Myopia

• What is myopia?

  Myopia is a common form of ametropia.
• How does myopia affect light entering the eye?

  Myopia causes parallel light to focus short of the retina, creating a blur circle.
• What happens to the far point in myopia?

  The far point moves closer to the eye, depending on the magnitude of myopia.
• What is the effect of light diverging from the far point in myopia?

  Light diverging from the far point focuses on the retina with the eye at rest.
• During which life stages does myopia primarily develop?

  Myopia primarily develops during childhood and early adulthood.
• What is the global prevalence of myopia in adults?

  The prevalence of myopia in adults is 10–30% in many countries.
• What is the prevalence of myopia in young adults in some parts of East and Southeast Asia?

  The prevalence can be as high as 80–90% in young adults in some regions.
• What is the primary cause of most cases of myopia?

  Most cases of myopia are associated with excessive axial eye growth.
• What are the two main types of myopia based on causation?

  Myopia can be caused by axial length or the strength of the refractive media.
• Why is myopia often referred to as shortsightedness?

  Myopia is called shortsightedness because it allows clear near vision but blurs distance vision.
• What lifestyle factor is linked to the development of myopia?

  A modern lifestyle with long periods of near-work activities is linked to myopia development.
• How is myopia defined in terms of spherical equivalent?

  Myopia is defined by a spherical equivalent (SE) ≤−0.5 dioptres (D).
• How can myopia typically be corrected?

  Myopia can typically be corrected with glasses, contact lenses, or refractive surgery.
• What risk increases with higher levels of myopia?

  Higher levels of myopia significantly increase the risk of harmful changes in the eye.
• What serious conditions can high myopia lead to?

  High myopia can lead to glaucoma, retinal detachment, and macular holes.
• What has happened to the prevalence of myopia over the past 30 years?

  The prevalence of myopia has risen sharply, leading to it being called an 'epidemic.'
• Why is myopia considered a significant public health issue?

  Myopia is a public health issue due to challenges in providing optical correction and managing vision problems.
• How can myopia be classified?

  • By presumed etiology (e.g., axial, correlation)
  • By age at onset (e.g., juvenile)
  • By progression pattern (e.g., stable, progressing)
  • By magnitude (e.g., low, moderate, high)
  • By structural complications (e.g., degenerative)
• What is the aim of myopia treatment?

  The aim of myopia treatment is to lower the risk of developing higher levels of myopia.
• What is the role of early intervention in myopia management?

  Early intervention is key in managing myopia effectively.
• What types of lenses are commonly used to manage myopia?

  • Standard single vision glasses
  • Bifocals
  • Progressive lenses
  • Lenses designed to control peripheral defocus
• What are the contact lens options for myopia management?

  Contact lens options include soft lenses and orthokeratology lenses.
• What option is available for adults with stable myopia?

  Refractive surgery offers a convenient, lens-free option for adults with stable myopia.
• What are the two types of myopia based on axial length and power?

  • Axial myopia: Normal power but longer axial length
  • Refractive myopia: Higher power but normal axial length
• What are the etiologies of axial myopia?

  • Congenital
  • Developmental
  • Acquired
  • Degenerative
• How does a minus lens correct myopia?

  A minus lens brings an image from optical infinity to the far point of a myopic eye.
• What happens to the image formed by a minus lens in a myopic eye?

  The image formed by the minus lens is sharply focused on the retina.
• What are the etiologies of refractive myopia?

  1. Corneal curvature
  2. Abnormal crystalline lens curvature or position
  3. Spasm of accommodation (pseudomyopia)
  4. Convergence-accommodation anomaly
  5. Increase in refractive index due to disease
  6. Night myopia
• What characterizes axial myopia in terms of imaging?

  Distant objects are imaged in front of the eye's retina in axial myopia.
• What is the relationship between axial length and the eye's second focal length in axial myopia?

  The axial length is longer than the eye's second focal length in axial myopia.
• What is the dioptric length of the eye in axial myopia?

  The dioptric length of the eye is calculated as $K' =$$n' k' =$$1.333 \times 1000 / 23 =$$+$$57.96 D$.
• How is ocular refraction calculated in axial myopia?

  Ocular refraction is calculated as $K =$$K' - F'' =$$57.96 - 60 =$$-2.04 D$.
• What is the far point in axial myopia?

  The far point is calculated as $K =$$1 \times 1000 / -2.04 =$$-490.2 \text{ mm}$.
• What happens if an object is situated 49.02 cm in front of the reduced eye?

  The object would be imaged on the retina because the far point plane and retina are conjugate points.
• How is magnification calculated in axial myopia?

  Magnification is calculated as $m =$$K / K' =$$-2.04 / 57.96 =$$-0.0352$.
• What does a magnification of -0.0352 indicate?

  It indicates that the retinal image size is 0.0352 times smaller than the object size.
• How is the size of the retinal image calculated in axial myopia?

  The size of the retinal image is calculated as $h' =$$-0.0352 \times 0.5 =$$-0.0176 \text{ mm}$.
• What characterizes refractive myopia in terms of imaging?

  Distant objects are imaged in front of the eye's retina in refractive myopia.
• How is the power of the eye calculated in refractive myopia?

  The power of the eye is calculated as $Fe =$$Ko' - K =$$60 - (-2) =$$62 D$.
• How is the far distant point calculated in refractive myopia?

  The far distant point is calculated as $k =$$n / K =$$1 \times 100 / -2 =$$-50 \text{ cm}$.