Today we're going to start a short video series called Astigmatism Made Easy.

今天，我們將開始一個名為 "輕鬆解決散光問題 "的視頻短片系列。

I recently received a comment on one of the videos I did covering the 10 types of astigmatism in that they wish there were more examples on it and to be honest it was a really short video for a lot of information that was just kind of condensed into it.

最近，我收到了一條評論，說我做的一個視頻介紹了散光的 10 種類型，他們希望視頻中能有更多的例子。

So this will be a time for us to kind of evaluate some different points in that video but on a slower level and kind of breaking it down a little better.

是以，這將是我們對視頻中的一些不同點進行評估的一次機會，但我們會放慢速度，把它分解得更好一些。

So first off, what is astigmatism?

首先，什麼是散光？

Astigmatism is when light does not come to a singular point focus on the retina.

散光是指光線不能在視網膜上形成單點聚焦。

We want light to generally focus on the macula and the fovea centralis of the retina.

我們希望光線通常聚焦於視網膜的黃斑和中央凹。

That's the point on the light sensitive tissue of the eye that receives the light image.

這是眼睛感光組織上接收光像的點。

So it has all the cone photoreceptor on it that have our clear central vision, our color vision, right?

是以，它上面的所有錐狀感光器都能產生清晰的中心視力和色覺，對嗎？

So with astigmatism, light doesn't come to a singular point focus.

是以，有了散光，光線就不會單點聚焦。

It comes to a linear focus.

這是一個線性聚焦。

So the light is kind of it's spread out.

是以，光線就像散開了一樣。

It's not to that singular sharp point and we illustrate this with a lot of times the oversimplification of a football image and I want to show that because it is a great illustration.

我們經常用過於簡單化的足球影像來說明這一點，我想展示一下，因為這是一個很好的說明。

So this is a football.

這就是足球。

We'll put the laces on there just for for the fun of it and you know we're going to compare that to a soccer ball or basketball or whatever.

我們會把鞋帶系在上面，只是為了好玩，你知道我們要把它和足球、籃球或其他東西進行比較。

So with a round spherical shape like a soccer ball, if you can imagine this radius is going to be the same curve as this radius.

是以，對於像足球這樣的圓形球體，如果你能想象這個半徑將是與這個半徑相同的曲線。

They're going to be the same steepness, right?

它們的陡度會一樣吧？

So from there to there it's going to be the same pattern and you could do that all throughout, right?

所以，從那裡到那裡都是同樣的模式，你可以一直這樣做，對嗎？

So that is the same.

所以是一樣的。

That line is going to be the same steepness as this line here.

這條線的陡度將與這條線相同。

That's if your eye was perfectly spherical and you did not have astigmatism.

前提是你的眼睛是完美的球形，沒有散光。

It doesn't mean you don't have a refractive error, right?

這並不意味著你沒有屈光不正，對嗎？

Because your eye could be too long like a myope or too short like a hyperope but it could still mean that light's coming to one singular point.

因為你的眼睛可能像近視眼一樣太長，也可能像遠視眼一樣太短，但這仍然意味著光線只射向一個點。

Astigmatism means more like a football that this meridian, right?

散光的意思更像是足球，對不對？

Our vertical 90 you know might be steeper and if you can imagine this curve on a football it's much less drastic.

我們的垂直 90 度可能會更陡一些，如果你能想象一下足球上的這條曲線，它就不會那麼劇烈了。

It's flatter, right?

更平整，對嗎？

So a football laying like this is a good example of with the rule of astigmatism.

是以，像這樣的足球鋪設就是散光規則的一個很好的例子。

Just something to remember your vertical meridian is steeper so it'd be like the cornea is steeper in the vertical meridian but this is astigmatism.

需要注意的是，你的垂直子午線比較陡，是以角膜在垂直子午線上會比較陡，但這是散光。

Light is entering at different steepnesses you know a flattest point and a steepest point and it's causing that light to enter and and fall upon the retina in a linear fashion instead of that point that we really want.

光線以不同的陡度進入視網膜，你知道有最平的點和最陡的點，這導致光線以線性方式進入視網膜並落在視網膜上，而不是我們真正想要的那個點。

So if that's what astigmatism is then we also need to define you know the anatomy of the eye that can cause astigmatism or yeah so like what are the refractive medium of the eye?

如果這就是散光，那麼我們還需要定義可能導致散光的眼球解剖結構，比如眼球的屈光介質是什麼？

What are the parts of the eye that are creating astigmatism?

眼睛的哪些部分會產生散光？

Well to refract means to bend, right?

折射的意思是彎曲，對嗎？

So we're talking about bending light so if the cornea was completely spherical like our soccer ball right no matter how light entered it it would enter at the same radius of curvature and it would provide the same refraction same refractive properties but then we have the if this is the anterior view of the eye coming through then you have the crystalline lens which is behind it kind of suspended in the anterior chamber of the eye.

如果角膜完全是球形的，就像我們的足球一樣，那麼無論光線如何進入角膜，它都會以相同的曲率半徑進入，並具有相同的折射特性。

That's another lens of the eye and it too can have torricity which is you know and create astigmatism.

那是眼睛的另一個晶狀體，也會產生散光。

Much more common on the cornea but you can find it on the crystalline lens.

在角膜上更為常見，但在晶狀體上也能發現。

So the cornea supplies roughly 43 diopters of strength that's plus 43 it's a plus power lens you know and just to take a step back of how amazing it is that the cornea is like half a millimeter thick in the center it's supplying 43 diopters of strength and the crystalline lens supplies on average about plus 17 diopters and that gives us our 60 diopters of strength but either one of those surfaces can be torric right can have a cylindrical component on it which is going to make light enter it differently.

是以，角膜大約能提供 43 度的鏡片強度，也就是正 43 度，這是一個強力鏡片，你知道的，退一步說，角膜的中心厚度只有半毫米，卻能提供 43 度的鏡片強度，而晶狀體平均能提供正 17 度的鏡片強度，這就給了我們 60 度的鏡片強度，但其中任何一個表面都可能是弧形的，也可能有圓柱形的成分，這會讓光線以不同的方式進入鏡片。

So the big question is you know how do we measure astigmatism?

是以，最大的問題是，我們如何測量散光？

Well the main instrument that's used to measure astigmatism is the keratometer.

測量散光的主要儀器是角膜計。

The keratometer is what we get our k readings from and interestingly it just measures the central three millimeters three to four millimeters of the cornea right so we know our cornea horizontally measures about 12 millimeters right and then vertically maybe 10 and a half millimeters.

有趣的是，角膜計只測量角膜中央三毫米處的三到四毫米，所以我們知道角膜水準測量約為 12 毫米，垂直測量約為 10.5 毫米。

So we're talking about you know the corneal cap it's measuring about three millimeters just this zone of it and it's measuring the steepness it's finding out what the flattest meridian is and what the steepest meridian of the cornea is.

所以我們說的是角膜蓋，它測量的是角膜蓋上大約三毫米的區域，它測量的是角膜的陡度，找出角膜最平的經線和最陡的經線。

The average keratometer is going to measure from 36 to 52 diopters and and what that's measuring is the power of the cornea but also the steepness of the cornea.

一般的角膜塑形鏡可以測量 36 到 52 個屈光度，測量的是角膜的力量和角膜的陡度。

Also remember just helpful on your test you can add a negative one auxiliary lens it's going to bring your case down to 30 diopters or you could add in the in the positive direction a plus one and a quarter lens and that's going to bring you up up nine more diopters up to 61 diopters from 52 to 61.

另外，請記住，您可以在測試時添加一個負1度的輔助鏡片，這將使您的視力下降到30度，或者您也可以在正方向上添加一個正1又1/4的鏡片，這將使您的視力上升9度，從52度上升到61度。

That's just a side note neither here nor there but we measure corneal astigmatism with k readings and I'm just going to give you an example of that.

這只是一個題外話，既不在這裡，也不在那裡，但我們用 K 讀數來測量角膜散光，我就舉個例子。

So let's say our k readings are 42 at 180, 43.50 at 90.

假設我們的 K 讀數在 180 時為 42，在 90 時為 43.50。

What this is telling us and I'll do another drawing here across our vertical meridian our 90 the power of the cornea is 43.5 diopters at our 180 it's 42 diopters.

這說明了什麼？我再畫一幅圖，在我們的垂直子午線上，90°角膜的角膜力是 43.5 度，180°角膜的角膜力是 42 度。

So the difference between those two our steepest and our flattest meridian is going to be our corneal astigmatism.

是以，這兩個最陡和最平子午線之間的差值就是我們的角膜散光。

So 43.50 from you know 42 from a 43.50 that's one and a half diopters of those two values that's the amount of toricity that's the amount of cylinder value on ascribed to the cornea because remember a keratometer or an ophthalmometer you might refer to as only measures corneal astigmatism.

是以，43.50 與 42 相比，43.50 就是一個半屈光度，這兩個值就是角膜的散光度數，也就是角膜的圓柱度數，因為角膜曲率計或眼壓計只能測量角膜散光。

I'm going to do one more example of that so if we have um I'll read this out so it's actually clear okay 44.50 at 70 and then 45 at 160.

我再舉一個例子，如果有的話，我會把這個念出來，這樣就很清楚了，好的，70 時 44.50，160 時 45。

So our flattest meridian our 44.50 is at 70 and we have 45 diopters of strength at the 160.

是以，我們最平的子午線 44.50 度在 70 度，而 160 度的強度為 45 度。

So there is a difference of what a half a diopter between those two uh meridians the steepest and the flattest meridian so there's a half a diopter of corneal astigmatism and this brings up a great point now um so if defining astigmatism there is regular astigmatism and irregular astigmatism.

是以，最陡和最平的兩條經線之間相差半個屈光度，所以角膜散光有半個屈光度，這就提出了一個很好的問題，如果定義散光，有規則散光和不規則散光之分。

Regular astigmatism means that the principal meridians are 90 degrees apart from one another so this is measured by keratometry um you could have with the rule against the rule oblique astigmatism these are all regular astigmatism but then you have irregular astigmatism.

規則散光是指主要經線之間相差 90 度，這是用角膜測量法測量出來的。

Irregular astigmatism cannot be we can't use a cylindrical eyeglass lens we can't use a cylindrical contact lens to correct irregular astigmatism.

我們不能使用圓柱形眼鏡片來矯正不規則散光，也不能使用圓柱形隱形眼鏡來矯正不規則散光。

Keratoconus is commonly associated with irregular astigmatism you know that's a thinning of the cornea and you have a an oblate like a protrusion of the cornea um pelucid marginal degeneration is kind of like keratoconus it's a thinning of the anterior um inferior part of the cornea the lower part of the cornea um you could have if trauma something you know punctures the cornea um different disease can cause um corneal thinning that gives you an irregular corneal shape so another word to remember now um i'll write on the board it's a fun word this is like bonus stuff right here ectasia so it's even fun to ectasia so you'll hear corneal ectasia that is thinning so this word means thinning so it's a thinning of the cornea um thinning of the cornea can create an irregular surface so we have irregular astigmatism which is like an ectasia of the cornea you know and for these for these patients you need to use some sort of a gas permeable lens you know a lens that's rigid enough that it's going to create a tear film behind the lens and it's going to provide a brand new optical surface um because we're it's not going to be able to you can't use like a soft contact lens that drapes the cornea to correct for irregular astigmatism so that's kind of the the foundation of astigmatism here shortly in the next video series i'm going to go over with the rule against the rule and oblique astigmatism and just do some examples and some example prescriptions with that um and then you know i'm going to do another uh video after that on like compound myopic simple myopic you know mixed astigmatism those types of classifications and you know that way we could just bring it all together and you could really have a solid foundation of what is astigmatism if this video has been helpful i definitely encourage you to subscribe to the channel share it with your friends and really just to keep watching it because you know i'm truly you know a firm believer in especially as opticians contact lenses it's you know it's really just um the heart of the medical side of what we do and just uh the more that we are subject matter experts on this the more that we'll be able to help our patients and provide good service to them because you know with just a surface uh level knowledge of contact lenses we're really not doing our patients any service so just keep watching if you're studying for your ncle um trust me just just watch the videos and study your material uh find a good comprehensive guide and just read through it um there's a number of good resources out there i know carrie wilson has a great book for ncle but if you're pairing the the question the answers up with these videos i know you'll be a success on the test you know these these videos truly are just geared towards the theory behind the material and helping you to understand it better if you're not necessarily like a textbook person and you weren't fortunate enough to go to opticianary school or be able to be lectured to these are kind of hopefully supplementing and taking the place of that so anyway stay tuned and i'm going to have another video in this series coming up shortly thank you

角膜炎通常伴有不規則散光，即角膜變薄，角膜呈扁球形突出，角膜邊緣變性與角膜炎相似，是角膜前部變薄，即角膜下部變薄，如果外傷刺傷角膜，也會導致角膜變薄。疾病會導致角膜變薄 角膜形狀不規則 要記住的另一個詞 我會寫在黑板上 這是個很有趣的詞 ectasia（角膜異位症）我們有不規則散光，這就像角膜異位，對於這些患者，你需要使用某種透氣鏡片，你知道透氣鏡片要足夠硬，能在鏡片後面形成淚膜，提供一個全新的光學表面，因為我們不能使用像軟性隱形眼鏡那樣的鏡片來矯正角膜異位。這就是散光的基礎，在下一個視頻系列中，我將介紹