Effectiveness of Orthokeratology in Myopia Control
Condition: Myopia
MeSH terms: Myopia
Study type: Interventional

Summary: 
      The high prevalence of myopia - especially in Asian countries - is well documented, as are
      the sight-threatening complications of high or degenerative myopia. Retinal detachment,
      glaucoma, vitreal degeneration and focal retinal changes may occur secondary to the
      progressive axial elongation of the eye with age. Specialty rigid lenses have long been shown
      to lessen this progression in the pediatric population; orthokeratology (ortho-k) lenses are
      worn at night and change the corneal topography to correct low to moderate amounts of myopia.
      Most of the studies on orthokeratology were conducted on Asian children. To the best of the
      investigators knowledge, no study has been done on African American (AA) children. The
      investigators' project seeks to investigate the efficacy of ortho-k in slowing axial
      elongation and myopic progression in AA children compared to that in other races.
    

Detailed description: 
      Orthokeratology (ortho-k), when used for partial or full correction of myopia, has been shown
      to slow myopic progression in children by 36-56% as compared to their spectacle or
      contact-lens wearing peers.1 This effect is achieved by limiting the axial elongation of the
      eye,1, 2,3, 4 which is of particular concern in high myopes (>6.00D) and children, where
      myopic progression has been shown to proceed at a faster rate than average.1 As early
      intervention is considered beneficial if not essential, Ortho-k as a treatment modality for
      diminishing myopic progression has, to our knowledge, been studied mostly in Asian children.

      The safety and efficacy of ortho-k as a means of decreasing myopic progression was well
      established by the Children's Overnight Orthokeratology Investigation (COOKI), who evaluated
      refractive error, visual changes and ocular health over a period of 6 months in myopic
      children. 7 The Longitudinal Orthokeratology Research in Children (LORIC) study looked at
      axial elongation in children as old as 12 years, and found that ortho-k decreased axial
      elongation by approximately 50% compared to be-spectacled controls. 2 They also noted,
      however, high variability amongst the children that limits the clinician's ability to predict
      the outcome of the intervention.2 The Corneal Reshaping and Yearly Observation of Myopia
      (CRAYON) study confirmed that patients fit with ortho-k lenses showed less change in axial
      length and vitreous chamber depth when compared to subjects wearing soft contact lenses. 3
      Other more recent studies by Santodomingo-Rubido et al, 7 Kakita et al4 and Charm et al1
      confirm this decrease in axial elongation using IOL Master measurements.

      The most commonly accepted theory on how orthokeratology decreases axial elongation relies on
      the peripheral defocus created on the retina by the corneal changes made by the rigid lens. 9
      Hoogerheide et al showed that those at greatest risk for myopic progression were those whose
      peripheral refraction was hypermetropic10 - that is, they had a hyperopic peripheral
      'defocus'. A number of studies have since suggested that treatment approaches to myopia
      correction should address this peripheral refraction as a means of slowing further axial
      elongation.9 When looking at subjects treated with ortho k, we see that the lenses do in fact
      introduce a peripheral myopic defocus while leaving the central refraction more or less
      emmetropic. 9 With this study, the investigators hope to expand potential application of
      orthokeratology to a novel population, AA children.
    

Intervention name(s): OrthoK
Intervention type(s): Device
Intervention description(s): orthok (orthokeratology) is the science of changing the curvature or shape of the cornea to change how light is focused on the retina at the back of one's eye. Specially designed molding retainer contact lenses are placed on the eye at night and are removed upon awakening.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Prevention