Many books on Ophthalmology did not explain what AXIS and MERIDIAN are. Indeed astigmatism is a bit tougher concept to understand initially. I think my explanation is right!

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AGAINST-THE-RULE ASTIGMATISM Horizontally cornea curve greater then vertically. In against-the-rule astigmatism, a plus cylinder is added in the horizontal axis (or a minus cylinder in the vertical axis).

I visualize “with the rule” like a football laying naturally on the ground. Flatter in the longer horizontal plane and steeper in the vertical. If you tee the ball up on its tips, you have against the rule. Flatter in the vertical and steeper in horizontal. The steeper plane requires more minus to correct ametropia.

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WRL- minus cylinder lenses in horizontal meridian ie 180 degrees; in young eyes ARL- minus cylinder lenses in vertical meridian ie 90 degrees.in older eyes

i am an optometrist student. this website is easier to understand stuffs. could you please tell me why the vertical meridian is more curved than the horizontal meridian in cornea???

Why don’t you just say “with the rule astig” is the curvature of the vertical meridian is steeper than that of the horizontal meridian? I don’t understand what you mean by “positive cynlinders at 90 degree”

“The correct Answer: This is when the axis of the positive cylinder in a pair of glasses is oriented at 180 degrees. or Answer: This is when the MERIDIAN of the positive cylinder in a pair of glasses is oriented at 90 degrees.”

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Astigmatism made simple using a football. With the rule astigmatism means that the front of your eye(cornea) is shaped like a football laying horizontally (180 degrees). Against the rule astigmatism means that the front of your eye(cornea) is shaped like a football standing vertically (90 degrees). Lenses that correct this astigmatism have an axis that is positioned along the length of the football. So to correct with the rule astigmatism the minus cylinder axis is at 180 degrees and against the rule axis is at 90 degrees.

(the steeper corneal meridian is opposite that of the AXIS of the correcting minus cylinder and same as that of the POWER of the correcting minus cylinder)

I’m confused. I’m 30yo and I got an prescription from my opthamologist that is -1.00 cylinder, 90 axis. But I read that opthamologists uses positive numbers instead. If I convert this to a positive cylinder, would I have with-the-rule astigmatism, or against-the rule (maybe I am too old to have with-the-rule astig, but too young to have against-the-rule?)

The comments are generally correct but the diagram at the top is incorrect. “With the rule” has the cylinder axis horizontally and the steep curve vertically – opposite to the diagram labelling.

Sorry to bother, if the cornea is physically steeper vertically, does this mean that it “the cornea” has more plus power in the horizontal meridian?

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“” What is “with the rule” astigmatism? Answer: This is when the axis of the positive cylinder in a pair of glasses is oriented at 90 degrees.””

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Now I’m gettin confused. if in “With The Rule” astigmatism the vertical meridian is steepest, this means the -Cyl should be on axis 90 or +Cyl on 180. Right?

Hence in WTR Astigmatism, where the cornea has a great convexity in its vertical plane, we must counteract that high positive power of cornea with negative power in the vertical position. So if we want to orient a negative cylinder such that it counteracts the vertical positivity, its MERIDIAN should be at 90 degrees and hence its AXIS at 180 degrees. But we prescribe cylindrical lens denoting the orientation of its AXIS.

It can be written in either format by either practitioner. It’s common for ophthalmologists to write in plus cylinder, but it looks like yours wrote it in minus form.

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im very much confused about with the rule astigmatism and against the rule astigmatism…each n everytime i hav to think for it….

Why? Look at my previous post: the power of the eye in the horizontal meridian is 44 D, but only 43 D in the vertical ie power H > power V, therefore ATR.

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I may just be an optometry student, but the author is correct. With-the-rule astigmatism means that the EYE is steeper in the vertical meridian (more plus).

I am not an optometrist but as an engineer I know that defining AGR as exactly 90 degrees makes no sense. It seems to me it should be a range, maybe 75 to 105? And as a volunteer optometric assistant, I have seen a number of Hispanic children with AGR astigmatism.

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AGAINST-THE-RULE ASTIGMATISM Horizontally cornea curve greater then vertically. In against-the-rule astigmatism, a plus cylinder is added in the horizontal axis (or a minus cylinder in the vertical axis)

WITH-THE-RULE ASTIGMATISM  Vertically cornea curve greater then horizontal. In with-the-rule astigmatism, a minus cylinder is placed in the horizontal axis to correct the refractive error (or a plus cylinder in the vertical axis).

With regard to Cylinder lenses (where there is no power along the axis), if working in positive cylinder then the axis would be at 90 degrees.

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You are confusing the drawing of the GLASSES (located to the left of the little kid) with the drawing of the CORNEAL STEEPNESS (drawn on the kid/adult’s eyeballs themselves).

To solve the confusion, optometrists use minus cylinders, ophthalmologists use plus cylinders, the author is an ophthalmologist so he explained in their way.

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The correct Answer: This is when the axis of the positive cylinder in a pair of glasses is oriented at 180 degrees. or Answer: This is when the MERIDIAN of the positive cylinder in a pair of glasses is oriented at 90 degrees.

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but, what about the case where the eye is more steeply curved in the vertical meridian but needs no correction because the curvature is just right, and the horizontal meridian is not curved enough so needs a positive cylinder correction lens with a vertical axis ? What does one call this astigmatism where text is smeared horizontally because it is the horizontal meridian which is ‘faulty’ regardless of the vertical meridian being steeper ?? Hence the Refractive Surgeon’s answer makes the most sense to me. There seems to be a lot of confusion here, so i wonder, is the WTR ATR terminology in actual practical use in eye correction and surgery ?

I am also an optometry student.I like this website very much.Many students confused between meridian and axis.when correcting the refraction by a cylindrical lens,we have to know they(meridian and axis)are opposite.If we want to give positive in vertical meridian,we will have to choose positive 180 degree.

ATR: the eye has more power HORIZONTALLY. Corrceted with -ve cyl axis 90. Causes least amount of letters lost on eye chart. Can be + or – 10 degres off axis

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As an “eye surgeon” you really ought to know this. After all … most elderly with cataracts have against-the-rule astigmatism (the old man in this drawing). This means that their CORNEA (not glasses) are steep along the 180 meridian (like in the illustration of the old man). If you create a temporal incision, this should flatten out this horizontal steepness and help a little with their astigmatism.

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I am an optometry student. Generally with the rule and against the rule is used with astigmatism. So what is the rule here?? Plz explain

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Okay folks, very little of all of that is understandable to me, a lay person. But I have a problem. The eye doctor told me (an old person with cataracts) that my astigmatism was unusual in that it was vertical. The eye surgeon operated on the right eye, implanting a distance vision lens and did a kertomony on the right eye. The right eye, after surgery, was 20/70 the first day, 20/50 on day 7, and 20/40 4 weeks later. The doctor said that it reduced my astigmatism by 50%. However, he said that my astigmatism was horizontal and the incisions he made were at the outside edge of the horizontal plane of the eye. I feel my astigmatism is hardly improved at all. He had said that I could use “over the counter” reading glasses; however, none of the drugstore strength of 325 is able to allow me to read very fine print that I can presently read with my left eye. Because the right eye is not where I had hoped, I’ve determined, at this point, that I need the left eye to have a distance lens so that between the two eyes, with glasses, I can see 20/20 for driving. Did the doctor slice my cornea in the correct places?? I really would appreciate your answers. I’m scheduled to have the left cataract removed next Monday, and I still don’t understand whether the doctor did the right thing. Please help!

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Regarding the term of AXIS and MERIDIAN, pls let me quote from http://www.laramyk.com/resources/education/lens-form-and-theory/lens-form-sphere-cylinder-and-axis/

As for the question which (if any) cyl is easiest to deal with my experience is this: Oblique is most difficult to adapt to. With the rule (plano-1.00×180) is probably the easiest to adapt to because you can squint and ‘cover’ the meridian of the power, leaving the horizontal meridian as essentially plano. This, of course, assumes no spherical power. If the patient had a script of +3.00-3.00×180 squinting would leave +3.00 and ‘cut out’ the plano vertical meridian. Oblique cyl is bad no matter how it comes. No noticed differences between [OD: 135 OS: 45] vs [OD: 45 OS: 135], although in my experience the former is more common than the latter (in minus cyl).

The definition of “with the rule” talks about the GLASSES. The cartoon people are simply a mneumonic to understand the actual CORNEAL steepnesses involved. EVERYTHING is correct in the illustration.

Remember the terminology of “at” and “axis” which are always 90 degrees apart. This is a problem I’ve had with ODs, OMDs, and techs alike especially with keratometry.

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it should also be noted that there is a 30 degree range of power for each type. Meaning, for with the rule, you can be positive between 60 and 120, and minus between 30 and 150.

WITH-THE-RULE ASTIGMATISM Vertically cornea curve greater then horizontal. In with-the-rule astigmatism, a minus cylinder is placed in the horizontal axis to correct the refractive error (or a plus cylinder in the vertical axis).

If the eye is more steeply curved in the vertical meridian then this will require a more negative prescription in order to place the focal point on the retina.

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There is no power along the AXIS of the cylindrical lens because they are bounded on each side by plane surfaces only. The maximum power for the cylindrical lens is along the plane perpendicular to that of the AXIS which is called the MERIDIAN.

Ophthalmic surgeons use + cyl as that is where we make the corneal incisions in cataract surgery if we intend to correct (partly) the astigmatism.

With respect to (+) or (-) cyl . . . refracting really doesn’t make a difference if you refract in plus or minus cyl. Doesn’t matter if your make corneal or LRI based on plus or minus cyl . . . as long as you realized WHAT it is you’re doing. Put a lens clock on any lens and you can read it in plus or minus cyl. Depends on your frame of reference. Same with a lenometer. They key is understanding WHERE the power is (90 degrees from the axis), be it plus or minus from the base sphere power.

WTR: the eye has more power VERTICALLY than horizontally. Think rugby ball/gridiron football with the steepest curve vertically. Corrected with -ve cylinder axis 180. In kids. Actually causes more defocus than ATR (lose more letters on eye chart). Can be + or minus 10 from 180. Defocuses horizonatal components of letters

To correct this astigmatism in a pair of eyeglasses, one would need to add more plus to the horizontal meridian or add more minus to the vertical meridian. The MERIDIAN of a positive cylinder lens would be at 180 degrees. The CYLINDER of this same positive lens is 90 degrees.

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” Note how the power in the meridian of the cylinder axis is plano, while the power of the meridian perpendicular to the cylinder axis is +4.00 D”

With the rule astigmatism: The cornea is squeezed from above and below by the lids. This creates astigmatism on the cornea with the axis of the positive cylinder at 180° but the power of the positive cylinder at 90°. It is corrected by prescribing glasses with negative cylinder, axis 180° (power at 90°), or positive cylinder, axis 90° (power at 180°).

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The continual, antiquated usage of these terms (WTR/ATR) is basically unexcusable, a vestigal for progressive optometry except when studying for NBEO and the unnecessary and financially lucrative ABO certification.

I am an optometry student. Generally with the rule and against the rule is used with astigmatism. So what is the rule here??? Plz explain

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pressure of lid compresses the eye ball vertically.cornea becomes steeper vertically ie.the radius of curvature decreases in the vertical meredian.so a sheet of rays in a vertical plane will be focussed in front of retina producing a horizontal line in front of retina.this is the error :and to rectify this we will need diverging lenses which will diverge rays in the vertical plane ie.90 degree and will have its axis at 180 degrees.ie minus cyl at180 degree.

with the rule- the steeper curvature is at 90 degrees. This means that there is positive power at 90, and negative power at 180.