Myopia, medically known as nearsightedness, is a common refractive error that causes distant objects to appear blurry while allowing near objects to be seen clearly. This condition occurs when the optical system of the eye focuses light in front of the retina instead of directly on it. Myopia is one of the leading causes of vision impairment worldwide, and its prevalence has been rapidly increasing in recent years.

Causes of Myopia

Myopia occurs due to one of the following reasons:

• Axial Myopia: The eyeball is longer than normal along its front-to-back axis.
• Refractive Myopia: The cornea or lens has excessive refractive power, causing light to focus in front of the retina.

In a normal eye (emmetropia), light is properly focused on the retina, forming a sharp image. However, in myopia, this focusing error causes distant objects to appear blurry. Myopia typically begins in childhood and can progress throughout adolescence, though it may also develop in adulthood due to environmental factors or medical conditions.

Severity Classification of Myopia:

• Mild Myopia: 0 to -1.5 diopters (D)
• Moderate Myopia: -1.5 to -6.0 D
• High Myopia: -6.0 D and above (also known as pathological myopia)

High myopia is associated with serious complications, including retinal detachment, glaucoma, cataracts, and myopic macular degeneration, all of which can lead to vision loss.

^{Normal Eye vs. Myopic Eye}

Prevalence of Myopia

Myopia is an increasing global public health issue. Current estimates suggest that approximately 30% of the world's population is affected by myopia, and this figure is expected to rise to 50% (around 5 billion people) by 2050. The prevalence of myopia is particularly high in East and Southeast Asia, where countries like South Korea, Japan, China, and Singapore have reported rates as high as 80-90%. In the United States, the prevalence of myopia has increased from 25% to 42% over the past 30 years. In Europe, myopia affects 30-40% of the population, while in Africa, prevalence rates range between 10-20%.

This increase is linked to both genetic predisposition and modern lifestyle changes.

Causes of Myopia

The development of myopia is influenced by a complex interaction between genetic and environmental factors:

• Genetic Factors:
• Myopia tends to run in families. If one parent is myopic, a child’s risk increases threefold; if both parents are myopic, the risk increases sixfold.
• Twin studies have shown that monozygotic (identical) twins have a higher likelihood of sharing myopia than dizygotic (fraternal) twins.
• Specific genetic loci and polymorphisms associated with high myopia have been identified.
• Environmental Factors:
• Prolonged near work (e.g., reading, computer use, and extended screen exposure) significantly increases the risk of myopia. Studies suggest that excessive screen use can increase the risk by 30%, while excessive computer use can elevate the risk by up to 80%.
• Lack of outdoor exposure has been identified as a key factor in myopia development. Natural light exposure is believed to regulate eye growth and prevent excessive elongation.
• Developmental Processes:
• At birth, most infants are hyperopic (farsighted). During early childhood, the eye undergoes a process called emmetropization, adjusting its refractive state. In some cases, this process overshoots, leading to myopia.

Symptoms of Myopia

The primary symptom of myopia is blurred vision when looking at distant objects. Other common symptoms include:

• Difficulty reading distant text (e.g., road signs, school blackboards)
• Squinting to see more clearly
• Eye strain
• Headaches
• In children, behaviors such as sitting close to screens, frequent eye rubbing, or difficulty recognizing distant objects may indicate myopia.

Since children may not recognize that their vision is abnormal, regular eye exams are essential for early detection.

Diagnosis of Myopia

Myopia is diagnosed through a comprehensive eye examination, including the following tests:

• Visual Acuity Test: The patient reads letters from an eye chart at 20 feet (6 meters). A result of 20/40 vision means that a myopic person sees at 20 feet what a normal eye sees at 40 feet.
• Retinoscopy: A light is shone into the eye to observe retinal reflexes.
• Phoropter Examination: Different lenses are placed in front of the eye to determine the correct prescription for clear vision.
• Cycloplegic Refraction: Eye drops that temporarily prevent focusing are used to detect hidden refractive errors, especially in children.

Myopia is typically diagnosed between ages 6-14, but it can also develop in adulthood due to visual stress (e.g., excessive near-work) or medical conditions like diabetes.

Treatment of Myopia

Myopia can be managed through optical or surgical methods:

• Glasses and Contact Lenses:
• The most common and accessible solution for correcting myopia.
• Prescriptions are expressed in negative diopters (-D).
• Mild myopia may require glasses only for specific activities (e.g., driving), while high myopia often requires full-time use.
• Refractive Surgery (for adults):
• LASIK: A flap is created in the cornea, and underlying tissue is reshaped with a laser.
• PRK: The corneal surface layer is removed and reshaped—ideal for those with thin corneas.
• SMILE: A minimally invasive procedure that removes a small piece of corneal tissue.
• Phakic IOLs or Lens Implantation: Artificial lenses are implanted inside the eye.
• Myopia Control Methods (for children):
• Orthokeratology (Ortho-K): Rigid contact lenses worn overnight temporarily reshape the cornea.
• Atropine Eye Drops: Low-dose atropine can slow myopia progression by up to 80%.
• Peripheral Defocus Contact Lenses: Help control eye elongation.
• Bifocal/Multifocal Lenses: Balance near and distant vision to slow myopia progression.

Prevention of Myopia

While myopia cannot be entirely prevented, certain strategies can reduce its risk and slow its progression:

• Outdoor Time: Spending at least 90 minutes per day in natural daylight may delay myopia onset.
• Reducing Near Work Strain: The 20-20-20 rule (every 20 minutes, look 20 feet away for 20 seconds) helps relieve eye strain.
• Regular Eye Exams: Early detection lowers the risk of complications.

Complications of Myopia

High myopia significantly increases the risk of severe eye conditions, including:

• Retinal Detachment: The elongation of the eyeball stretches the retina, making it prone to detachment.
• Glaucoma: Increased eye pressure can damage the optic nerve.
• Cataracts: Myopia raises the risk of early cataract formation.
• Myopic Macular Degeneration: Damage to the central retina can cause central vision loss.

Myopia is a rapidly growing refractive error influenced by both genetic and environmental factors. With early diagnosis and proper management, individuals can maintain good visual quality and reduce complications. From simple solutions like glasses and contact lenses to advanced treatments like laser surgery and myopia control strategies, a variety of options exist to manage this condition. Ongoing scientific research continues to improve our understanding of myopia and enhance prevention strategies. Regular eye exams and healthy visual habits remain essential in minimizing the impact of myopia.