Childhood Refractive Errors

Refractive errors in children include hypermetropia, myopia, astigmatism and anisometropia. They are the commonest cause of correctable visual impairment in school age children.

• Normal development: newborns are hypermetropic (+2.00 to +3.00 dioptres on average) with astigmatism that declines by age 2 to 3; emmetropisation reduces hypermetropia during the first 5 to 6 years.
• Myopia prevalence has risen sharply (about 30 to 80 percent in East Asian urban teenagers, 5 to 10 percent in preschool children in Europe and North America). Risk factors: parental myopia (one parent doubles, two parents quadruples risk), prolonged near work, little outdoor time, early onset.
• High hypermetropia or astigmatism and anisometropia lead to amblyopia and strabismus; high myopia raises the lifetime risk of retinal detachment, myopic maculopathy, glaucoma and cataract.
• Pathological myopia: syndromic (Stickler, Marfan), retinopathy of prematurity, congenital stationary night blindness.

• Myopia: poor distance vision, squinting, sitting close to the television, holding books near, headaches, classroom difficulty, progression through adolescence.
• Hypermetropia: usually asymptomatic in children due to accommodation; asthenopia, headaches, intermittent blur, and accommodative esotropia in high hypermetropia (above +3.00).
• Astigmatism: blur at all distances, head tilt, squinting; meridional amblyopia.
• Anisometropia: amblyopia and strabismus without symptoms.
• Children rarely complain; screening catches most.

• Cycloplegic refraction: cyclopentolate 1 percent, 1 drop in each eye, repeat once after 5 minutes, measure at 30 to 45 minutes (use 0.5 percent below 12 months; atropine 1 percent twice daily for 3 days in strabismus with high hypermetropia or dark irides); tropicamide 1 percent is acceptable for myopia screening.
• Retinoscopy, autorefraction, and photoscreening; visual acuity (logMAR or Snellen); axial length by optical biometry (essential for monitoring myopia progression); keratometry.
• Dilated fundus examination for pathological myopia and other diseases; cover test and ocular motility.
• Corneal topography when irregular astigmatism or keratoconus suspected (progressive astigmatism in teenagers).
• Cycloplegic refraction repeated annually (6 monthly during rapid myopia progression).

• Correction thresholds (guide; treat earlier when strabismus, amblyopia or symptoms are present):
  • Infants under 1 year: myopia above -5.00, hypermetropia above +6.00 (above +3.00 with esotropia), astigmatism above 3.00.
  • Age 1 to 2: myopia above -4.00 to -5.00, hypermetropia above +5.00, astigmatism above 2.50.
  • Age 2 to 3: myopia above -3.00, hypermetropia above +4.50, astigmatism above 2.00.
  • Children 4 years and above: myopia above -1.50 to -0.75 when symptomatic, hypermetropia above +2.50 to +3.50 depending on symptoms, astigmatism above 1.50, anisometropia above 1.00.
• Spectacles: polycarbonate lenses, durable frames; full correction in esotropia and amblyopia; contact lenses for high anisometropia and keratoconus.
• Myopia control (for progressing myopia, age 6 to 16 years):
  • Atropine 0.01 to 0.05 percent drops nightly (slows progression by about 30 to 60 percent; rebound on stopping, photophobia, near blur at higher doses).
  • Multifocal soft contact lenses designed for myopia control, orthokeratology (overnight rigid lenses), and spectacle lenses with defocus or multi lenslet designs.
  • Behavioural: at least 2 hours outdoors daily, limiting near work, 20-20-20 rule (every 20 minutes of near work, look 20 feet away for 20 seconds).
  • Avoid undercorrection (it accelerates progression).
• Refractive surgery is not used in children except in special cases (high anisometropia with contact lens intolerance, severe neurodevelopmental disease).
• Monitor with 6 monthly visits during myopia progression; screen high myopes for retinal tears and detachment, and give retinal detachment symptoms advice (flashes, floaters, curtain).