在这篇文章中, PC shared with the Myopia Profile community a successful orthokeratology fitting on a patient who had moderate myopia with moderate astigmatism. PC fitted this patient with a custom designed toric orthoK lens. Here are some orthokeratology fitting tips from the Facebook community.
Before fitting orthokeratology, ensure there is no irregular astigmatism or any corneal disease. From the topography results, this patient’s astigmatism is mainly contributed by corneal toricity. The discussion turned to the type of lens design to achieve this ideal fitting.
Spherical vs Toric orthokeratology lens?
- The decision to prescribe a toric orthoK lens depends on the amount corneal toricity instead refractive astigmatism. A spherical orthoK lens can typically be fit on up to 1.50D corneal astigmatism with-the-rule. However, higher amounts of corneal toricity lead to increased likelihood of treatment zone decentration.1
- Hence, toric orthoK lenses are the better option in cases of moderate to high corneal astigmatism as it helps in achieving good lens centration compared to spherical orthoK.2One could also choose a toric orthoK lens when there is an elevation difference of 30-45μm or more between the steep and flat corneal meridians.
- Orthok的紫色是在返回曲线和对齐曲线上设计的，以更好地对齐。这将确保良好的合适。
- 在确定良好的透镜拟合度后，可以使用球形或感谢您的光学元件来纠正残留的散光。球形光学元件通常可以校正高达1.50d的散光，而感谢您的光学元件非常适合校正以外的水平。
年轻的眼角膜更快响应orthokeratolo吗gy?
- This patient was a 5D myope who achieved unaided vision of 6/6 (20/20) after only one week. With such a swift response, there was a small thread that discussed how quickly a cornea responds to orthoK treatment. Jayakumar et al3发现年龄增长的上皮反应减少了 - 儿童和年轻人（平均25岁）的反应类似，而老年人（平均44岁）的反应速度较慢。
- OrthoK does not permanently change the corneal biomechanical properties such as corneal hysteresis (CH) and corneal resistance factor (CRF).4Research has indicated, however, some baseline biomechanical differences in corneal stiffness and modulus in poor-responders compared to good-responders wearing orthoK.5Low CH and CRF may also be risk factor of myopia progression. Research has indicated that patients with low CH may benefit from OrthoK to slow myopia progression.6
带回家消息
- When deciding between spherical or toric orthoK lenses, check for corneal toricity rather than refractive astigmatism to achieve a good seal and lens fit.
- 然后，可以用球形或感谢您的光学元件校正折射率，以允许良好的视觉校正。
- Younger eyes tend to respond faster to orthoK treatments - you can expect patients over 40 to take longer to reach full correction.
- 角膜l biomechanical factors also appear to influence orthoK results - but since these are not measured in practice we can expect to see some variation between individuals in the swiftness and maximum treatment level of their orthoK response.
About Kimberley
Kimberley Nguis a clinical optometrist from Perth, Australia, with experience in patient education programs, having practiced in both Australia and Singapore.
About Connie
Connie Ganis a clinical optometrist from Kedah, Malaysia, who provides comprehensive vision care for children and runs the myopia management service in her clinical practice.
参考：
- Maseedupally VK，Gifford P，Lum E，Naidu R，Sidawi D，Wang B，Swarbrick HA。在角膜紫红色眼睛的正差异学期间的治疗区分散。验光和视觉科学。2016; 93（9）：1101-11。（（关联)
- Jiang J, Lian L, Wang F, Zhou L, Zhang X, Song E. Comparison of Toric and Spherical Orthokeratology Lenses in Patients with Astigmatism. Journal of Ophthalmology. 2019（（关联)
- Jayakumar J，Swarbrick HA。年龄对短期正常人学的影响。验光和视觉科学。2005; 82（6）：505-11。（（关联)
- Mao XJ，Huang CC，Chen L，LüF。关于隔夜正常分类的角膜生物力学特性的影响。[中国Yan Ke Za Zhi]中国眼科杂志。2010年3月； 46（3）：209-13。（（关联)
- Lam, A.K.C., Hon, Y., Leung, S.Y.Y.等。Association between long-term orthokeratology responses and corneal biomechanics. Sci Rep 9,12566（2019）。（（关联)
- Wan K，Cheung SW，Wolffsohn JS，Orr JB，Cho P.角膜生物力学特性在预测佩戴正差异镜片或单视感眼镜的儿童中近视进展的速度中的作用。BMJ开放眼科。2018; 3（1）：E000204。（（关联)
