar border size among different cell shapes). Large defects in this layer leads to corneal decompensation and corneal opacity. Endothelial integrity is analyzed by specular endothelial microscopy. Specular reflection is normal reflection bouncing of a surface and seen when there is a regular smooth surfaced optical interface between two different medias of unequal refractive indices and incident light angle equals with reflection angle to observer. Due to 0.022% difference between endothelium and aqueous humor, its reflection is observed on aqueous and it's image can be captured. This method provides us with an image of endothelial mosaic which lets us to check number, density and shape of endothelium layer. Contact and noncontact methods are two types of microscopy. Former one needs anaesthesia and lets us capture more cells. Latter method is more common but can visualize fewer cells. Comparison method, frame method, corner to corner method and center method are methods used for cell counting. Cell density, polymegathism (coefficient of variance) and pleomorphism (percent of hexagonal cells) are important factors TO NOTE to decide on integrity of endothelium. These factors can be abnormal in different conditions eg. Long term CL use, glaucoma and corneal dystrophies. There are some factors which can affect endothelial analyzing: quality of image, expertise of analyzer in determining single cell, number of cells in each sample