Microphthalmus

Microphthalmus (microphthalmus), abnormal reduction in the size of the eyeball, clearly disproportionate to the age of the individual; always congenital and usually bilateral change, often having a familial hereditary character. The degree of M. can vary. Sometimes there is only a slight reduction in all dimensions of the eye, which is generally well-developed. Due to the reduction in longitudinal size, the refraction of such an eye is always hypermetropic. The small size and shallow anterior chamber predispose to glaucoma. In more severe cases of M., other developmental defects are usually found on the eye: on the cornea - its flattening and opacities, especially peripheral ones, blurring the boundary between the transparent corneal tissue and the sclera; on the lens - opacities, displacement, and even its absence; in the vitreous body - remnants of the hyaloid artery or development of connective, fatty, and even bone tissue. - Very often M. is combined with coloboma of the iris and choroid. In pronounced cases of M., the size of the orbit is also reduced; underdevelopment of the corresponding half of the face and skull, as well as other developmental defects of the body, are often observed. In some cases, M. is combined with a serous cyst located in the orbit below the eye and protruding forward the lower eyelid, through which it appears bluish in color (M. with cyst of the lower eyelid). The cyst always communicates with the cavity of the eye. Its wall is formed by connective tissue that is an extension of the sclera, and its cavity is filled with serous fluid and lined with underdeveloped retina. The size of the eye in such cases varies within very wide limits; sometimes only a rudiment the size of a pea remains of it. These cases were previously incorrectly designated as absence of the eye (anophthalmos).- The genesis of M. is not yet sufficiently clear. The formal cause is probably disorders in the separation of the lens and in the development of the vitreous body in connection with disorders in the closure of the optic fissure.

V. Odggafov. The purpose of the microscopic chemical study of the tissues of the organism is to establish the chemical nature through various methods of processing: 1) individual components of the organism distinguishable only under the microscope, 2) various products arising in it during pathological conditions, and 3) foreign bodies deposited in the tissues. For this purpose, both tissue sections and fluids containing suspensions of microscopically small particles (secretions of glands, feces, scrapings, exudates, etc.) can be examined. Both fixed (e.g., with formalin) tissues and unfixed objects (frozen sections, tissue fluids), as well as living (viable) tissues can be subjected to processing. - The degree of accuracy of microchemical reactions varies greatly. In some cases (e.g., detection of certain mineral substances in tissues), the reaction is performed by the same method as in a test tube and gives an equally accurate qualitative result. In other cases, only individual chemical properties of the structures and cellular inclusions being studied (e.g., acidic or alkaline reaction) can be determined and an approximate idea of the elements contained in them can be obtained (e.g., many reactions determining the chemical composition of lipoids). The chemical nature of the first group of microchemical reactions is quite clear, while a significant number of tests based on the tinctorial properties of chemical substances found in the organism represent only empirically established facts, and the exact mechanism of these reactions cannot yet be established. The ability of various structural elements of the organism's tissues to take up different dyes depends to a certain extent on the chemical peculiarities of these elements, whereby many tinctorial reactions used in histological practice make it possible to determine some chemical properties of the colored tissue structures. This includes, for example, the ability of the nucleus and cell protoplasm to take up different dyes already by virtue of the fact that the nucleus has an acidic, while the protoplasm has a weakly alkaline reaction; thus, cell nuclei take up mainly basic aniline dyes (methylene blue, gentian violet, toluidine blue, etc.), while the protoplasm is stained with acidic dyes (eosin, acid fuchsin, etc.). However, one must be very cautious in connecting the ability to predominantly take up one or another dye with the chemical properties of the substance being stained. Although the theoretical foundations of staining are not yet fully clear to us, it is beyond doubt that the ability of tissue elements to be stained with different dyes depends both on the chemical reaction between the tissue and the dye and on their physical properties (different degrees of adsorption of the coloring substance). The microchemical reactions applied to the tissues of the animal organism can be divided into three main groups: 1) reactions establishing the chemical nature of various protein substances, 2) reactions serving for the differential diagnosis of various groups of fats (lipoids), and 3) methods for detecting various inorganic substances and organic compounds deposited in the tissues and cells. See also Microscopic technique, Histological technique. s. vayl.