Myopia, commonly known as nearsightedness, is a vision condition where light from distant objects focuses in front of the retina rather than directly on its surface. This occurs because the eyeball has become too long (axial myopia) or, less commonly, because the cornea or lens has too much focusing power. The result is that faraway objects appear blurred, while objects up close remain clear. This refractive error is a widespread public health concern, with projections estimating that nearly half of the global population could be affected by 2050. Higher degrees of nearsightedness are associated with a greater risk of severe eye conditions later in life, including glaucoma, cataracts, and retinal detachment. Early intervention to manage the condition is important.
Standard Correction Methods
The most common and safest method to immediately correct the blurry distance vision caused by myopia is through the use of corrective lenses. These methods provide clear vision by redirecting light onto the retina, but they do not address the underlying cause or slow the progression of the condition.
Eyeglasses use concave lenses, which are thinner in the center and thicker at the edges. These minus lenses diverge the incoming light rays. By causing the light to diverge, the lens effectively pushes the focal point backward, allowing the image to land sharply on the retina instead of in front of it. The degree of divergence required determines the strength of the concave lens prescribed, which is represented by a negative number on the prescription.
Conventional contact lenses offer a direct alternative to glasses, resting on the surface of the eye to correct the refractive error. Soft contact lenses are the most widely used type, as they are comfortable and made of flexible plastic materials. Rigid gas-permeable (RGP) contact lenses are another option, holding their shape firmly and providing sharper vision correction for certain irregularities. Both soft and RGP lenses work on the same optical principle as glasses, using a minus power to shift the focal point to the retina for clear daytime vision.
Myopia Progression Management
Newer treatments focus on slowing the elongation of the eyeball, which is particularly important for children and adolescents. This progression management can significantly reduce the risk of developing high myopia and its associated complications. These interventions aim to manipulate the visual signals that guide the eye’s growth.
Low-dose atropine eye drops represent a pharmaceutical approach to progression management. These drops are administered once daily, typically at night, in very low concentrations (e.g., 0.01% to 0.05%). The exact mechanism by which atropine slows eye growth is not fully understood, but it is believed to involve blocking muscarinic receptors in the retina and sclera that regulate eye growth signals. Clinical studies have demonstrated that concentrations like 0.05% atropine can reduce myopia progression by approximately 50% compared to a placebo, with minimal side effects like light sensitivity or blurred near vision.
Orthokeratology (Ortho-K) uses specialized rigid gas-permeable contact lenses worn overnight. While the patient sleeps, these lenses gently reshape the cornea, the clear front surface of the eye. The lenses create a controlled mechanical force that flattens the central cornea, which temporarily corrects the nearsightedness for clear daytime vision.
The myopia control effect is attributed to the unique corneal shape profile, which causes light rays in the peripheral retina to focus in front of the retina. This deliberate creation of myopic defocus acts as a “stop signal” that slows the excessive elongation of the eyeball. Ortho-K has been shown to reduce myopia progression in children by up to 50%.
Specialized dual-focus soft contact lenses, such as the MiSight 1 Day, are another optical method for progression control. These lenses feature two distinct zones. The central zone provides the necessary distance correction for clear vision. The outer, concentric ring zones incorporate an added power, typically around $+2.00$ diopters, which intentionally creates a constant myopic defocus. This means that in the periphery, light is focused in front of the retina. This continuous myopic defocus signal is thought to inhibit the eye’s tendency to grow longer, thereby slowing the progression of nearsightedness.
Surgical Vision Correction
Surgical options provide a more permanent solution for correcting the refractive error, and they are generally reserved for adults whose myopia prescription has stabilized. These procedures modify the eye’s structure to change how light is focused onto the retina. The primary goal is freedom from glasses or contact lenses, not myopia control.
Laser-Assisted In Situ Keratomileusis (LASIK) is the most widely known laser procedure. It involves creating a thin, hinged flap on the cornea’s surface. The surgeon lifts this flap and uses an excimer laser to precisely reshape the underlying corneal tissue. The flap is subsequently repositioned, where it naturally adheres without the need for stitches, allowing for a rapid visual recovery, often within 24 hours.
Photorefractive Keratectomy (PRK) is an alternative laser procedure that does not involve creating a corneal flap. Instead, the outer layer of the cornea (the epithelium) is gently removed before the excimer laser reshapes the underlying corneal tissue. Because the flap is eliminated, PRK is suitable for individuals with thinner corneas or those whose lifestyle involves a higher risk of eye trauma. The primary drawback is a longer recovery period, as the corneal epithelium must regenerate over several days to weeks.
Implantable Collamer Lenses (ICLs) do not involve removing corneal tissue. This procedure involves implanting a microscopic, biocompatible lens between the iris and the natural lens of the eye. ICLs are particularly beneficial for patients with high myopia or thin corneas, where laser-based procedures may not be suitable. Unlike LASIK or PRK, the ICL procedure is reversible, as the lens can be removed if necessary, providing a unique advantage for some patients.