Orthokeratology : Compendium of latest research


The SMART Study (Year 3 Update) - Stablizing Myopia by Accelerated Reshaping Technique

The SMART Study is the largest clinical investigation so far into whether Overnight Vision Correction (OVC) can stop the progression of short-sightedness in children once they start wearing i-GO OVC lenses. Almost 200 children between the ages of 8 and 14 at the start of the Study are being assessed over a five year period and the Study separated these children into two groups - one group wearing i-GO OVC lenses and the other wearing conventional soft contact lenses. After completing three years, the interim results have revealed that those children wearing i-GO OVC lenses have experienced no material change in their short-sightedness whilst those wearing conventional soft contact lenses have experienced a further deterioration of a full diopter so their short-sightedness has worsened significantly. Additionally, there have been no significant health or safety issues identified so far during the Study. 
YEAR 3 INTERIM RESULTS (Released January 2011): 
Test Group subjects experienced minimal change in myopia with an average prescription level of -0.17D after three years of wearing overnight orthokeratology corrective contact lenses.
Control Group subjects, the average prescription level had worsened further to -1.01D after three years of wearing conventional soft contact lenses.
These results confirm the evidence of Years 1 and 2 which revealed for each year that Test Group subjects experienced minimal change to their level of myopia as measured at the beginning of the Study whilst Control Groups subjects experienced continued worsening of their myopia.
Based on Year 3 results, Control Group subjects are experiencing a worsening of their myopia by an average of over one-third of a diopter per year. No statistically significant change in either Axial Length or Vitreous Chamber Depth was evident from ultrasound biometry to explain refractive differences between the Test and Control Groups.
The significant (grade 2 or greater) biomicroscopic events recorded at the end of Year 3 comprised 3 cases of corneal infiltrative keratitis within the Control Group, 12 cases of corneal staining (8 in Test Group and 4 in Control Group) and 10 cases of hyperaemia (5 each in the Test and Control Groups).
109 subjects in the Test Group (wearing overnight orthokeratology corrective contact lenses) and 65 subjects in the Control Group (wearing conventional soft contact lenses replaced monthly) completed the third year of the Study. 

STRUCTURE OF THE STUDY: To determine if wearing overnight orthokeratology corrective contact lenses lenses influences the progression of myopia in children by measuring results over a 5 year longitudinal US study across 10 clinical sites. The Study compares outcomes at an annual interval between a Test Group comprising subjects wearing overnight orthokeratology corrective contact lenses and a Control Group comprising subjects wearing silicone hydrogel soft lenses for daily use and monthly replacement. Recruitment for the Study was focused on children between the ages of 8 and 14 at the Study commencement date, with a myopic prescription level of between -0.75D and -5.00D and astigmatism of no greater than -1.50D. None of the children had previously worn overnight orthokeratology corrective contact lenses but some had previously worn soft contact lenses for daily wear. The Study also seeks to establish whether there is a statistically significant change in Axial Length or Vitreous Chamber Depth to corroborate any identified refractive changes. Finally, the Study records all safety and efficacy outcomes to ensure any health and/or performance issues associated with children wearing overnight orthokeratology corrective contact lenses are properly documented.Year 1 Interim Results: 138 subjects in the test group and 90 from the control group completed the first year. The findings from the first year showed that overall mean prescription change in control group was almost 0.50 diopters whereas there was no change in the test group. The study continues.

BACKGROUND: The use of Orthokeratology for overnight wear raises many questions of safety, efficacy and the effects of myopia stabilization. Orthokeratology or corneal reshaping produces a temporary reduction of myopia by changing the shape (flattening) of the cornea, which is elastic in nature. Flattening the cornea reduces the focusing power of the eye, and if the amount of corneal flattening is properly controlled, it is possible to bring the eye into correct focus and compensate for myopia. Upon removal of the contact lens, the cornea retains its altered shape for a period of time. The global prevalence of myopia is increasing significantly in the school age population. It is estimated that one billion of the six billion people in the world are myopic. (3) Not only is the prevalence increasing but the degree of myopia has also increased. The prevalence of myopia in the United States is estimated to be 25%, in India to be 19% and in the Asian nations the rates of myopia are greater than 75%(1,2,3).

Studies have shown that complications from myopia, such as chorioretinal degeneration and retinal detachment will increase with increasing myopia. The application of corneal reshaping or orthokeratology may potentially stabilize the progressive nature of myopia throughout the adolescent years. Additionally, if wearing corneal reshaping lenses controls the progression of myopia, there also may be a reduction in the rates of adverse effects of advancing myopia. The fact that myopia is on the rise indicates that although the wearing of spectacles clears the vision, it does nothing to control the progression of myopia and its adverse effects.

Presented at the Global Speciality Lens Conference January 2011. Sponsored by " EyeVis"- Eye & Vision Research Institute: Giving Vision Through Research. 5 Year Longitudinal Study (In Progress - Commenced In January 2008) Due To Complete In January 2013, Barry Eiden, OD, FAAO & Robert L Davis, OD, FAAO (Principle Investigators) Ed Bennett,OD, FAAO; Cary Herzberg OD, FAAO; Michael Lipson OD, FAAO; LaMar Zigler, OD FAAO; Doug Becherer, OD, FAAO; Bruce Koffler MD; Rob Gerowitz OD, FAAO (Participating Optometrists) 


For a review of SMART Year 1 go to: Contact Lens Spectrum

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