Already at birth, a baby has some unconditioned visual reflexes: direct and cooperative reaction of the pupils to light, a short-term reflex of turning the eyes and head to a light source, an attempt to follow a moving object. Later on, as the child grows, all other visual functions gradually develop and improve.
Light sensitivity emerges immediately after birth. From the very first days of life, light has a stimulating effect on the development of the visual system as a whole and serves as the basis for the formation of all its functions. However, a newborn does not develop a visual image under light, but mainly induces inadequate protective reactions. Light sensitivity increases significantly and corresponds to 2/3 of its level in an adult by the end of the first six months of a child’s life. Reduced light sensitivity in newborns is explained by insufficient development of the visual system, in particular, the retina being the thinnest inner membrane of the eye perceiving light and converting it into nerve impulses.
In the dark, pupil dilation in children under one year of age is slower than its contraction in the light. However, by the 2nd-3rd week, owing to the conditioned reflex connections, the activity of the visual system becomes more complex, and the functions of an object, color, and spatial vision are formed and perfected.
Central vision appears in the child only by the 2nd to 3rd months of life. Later on, it gradually improves from the ability to detect an object to the ability to distinguish and recognize it. The appropriate level of visual development allows us to distinguish the simplest objects, but the ability to recognize complex images is related to intellectual development.
At the 4th to 6th months of life, the baby reacts to the faces nearby, and even earlier, at the 2nd to 3rd months, he/she notices the mother’s breast. At the 7th to 10th months, the baby can recognize geometric shapes (cube, pyramid, cone, ball). A full perception of the shape and normal visual acuity develops in children only by the school period.
Newborn visual acuity is extremely low. According to studies, it is between 0.005 and 0.015. During the first months, it gradually increases to 0.01-0.03, and only by the age of 6-7 years reaches 0.8-1.
Color perception develops along with visual acuity. Studies show that the ability to recognize color first appears in the child at the age of 2-6 months. Color recognition begins first with the red color, while the ability to recognize the colors of the short-wave spectrum (green, blue) emerges later. By the age of 4-5, color vision in children is already well developed but continues to improve. Abnormalities in their color perception occur with approximately the same frequency and in the same quantitative proportions between males and females as in adults.
The borders of the visual field in preschool children are about 10% narrower than in adults. By school age, they reach normal values.
Binocular (volumetric, stereoscopic) vision
Binocular vision develops after the other visual functions. The main feature of binocular vision consists in a more accurate assessment of the third spatial dimension – the depth of space. The following basic stages in the development of spatial vision in children can be singled out:
- At birth, the baby does not have a conscious vision. Under the bright light, the pupil narrows, eyelids close, head jerks back, but the eyes aimlessly wander independently of each other.
- 2-5 weeks after birth, strong light forces the infant to keep his/her eyes relatively still and stare closely at the light surface.
- By the end of the first month of life, optical stimulation of the retinal periphery causes a reflex movement of the eye, resulting in the perception of a light object by the center of the retina. The aimless wandering of each eye is replaced by coordinated movement of both eyes. The physiological basis of binocular vision is formed.
Thus, the binocular visual system is formed despite the obvious inferiority of the monocular visual systems and is ahead of its development. This occurs primarily to ensure spatial perception, which mostly facilitates the organism’s adaptation to environmental conditions.
During the second month of life, the baby begins to master the near space. At first, close objects are visible in two dimensions (height and width), but they become tangible in three dimensions (height, width, and depth) through touch. The first notions of objects’ three-dimensionality are established.
In the fourth month, children develop the grasping reflex. Most children determine the direction of objects correctly, but the distance is estimated incorrectly. The child also makes mistakes in determining the volume of objects by trying to grasp the glare of the sun and moving shadows.
Mastering distant space begins from the 6th month of life. Touch is replaced by crawling and walking. This enables a comparison of the distance the body moves with changes in the size of images on the retina and the tone of the oculomotor muscles. Besides, visual ideas of distance are created. This function provides a 3D space perception and is compatible only with complete coordination of the eyeball movements and symmetry in their position. The mechanism of spatial orientation goes beyond the visual system and is a product of complex brain activity. In this regard, further improvement of spatial perception is closely connected with the cognitive activity of the child.
When to visit a pediatric ophthalmologist
The first examination of a child by an ophthalmologist is carried out even in the maternity hospital, his task is to identify congenital diseases (cataract, retinal tumor, glaucoma, inflammatory diseases). It is mandatory to examine children born prematurely to exclude retinal pathology – retinopathy of prematurity and optic nerve atrophy.
There are certain periods up to a year when, even in the absence of pathologies, you need to check your eyesight: at the age of a month and six months.
In the ophthalmological center “Excimer” (Kyiv), a complete eye examination of children under one year old is carried out using computerized equipment. Accurate diagnosis of children with visual impairments will allow you to find out the cause and degree of the disease and prescribe effective treatment.
Studies included in the program for diagnosing the disease in children under one year old at the Excimer clinic:
- determination of visual acuity;
- refraction measurement;
- examination of the fundus with a dilated pupil;
- measuring the length of the eyeball, the curvature of the cornea, the depth of the anterior chamber of the eye and the size of the lens;
- checking binocular functions (the ability of the brain to create one three-dimensional image from those that each eye sees separately);
- visual field check;
- determination of the stock of accommodation.