Ortho-K Studies

CLAMP
(Contact Lens And Myopia Progression)

This study had several goals. To evaluate the effect of rigid lenses on myopia progression in children. To determine the mechanism of effect if one exists. To examine the efficacy of rigid contact lenses for the treatment of myopia in young children. To compare vision and comfort issues between rigid and soft contact lens wearers. The conclusions of this study are as follows: Rigid gas permeable lenses produce a slower rate of progression of myopia in children than soft contact lenses. Although corneal curvature changed, the axial growth was not significantly different between the groups. The decreased refractive error progression is not accompanied by slowed axial growth. The corneal curvature changes during corneal reshaping contact lens wear are reversible. The treatment effect experienced in the CLAMP study may not be permanent. Most of the effect on refractive error was limited to the first year of the trial. The study did not indicate that rigid gas permeable lenses should be prescribed primarily for the intent of myopia control.

MYOPIA CONTROL (Houston Study)

This study examined the control of myopia progression comparing rigid gas permeable contact lenses versus spectacles. The results showed that the mean increase in myopia for the gas permeable lens was 0.42 diopters per year versus a mean increase in myopia for the spectacle wearers of 0.78 diopters per year. The mean increase in axial length for the gas permeable lens was 0.22 mm per year versus a mean increase in axial length for the spectacle wearers of 0.31 mm per year. The study showed that the decrease in progression of myopia using gas permeable lenses is attributable to mix of axial length growth reduction and corneal flattening.

LORIC
(The Longitudinal Ortho-k Research In Children)

This study looked at several factors. It was to determine whether Orthokeratology can effectively reduce and control myopia in children. It also compared Orthokeratology treatment with single vision spectacles. It monitored the growth of axial length and the vitreous chamber depth. It also monitored corneal curvature and the relationships with changes of refractive errors. The conclusions of the study found that the subjects found post Orthokeratology unaided vision acceptable in the daytime. The mean increase in axial length for the Orthokeratology group was 0.14 mm per year compared with the mean increase in axial length for the spectacle lens wearers of 0.27 mm per year. In the spectacle wearing group, the eye elongation is faster in those with higher baseline prescriptions. Orthokeratology would benefit higher baseline prescriptions as eye elongation is slower in these subjects. Higher myopia showed greater slowing of progression in the Orthokeratology group.

SMART
(Stabilizing Myopia by Accelerating Reshaping Technique)

This study is to determine if wearing Orthokeratology lenses on an overnight basis stops or slows the progression of myopia in children. The group being studied is eight to eleven years old. This group will be compared to spherical soft lens wearers. This study is currently underway so no data is yet available.

Abstract: 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.

Conclusions: The initial recruitment phase, fitting statistics, and demographics provide the structure for the five year SMART investigation. Initial dispensing data for corneal reshaping test subjects showed a high first lens success rate to achieve 20/20 unaided acuity. Long term results of this study will provide fitting information, myopia progression comparative data, anatomical differences, and subjective responses to each lens modality. 80.5% of the test group were fit able to use the initial empirically fit lens and did not require a lens change.