Effectiveness of Orthokeratology in Myopia Control

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.

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.

The study will be a randomized control study using a single-masked design to investigate axial elongation and myopic progression in children wearing ortho-k lenses (study group) versus single-vision spectacles or soft contact lenses (control group) for a period of 24 months. A minimum of 40 and a maximum of 60 subjects will be recruited from patients at Illinois Eye Institute. Once eligibility has been determined by an unmasked observer, patients will be randomly assigned to either the orthokeratology group or the single-vision contact lens /spectacle group

The study will be a randomized control study using a single-masked design to investigate axial elongation and myopic progression in children wearing ortho-k lenses (study group) versus single-vision spectacles (control group) for a period of 24 months. A minimum of 40 and a maximum of 60 subjects will be recruited from patients at Illinois Eye Institute. Once eligibility has been determined by an unmasked observer, patients will be randomly assigned to either the orthokeratology group or the single-vision contact lens /spectacle group

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.

Axial Length was measured at baseline and again at the 2 year mark. Units are given in mm. The average of axial length at the 2 year period is provided.

Inclusion Criteria: myopia progression more than -1.00D in one year myopic prescription between -1.00D and -6.00D in at least one eye with refractive astigmatism <1.50D Best corrected VA 20/25 or better subjects willing to present to clinic for all necessary follow up care willing to be randomized to either group Exclusion Criteria: non-compliance with treatment protocol contraindications for orthok as per company guidelines history of refractive surgery current gas permeable contact lens wearers

Charm J, Cho P. High myopia-partial reduction ortho-k: a 2-year randomized study. Optom Vis Sci. 2013 Jun;90(6):530-9. doi: 10.1097/OPX.0b013e318293657d.

Cho P, Cheung SW, Edwards M. The longitudinal orthokeratology research in children (LORIC) in Hong Kong: a pilot study on refractive changes and myopic control. Curr Eye Res. 2005 Jan;30(1):71-80. doi: 10.1080/02713680590907256.

Walline JJ, Jones LA, Sinnott LT. Corneal reshaping and myopia progression. Br J Ophthalmol. 2009 Sep;93(9):1181-5. doi: 10.1136/bjo.2008.151365. Epub 2009 May 4.

Kakita T, Hiraoka T, Oshika T. Influence of overnight orthokeratology on axial elongation in childhood myopia. Invest Ophthalmol Vis Sci. 2011 Apr 6;52(5):2170-4. doi: 10.1167/iovs.10-5485.

Loman J, Quinn GE, Kamoun L, Ying GS, Maguire MG, Hudesman D, Stone RA. Darkness and near work: myopia and its progression in third-year law students. Ophthalmology. 2002 May;109(5):1032-8. doi: 10.1016/s0161-6420(02)01012-6.

Kinge B, Midelfart A. Refractive changes among Norwegian university students--a three-year longitudinal study. Acta Ophthalmol Scand. 1999 Jun;77(3):302-5. doi: 10.1034/j.1600-0420.1999.770311.x.

Walline JJ, Rah MJ, Jones LA. The Children's Overnight Orthokeratology Investigation (COOKI) pilot study. Optom Vis Sci. 2004 Jun;81(6):407-13. doi: 10.1097/01.opx.0000135093.77007.18.

Santodomingo-Rubido J, Villa-Collar C, Gilmartin B, Gutierrez-Ortega R. Myopia control with orthokeratology contact lenses in Spain: refractive and biometric changes. Invest Ophthalmol Vis Sci. 2012 Jul 31;53(8):5060-5. doi: 10.1167/iovs.11-8005.