Myopia, commonly known as nearsightedness, is a vision condition where distant objects appear blurry while close objects remain clear. This refractive error occurs because the eye is either too long or the cornea is too steeply curved, causing light to focus in front of the retina instead of directly on its surface. The global prevalence of myopia is increasing, making effective methods for correcting vision and slowing progression a major public health focus.
Corrective Lenses: Temporary Solutions
The most common and least invasive method for managing myopia involves corrective lenses, which provide immediate visual clarity. These lenses manipulate the path of light entering the eye, ensuring it is properly focused onto the retina. A concave or “minus” lens is used, characterized by being thinner in the center and thicker at the edges. This concave shape causes light rays to diverge slightly, pushing the focal point backward to land precisely on the retina.
Eyeglasses are the simplest option, offering a safe and customizable correction. Contact lenses provide a similar optical correction directly on the surface of the eye, offering a wider field of corrected vision and freedom from frames. They are available in various forms, including soft, rigid gas permeable, and disposable options.
While corrective lenses effectively correct blurry vision, they serve only as temporary optical aids. They do not alter the underlying structure of the eye or stop the progressive elongation of the eyeball. These solutions require consistent use and regular prescription updates as the myopia progresses.
Surgical Procedures for Permanent Correction
Several surgical procedures offer long-term or permanent vision correction for individuals seeking to eliminate dependence on temporary lenses. These methods physically alter the eye’s focusing power to ensure light converges directly on the retina. Eligibility depends on factors like age, corneal thickness, and prescription stability.
LASIK, or Laser-Assisted In Situ Keratomileusis, is the most widely known refractive surgery, involving the use of a laser to reshape the cornea. The surgeon first creates a thin, hinged flap on the cornea’s surface, which is then lifted to expose the underlying tissue. An excimer laser precisely removes tissue to flatten the central cornea, and the flap is then repositioned, often allowing for rapid visual recovery within 24 to 48 hours.
Photorefractive Keratectomy (PRK) also uses an excimer laser to reshape the cornea but differs in its initial step. Instead of creating a flap, the surgeon removes the thin outer layer of the cornea, known as the epithelium. The laser reshapes the exposed corneal surface, and the epithelium naturally regenerates over the next few days to weeks. PRK is often preferred for patients with thinner corneas or those with active lifestyles.
For high myopia or in cases where the cornea is too thin or irregular for laser ablation, the Implantable Collamer Lens (ICL) is a viable option. This procedure involves surgically placing a biocompatible lens, similar to a permanent contact lens, between the iris and the natural lens of the eye. Unlike LASIK and PRK, the ICL procedure does not remove corneal tissue and is reversible.
Strategies for Controlling Myopia Progression
Specific strategies focus on slowing the axial elongation of the eye, which causes myopia to worsen over time. This proactive approach, known as myopia control, is important for children and adolescents whose eyes are still developing. Effective progression control reduces the risk of developing high myopia, a condition associated with severe complications like retinal detachment and macular degeneration.
Orthokeratology, or Ortho-K, involves wearing specially designed rigid gas permeable contact lenses overnight. These lenses gently flatten the central cornea, temporarily correcting the refractive error so the wearer sees clearly during the day without glasses. This reshaping alters how light is focused on the peripheral retina, creating myopic defocus that is believed to inhibit excessive eyeball growth.
Low-dose atropine eye drops are a pharmacological approach, typically administered daily. Atropine slows the elongation of the eye by affecting muscarinic receptors that regulate eye growth signals. Studies show that low doses (0.01% to 0.05%) are effective in slowing progression by up to 50% to 60%, while minimizing side effects like light sensitivity and near vision blur.
Lifestyle and environmental factors also play a role in myopia progression. Increased time spent outdoors, with a recommended minimum of at least two hours per day, is linked to a lower risk of onset and slower progression. Reducing prolonged near-work strain, such as taking short breaks every 20 minutes, can help manage the visual demands that contribute to progression.