Myopia, commonly known as nearsightedness, is a refractive error that causes distant objects to appear blurry while close-up vision remains relatively clear. This condition arises when the eye focuses light in front of the retina instead of directly on it. Myopia is a significant and growing worldwide health concern, with projections suggesting that by 2050, it could affect approximately 50% of the global population. This article explores the science behind myopia, explaining why it is a permanent change, the factors that cause it to progress, and the modern medical approaches used for correction and control.
The Structural Basis of Myopia
Myopia does not naturally go away once it has developed because it is caused by permanent physical changes to the structure of the eye. The most frequent structural change is known as axial elongation, where the eyeball grows too long from front to back. This abnormal lengthening causes incoming light rays to focus in front of the retina, resulting in distant blur. A less common, but still contributing, factor is an overly curved cornea or lens, which increases the eye’s focusing power beyond what is normal. These physical alterations—whether excessive length or excessive curvature—are structural modifications that cannot be reversed by the body, making the resulting refractive error permanent.
Factors Influencing Myopia Progression
Myopia typically begins in childhood and progresses throughout the school-age years and adolescence, often stabilizing in early adulthood, usually between the ages of 15 and 24. The worsening of nearsightedness is primarily driven by a combination of genetic and environmental influences that affect the rate of axial elongation. Although genetics play a part, with the risk increasing if one or both parents are myopic, environmental and behavioral factors are considered highly significant in the recent surge of cases. A lack of time spent outdoors has been strongly identified as a risk factor for the onset of myopia in children. The protective effect is thought to be related to the bright light exposure found outdoors, which may help regulate eye growth. Conversely, prolonged near work, such as reading or intense screen time, is associated with a higher risk of progression. The goal of eye care is to manage these factors during the progression years to minimize the final degree of nearsightedness.
Standard Approaches to Correcting Blurry Vision
Once the structural changes have occurred and myopia is established, the primary focus is correcting the blurred distant vision. The simplest and most common method involves the use of eyeglasses, which employ concave or “minus” lenses to shift the focal point back onto the retina. Contact lenses provide a similar optical correction but are worn directly on the eye’s surface, offering a wider field of corrected vision. Refractive surgery, such as LASIK or PRK, offers a permanent correction option for adults whose vision has stabilized. These procedures reshape the cornea to alter its curvature, compensating for the eye’s longer length. However, surgery only corrects the focus; it does not change the eye’s underlying axial length or eliminate the health risks associated with high myopia.
Medical Strategies to Slow Axial Elongation
Modern interventions shift the focus from merely correcting the blur to actively slowing the progression of axial elongation, particularly in children. Slowing this physical lengthening is important because a lower final prescription reduces the lifetime risk of severe eye complications. These treatments are known as myopia control methods and do not cure the condition but instead manage its worsening.
Pharmacological Approaches
One pharmacological approach uses low-dose atropine eye drops, typically at concentrations of 0.01% to 0.05%. While the exact mechanism is not fully understood, the drops are believed to act on receptors in the eye to slow the growth of the eyeball.
Optical Interventions
Optical interventions include specialized spectacle lenses, such as Defocus Incorporated Multiple Segment (DIMS) designs, which use multiple small segments to create myopic defocus in the peripheral visual field. Another effective optical strategy is orthokeratology (Ortho-K), which involves wearing rigid contact lenses overnight. These lenses temporarily reshape and flatten the central cornea, correcting the vision for the day and simultaneously providing a peripheral defocus signal that helps slow the eye’s lengthening. Clinical studies show that these specialized optical and pharmacological treatments can effectively reduce the rate of myopia progression in children.