الفهرس 
Anatomy and Physiology of the CorneaOnly 14 pages are availabe for public view
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Abstract
Today, it is imperative that all doctors involved in corneal surgery understand thoroughly the science and clinical application of corneal imaging and topography due to the ever-increasing sophistication of corneal treatment technologies for better visual quality outcome.
Corneal measurement devices continue to advance terribly to become so many and very complicated. So, it was mandatory to have comparative studies to demonstrate the difference in their accuracy, capabilities, and data analysis.
Methods of measuring corneal topography fall into two broad categories. Those which use the reflection principal to measure the slope of the corneal surface and calculate the curvature and elevation, they are represented by the placido disc systems. The other category includes elevation based systems that measure the true corneal shape directly in terms of elevation from which curvature can be calculated, they are represented by rasterphotogrammeter, Orbscan and the Scheimpflug camera, which had become the most important and accurate topographic device. These new diagnostic systems now allow to image the back surface of the cornea enabling point-to-point pachymetry.
Tomographers create three-dimensional models of the cornea from cross-sectional images in many devices. Some of these new technologies enable modeling of the cornea, yielding information about curvature, power, and shape as slit scanning (Orbscan) and Scheimpflug imaging. Others are better suited for measurement of corneal anatomy (including flap placement, stromal scar depth, and intrastromal corneal ring segments evaluation) as ultrasound biomicroscopy and anterior segment optical coherence tomography.
For sufficient magnification to allow observation of cellular details there are; confocal microscopy that produce images of thick specimens at various depths taken point by point and reconstructed with a computer, with the possibility to choose the corneal layers to be scanned or full cornea in one unique exam. In addition, there are specular microscopes that were used primarily to evaluate the corneal endothelium, whoever the corneal epithelium and stroma as well as the crystalline lens can also be visualized and evaluated.
Corneal thickness is used by corneal specialists, refractive surgeons, and glaucoma specialists daily for patient management. Several technologies enable measurement of corneal thickness; including optical systems like slit scan imaging, contact and noncontact specular microscopy, AS-OCT, confocal microscopy and ultrasound systems like UBM and ultrasound pachymetry.
Corneal hysteresis is an important indication of the biomechanical properties of the cornea. It is an indicator of viscous damping in the cornea during inward and outward applanation pressure events that is the ability of the tissue to absorb and dissipate energy, a property that is determined by the visco-elastic properties of the corneoscleral shell.
The ocular response analyzer is a new instrument introduced by the Reichert ophthalmic instruments. It is a non contact tonometer which uses an air current to applanate the cornea and records the corneal response to it. This record corresponds to the corneal hystresis and it also measures the corneal compensated IOP, the Goldmann correlated IOP and the corneal resistance factor. It is particularly important in patient’s undergone refractive surgery.