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怎样在角膜塑形镜的验配中优化角膜地形图的设置
How to Optimize Corneal Topography Settings for Orthokeratology Fitting
Understanding the shape of the cornea is essential for selecting or designing an orthokeratology (ortho-k) lens. Initial lens selection typically relies on keratometry (K’s), but it is important to remember that K’s are limited to measuring the central 3 mm of the cornea. When fitting an ortho-k lens that occupies 10-12mm of the cornea, more information about the corneal shape is necessary.
认识角膜的形态针对选取或设计角膜塑形镜至关重要。最初的镜片选取一般依赖角膜曲率（K’s），但重要的是要记住，这个K值仅限于所测绘角膜的中心3mm区域。当咱们在10-12mm的角膜上验配镜片时，需要更加多关于角膜形态的信息。
Most topographers in contact lens practices are reflection systems (e.g., Medmont), which project Placido rings onto the corneal surface and measure the displacement of those rings to determine the curvature. For pre-fit analysis, data should be visualized using the sagittal (axial) curvature setting, taking extra care to adjust the color scale from the standard range to one that better fits the range of curvatures from the individual patient’s K readings. Tangential curve maps provide a much more detailed representation of the corneal shape and can help guide post-wear analysis.
在接触镜临床的验配中大部分运用的都是反射系统的角膜地形图仪（如Medmont），这种地形图仪是将Placido环投射到角膜表面，并测绘这些环的位移以确定曲率。针对验配前的分析，数据应调节到矢状（轴向）图的设置，尤其重视将色阶从标准范围调节为更适合病人K值曲率范围的色阶。切线图供给了更仔细的角膜形态表示，有助于指点塑形镜配戴后的分析。
Importantly, the axial map assumes that the center of the radius of curvature is on the central axis and uses that reference to compare the overall shape of the cornea to a best-fit sphere (Figure 1). Because of this assumption, it is important to ensure that we are aligning the true geometric center of the eye with the optical path. Many patients have a large angle kappa deviation, meaning that the visual axis has a slight misalignment with the geometric axis of the eye, which can cause erroneous readings if this is not taken into consideration. Figure 2 shows a post-treatment tangential curvature map of a patient’s right eye when they are looking at the center fixation point, and the lens appears to be temporally decentered. However, by having the patient look one ring nasally, which aligns the geometric center of the cornea with the optical path, we see that this lens is well-centered.
很重要的是轴向图假设曲率半径的中心位置于中心轴上，并运用该数据将角膜的整体形态与最佳拟合球面进行比较（图1）。因为这一假设，保证眼睛的真实几何中心与视轴对齐非常重要。许多病人的kappa角偏差很强，这寓意着视轴与眼睛的几何轴有轻微的错位，倘若不思虑这一点，可能会引起数据诠释错误。图2表示了病人在塑形镜配戴后注视中心固选定时右眼的切线图，镜片看起来颞侧偏位。然而，检测时经过让病人向鼻侧方向看多一个环，将角膜的几何中心与视轴对齐，咱们能够看到该镜片的中心位置定位良好。
图1
Figure 1: Baseline axial power maps of the corneal surface of a prospective orthokeratology lens wearer. By adjusting the scale from the standard power (A) to a custom power (B), the limbus-to-limbus corneal toricity becomes easily apparent.
图1：角膜塑形术配戴者角膜表面的基线轴向图。
经过将标准标尺曲率（A）调节为自定义曲率（B），角膜上边到边环曲的形态变得更加显著。
图2
Figure 2: Angle kappa adjustment. This patient has a significant angle kappa, which creates the appearance of a temporally decentered lens (A). If we were to remove the color overlay, we would observe that the center of the mires do not align with the center of the pupil. By having the patient look one ring to the left (B), we can center the geometric center of the eye with the optical path, adjusting for angle kappa, and acquire a more accurate representation of the lens fit.
图2：kappa角调节。
该病人拥有显著的kappa角，这导致镜片看起来颞侧偏位（A）。倘若咱们去除颜色覆盖，咱们会发掘环的中心与瞳孔的中心无对齐。经过让病人向左看进去一个环（B），咱们能够将眼睛的几何中心与视轴对齐来调节kappa角，并得到更精细的镜片配适图。
A careful assessment of axial topography maps can help to identify when a toric posterior surface lens design may be warranted. Figure 3 shows axial maps from two patients who have nearly identical refractive errors and K’s. However, by looking at the topography and considering where the lenses will land, these two patients will need very different lens designs to best match the corneal shape for a successful fit.
仔细评定轴向图有助于确定何时需要环曲面设计的镜片。图3表示了两名屈光度和K值几乎相同的病人的轴向图。然而，经过观察地形图并思虑镜片将在角膜上的定位，这两名病人将需要完全区别的镜片设计来更好地匹配角膜形态，从而达到成功的验配。
图3
Figure 3: Baseline K’s and Autorefraction for two patients with similar refractive error. Patient A and Patient B have nearly identical refractive errors and K’s. K readings only describe the central 2-3mm of the cornea (grey dashed line). This information is critical for determining the appropriate base curve of the lens, however, when we consider the lens design, we need information about the peripheral corneal toricity where the lens will align with the cornea (black dashed line). These patients will likely use the same base curve radius, but Patient A will likely require a toric ortho-k lens design, whereas patient B will likely do well with a spherical lens design. Topography provides important information that we cannot obtain from keratometry alone.
图3：电脑验光仪表示的这两名病人拥有类似的屈光度和基线K值。
病人A和病人B的屈光度和K值几乎相同。K值仅描述角膜中央2-3mm（灰色虚线）的数据。该信息针对确定合适的镜片基弧至关重要，然而，当咱们考虑镜片设计时，咱们需要相关角膜周边环曲量的信息，由于这和镜片在角膜周边的配适相关（黑色虚线）。这些病人可能运用相同的基弧曲率半径，但病人A可能需要环曲面的镜片设计，而病人B可能需要球面的镜片设计。地形图为咱们供给了没法单独从角膜曲率中得到的重要信息。
SARAH
SINGH
OD PHD FAAO
Dr. Sarah Singh is an Assistant Clinical Professor at the UC Berkeley School of Optometry, where she cares for pediatric patients in the Infant/Toddler Clinic and the Myopia Control Clinic. She graduated from Berkeley Optometry in 2014 and went on to pursue residency training in Pediatrics and Primary Care, where she was first exposed to myopia control under the mentorship of Dr. Maria Liu. During her residency, she became very passionate about myopia control and how treatments might be optimized for individual patients and went on to complete a Ph.D. researching some of these mechanisms in an animal model. Throughout her Ph.D. training, Dr. Singh continued to see patients in the Myopia Control Clinic at Berkeley, as well as train optometric interns and residents in myopia control techniques.
Sarah Singh博士是加州大学伯克利分校视光学院的助理临床教授，她在该校的婴幼儿诊所和近视掌控诊所护理这些儿童病人。她于2014年毕业于伯克利视光学院，并继续在儿科和基本护理行业接受住院医师的培训，她在Maria Liu博士的指点下首次接触到了近视掌控方面的内容。她在住院医师时期针对近视掌控以及怎样针对个别病人优化治疗非常感兴趣，同期她的博士学位科研内容亦有在动物模型中科研了近视掌控的有些机制。在博士培训时期，Singh博士继续在伯克利的近视掌控诊所治疗病人，并对视光实习生和住院医师进行近视掌控方面的技术培训。
本文转载：欧几里德
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发表于 2024-8-30 23:29:00
