Amblyopia

• What does the Greek word "amblyopia" mean?

  Dull sight or blunt sight
• What is the definition of amblyopia?

  Reduction in visual acuity due to neurological deficits
• What is the most common cause of vision loss in children?

  Amblyopia
• How is amblyopia characterized in terms of visual acuity?

  Reduced visual acuity not due to current pathology
• What is the reported incidence of amblyopia worldwide?

  1. 5%
• In which populations is amblyopia more prevalent?

  Medically underserved and lower socioeconomic classes
• What are the four parts of visual function?

  1. Light sense: Distinguish light and dark
  2. Form sense: Distinguish size and shape
  3. Motion sense: Detect movement
  4. Colour sense: Distinguish wavelengths
• What is required for normal visual experience?

  Normal visual experience is required for development
• What do rods and cones synapse with in the retina?

  Ganglion cells
• What is the role of rods in vision?

  Movement detection and night vision
• What is the role of cones in vision?

  Colour detection and central vision
• What is the parvocellular (X) system's requirement for visual acuity?

  Needs a stable, well-focused image
• What is the lateral geniculate body?

  A relay station for visual information
• What percentage of visual cortex responds to vision from either eye?

  80-85%
• What percentage of visual cortex responds to an eye with strabismus?

  15-17%
• What are the periods of visual development?

  1. Birth to 3-5 years: Development of visual acuity
  2. Critical period: Few months to 7-8 years
  3. Sensitive period: Time of deprivation to teenage years
• What happens during the critical period of visual development?

  Deprivation results in loss of function
• What is neural plasticity in relation to amblyopia?

  Vulnerable visual system to abnormal experiences
• At what age does amblyopia typically start?

  When the baby is binocular (2-4 months)
• When is amblyopia treatment most effective?

  The younger the patient, the more rapid the response
• What can interfere with normal visual development?

  Cataract, ptosis, injury, infection
• What are the mechanisms of amblyopia?

  1. Deprivation of form vision

  • Complete: No stimulus reaches fovea
  • Partial: Degraded image

  1. Abnormal binocular interaction or competition

  • Involved in all unilateral amblyopia
• What are the effects of amblyopia beyond reduced vision?

  Loss of Snellen acuity, contrast sensitivity
• What is the crowding phenomenon in amblyopia?

  Identifying letters is harder in groups than alone
• What are the types of amblyopia?

  1. Stimulus deprivation
  2. Strabismic
  3. Anisometropic
  4. Ametropic
  5. Meridional
  6. Idiopathic
  7. Hysterical / psychogenic
  8. Organic
  9. Toxic
• What is stimulus deprivation amblyopia?

  Affects one or both eyes due to form vision deprivation
• What is strabismic amblyopia caused by?

  Abnormal binocular interaction or competition
• What is anisometropic amblyopia characterized by?

  Significant difference in refraction between eyes
• What is ametropic amblyopia often associated with?

  High degree of insuperable refractive error
• What is meridional amblyopia associated with?

  Moderate or high degree of uncorrected astigmatism
• What characterizes idiopathic amblyopia?

  No refractive error and normal BSV
• What is hysterical/psychogenic amblyopia?

  Apparent amblyopia from psychosomatic disorder
• What is organic amblyopia?

  Often irreversible and cannot be treated
• What is toxic amblyopia caused by?

  Absorption of toxic agents like cyanide
• What are the investigations for amblyopia diagnosis?

  1. Case history
  2. Fundus and media check
  3. Refraction
  4. Visual acuity
  5. Contrast sensitivity
  6. Cover test
  7. 10^ prism test
  8. Neutral density filter test
• What does the cover test assess in amblyopia?

  Fixation pattern and likelihood of amblyopia
• What does the 10^ fixation test observe?

  Fixation preference in strabismus
• What is the purpose of the direct ophthalmoscope?

  To visualize the retina clearly
• What is the first step in using a direct ophthalmoscope?

  Position the patient at eye level
• Why is it essential to darken the room during examination?

  To enable clearer visualization of the retina