什么是散光数和轴位数？散光Astigmatism
什么是散光数和轴位数？散光AstigmatismAs a student Thomas Young discovered that he had problems with one eye in 1793. In the following years he did research on his vision problems. He presented his findings in a Bakerian Lecture in 1801. Independent from Young George Biddell Airy discovered the phenomenon of astigmatism on his own eye. Airy presented his observations on his own eye in February 1825 at the Cambridge Philosophical Soc
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Overview
Astigmatism is a common vision condition that causes blurred vision. The curvature of the cornea and lens bends the light entering the eye in order to focus it precisely on the retina at the back of the eye. In astigmatism the surface of the cornea or lens has a somewhat different curvature. The surface of the cornea is shaped more like a football instead of round like a basketball the eye is unable to focus light rays to a single point. Vision becomes out of focus at any distance. In addition the curvature of the lens inside the eye can change resulting in an increase or decrease in astigmatism. This change frequently occurs in adulthood and can precede the development of naturally occurring cataracts.
概述
散光是一种常见的视力问题，导致视力模糊。角膜和晶状体的曲度使进入眼睛的光线弯曲，以便精确地聚焦在眼睛后部的视网膜上。在散光中，角膜或晶状体表面有不同的曲率，角膜表面的形状更像一个橄榄球而不是圆形的篮球，眼睛无法聚集光线到一点，视觉在任何距离都变得模糊。此外，眼内晶状体的曲率也会改变，导致散光的增加或减少，这种变化经常发生在成年人，并可能先于自然发生的白内障的发展。
History
As a student Thomas Young discovered that he had problems with one eye in 1793. In the following years he did research on his vision problems. He presented his findings in a Bakerian Lecture in 1801. Independent from Young George Biddell Airy discovered the phenomenon of astigmatism on his own eye. Airy presented his observations on his own eye in February 1825 at the Cambridge Philosophical Society. Airy produced lenses to correct his vision problems by 1825 while other sources put this into 1827 when Airy obtained cylindrical lenses from an optician from Ipswich. The name for the condition was not given by Airy but from William Whewell. By the 1860s astigmatism was a well established concept in ophthalmology.
历史
一名叫托马斯·杨（Thomas Young）的学生在1793年发现自己的一只眼睛有问题，在随后的几年中，他对视力问题进行了研究，他在1801年的贝克演讲中介绍了他的发现。乔治·比德尔·艾里（George Biddell Airy）也独自发现了自己的散光问题， 艾里（Airy）于1825年2月在剑桥哲学学会上发表了他的观察结果，在1825年前艾里制作了镜片来纠正他的视力问题，直到1827年，艾里才从伊普斯威奇（Ipswich）的配镜师那里获得了圆柱透镜。 散光的名称不是艾里（Airy）提出的，是威廉·惠威尔（William Whewell）提出的。到19世纪60年代，散光成为眼科界公认的概念。
Pathophysiology
Axis of the principal meridian
1. Regular astigmatism – principal meridians are perpendicular. (The steepest and flattest meridians of the eye are called principal meridians.)
- With-the-rule astigmatism – the vertical meridian is steepest (a rugby ball or American football lying on its side).
- Against-the-rule astigmatism – the horizontal meridian is steepest (a rugby ball or American football standing on its end).
- Oblique astigmatism – the steepest curve lies in between 120 and 150 degrees and 30 and 60 degrees.
2. Irregular astigmatism – principal meridians are not perpendicular.
病理生理学
主轴
1、规则散光：主轴是垂直的。（眼睛最陡和最平坦的轴称为主轴。）
- 顺规散光：垂直轴最陡（橄榄球卧着）。
- 逆规散光：水平轴最陡（橄榄球立着）。
- 斜散光：最陡的曲线轴在120至150度和30至60度之间。。
2、不规则散光：主轴不垂直。
In with-the-rule astigmatism the eye has too much "plus" cylinder in the horizontal axis relative to the vertical axis (i.e. the eye is too "steep" along the vertical meridian relative to the horizontal meridian). Vertical beams of light focus in front (anterior) to horizontal beams of light in the eye. This problem may be corrected using spectacles which have a "minus" cylinder placed on this horizontal axis. The effect of this will be that when a vertical beam of light in the distance travels towards the eye the "minus" cylinder (which is placed with its axis lying horizontally – in line with the patient's excessively steep horizontal axis/vertical meridian) will cause this vertical beam of light to slightly "diverge" or "spread out vertically" before it reaches the eye. This compensates for the fact that the patient's eye converges light more powerfully in the vertical meridian than the horizontal meridian. Hopefully after this the eye will focus all light on the same location at the retina and the patient's vision will be less blurred.
在顺规散光中，眼睛在水平轴上相对于垂直轴的“正”圆柱过多（即，眼睛在垂直轴上相对于水平轴“过于”陡峭）。垂直光束在眼中聚集在水平光束的前面，可以使用在此水平轴上放置负柱镜来纠正，这样的效果是，当远距离的垂直光束朝着眼睛传播时，负柱镜（其轴水平放置与患者过分陡峭的水平轴即垂直轴一致）将使此垂直光束在到达眼睛之前稍微“发散”或“垂直散开”。这就弥补了以下问题：患者的眼睛在垂直轴上比水平轴上会聚光更强，经此矫正后，眼睛将所有光线聚焦在视网膜的同一位置上，这样患者视力模糊问题得以减轻。
In against-the-rule astigmatism a plus cylinder is added in the horizontal axis (or a minus cylinder in the vertical axis). Axis is always recorded as an angle in degrees between 0 and 180 degrees in a counter-clockwise direction. Both 0 and 180 degrees lie on a horizontal line at the level of the center of the pupil and as seen by an observer 0 lies on the right of both the eyes. Irregular astigmatism which is often associated with prior ocular surgery or trauma is also a common naturally occurring condition. The two steep hemimeridians of the cornea 180° apart in regular astigmatism may be separated by less than 180° in irregular astigmatism (called nonorthogonal irregular astigmatism); and/or the two steep hemimeridians may be asymmetrically steep—that is one may be significantly steeper than the other (called asymmetric irregular astigmatism). Irregular astigmatism is quantified by a vector calculation called topographic disparity.
在逆规散光中，在水平轴上添加一个正柱镜（或在垂直轴上添加一个负柱镜）。轴以角度记录，以度为单位，在逆时针方向上介于0到180度之间。0度和180度都位于瞳孔中心水平线上，如观察者视角，0度位于两只眼睛的右侧。不规则散光通常与眼部手术或外伤有关，也是常见的一种情况。角膜的两个陡峭轴，在规则散光中本应间隔180度，但在不规则散光中可能间隔不到180度；和/或两个陡峭的半球偏斜可能是不对称陡峭的，也就是说，一个可能比另一个陡峭得多（称为不对称不规则散光）。不规则散光通过称为地形差异的矢量计算来量化。
Focus of the principal meridian
With accommodation relaxed:
1. Simple astigmatism
- Simple hyperopic astigmatism – first focal line is on the retina while the second is located behind the retina.
- Simple myopic astigmatism – first focal line is in front of the retina while the second is on the retina.
2. Compound astigmatism
- Compound hyperopic astigmatism – both focal lines are located behind the retina.
- Compound myopic astigmatism – both focal lines are located in front of the retina.
3. Mixed astigmatism – focal lines are on both sides of the retina (straddling the retina)
主轴焦点
不调节状态：
1.简单的散光
- 简单的远视散光：第一条焦线在视网膜上，而第二条焦线在视网膜后。
- 简单的近视散光：第一条焦线在视网膜前面，而第二条焦线在视网膜上。
2.复合散光
- 复合远视散光：两条焦线均位于视网膜后面。
- 复合性近视散光：两条焦线均位于视网膜前方。
3.混合散光–焦线在视网膜的两侧（横跨视网膜）
散光的矫正
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