Nearsightedness, medically known as myopia, is a common refractive error where the eye does not focus light properly, causing distant objects to appear blurry. Globally, a significant portion of the population has myopia, and its prevalence is rising, especially among children. While nearby objects remain clear, the lack of sharp long-distance vision can impact daily activities like driving or recognizing faces from afar.
How Myopia Affects Vision
A person with myopia can usually see things up close without difficulty. The line where vision transitions from clear to blurry is known as the far point, and this point is much closer to the eye than it is for a person with normal vision. Distant objects, such as road signs or writing on a classroom whiteboard, appear fuzzy or out of focus.
This visual struggle can lead to noticeable behavioral signs and discomfort. Individuals with uncorrected myopia often squint to momentarily improve focus by reducing the size of the pupil. This continuous straining may result in symptoms like eye fatigue, eye strain, and recurring headaches. In children, signs might include sitting too close to the television or holding books very near their face.
The Underlying Anatomical Cause
Myopia occurs because the eye focuses light in front of the retina, rather than directly onto its light-sensitive surface. To achieve clear vision, the cornea and lens must precisely focus incoming light rays onto the retina, which then transmits the image to the brain. This misalignment is usually due to one of two main anatomical factors, or a combination of both.
The most frequent cause is an eyeball that has grown too long, a condition known as axial myopia. A second contributing factor is a cornea or lens that is too steeply curved, which increases the eye’s overall focusing power. In either case, the optical power of the eye is too strong for its length, causing the light to converge prematurely. This results in a blurred image by the time the light reaches the retina.
Methods of Vision Correction
Correcting existing myopia involves redirecting the light’s focal point backward so it lands precisely on the retina. The most common solution is the use of spectacles, or eyeglasses, which utilize concave lenses. These lenses are thinner in the center and thicker at the edges, acting to diverge the light rays slightly. This effectively pushes the focal point back onto the retina.
Contact lenses function on the same optical principle as glasses but rest directly on the surface of the eye. They offer the advantage of a wider field of view and a more natural appearance. Options range from soft daily disposables to rigid gas permeable lenses. Both provide a temporary, non-invasive correction, meaning vision reverts to its uncorrected state when removed.
For a more permanent change, refractive surgery procedures are available that physically reshape the cornea. Laser-Assisted In Situ Keratomileusis (LASIK) is a popular procedure where a precise laser reshapes the underlying corneal tissue after a thin flap is created. Photorefractive Keratectomy (PRK) removes the outer layer of the cornea, called the epithelium, before reshaping the surface. These surgical methods aim to reduce or eliminate the need for daily corrective lenses by permanently altering the eye’s focusing power.
Myopia Management and Progression
Myopia management focuses on slowing the condition’s progression, especially in children and adolescents, rather than just treating blurry vision. The goal is to limit the excessive lengthening of the eyeball, which is the primary mechanism for increasing myopic power. Limiting progression is important because high myopia significantly increases the lifetime risk of developing eye diseases like retinal detachment and myopic macular degeneration.
Increased time spent outdoors is a lifestyle factor that helps reduce the risk of myopia onset and slow its progression. Doctors recommend children spend at least 60 to 80 minutes outside daily, as natural light may help regulate eye growth. Specialized optical treatments are also used, including low-dose atropine eye drops, which slow the rate of axial elongation.
Orthokeratology (Ortho-K) involves wearing custom rigid gas permeable contact lenses only while sleeping. These lenses gently reshape the cornea overnight, providing clear vision during the day without glasses. Multifocal soft contact lenses are another effective tool, used to correct central vision while creating a peripheral defocus that signals the eye to slow its growth.