Myopia (nearsightedness): Causes, progression and management
Best Eye Clinic in Panipat
August 22, 2024
Panipat
August 28, 2024
What is Myopia?
Myopia (nearsightedness) is a refractive error that causes blurry distance vision. It is the most common cause of impaired vision in people under the age of 40. Myopia usually begins in childhood, but it can continue to worsen into early adulthood. This is called myopia progression.
Almost half of children with progressive myopia reach a stable prescription by age 15. About three-quarters stabilize by age 18, and almost all stabilize by age 24. However, myopia can progress rapidly to become high myopia without proper management. High myopia can lead to sight-threatening complications in adulthood.
The number of people who have myopia is growing at an alarming rate. In the year 2000, roughly 25% of the world's population was myopic. Research suggests that by the year 2050, roughly half the world’s population will be nearsighted.
What causes Myopia?
Myopia (nearsightedness) occurs when the eye focuses light rays in front of the retina, instead of on the retina. This makes distant objects look blurry.
A few different factors contribute to focusing light properly onto the retina:- The length of the eye from front to back
- The shape of the cornea and lens
- The location of the lens and the cornea relative to each other inside the eye
Emmetropization
- In the first years of life, children’s eyes grow and develop rapidly. During this time, the shape of the cornea and lens and the length of the eye come into balance to produce clear vision.
- This process is called emmetropization. When there is no refractive error in the eyes, this is called emmetropia.
- Most children are born farsighted (hyperopia). This is because the eyes are still too short from front to back at birth.
- As the child grows, the emmetropization process continues until around age 6 to 8. At this point, most children have low hyperopia, and only a small percentage have myopia.
Myopia Development and Progression
In some cases, the process continues. When this happens, the eyes develop past emmetropia and toward myopia. The eyeball may become too long, or the curve of the cornea or lens may become too steep. In rare cases, the lens may move too close to the cornea.
The peak years of myopia progression are often in early childhood. The development and progression of myopia at this age are influenced by several factors, including:- Genetics
- Time spent outdoors
- Near work activities (like reading and digital screen time)
A person may have a three times higher risk of nearsightedness if one of their parents is nearsighted. They may have a six times higher risk if both parents are nearsighted.
But recent studies show strong evidence that lifestyle factors may also cause myopia. For example, prolonged near work is associated with higher odds of becoming nearsighted. And spending more time outdoors can delay the onset of myopia.
Types of Myopia
Myopia is often divided into two categories depending on its cause: `- Axial myopia is due to the eyeball being too long from front to back (the axial length). It's the most common cause of myopia, especially in childhood.
- Refractive myopia can occur if the cornea or lens are too curved. It can also occur if the lens sits too close to the cornea, but this is rare.
Some people can have a combination of axial and refractive myopia.
Myopia Symptoms
People with myopia have difficulty seeing distant objects, like road signs, clearly. They usually have better vision during near tasks, such as reading and computer use. This is why myopia is often called nearsightedness.
- Squinting: Partially closing the eyes to see more clearly.
- Needing to Move Closer: Moving closer to objects to see them more clearly.
- Difficulty with Distance Vision: Struggling with activities that require good distance vision, such as driving or playing sports.
- Headaches: Frequent headaches due to eye strain.
- Headaches: Frequent headaches due to eye strain.
- Eye Strain: Feeling tired or strained eyes from focusing on distant objects.
If you experience these symptoms even while wearing glasses or contact lenses, it’s a good idea to schedule an eye exam with your optometrist, as you may need an updated prescription.
Myopia Management
Myopia management involves all the aspects of eye care a person with myopia may need. It aims to correct blurred vision, control myopia progression and decrease the risk of complications from high myopia. Myopia management includes:
- Early detection and diagnosis.
- Timely myopia correction and control.
- At-home practices like the 20-20-20 rule and limiting screen time.
- Addressing any myopia-related complications.
Myopia Detection and Diagnosis
Early detection and intervention are crucial for managing myopia and slowing its progression. Since many children with myopia may not show obvious signs or may not realize their vision is blurry compared to others, regular eye exams are essential. The recommended schedule for eye exams is:
- First Eye Exam: At 6 months
- Second Eye Exam: Between ages 3 and 5
- Third Eye Exam: Before starting first grade
- Annual Eye Exams: Throughout school years
- Third Eye Exam: Before starting first grade
Children with a family history of myopia or those already diagnosed with myopia may need more frequent exams.
Prescription Details:
For those needing corrective lenses, prescriptions for myopia are indicated with a minus sign (-) followed by a number. Higher numbers reflect higher levels of myopia:
- Low Myopia: Ranges from -0.50 to -5.75
- High Myopia: -6.00 or greater
Complications of High Myopia:
High myopia can lead to serious complications, including:
- Posterior Subcapsular Cataracts
- Glaucoma
- Myopic Macular Degeneration
- Retinal Detachment
If at risk for high myopia, your eye doctor will monitor for these complications and discuss preventive measures. Regular eye exams are critical to assess myopia progression and implement early interventions to prevent high myopia and associated complications.
