Swarbrick Helen A
School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
Clin Exp Optom. 2006 May;89(3):124-43. doi: 10.1111/j.1444-0938.2006.00044.x.
Orthokeratology (OK) is a clinical technique that uses specially designed rigid contact lenses to reshape the cornea to temporarily reduce or eliminate refractive error. This article reviews the history of traditional daily-wear OK (1960s to 1980s) and discusses the reasons for the recent resurgence in interest in the new modality of overnight OK, using reverse-geometry lens designs (1990s to the present). The clinical efficacy of the current procedure is examined and outcomes from clinical studies in terms of refractive error change and unaided visual acuity are summarised. Onset of the effects of overnight OK lens wear is rapid, with most change after the first night of lens wear and stability of refractive change after seven to 10 days. Mean reductions in myopic refractive error of between 1.75 and 3.33 D and individual reductions of up to 5.00 D have been reported. There appear to be slight reductions or minimal changes in astigmatism with the use of reverse-geometry lenses and most patients are reported to achieve 6/6 unaided vision or better. The induction of higher order aberrations, in particular, spherical aberration, has been reported and this may affect subjective vision under conditions of low contrast and pupil dilation. Patient satisfaction with overnight OK has been reported as similar to or better than with other popular modalities of contact lens wear. Available evidence suggests that the corneal changes induced by overnight OK are fully reversible. The refractive effect in OK is achieved by central epithelial thinning and this has raised concerns about compromise of the epithelial barrier to microbial infection. Recent reports of microbial keratitis in the modality are reviewed and the overall safety of the procedure is examined critically. Recent research on stromal contributions to the OK effect, particularly relating to overnight oedema, is summarised. Emerging issues in OK, including myopic control, correction of other refractive errors and permanency of the OK effect, are discussed.
角膜塑形术（OK）是一种临床技术，它使用特殊设计的硬性接触镜来重塑角膜，以暂时减少或消除屈光不正。本文回顾了传统日戴型角膜塑形术的历史（20世纪60年代至80年代），并讨论了近期对新型过夜型角膜塑形术重新产生兴趣的原因，这种新型角膜塑形术采用了反转几何镜片设计（20世纪90年代至今）。本文考察了当前该手术的临床疗效，并总结了临床研究在屈光不正变化和裸眼视力方面的结果。过夜佩戴角膜塑形镜的效果起效迅速，大多数变化发生在佩戴镜片的第一晚之后，屈光变化在7至10天后稳定。据报道，近视屈光不正平均降低1.75至3.33 D，个别降低可达5.00 D。使用反转几何镜片时，散光似乎有轻微降低或变化极小，据报道大多数患者能达到6/6或更好的裸眼视力。有报道称会诱导高阶像差，尤其是球差，这可能会在低对比度和瞳孔散大的情况下影响主观视觉。据报道，患者对过夜型角膜塑形术的满意度与其他流行的隐形眼镜佩戴方式相似或更高。现有证据表明，过夜型角膜塑形术引起的角膜变化是完全可逆的。角膜塑形术中的屈光效应是通过中央上皮变薄实现的，这引发了人们对上皮屏障抵御微生物感染能力受损的担忧。本文回顾了该方式近期关于微生物性角膜炎的报道，并对该手术的总体安全性进行了批判性审视。总结了近期关于基质对角膜塑形术效果的贡献，特别是与过夜水肿相关的研究。讨论了角膜塑形术中出现的新问题，包括近视控制、其他屈光不正的矫正以及角膜塑形术效果的持久性。
