COLOBOMA (coloboma; grech, koloboma a missing part) — defect of edge of a century or any of covers of an eyeglobe — irises, an idiovascular cover, a retina or an optic nerve. Distinguish inborn and acquired To.
Inborn To. covers of an eye are sometimes combined with small defects of edge of a crystalline lens and ciliary body in the relevant sector. In rare instances they are combined with defects of wings of a nose (fig. 1). Typical inborn To. are located usually from top to bottom from a pupil and represent result of a delay of short circuit of a secondary palpebral fissure of an embryonal eye. To. irises happen full, (fig. 2, a), or continuous, from edge of a pupil to the root of an iris, and partial — to preservation of the bridge of an iris in a zone of an arrangement of a sphincter of a pupil (fig. 2,6). At full inborn To. irises the pupil takes the extended pear-shaped form, but pupillary tests are not broken since the sphincter of a pupil remains on all edge of a pupil and To.
If To. irises (iridokoloboma) it is combined with To. an idiovascular cover or edge of a crystalline lens, for their detection it is necessary to resort to a research by means of the ophtalmoscope. At such research (in a transmitted light) in the area K. irises the bottom edge of a crystalline lens, in Krom in the presence is visible To. a crystalline lens it is possible to find semicircular defect. To. an idiovascular cover comes to light at an oftalmoskopiya as limited defect of a red reflex of an eyeground. At the same time directly from top to bottom from an optic disk, at small distance from it, accurately konturirovanny site of white or light gray color (color of a naked sclera) is found. If the transparent retina on this site is kept, then on a white background To. retinal blood vessels are visible.
At limited To. an idiovascular cover visual acuity, as a rule, does not decrease. Narrowing is noted fields of vision (see), at perimetria (see) to-rogo in the relevant sector wedge-shaped defect comes to light. Visual acuity (see) sharply decreases at extensive To. an idiovascular cover, occupying the macular area. At To. an optic nerve sight is absent.
Inborn To. covers of an eyeglobe, as well as the majority of congenital anomalies and uglinesses of an eye, are genotypic caused and have clearly the expressed family, hereditary character.
In certain cases they can result also from the heavy pre-natal inflammatory process which led to education rough amniotic tyazhy, disturbing normal fetation.
The term «coloboma» is applied also to the limited acquired defects, hl. obr. irises. If at an injury it is damaged or at operation is removed (including influence of a laser beam) a part of an iris, arises traumatic or postoperative To. irises.
Bibliography: Dymshits L. A. Fundamentals of ophthalmology of children's age, page 485, M., 1970; Katsnelson A. B. Anomalies of development and a disease of eyes at early children's age, page 66, L., 1957; System of ophthalmology, ed. by S. Duke-Elder, v. 8, L., 1965.
A. Ya. Samoylov.