Chapter 1 - Astigmatism

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Slide 1

Frequently, presenters must deliver material of a technical nature to an audience unfamiliar with the topic or vocabulary. The material may be complex or heavy with detail. To present technical material effectively, use the following guidelines from Dale Carnegie Training®.   Consider the amount of time available and prepare to organize your material. Narrow your topic. Divide your presentation into clear segments. Follow a logical progression. Maintain your focus throughout. Close the presentation with a summary, repetition of the key steps, or a logical conclusion.   Keep your audience in mind at all times. For example, be sure data is clear and information is relevant. Keep the level of detail and vocabulary appropriate for the audience. Use visuals to support key points or steps. Keep alert to the needs of your listeners, and you will have a more receptive audience.

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In your opening, establish the relevancy of the topic to the audience. Give a brief preview of the presentation and establish value for the listeners. Take into account your audience’s interest and expertise in the topic when choosing your vocabulary, examples, and illustrations. Focus on the importance of the topic to your audience, and you will have more attentive listeners.

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Understanding Astigmatism R. Joe Simmons Professor Miami Dade College Sponsored by: Essilor of America

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Upon completion the participant will be able to: State the most common causes of astigmatism; Classify the different types of astigmatism; Identify with the rule, against the rule and oblique astigmatism, given a spectacle Rx; Identify with the rule, against the rule and oblique astigmatism, given K readings;

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Upon completion the participant will be able to: Discuss methods of correcting for astigmatism; Explain astigmatism to a patient/customer, in practical terms.

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Astigmatism Astigmatism is one of those terms that every patient thinks they know. How many times have you had a patient proclaim, “I ain’t got no stigmatism”. To me that’s right up there with the phrase “I need more medicine in my lenses”.

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Astigmatism The term astigmatism literally means “not a point focus”. A very basic explanation that all patients can understand is that when the front part of your eye is shaped like a basketball, all of the curves are equal, you do not have any astigmatism.

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Astigmatism When the front part of your eye is shaped like a football, one part is steeper than the other, you have astigmatism. The incoming rays of light do not all focus at the same point.

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Astigmatism In this example the patient is farsighted in the vertical meridian and nearsighted in the horizontal meridian.

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Astigmatism To correct the vision the patient would need a lens with plus power in the vertical meridian and minus power in the horizontal meridian. +2.00 – 4.00 X 090

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Astigmatism There are different types of astigmatism and not all astigmatism is as a result of the shape of the cornea. The crystalline lens could be toric. The retina could be misshapen. The zonules could contract unevenly.

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Astigmatism Testing for astigmatism can be accomplished by using an Astigmatic Clock

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Classifications of Astigmatism Regular Irregular

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Regular Astigmatism With regular astigmatism the maximum and minimum powers of the eye are at ninety degrees to each other. Regular astigmatism can be corrected by using sphere-o-cylinder spectacle lenses, rigid spherical contact lenses or toric rigid or toric soft contact lenses.

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Irregular Astigmatism There are two types of irregular astigmatism. One type of irregular astigmatism the maximum and minimum powers are not at ninety degree angles to each other. In the other type of irregular astigmatism the power varies in a single meridian. Irregular astigmatism is best corrected with rigid contact lenses as apposed to spectacles.

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Regular Astigmatism Classification For contact lens fitting we will categorize astigmatism as either “with the rule”, “against the rule” or “oblique”. Contact lens fitters will also want to calculate for residual astigmatism. Residual astigmatism is that astigmatism that is not found on the cornea.

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Regular Astigmatism Classification When dealing only with the spectacles we will categorize astigmatism into five different types; “simple myopic astigmatism” “compound myopic astigmatism” “mixed astigmatism” “simple hyperopic astigmatism” “compound hyperopic astigmatism”.

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Astigmatism of Major Concern To Contact Lens Fitters With the Rule Astigmatism Against the Rule Astigmatism Oblique Astigmatism

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With the Rule Astigmatism Whenever the vertical meridian of the cornea is steeper than the horizontal meridian of the cornea. The vertical meridian is considered to be between the 60th degree meridian and the 120th degree meridian.

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With the Rule Astigmatism The keratometry reading might be: +46.00 @ 090 / +44.00 @ 180 These “K’s” indicate 2.00 D of with the rule astigmatism

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With the Rule Astigmatism The spectacle Rx written in minus cylinder form would have an axis within 30 degrees of 180. 001 to 030 or 150 to 180

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Against the Rule Astigmatism The horizontal meridian of the cornea is steeper than the vertical meridian. The Horizontal meridian is considered to be between the 0 degree meridian and 30th degree meridian and between the 150th degree meridian and the 180th degree meridian.

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Against the Rule Astigmatism The keratometry reading might be: +42.00 @ 090 / +44.00 @ 180 These “K’s” indicate 2.00 D of against the rule astigmatism

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Against the Rule Astigmatism The spectacle Rx written in minus cylinder form would have an axis within 30 degrees of 090 (either side of 090). 060 to 120

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Oblique Astigmatism The steepest meridian is not in either the vertical or the horizontal meridians. The oblique meridians are considered to be between the 31st degree meridian and the 59th degree meridian on one side and between the 121st degree meridian and the 149th degree meridian on the other side.

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Oblique Astigmatism The keratometry reading might be: +46.00 @ 045 / +43.00 @ 135 These “K’s” indicate 3.00 D of oblique astigmatism

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Oblique Astigmatism The spectacle Rx written in minus cylinder form would have an axis not within 30 degrees of 090 and not within 30 degrees of 180. 031 to 059 or 121 to 149

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What Is It? +45.00 @ 090 / +49.00 @180 Against the Rule

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What Is It? +45.00 @ 090 / +44.00 @180 With the Rule

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What Is It? +45.00 @ 045 / +49.00 @135 Oblique

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What Is It? +45.00 @ 090 / +45.00 @180 No Astigmatism

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What Is It? +47.00 @ 090 / +49.00 @180 Against the Rule

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What Is It? +46.00 @ 090 / +44.00 @180 With the Rule

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Regular Astigmatism Classification When dealing only with the spectacles we will categorize astigmatism into five different types; “simple myopic astigmatism” “compound myopic astigmatism” “mixed astigmatism” “simple hyperopic astigmatism” “compound hyperopic astigmatism”.

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Simple Myopic Astigmatism Rays of light entering the uncorrected eye focus at two different distances. One set focuses on the retina and the other set focuses in front of the retina

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Simple Myopic Astigmatism To determine if the Rx corrects for Simple Myopic Astigmatism you will need to find the maximum and minimum powers on the lens. This can be accomplished by writing down the Rx then flat transposing it.

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Simple Myopic Astigmatism Now you want to look only at the two sphere powers. If one of the powers is plano and the other power is minus the Rx will correct for Simple Myopic Astigmatism.

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Simple Myopic Astigmatism -2.00 +2.00 X 080 1st transpose Plano -2.00 x 170 Now look at the two sphere powers One is minus and the other is Plano

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Compound Myopic Astigmatism When rays of light entering the uncorrected eye focus at two different distances; Both sets focus in front of the retina.

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Compound Myopic Astigmatism To determine if the Rx corrects for Compound Myopic Astigmatism you will need to find the maximum and minimum powers on the lens. This can be accomplished by writing down the Rx, then flat transposing it.

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Compound Myopic Astigmatism Now you want to look only at the two sphere powers. If both powers are minus the Rx will correct for Compound Myopic Astigmatism.

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Compound Myopic Astigmatism -2.00 –3.00 x 025 1st transpose -5.00 +3.00 x 115 Now look at the two sphere powers Both are minus

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Mixed Astigmatism When rays of light entering the uncorrected eye focus at two different distances; One set focuses behind the retina and the other set focuses in front of the retina

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Mixed Astigmatism To determine if the Rx corrects for Mixed Astigmatism you will need to find the maximum and minimum powers on the lens. This can be accomplished by writing down the Rx, then flat transposing it.

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Mixed Astigmatism Now you want to look only at the two sphere powers. If one power is minus and the other power is plus the Rx will correct for Mixed Astigmatism.

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Mixed Astigmatism +2.00 –3.00 x 025 1st transpose -1.00 +3.00 x 115 Now look at the two sphere powers One is Plus and one is Minus

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Simple Hyperopic Astigmatism When rays of light entering the uncorrected eye focus at two different distances; One set focuses on the retina and the other set focuses behind the retina.

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Simple Hyperopic Astigmatism To determine if the Rx corrects for Simple Hyperopic Astigmatism you will need to find the maximum and minimum powers on the lens. This can be accomplished by writing down the Rx then flat transposing the Rx.

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Simple Hyperopic Astigmatism Now you want to only look at the two sphere powers. If one of the powers is Plano and the other power is plus the Rx will correct for Simple Hyperopic Astigmatism.

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Simple Hyperopic Astigmatism +2.00 –2.00 X 080 1st transpose Plano +2.00 x 170 Now look at the two sphere powers One is plus and the other is Plano

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Compound Hyperopic Astigmatism When rays of light entering the uncorrected eye focus at two different distances. Both sets focus behind the retina.

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Compound Hyperopic Astigmatism To determine if the Rx corrects for Compound Hyperopic Astigmatism you will need to find the maximum and minimum powers on the lens. This can be accomplished by writing down the Rx, then flat transposing the Rx.

Slide 56

Compound Hyperopic Astigmatism Now you want to only look at the two sphere powers. If both powers are plus the Rx will correct for Compound Hyperopic Astigmatism.

Slide 57

Compound Hyperopic Astigmatism +5.00 –2.00 X 080 1st transpose +3.00 +2.00 x 170 Now look at the two sphere powers Both are plus

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What Is It? +2.00 –1.00 X 135 +2.00 –1.00 X 135 +1.00 +1.00 X045 Both are Plus Compound Hyperopic Astigmatism

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What Is It? +2.00 –3.00 X 135 +2.00 –3.00 X 135 -1.00 +3.00 X045 One is Plus and one is Minus Mixed Astigmatism

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What Is It? +3.00 –3.00 X 135 +3.00 –3.00 X 135 Plano +3.00 X045 One is Plano and one is Plus Simple Hyperopic Astigmatism

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What Is It? Plano –3.00 X 135 Plano –3.00 X 135 -3.00 +3.00 X045 One is Plano and one is Minus Simple Myopic Astigmatism

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Conclusion By understanding astigmatism and explaining it to your patients you will be doing two things. You will help your patients to finally understand a term that they have heard for years. More importantly you will be elevating your position from a frame salesperson to a professional.

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Conclusion Your patients will view you as more knowledgeable and more caring because you took the time to evaluate their prescription and explain it to them.

Summary: Chapter 1 - Astigmatism

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