الفهرس 
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Abstract
The cornea is the transparent a vascular tissue with a smooth, convex outer surface and concave inner surface. Cornea covers the iris, pupil, and anterior chamber. The cornea, with the anterior chamber and lens, refracts light, with the cornea accounting for approximately two-thirds of the eye’s total optical power. In humans, the refractive power of the cornea is approximately 43 diopters.
Dimension of the anterior Surface Vertical is 11.7 mm and Horizontal is 10.6 mm .Horizontal corneal diameter (WTW) is an important measurement that has diverse clinical applications (micropthalmia , microcornea , macropthalmia , macrocornea , sizing some types of intraocular lenses).The accepted general standard of normal horizontal WTW from >11 to < 13 mm.
Anterior chamber is an angular space, anteriorly by inner surface of the cornea and posteriorly by the lens within the papillary aperture, anterior surface of the iris and apart of ciliary body. Anterior chamber 3mm deep and it contains 0.25 ml of the aqueous humor. Anterior chamber depth is shallower in the hypermetropic eye than the myopic eye. Also shallower in children and in older people. Volume: 220 MicroL. (Chamber volume decreases by 0.11 MicroL per year life).Diameter: 11.3 – 12.4 mm .Depth: 3.15 mm (2.6 – 4.4 mm) (chamber depth decreases by 0.01 mm per year life) .Chamber deepens by 0.06 mm for each diopters of myopia. Chamber depth is slightly diminished during accommodation, partly by increased lens curvature & partly by forward translocation of the lens. Wide angle of anterior chamber denotes the eye in which the angle between iris and surface of the Trabecular meshwork is between 20 to 45 degrees. Angles less than 20 degrees are termed as narrow angle.
The white to white corneal diameter is the horizontal distance between the borders of the corneal limbus, The accepted general standard of normal horizontal WTW from >11 to < 13 mm. or approximately 75% to 80% the size of the adult human cornea. Several factors influence the values of the corneal parameters; these factors include age, gender, race and ethnicity.
There are several techniques for measurement of white to white diameter, which can be divided into two main groups: manual (calipers and scales in slit-lamp) and automated devices (ultrasonic biomicroscopy, IOLmaster,pentacam rotating Scheimpflug camera imaging ,magnetic resonance imaging (MRI), and optical coherence tomography (OCT).
Rotating Scheimpflug imaging technology is used by instruments to measure the anterior and posterior corneal surfaces, as well as other anterior segment structures. Initially Scheimpflug photography was used to obtain images of lens opacities for objective evaluation, but pentacam-scheimpflug camera is much wider in its clinical applications as a diagnostic tool for not only corneal diseases like Keratoconus but cataract and refractive surgeons as well as glaucomatologists than the Scheimpflug photography alone.
Myopia is a progressive visual disorder that results in poor distance vision. If the myopia is severe, it will impair near vision as well. Near-sightedness or short-sightedness is a condition of the eye where light focuses in front of instead of on retina. This causes distant objects to be blurry while close objects appear normal. The underlying cause believed to be a combination of genetic and environmental factors. In addition to weakening vision, it also changes the physical structure of the eye. It can steepen the front surface of the eye (cornea) and/or stretch the retina (axial elongation). Near sightedness is the most common eye problem and is estimated to affect 1.5 billion people (22% of population). Rates vary significantly in different areas of the world. Rates among adults are between 15 and 49, similar in males and females. Among children it affects 1% of rural Nepalese, 4% of south Africans, 12% of American, 37% in some large Chinese cities.
This study included 60 myopic patients ( 20 patients for each group of myopia)
In all types of myopia ( low : less than or equal -3.00 diopter ) ( moderate: more than -3.00 and less than -6.00 diopter) ( high: more than -6.00 diopter) , to assess anterior chamber angle and white to white distance.
There was no statistically significant relation found between degree of myopia and anterior chamber angle while there was highly statistically significant increase in white to white with the increase of degree of myopia with p-value < 0.001.