为什么做眼镜不用瞳高

眼镜是一种常见的视力矫正工具，可以帮助人们改善近视、远视或散光等眼睛问题。在订制眼镜时，医生通常会测量瞳孔的大小，而不是瞳高。那么，为什么做眼镜不用瞳高呢？

首先，我们需要了解瞳高和瞳孔大小之间的区别。瞳高指的是从地面到瞳孔的距离，而瞳孔大小是指瞳孔的直径。虽然这两个参数都与眼镜的配戴有关，但它们的作用和测量方法不同。

瞳高主要用于定位多焦点镜片的近视段（也称为加法镜片）。通过测量瞳高，配镜师可以确定近视段的位置，以确保用户在视线转动时能够看清物体。

然而，当选择单焦点镜片（如近视镜或远视镜）时，瞳高就不再起作用。因为单焦点镜片是为特定视距设计的，用户只需保持注视前方即可获得清晰视觉。在这种情况下，瞳孔大小成为了更为重要的测量参数。

瞳孔大小对眼镜配戴的影响很大。通过测量瞳孔大小，医生可以调整镜片的直径，确保光线能够进入瞳孔的中心。如果镜片过小，可能会导致光线被截断，从而限制了视野。而如果镜片过大，光线可能会在镜片边缘产生扭曲，影响视觉质量。

此外，瞳孔大小还与眩光有关。瞳孔在弱光环境下会放大，而在强光环境下会收缩。当瞳孔放大时，更多的光线进入眼睛，容易引起眩光和视觉不适。因此，为了避免这种情况，镜片的直径通常会稍微大于瞳孔的平均直径。

总之，虽然瞳高在多焦点镜片的订制中起到了重要作用，但在单焦点镜片（如近视镜或远视镜）中，瞳孔大小更为关键。通过测量瞳孔大小，医生可以调整镜片的直径，确保视觉质量和舒适度。因此，在订制眼镜时，瞳高不是一个必需的测量参数。

Why Pupillary Distance is Not Used for Making Eyeglasses

Eyeglasses are a common tool for correcting vision problems such as nearsightedness, farsightedness, or astigmatism. When ordering prescription glasses, eye doctors typically measure the size of the pupils instead of the pupillary distance (PD). So why isn't the pupillary distance used for making eyeglasses?

Firstly, it is important to understand the difference between pupillary distance and pupil size. Pupillary distance refers to the distance from the ground to the pupils, while pupil size refers to the diameter of the pupils. Although both parameters are related to eyeglass fitting, they have different roles and measurement methods.

Pupillary distance is primarily used for positioning the near segment of multifocal lenses (also known as progressive lenses). By measuring the pupillary distance, an optician can determine the location of the near segment to ensure that the user can see objects clearly when shifting their gaze.

However, when selecting single vision lenses (e.g., for nearsightedness or farsightedness), the pupillary distance is no longer relevant. Single vision lenses are designed for specific viewing distances, and users only need to maintain their focus straight ahead to achieve clear vision. In this case, pupil size becomes a more important measurement parameter.

Pupil size has a significant impact on eyeglass fitting. By measuring the pupil size, an eye doctor can adjust the diameter of the lenses to ensure that light enters the center of the pupils. If the lenses are too small, light may be cut off, limiting the field of view. Conversely, if the lenses are too large, light can produce distortions at the lens periphery, affecting visual quality.

Additionally, pupil size is also related to glare. The pupils dilate in low-light conditions and constrict in bright light environments. When the pupils are dilated, more light enters the eyes, which can cause glare and visual discomfort. To avoid this, the diameter of the lenses is typically slightly larger than the average pupil diameter.

In summary, while pupillary distance plays an important role in the customization of multifocal lenses, it is not a necessary measurement parameter for single vision lenses (e.g., for nearsightedness or farsightedness). Pupil size is more crucial in such cases. By measuring the pupil size, eye doctors can adjust the lens diameter to ensure visual quality and comfort. Therefore, pupillary distance is not essential when ordering prescription glasses.