| MOD | magnetic optic disk; maturity onset diabetes; Medical Officer of the Day; mesio-occlusodistal |
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| OA | obstructive apnea; occipital artery; occipito-anterior; occiput anterior; octanoic acid; ocular albi... |
| OAK | Kjer optic atrophy |
| OC | obstetrical conjugate; occlusocervical; office call; on call; only child; optic chiasma; oral contra... |
| OG | obstetrics and gynecology; occlusogingival; oligodendrocyte; optic ganglion; orange green; orogastri... |
| optic tectum | <anatomy> A region of the midbrain in which input from the optic nerve is processed. Because the retinally derived neurons of the optic nerve map onto the optic tectum in a defined way, the question of how this specificity is determined has been a long standing problem in cell biology. Although there is some evidence for adhesion gradients and for some adhesion specificity, the problem is unresolved. (11 Jan 1998) |
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| optic tract | The continuation of the optic nerve fibres beyond (behind) the latter's hemidecussation in the optic chiasm; each of the two symmetrical optic tracts is composed of fibres originating from the temporal half of the retina of the ipsilateral eye and a nearly equal number of fibres from the nasal half of the contralateral retina; it forms a compact, somewhat flattened fibre band passing caudolaterally alongside the base of the hypothalamus and over the basal surface of the crus cerebri; most of its fibres terminate in the lateral geniculate body; a smaller number of fibres enter the brachium of the superior colliculus, to terminate in the superior colliculus and the pretectal region. Synonym: tractus opticus. (05 Mar 2000) |
| optic vesicle | In the embryo, one of the paired evaginations from the ventrolateral walls of the forebrain from which the sensory and pigment layers of the retina develop. Synonym: vesicula ophthalmica, ocular vesicle, optic vesicle. (05 Mar 2000) |
| excavation of optic disc | The normally occurring depression or pit in the centre of the optic disc. Synonym: excavatio disci, depression of optic disk, excavatio papillae, physiologic cup, physiologic excavation. (05 Mar 2000) |
| lateral root of optic tract | The larger division of the posterior end of the optic tract that terminates in the lateral geniculate body. Synonym: radix lateralis tractus optici. (05 Mar 2000) |
| Leber's hereditary optic atrophy | Hereditary degeneration of the optic nerve and papillomacular bundle with resulting rapid loss of central vision, progressive for several weeks, then usually stationary with permanent central scotoma; age of onset is variable, most often in the third decade; more males than females are affected and transmission is cytoplasmic and strictly on the female side. Mutation on the mitochondrial chromosome involved, which presumably interacts with an X-linked mutant. This mechanism may explain the bizarre sex ratio, which differs significantly from one country to another. (05 Mar 2000) |
| lenticulo-optic | Relating to the lentiform nucleus and the optic tract; specifically refers to branches of the middle cerebral artery considered to supply these structures. (05 Mar 2000) |
| bladder neoplasms | Cancers or tumours of the bladder. The majority of bladder neoplasms are of the transitional cell variety and are usually papillary and multicentric. (12 Dec 1998) |
| bone marrow neoplasms | Neoplasms located in the bone marrow. They are differentiated from neoplasms composed of bone marrow cells, such as myeloma. most bone marrow neoplasms are metastatic. (12 Dec 1998) |
| breast neoplasms, male | Any neoplasms of the male breast. These occur infrequently in males in developed countries, the incidence being about 1% of that in females. Two-thirds of patients present with intraductal carcinoma. The average age of onset is 60 years for men. Orchiectomy was the standard treatment but it has been replaced by tamoxifen as the initial therapy since oestrogen-receptor-positive tumours are predominant in males. Orchiectomy and mastectomy may be used if initial drug therapy is not successful. The prognosis is worse than that for females. (12 Dec 1998) |
| vascular neoplasms | <oncology> Neoplasms located in vascular tissue or specific veins. They are differentiated from neoplasms, vascular tissue which are neoplasms composed of vascular tissue, such as angiofibroma or haemangioma. (12 Dec 1998) |
| pancreatic cystic neoplasms | <radiology> Microcystic adenoma, glycogen, benign, mucinous cystic neoplasm, macrocystic adenoma, cystadenoma/cystadenocarcinoma, mucin, pre-malignant, Both occur more commonly in women, peak in middle age (12 Dec 1998) |
| pancreatic neoplasms | <radiology> Adenocarcinoma, most common, usually in pancreatic head, nasty (1-2% survival at 1 yr!), cystic neoplasms, slow-growing, more common in women, isleT-cell tumours, soft-tissue tumours (rare), metastases (breast, lung, melanoma, stomach, colon) (12 Dec 1998) |
| mammary neoplasms | Tumours of the mammary gland. Their occurrence is uncommon with the exception of the female dog, in which they account for 25% of all neoplasms. (12 Dec 1998) |
| paranasal sinus neoplasms | Neoplasms or tumours of the paranasal sinuses. Malignant neoplasms are rare, comprising 3% of all head and neck neoplasms. The majority arise in the maxillary sinus with malignancies of the ethmoid sinus constituting virtually all the remaining tumours. (12 Dec 1998) |