Understanding Vision and Hearing Development in Infants

Vision Development in Infants

The visual system is designed to capture light effects. The apparatus of global vision allows us to perceive images based on the amount of light reflected. Light enters through the cornea, passes through the pupil to the lens, and is then sent to the retina.

Developmental Milestones

• Newborn: Distinguishes between light and dark (chiaroscuro).
• 1 Month: Can stare at a large object.
• 2 Months: Can accommodate and converge their vision.
• 3 Months: Can follow a moving object by turning their head.
• 4 Months: Has a vertical and horizontal visual field of 180 degrees.
• 6 Months: Acquires eye-hand coordination.
• 8 Months: Examines objects with more detail.
• 12 Months: Acquires adult-like visual acuity.

Vision Disorders

Refractive Errors

• Myopia (Nearsightedness): Light rays converge before reaching the retina, making distant objects appear blurry. Only close objects are seen clearly.

• Hypermetropia (Farsightedness): Light rays converge behind the retina, making close objects appear blurry. Only distant objects are seen clearly.

• Astigmatism: The cornea refracts light unevenly, causing distorted and blurred vision.

Mobility Disorders

• Strabismus: Loss of parallelism in the eyes. It can be unilateral or bilateral and is classified as convergent, divergent, or vertical. Correction involves covering the stronger eye to force the brain to receive images from the weaker eye. Mild strabismus is normal in newborns due to a lack of eye muscle control.

Reception Disorders

• Daltonism (Color Blindness): Alteration of color perception due to a deficiency in the cones.

Severe Disorders

• Amblyopia (Lazy Eye): Decreased vision in one eye, with difficulty distinguishing details, due to an ocular disease process.

• Blindness: Lack of vision.

Hearing Development in Infants

The ear collects sound vibrations from the environment and transforms them into electrical impulses that are interpreted in the corresponding area of the cerebral cortex. It is divided into three parts:

1. External Ear: Consists of the pinna (auricle) and the ear canal.
2. Middle Ear: Contains the eardrum, the Eustachian tube, and the oval and round windows.
3. Inner Ear: Composed of the cochlea, the organ of Corti, and the acoustic nerve.

Developmental Milestones

Infants initially have some hearing loss due to the immaturity of the auditory nerve. They may not distinguish the intensity, timbre, and tone of sounds. They can hear whispers but may not react to monotonous sounds.

• 12 Hours: Can differentiate human language.
• 2 Days: Reacts to intense sounds.
• 7 Days: Recognizes the parents' voices.
• 2 Months: Shakes their head when they hear a sound.
• 4 Months: Can concentrate on a sound.

Hearing Disorders

• Deafness: Hearing loss due to the destruction of auditory structures.

• Hearing Loss: Hearing loss of varying degrees.

  • Mild Deafness: Hearing loss below 40 dB.
  • Moderate Deafness: Hearing loss between 40 and 65 dB.
  • Severe Deafness: Hearing loss between 65 and 85 dB.
  • Profound Deafness: Hearing loss over 85 dB.