ISSN 2415-3060 (print), ISSN 2522-4972 (online)
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УЖМБС 2020, 5(3): 378–386
https://doi.org/10.26693/jmbs05.03.378
Lectures

Anatomical Structure of the Organ of Vision. Visual Analyzer. Development of the Organ of Sight. Congenital Malformations of the Eye

Stepanchuk A. P.
Abstract

The length of the outer and inner axis, as well as the transverse diameter of the eye is about 24 mm. If the shape of the eye and the magnitude of the axis of the eye changes significantly during development, then a congenital malformation of the eye occurs, including: microphthalmia, myopia, hyperopia, cyclopia. The capsule of the eye consists of three membranes: fibrous and vascular membranes and retina. The fibrous membrane is represented by a transparent cornea and sclera. The latter has a venous sinus, which is the main way of the outflow of aqueous humor from the eye. The shape and transparency of the cornea affect the refraction of light and the quality of vision. If the structure of the cornea and its curvature are disturbed, congenital anomalies arise: keratoglobus, keratoconus, macrocornea, microcornea. The choroid of the eye is rich in pigment and blood vessels. It is divided by function and structure into three different departments: the choroid itself, the ciliary body, and the iris. The unique structure of the ciliary body provides accommodation (change in the curvature of the lens) with contraction of the ciliary muscle and secretion of aqueous humor of the eye by the ciliary processes. The iris is the diaphragm of the eye and separates the front camera from the back. It regulates the diameter of the light that falls on the retina through the presence of a pupil in its center. The shape of the pupil and its diameter depend on the tone of the dilator muscle and pupillary constrictor. The color of the iris is determined by the presence of pigment cells in its stroma. Congenital malformations of the choroid are: absence of the iris, pupil; slit pupil, slit-like defect of the iris; narrowing and expansion of the pupil, different diameters of the pupils. In the most important membrane of the eye, the retina, the rods and cones (photoreceptor cells) are situated. They provide the perception of twilight, daytime and color vision. The optic disc (blind spot) is located in the center of the retina, and the yellow spot is located laterally from it (the region of the best vision of the eye). Violation of the intrauterine development of the retina leads to congenital anomalies, including retinal aplasia, retinal hypoplasia, retinal coloboma, achromasia. The optic nerve is formed by the axons of the ganglion nerve cells of the retina (III neuron of the optic pathway). Rods and cones (I neuron) with their processes end on the bipolar cells of the retina (II neuron). The optic nerves pass through the optic canal into the cranial cavity and form a visual cortex. Further, the optic pathway enters the lateral geniculate body (IV neuron) and ends in the cerebral cortex. Intrauterine maldevelopments of ganglion cells and their number leads to congenital anomalies of the optic nerves, including aplasia, hypoplasia, coloboma of the optic nerve head. Conscious and reflex eye movements can occur around the frontal and vertical axes. These rotations of the eye are provided by the external muscles. If their innervation is disturbed, divergent and convergent strabismus, blepharoptosis are observed. The eyes are protected from drying out by the tears secreted by the lacrimal gland. The lacrimal path (lacrimal stream, lake, papillae, dots, lacrimal tubules, lacrimal sac, nasal-lacrimal duct) remove the tears from the conjunctival sac.

Keywords: eye, sclera, cornea, iris, retina, ciliary body, optic nerve

Full text: PDF (Ukr) 248K

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