Overnight contact lens treatment for myopia (short-sight) progression in children

None listed

Scientific summary Myopia (short-sight) is a condition in which close objects are seen clearly but distant objects appear blurred. The prevalence of myopia is very high in Asia (Seet, Wong et al. 2001) and is increasing in Europe, Australia and the U.S. (Kempen, Mitchell et al. 2004). It has been shown in several animal species that ocular growth can be modified by retinal defocus (Smith, Kee et al. 2005). Hyperopic retinal defocus (image plane focused posterior to the retina) causes eye elongation, while myopic defocus (image plane focused anterior to the retina) causes a reduction in eye growth (Winawer and Wallman 2002). It has recently been suggested that in addition to correcting myopia, conventional OK may also slow the progressive eye elongation, which is the basis of myopia progression. The process of flattening the central cornea in conventional OK inevitably results in steepening the peripheral cornea. It has been hypothesised that the steepening in the peripheral cornea with OK may cause myopic retinal defocus in the peripheral retina, which may in turn slow myopia progression. Another recent innovation, shown to be effective in slowing myopia progression is the Dual-Focus soft contact lens (Anstice 2009). This lens has a central correction zone with concentric treatment zones providing 2.00 dioptres of myopic defocus. Duplex orthokeratology: We have designed a Duplex OK lens aimed at enhancing the efficacy of conventional OK in slowing progression by combining (adding) the optical treatment effect of the Dual-focus lens with the treatment effect of conventional OK lenses. The lens moulds the corneal surface into a correction zone in the centre surrounded by an annular treatment zone within the confines of the pupil, similar to a Dual-Focus contact lens. Evidence that the corneal surface can indeed be moulded in this way comes from the use of similar multi-zone orthokeratology lenses for presbyopia. The aim of this study is to test the efficacy of this new lens design in slowing myopia progression, using conventional OK as control. Aim The hypothesis is that progression of myopia (axial eye elongation) in eyes wearing the Duplex Orthokeratology (DOK) lens overnight will be reduced compared to eyes wearing a conventional orthokeratology (OK) lens overnight, over a period of 18 months. It is not possible to test this hypothesis on the basis of change in refraction because both DOK and conventional OK will correct refractive error in both eyes. In order to test the hypothesis we will compare changes in vitreous chamber depth (VCD) between the two eyes over time and the vitreous chamber depth difference will be the primary outcome measure. Study Design This is a prospective, randomized, paired-eye control, investigator-masked, single-centre trial. Thirty children will wear a conventional OK lens (randomly assigned) in one eye (control eye) and a Duplex OK lens in the contra-lateral (treatment) eye. The study will be conducted with children aged between 10 to 14 years. During 18 months of lens wear, we will compare the elongation of vitreous chamber depth between the treatment and control eye measured at time 0, 6, 12 and 18 months. Elongation of vitreous chamber depth will be the outcome measurement that will directly show whether the DOK treatment is more effective than conventional OK. Vitreous chamber depth will be measured by low coherence reflectometry (Haag Streit Lenstar LS 900). Secondary outcome measures will monitor the visual performance of each participant. These include refractive error, accommodation performance and contrast sensitivity with conventional and duplex orthokeratology.

No related papers found yet.