The human eyeball does indeed grow, a natural process of development occurring from birth through adolescence. While many body parts grow continuously, the eye’s growth is primarily concentrated in specific periods, eventually stabilizing in early adulthood. This complex process is essential for clear vision.
How Our Eyes Grow
At birth, a baby’s eyes are relatively small, measuring approximately 16.5 millimeters in axial length. This is about two-thirds of their adult size. The most rapid phase of eyeball growth occurs during the first two years of life, where the eye undergoes significant elongation.
Following this initial rapid growth, the eye continues to grow more gradually throughout childhood. A second notable growth spurt happens during puberty, aligning with other bodily changes. The eye’s axial length increases to about 24 millimeters by the time an individual reaches their late teens or early twenties. This marks the point when the eyeball stops increasing in length, reaching its mature size.
Vision and Eye Shape
The final size and shape of the eyeball, particularly its axial length, influence a person’s vision. Minor variations in this length can lead to common refractive errors. For instance, if the eyeball grows slightly too long, light entering the eye focuses in front of the retina, resulting in myopia, or nearsightedness. Myopic eyes have longer axial lengths, exceeding 24 millimeters.
Conversely, if the eyeball’s axial length is shorter than average, light focuses behind the retina, causing hyperopia, or farsightedness. Hyperopic eyes have shorter axial lengths, around 22.62 millimeters. These conditions result from the eye’s physical dimensions relative to its optical power, not ongoing growth or shrinking in adulthood. The goal of managing conditions like myopia is to control excessive axial length elongation, as longer eyes increase the risk of certain eye problems later in life.
The Adult Eye
Once the eyeball reaches its full size, by age 20 or 21, its overall length remains stable throughout adulthood. The average adult eyeball measures 24.2 millimeters in transverse diameter, with axial length varying between 22.0 and 24.8 millimeters. While the eyeball itself maintains a consistent size, other components within the eye undergo changes with age.
For example, the lens inside the eye continues to increase in weight throughout a person’s lifetime. Changes in the lens can lead to age-related vision issues like presbyopia, which is the reduced ability to focus on near objects, or the development of cataracts, where the lens becomes cloudy. Therefore, any changes in vision experienced in later life are due to alterations in these internal structures or other age-related eye conditions, not a change in overall eyeball size.