Pediatric Refraction Pediatric Refraction
when to prescribe ?when to prescribe ?
· Mohamed Zaki (M.Sc) · Tanta University
1. Interfere with normal emmetropisation
2. Expense of spectacles3. Inconvenience to parents 4. Lack of perceived benefit to child
5- Prismatic effect and ↓ field of vision
Emmetropisation is both an active and a passive process i.e. error stimulate the
eye to correct it
requires normal visual experience
Atkinson et al (2007)
2-Risk of Amblyopia
Emmetropisation fails when refractive errors are outside normal range for age and the risk of amblyopia and
strabismus is increased
Glasses reduce the risk
· Atkinson et al (2007)
3- Power of accommodation
· The mean accommodative amplitude is
14 diopters for 8 years old child.
Southall, 1937
General RulesSmall errors usually don’t need correction
(stimulus of emmetropization)Large errors shouldn’t be fully corrected
(but converted to small errors)No emmetropization after 3 years.
(i.e. do full correction)Hypermetropia shouldn’t be fully corrected
(except …)
If you prescribe .. follow up refraction after 3 months.
Cycloplegic refraction is routine.
A child with VA ( 6/6 ) and dry autorefraction (+0.00) may need glasses.
0.5% to 1.0% Cyclopentolate1 drop tid x 3 days
Potentially Amblyogenic Refractive Errors
Isoametropia Anisometropia
Myopia > -8 to -10 > -3
Hyperopia > +5 > +1
Astigmatism > 2.5 > 1.5 (1 oblique)
As accomodation of both eyes is equal so it will correct the least hyperopic eye and the other remains not corrected ,,, so > 1D difference in hyperopia or hyperopic astigmatism should be corrected
Many guidelines …
Glasses prescription in children is a decision not just refraction
· Age ,
· History : child and family.
· Examination : ocular alignment , binocular vision.
History· School performance· Medical history (e.g., CP or Down syndrome)· Family history (hyperopia, aniso, strab, ambly)· Previous SRx & compliance
Symptoms/Signs· Tearing / redness Asthenopia
Blinking· Blurred vision Difficulty with reading/near
work
Myopia
< 3 years old:
partial correction of large error (>-3 to -4 D )
(subtract 1-2D)
>3-4 years old : full correction
Functional concern :
Vision / presence of XT
Astigmatism
< 3 years old:
partial correction of large error (>2)
(subtract 1-2 D or 50%)
>3-4 years : Full correction
Oblique axis (>1D) and Stable with repeated measures
Hyperopia why to treat ?
correcting hyperopia improves cognitive and visuo-perceptual abilities
(Rosner & Rosner 1987, Williams et al 2005,)
Atkinson prospective study
• Treated vs. untreated hyperopes
• If hyperopia > + 3.50
– 13x risk of strabismus or amblyopia
– Treatment decreases to 4 X
Hyperopia
< 3 years old: partial correction of large error (>+3.5 – 4.5 D)
(Subtract 1-2 D)
3-4 years : partial correction of large error (>+2.5)
School children : Vision / Any child with any hyperopia have learning or
other difficulties
Functional concern :/ presence of ET/ family history of squint / / children with
special needs /
Aphakia or Pseudophakia
· Overcorrect by 2 to 3.00D because child’s world is near.
· After 2 to 3 years, distance correction with bifocal is better option
· Aphakia correction not > +13
LASIK in children
· at least 4 D difference between the two eyes, but most of the time it is at least 6 D in the patients I treat. The second group includes patients with neurobehavioral disorders with severe anisometropia who just won't wear glasses despite the need,
· craniofacial abnormalities that make spectacle or contact lens wear impractical (e.g., Goldenhar's with microtia and/or limbal dermoids) and those with severe neck weakness (e.g., some children with cerebral palsy) whose spectacles fall down their nose.
· LASEK or PRK e MMC is best use , not LASIK
· Age < 7 ys
· Intolerant to glasses and CL Poor compliance can be defined as wearing glasses for 25% or less of waking time (only one out of every four waking hours, a permissive
· boundary)