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??????????? Arteriosclerosis is the generic term for three patterns of vascular disease, all of which cause thickening and inelasticity of arteries. The dominant pattern is atherosclerosis, characterized by the formation of intimal fibrofatty plaques that often have a central grumous core rich in lipid.
??????? The second morphologic form of arteriosclerosis is the rather trivial Monkeberg’s medial calcific sclerosis, characterized by calcifications in the media of muscular arteries. It is usually encountered in medium-sized muscular arteries in persons older than 50 years. These medial lesions do not encroach on the vessel lumen.
??????? Disease of small arterioles (arterilosclerosis is the third pattern. Small vessel sclerosis is most often associated with hypertension and diabetes mellitus. There are two anatomic variants, hyaline and hyperplastic, depending on the cause and rate of progression of disease.
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??????????? This is the only benign tumour of importance in the nasopharynx. It is a tough rubbery tumour, which usually arises from the lateral wall of the nasopharynx
??????????? Histologically the tumour consists of vascular spaces, with no contractile elements in the wall, surrounded by fibrous tissue.
??????????? The patient is nearly always a young boy with a complaint of nasal obstruction or epistaxis.
??????????? On examination a mass, which is smooth, lobulated and hard is seen on posterior rhinoscopy. Biopsy is too risky and should only be done if radiotherapy is contemplated.
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Definition: It is a refractive condition of the eye in which there is a difference in degree of refraction in different meridians.
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I.??????????????????? Regular astigmatism: is that form in which though the refraction in a meridian is the same throughout, there is a difference in the degree of refraction in every meridian; the curvature of the cornea is different in different meridians. One meridian exhibits the maximum and the other the minimum refraction; these are called the principal meridians and are always at right angle to each other.
1.????? Regular astigmatism according to rule-when the vertical meridian is more curved than the horizontal.
2.????? Regular astigmatism against the rule-when the horizontal meridian is more curved than the vertical
Simple astigmatism: in which one meridian is emmetropic and the other hypermetropic or myopic
Compound astigmatism?: in which both meridians are either hypermetropic or myopic but unequal in degree
Mixed: in which one meridian is hypermetropic and the other myopic
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II.???????????????? Irregular astigmatism: is that form in which there is a difference in degree of refraction not only in different meridians but also in different parts of the same meridian.
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