| loop excision | A diagnostic and therapeutic gynecological surgical technique for removing dysplastic cells from the cervix. In this office procedure conducted with the aid of colposcopy, a small wire loop is used to excise visible patches of cervical intraepithelial neoplasia. Like cauterization, cryosurgery, and CO2 laser procedures, loop excision can be done with local anaesthetic, and is an uncomplicated, relatively inexpensive way of removing dysplastic cells; in addition, it provides material for biopsy. It is not advised for cases of severe dysplasia or carcinoma in situ, which are better addressed by cervical conization, an inpatient procedure. Synonym: loop resection. (05 Mar 2000) |
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| loop of henle | A u-shaped turn in the medullary portion of a renal tubule, with a descending limb from the proximal convoluted tubule and an ascending limb to the distal convoluted tubule. (12 Dec 1998) |
| loop of hypoglossal nerve | A loop in the cervical plexus consisting of fibres from the first three cervical nerves. Fibres from a loop between the C-1 and C-2 spinal nerves accompany the hypoglossal nerve for a short distance, leaving it as the superior root of the ansa cervicalis. Fibres from a loop between the C-2 and C-3 spinal nerves form the inferior root of the ansa cervicalis. Most commonly, the roots merge, forming the ansa cervicalis, which gives rise to branches innervating infrahyoid muscles. Synonym: cervical loop, loop of hypoglossal nerve. (05 Mar 2000) |
| loop resection | A diagnostic and therapeutic gynecological surgical technique for removing dysplastic cells from the cervix. In this office procedure conducted with the aid of colposcopy, a small wire loop is used to excise visible patches of cervical intraepithelial neoplasia. Like cauterization, cryosurgery, and CO2 laser procedures, loop excision can be done with local anaesthetic, and is an uncomplicated, relatively inexpensive way of removing dysplastic cells; in addition, it provides material for biopsy. It is not advised for cases of severe dysplasia or carcinoma in situ, which are better addressed by cervical conization, an inpatient procedure. Synonym: loop resection. (05 Mar 2000) |
| achromatic lens | A compound lens made of two or more lens's having different indices of refraction, so correlated as to minimise chromatic aberration. (05 Mar 2000) |
| acoustic lens | In ultrasonography, a lens used to focus or diverge a sound beam; may be simulated by electronic manipulation of signals. (05 Mar 2000) |
| anterior pole of lens | The central point on the anterior surface of the lens of the eye. Synonym: polus anterior lentis. (05 Mar 2000) |
| anterior surface of lens | The anterior surface of the lens of the eye. Synonym: facies anterior lentis. (05 Mar 2000) |
| aplanatic lens | A lens designed to correct spherical aberration and coma (q.v.). Synonym: periscopic meniscus. (05 Mar 2000) |
| apochromatic lens | A compound lens designed to correct both spherical and chromatic aberrations. (05 Mar 2000) |
| asphenc lens | <physics> A lens made aplanatic by grinding the outer zones to a greater radius than the inner zones. Aplanatic condensers can be made in this way. A simple aspheric lens is widely used as a lamp condenser because of its efficiency in converging light rays to one focal plane. (05 Aug 1998) |
| aspheric lens | A lens with a paraboloidal surface that eliminates spherical aberration. (05 Mar 2000) |
| astigmatic lens | A lens in which one of the surfaces is curved in one meridian and less curved in the opposite meridian; e.g., a teaspoon or a football. Synonym: astigmatic lens. (05 Mar 2000) |
| axis of lens | A line connecting the anterior and posterior poles of the lens of the eye. Synonym: axis lentis. (05 Mar 2000) |
| back lens | <physics> In any compound lens (a lens system composed of more than one lens element), the last lens through which the light passes is called the back lens. It may be a single simple lens, a doublet, or triplet. See: front lens (05 Aug 1998) |