SlideShare a Scribd company logo
ASTIGMATISM
PRESENTED BY,
MR.SUBHAM KUMAR
BACHELOR OF OPTOMETRY 2ND YEAR
2017
RIDLEY COLLEGE OF OPTOMETRY,
JORHAT,ASSAM.
CONTENTS
 DEFINITION
 OCCURANCE
 STURM’S CONOIDS
 ETIOLOGY
 TYPES
 ETIOLOGY OF REGULAR ASTIGMATISM
 REGULAR ASTIGMATISM
 TYPES OF REGULAR ASTIGMATISM
CONTENTS
WITH THE RULE ASTIGMATISM
AGAINST THE RULE ASTIGMATISM
OBLIQUE ASTIGMATISM
BI-OBLIQUE ASTIGMATISM
REFRACTIVE TYPES
SIGN AND SYMPTOMS
CONTENTS
 INVESTIGATION
 TREATMENT
 IRREGULAR ASTIGMATISM
 ETIOLOGY OF IRREGULAR ASTIGMATISM
 DIFFERENCE BETWEEN REGULAR AND IRREGULAR ASTIGMATISM
 SYMPTOMS
 TREATMENT
 REFERENCES
 THANK YOU
DEFINITION
A refractive condition that is the result of two principal
meridians of the eye having different refractive power
OCCURRENCE
Astigmatism occurs when the cornea or the lens ,has a
slightly different surface curvature in one direction from
the other
There is a steep meridian and a flat meridian
Varying refractive index
STURM’S CONOID
– In a toric surface, one principle meridian is more curved than the second
principle meridian. The principle meridian with minimum curvature,and
therefore with minimum power is called base curve of a toric lens.
The configuration of rays refracted through a toric surface is called strum’s conoid .
The shape of bundle of the light rays at different levels in strum’s conoid is as
follows:-
1. At point A, the vertical rays(V) are converging more than the horizontal rays (H). So
,the selection here is horizontal oval or an oblate ellipse
2. At point B (first focus) the vertical rays have come to a focus while the horizontal
rays are still converging and so they form a horizontal line
3. At point C the vertical rays are diverging and their divergence is less than the
convergence of the horizontal rays so a horizontal oval is formed here
4. At point D , the divergence of vertical rays is exactly equal to the convergence of
the horizontal rays form the axis . So here the section is a circle , which is called the
circle of least diffusion
5. At point E , the divergence of vertical rays is more than the convergence of
horizontal rays, so the section here is a vertical oval.
6. At point F (second focus) the horizontal rays have come to a focus while the
vertical rays are divergent and so a vertical line is formed here.
7. Beyond F (as point G ) both horizontal and vertical rays are divergent and so the
section will always be a vertical oval or prolate ellipse
The distance between two
foci(B and F) is called the focal interval of sturm.
ETIOLOGY
Asymmetry of the cornea, or the lens or the posterior
retina
Any variation in refractive index
Tilting of the lens
Any eye mass lesion
The weight of the upper eyelid resting on the eyeball
Any healed aberration or injury of the cornea which can be
due to any infection or trauma
TYPES
Regular Astigmatism
Irregular Astigmatism
ETIOLOGY OF REGULAR
ASTIGMATISM
Corneal Astigmatism
Lenticular astigmatism
a. Curvatural
b. Positional
c. Index
Retinal astigmatism
TYPES OF REGULAR
ASTIGMATISM
With the rule astigmatism
Against the rule astigmatism
Oblique astigmatism
Bi-oblique astigmatism
WITH THE RULE
ASTIGMATISM
NOTES-Vertical meridian is more myopic than horizontal
Near vertical is usually defined as between 70˚-110˚ i.e
±20˚ of the vertical
The axis of the negative cylindrical correction in with the
rule astigmatism will be between 0˚-20˚ or 160˚-180˚ i.e
±20˚ of the horizontal
AGAINST THE RULE
ASTIGMATISM
The horizontal curvature is greater than the vertical
curvature i.e the correction of astigmatism will require
the prescription of a concave cyl at 90˚ or a convex cyl at
180˚
NOTE:-Horizontal meridian is more myopic than vertical
The axis of the correcting negative cylinder will be
between70˚-110˚ i.e within ±20 of the vertical
OBLIQUE ASTIGMATISM
The power meridian is neither horizontal nor vertical
The principal meridian are more than 30˚ from vertical or
horizontal
The axis of the negative correcting cylindrical axis will be
between 20˚-70˚and 110˚-160˚
BI-OBLIQUE ASTIGMATISM
The two principle meridian are not at right angle to each
other i.e one may be at 30˚ and the other at 100˚
REFRACTIVE TYPES
Simple astigmatism
Compound astigmatism
Mixed astigmatism
SIGNS AND SYMPTOMS
Blurring of vertical , horizontal or diagonal lines
Eyestrain or fatigue
Headaches
Distortion in portions of the visual field
Squinting
NOTES:- The astigmatic patients tend to squeeze the eyes
producing a narrow stenopic slit effect
INVESTIGATION
Retinoscopy
Keratometry
Astigmatic fan test
Jackson cross cylinder test
TREATMENT
– Spectacles (spherocyl.)
– Contact lenses(toric lens)
SURGICAL TREATMENT
– Lasik
– PRK
IRREGULAR ASTIGMATISM
It can defined as if the parallel rays of light
coming from infinity is focused in more than
two points is called Irregular Astigmatism.
ETIOLOGY OF IRREGULAR
ASTIGMATISM
corneal irregular astigmatism
Lenticular irregular astigmatism
Retinal irregular astigmatism
DIFFERENCE BETWEEN
REGULAR AND IRREGULAR
REGULAR
It is the condition in which
there are two principle
meridians separated by 90
degree
This is the most common
form of astigmatism
IRREGULAR
It is the condition in which
there are more than two
principle meridians which
are not separated by 90
degree
This is less common form of
astigmatism
REGULAR
It can be corrected by a
cylinder or
spherocylindrical lens
IRREGULAR
 Irregular astigmatism will
not be corrected by
spherocylindrical lens,
Rather it is correct by
special contact lens ie RGP,
Miniscleral lens etc.
SYMPTOMS
Defective vision
Distortion of object
Polyopia
Aberration
TREATMENT
 Special contact lens such as RGP, Rose-K and Miniscleral
contact lenses etc
Penetrating keratoplasty
REFERENCE
– Optic and refraction …….. BY A.K KHURANNA
Page no 24,79-83
– Refraction and lens prescription ….. BY MONICA
CHAUDHARY
Astigmatism

More Related Content

What's hot

Binocular anomalies What we should know?
Binocular anomalies What we should know?Binocular anomalies What we should know?
Binocular anomalies What we should know?
Anis Suzanna Mohamad
 
Cycloplegic refraction ppt
Cycloplegic refraction pptCycloplegic refraction ppt
Cycloplegic refraction ppt
Mehedi Hasan
 
Maddox rod, Maddox wing, Bagolini striated glasses, RAF ruler and Prism bar
Maddox rod, Maddox wing, Bagolini striated glasses, RAF ruler and Prism barMaddox rod, Maddox wing, Bagolini striated glasses, RAF ruler and Prism bar
Maddox rod, Maddox wing, Bagolini striated glasses, RAF ruler and Prism bar
Bhageesh Bhaskar
 
Physiology of cornea
Physiology of corneaPhysiology of cornea
Physiology of cornea
shovon2026
 
Detail of suppression and AC
Detail of suppression and ACDetail of suppression and AC
Detail of suppression and AC
Raju Kaiti
 
AMBLYOPIA AND ITS MANAGEMENT
AMBLYOPIA AND ITS MANAGEMENTAMBLYOPIA AND ITS MANAGEMENT
AMBLYOPIA AND ITS MANAGEMENT
SSSIHMS-PG
 
binocular single vision
binocular single visionbinocular single vision
binocular single vision
DrShrey Maheshwari
 
Objective refraction
Objective refractionObjective refraction
Objective refraction
sneha_thaps
 
Trial box
Trial boxTrial box
Trial box
vivek parmar
 
Correction of ametropia
Correction of ametropiaCorrection of ametropia
Correction of ametropia
AmritJha7
 
Eccentric Fixation
Eccentric FixationEccentric Fixation
Eccentric Fixation
Hossein Mirzaie
 
Diagnosis evaluation in strabismus
Diagnosis evaluation in strabismusDiagnosis evaluation in strabismus
Diagnosis evaluation in strabismus
Jayarajini
 
Cover test.pptx
Cover test.pptxCover test.pptx
Cover test.pptx
jyotishah48
 
Esotropia
EsotropiaEsotropia
Esotropia
ShreyaGupta323
 
Astigmatism
AstigmatismAstigmatism
Astigmatism
avinas
 
Biometry
BiometryBiometry
Biometry
Binny Tyagi
 
Corneal Topography
Corneal TopographyCorneal Topography
Corneal Topography
Raman Gupta
 
Binocular Single Vision Tests
Binocular Single Vision TestsBinocular Single Vision Tests
Binocular Single Vision Tests
Rabia Ammer
 
Pediatric refraction
Pediatric       refractionPediatric       refraction
Pediatric refraction
Yashaswee Bhattarai
 
Astigmatism
AstigmatismAstigmatism
Astigmatism
Harsh Jain
 

What's hot (20)

Binocular anomalies What we should know?
Binocular anomalies What we should know?Binocular anomalies What we should know?
Binocular anomalies What we should know?
 
Cycloplegic refraction ppt
Cycloplegic refraction pptCycloplegic refraction ppt
Cycloplegic refraction ppt
 
Maddox rod, Maddox wing, Bagolini striated glasses, RAF ruler and Prism bar
Maddox rod, Maddox wing, Bagolini striated glasses, RAF ruler and Prism barMaddox rod, Maddox wing, Bagolini striated glasses, RAF ruler and Prism bar
Maddox rod, Maddox wing, Bagolini striated glasses, RAF ruler and Prism bar
 
Physiology of cornea
Physiology of corneaPhysiology of cornea
Physiology of cornea
 
Detail of suppression and AC
Detail of suppression and ACDetail of suppression and AC
Detail of suppression and AC
 
AMBLYOPIA AND ITS MANAGEMENT
AMBLYOPIA AND ITS MANAGEMENTAMBLYOPIA AND ITS MANAGEMENT
AMBLYOPIA AND ITS MANAGEMENT
 
binocular single vision
binocular single visionbinocular single vision
binocular single vision
 
Objective refraction
Objective refractionObjective refraction
Objective refraction
 
Trial box
Trial boxTrial box
Trial box
 
Correction of ametropia
Correction of ametropiaCorrection of ametropia
Correction of ametropia
 
Eccentric Fixation
Eccentric FixationEccentric Fixation
Eccentric Fixation
 
Diagnosis evaluation in strabismus
Diagnosis evaluation in strabismusDiagnosis evaluation in strabismus
Diagnosis evaluation in strabismus
 
Cover test.pptx
Cover test.pptxCover test.pptx
Cover test.pptx
 
Esotropia
EsotropiaEsotropia
Esotropia
 
Astigmatism
AstigmatismAstigmatism
Astigmatism
 
Biometry
BiometryBiometry
Biometry
 
Corneal Topography
Corneal TopographyCorneal Topography
Corneal Topography
 
Binocular Single Vision Tests
Binocular Single Vision TestsBinocular Single Vision Tests
Binocular Single Vision Tests
 
Pediatric refraction
Pediatric       refractionPediatric       refraction
Pediatric refraction
 
Astigmatism
AstigmatismAstigmatism
Astigmatism
 

Similar to Astigmatism

Astigmatism
AstigmatismAstigmatism
Astigmatism
Nishita Afrin
 
Astigmatism
AstigmatismAstigmatism
Astigmatism
kausar Ali
 
Astigmatism By Sumayya Naseem
Astigmatism By Sumayya NaseemAstigmatism By Sumayya Naseem
Astigmatism By Sumayya Naseem
Sumayya Naseem
 
Astigmatism, presbyopia and aphakia
Astigmatism, presbyopia and aphakiaAstigmatism, presbyopia and aphakia
Astigmatism, presbyopia and aphakia
tutsimundi
 
Sturms conoid
Sturms conoidSturms conoid
Sturms conoid
Yasir Maqsood
 
Sturms conoid
Sturms conoidSturms conoid
Sturms conoid
Yasir Maqsood
 
astigmatism sturms cnoid
astigmatism sturms cnoidastigmatism sturms cnoid
astigmatism sturms cnoid
Yasir Maqsood
 
Astigmatism, presbyopia and aphakia
Astigmatism, presbyopia and aphakiaAstigmatism, presbyopia and aphakia
Astigmatism, presbyopia and aphakia
tutsimundi
 
All atigmatism
All atigmatismAll atigmatism
All atigmatism
ibrahim ali
 
Astigmatism
AstigmatismAstigmatism
Astigmatism
AstigmatismAstigmatism
Astigmatism
Praful SonnePatil
 
ASTIGMATISM & ITS MANAGEMENT.pptx
ASTIGMATISM & ITS MANAGEMENT.pptxASTIGMATISM & ITS MANAGEMENT.pptx
ASTIGMATISM & ITS MANAGEMENT.pptx
PurushotamSahani1
 
Astigmatism correction
Astigmatism correctionAstigmatism correction
Astigmatism correction
Farhana Islam
 
Sturm's conoid
Sturm's conoidSturm's conoid
Sturm's conoid
Dr Samarth Mishra
 
Astigmatism ppt
Astigmatism pptAstigmatism ppt
Astigmatism ppt
Azizul Islam
 
Astigmatism
AstigmatismAstigmatism
Astigmatism
Rohit Rao
 
Esotropia ophthalmology presentation HSAH.pptx
Esotropia ophthalmology presentation HSAH.pptxEsotropia ophthalmology presentation HSAH.pptx
Esotropia ophthalmology presentation HSAH.pptx
Vishnu645963
 
Astigmatism, anisometropia, anisekonia.
Astigmatism, anisometropia, anisekonia.Astigmatism, anisometropia, anisekonia.
Astigmatism, anisometropia, anisekonia.
Vishy Srivastava
 
11. Refractive errors.pptx
11. Refractive errors.pptx11. Refractive errors.pptx
11. Refractive errors.pptx
Annie Amjad
 
11. Refractive errors.pptx
11. Refractive errors.pptx11. Refractive errors.pptx
11. Refractive errors.pptx
annieamjad1
 

Similar to Astigmatism (20)

Astigmatism
AstigmatismAstigmatism
Astigmatism
 
Astigmatism
AstigmatismAstigmatism
Astigmatism
 
Astigmatism By Sumayya Naseem
Astigmatism By Sumayya NaseemAstigmatism By Sumayya Naseem
Astigmatism By Sumayya Naseem
 
Astigmatism, presbyopia and aphakia
Astigmatism, presbyopia and aphakiaAstigmatism, presbyopia and aphakia
Astigmatism, presbyopia and aphakia
 
Sturms conoid
Sturms conoidSturms conoid
Sturms conoid
 
Sturms conoid
Sturms conoidSturms conoid
Sturms conoid
 
astigmatism sturms cnoid
astigmatism sturms cnoidastigmatism sturms cnoid
astigmatism sturms cnoid
 
Astigmatism, presbyopia and aphakia
Astigmatism, presbyopia and aphakiaAstigmatism, presbyopia and aphakia
Astigmatism, presbyopia and aphakia
 
All atigmatism
All atigmatismAll atigmatism
All atigmatism
 
Astigmatism
AstigmatismAstigmatism
Astigmatism
 
Astigmatism
AstigmatismAstigmatism
Astigmatism
 
ASTIGMATISM & ITS MANAGEMENT.pptx
ASTIGMATISM & ITS MANAGEMENT.pptxASTIGMATISM & ITS MANAGEMENT.pptx
ASTIGMATISM & ITS MANAGEMENT.pptx
 
Astigmatism correction
Astigmatism correctionAstigmatism correction
Astigmatism correction
 
Sturm's conoid
Sturm's conoidSturm's conoid
Sturm's conoid
 
Astigmatism ppt
Astigmatism pptAstigmatism ppt
Astigmatism ppt
 
Astigmatism
AstigmatismAstigmatism
Astigmatism
 
Esotropia ophthalmology presentation HSAH.pptx
Esotropia ophthalmology presentation HSAH.pptxEsotropia ophthalmology presentation HSAH.pptx
Esotropia ophthalmology presentation HSAH.pptx
 
Astigmatism, anisometropia, anisekonia.
Astigmatism, anisometropia, anisekonia.Astigmatism, anisometropia, anisekonia.
Astigmatism, anisometropia, anisekonia.
 
11. Refractive errors.pptx
11. Refractive errors.pptx11. Refractive errors.pptx
11. Refractive errors.pptx
 
11. Refractive errors.pptx
11. Refractive errors.pptx11. Refractive errors.pptx
11. Refractive errors.pptx
 

Recently uploaded

How to Add Chatter in the odoo 17 ERP Module
How to Add Chatter in the odoo 17 ERP ModuleHow to Add Chatter in the odoo 17 ERP Module
How to Add Chatter in the odoo 17 ERP Module
Celine George
 
Cognitive Development Adolescence Psychology
Cognitive Development Adolescence PsychologyCognitive Development Adolescence Psychology
Cognitive Development Adolescence Psychology
paigestewart1632
 
NEWSPAPERS - QUESTION 1 - REVISION POWERPOINT.pptx
NEWSPAPERS - QUESTION 1 - REVISION POWERPOINT.pptxNEWSPAPERS - QUESTION 1 - REVISION POWERPOINT.pptx
NEWSPAPERS - QUESTION 1 - REVISION POWERPOINT.pptx
iammrhaywood
 
The Diamonds of 2023-2024 in the IGRA collection
The Diamonds of 2023-2024 in the IGRA collectionThe Diamonds of 2023-2024 in the IGRA collection
The Diamonds of 2023-2024 in the IGRA collection
Israel Genealogy Research Association
 
Walmart Business+ and Spark Good for Nonprofits.pdf
Walmart Business+ and Spark Good for Nonprofits.pdfWalmart Business+ and Spark Good for Nonprofits.pdf
Walmart Business+ and Spark Good for Nonprofits.pdf
TechSoup
 
Your Skill Boost Masterclass: Strategies for Effective Upskilling
Your Skill Boost Masterclass: Strategies for Effective UpskillingYour Skill Boost Masterclass: Strategies for Effective Upskilling
Your Skill Boost Masterclass: Strategies for Effective Upskilling
Excellence Foundation for South Sudan
 
Advanced Java[Extra Concepts, Not Difficult].docx
Advanced Java[Extra Concepts, Not Difficult].docxAdvanced Java[Extra Concepts, Not Difficult].docx
Advanced Java[Extra Concepts, Not Difficult].docx
adhitya5119
 
RHEOLOGY Physical pharmaceutics-II notes for B.pharm 4th sem students
RHEOLOGY Physical pharmaceutics-II notes for B.pharm 4th sem studentsRHEOLOGY Physical pharmaceutics-II notes for B.pharm 4th sem students
RHEOLOGY Physical pharmaceutics-II notes for B.pharm 4th sem students
Himanshu Rai
 
Life upper-Intermediate B2 Workbook for student
Life upper-Intermediate B2 Workbook for studentLife upper-Intermediate B2 Workbook for student
Life upper-Intermediate B2 Workbook for student
NgcHiNguyn25
 
Hindi varnamala | hindi alphabet PPT.pdf
Hindi varnamala | hindi alphabet PPT.pdfHindi varnamala | hindi alphabet PPT.pdf
Hindi varnamala | hindi alphabet PPT.pdf
Dr. Mulla Adam Ali
 
PCOS corelations and management through Ayurveda.
PCOS corelations and management through Ayurveda.PCOS corelations and management through Ayurveda.
PCOS corelations and management through Ayurveda.
Dr. Shivangi Singh Parihar
 
ANATOMY AND BIOMECHANICS OF HIP JOINT.pdf
ANATOMY AND BIOMECHANICS OF HIP JOINT.pdfANATOMY AND BIOMECHANICS OF HIP JOINT.pdf
ANATOMY AND BIOMECHANICS OF HIP JOINT.pdf
Priyankaranawat4
 
Wound healing PPT
Wound healing PPTWound healing PPT
Wound healing PPT
Jyoti Chand
 
How to Manage Your Lost Opportunities in Odoo 17 CRM
How to Manage Your Lost Opportunities in Odoo 17 CRMHow to Manage Your Lost Opportunities in Odoo 17 CRM
How to Manage Your Lost Opportunities in Odoo 17 CRM
Celine George
 
Pollock and Snow "DEIA in the Scholarly Landscape, Session One: Setting Expec...
Pollock and Snow "DEIA in the Scholarly Landscape, Session One: Setting Expec...Pollock and Snow "DEIA in the Scholarly Landscape, Session One: Setting Expec...
Pollock and Snow "DEIA in the Scholarly Landscape, Session One: Setting Expec...
National Information Standards Organization (NISO)
 
Film vocab for eal 3 students: Australia the movie
Film vocab for eal 3 students: Australia the movieFilm vocab for eal 3 students: Australia the movie
Film vocab for eal 3 students: Australia the movie
Nicholas Montgomery
 
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UP
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPLAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UP
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UP
RAHUL
 
Chapter wise All Notes of First year Basic Civil Engineering.pptx
Chapter wise All Notes of First year Basic Civil Engineering.pptxChapter wise All Notes of First year Basic Civil Engineering.pptx
Chapter wise All Notes of First year Basic Civil Engineering.pptx
Denish Jangid
 
A Independência da América Espanhola LAPBOOK.pdf
A Independência da América Espanhola LAPBOOK.pdfA Independência da América Espanhola LAPBOOK.pdf
A Independência da América Espanhola LAPBOOK.pdf
Jean Carlos Nunes Paixão
 
Digital Artefact 1 - Tiny Home Environmental Design
Digital Artefact 1 - Tiny Home Environmental DesignDigital Artefact 1 - Tiny Home Environmental Design
Digital Artefact 1 - Tiny Home Environmental Design
amberjdewit93
 

Recently uploaded (20)

How to Add Chatter in the odoo 17 ERP Module
How to Add Chatter in the odoo 17 ERP ModuleHow to Add Chatter in the odoo 17 ERP Module
How to Add Chatter in the odoo 17 ERP Module
 
Cognitive Development Adolescence Psychology
Cognitive Development Adolescence PsychologyCognitive Development Adolescence Psychology
Cognitive Development Adolescence Psychology
 
NEWSPAPERS - QUESTION 1 - REVISION POWERPOINT.pptx
NEWSPAPERS - QUESTION 1 - REVISION POWERPOINT.pptxNEWSPAPERS - QUESTION 1 - REVISION POWERPOINT.pptx
NEWSPAPERS - QUESTION 1 - REVISION POWERPOINT.pptx
 
The Diamonds of 2023-2024 in the IGRA collection
The Diamonds of 2023-2024 in the IGRA collectionThe Diamonds of 2023-2024 in the IGRA collection
The Diamonds of 2023-2024 in the IGRA collection
 
Walmart Business+ and Spark Good for Nonprofits.pdf
Walmart Business+ and Spark Good for Nonprofits.pdfWalmart Business+ and Spark Good for Nonprofits.pdf
Walmart Business+ and Spark Good for Nonprofits.pdf
 
Your Skill Boost Masterclass: Strategies for Effective Upskilling
Your Skill Boost Masterclass: Strategies for Effective UpskillingYour Skill Boost Masterclass: Strategies for Effective Upskilling
Your Skill Boost Masterclass: Strategies for Effective Upskilling
 
Advanced Java[Extra Concepts, Not Difficult].docx
Advanced Java[Extra Concepts, Not Difficult].docxAdvanced Java[Extra Concepts, Not Difficult].docx
Advanced Java[Extra Concepts, Not Difficult].docx
 
RHEOLOGY Physical pharmaceutics-II notes for B.pharm 4th sem students
RHEOLOGY Physical pharmaceutics-II notes for B.pharm 4th sem studentsRHEOLOGY Physical pharmaceutics-II notes for B.pharm 4th sem students
RHEOLOGY Physical pharmaceutics-II notes for B.pharm 4th sem students
 
Life upper-Intermediate B2 Workbook for student
Life upper-Intermediate B2 Workbook for studentLife upper-Intermediate B2 Workbook for student
Life upper-Intermediate B2 Workbook for student
 
Hindi varnamala | hindi alphabet PPT.pdf
Hindi varnamala | hindi alphabet PPT.pdfHindi varnamala | hindi alphabet PPT.pdf
Hindi varnamala | hindi alphabet PPT.pdf
 
PCOS corelations and management through Ayurveda.
PCOS corelations and management through Ayurveda.PCOS corelations and management through Ayurveda.
PCOS corelations and management through Ayurveda.
 
ANATOMY AND BIOMECHANICS OF HIP JOINT.pdf
ANATOMY AND BIOMECHANICS OF HIP JOINT.pdfANATOMY AND BIOMECHANICS OF HIP JOINT.pdf
ANATOMY AND BIOMECHANICS OF HIP JOINT.pdf
 
Wound healing PPT
Wound healing PPTWound healing PPT
Wound healing PPT
 
How to Manage Your Lost Opportunities in Odoo 17 CRM
How to Manage Your Lost Opportunities in Odoo 17 CRMHow to Manage Your Lost Opportunities in Odoo 17 CRM
How to Manage Your Lost Opportunities in Odoo 17 CRM
 
Pollock and Snow "DEIA in the Scholarly Landscape, Session One: Setting Expec...
Pollock and Snow "DEIA in the Scholarly Landscape, Session One: Setting Expec...Pollock and Snow "DEIA in the Scholarly Landscape, Session One: Setting Expec...
Pollock and Snow "DEIA in the Scholarly Landscape, Session One: Setting Expec...
 
Film vocab for eal 3 students: Australia the movie
Film vocab for eal 3 students: Australia the movieFilm vocab for eal 3 students: Australia the movie
Film vocab for eal 3 students: Australia the movie
 
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UP
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPLAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UP
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UP
 
Chapter wise All Notes of First year Basic Civil Engineering.pptx
Chapter wise All Notes of First year Basic Civil Engineering.pptxChapter wise All Notes of First year Basic Civil Engineering.pptx
Chapter wise All Notes of First year Basic Civil Engineering.pptx
 
A Independência da América Espanhola LAPBOOK.pdf
A Independência da América Espanhola LAPBOOK.pdfA Independência da América Espanhola LAPBOOK.pdf
A Independência da América Espanhola LAPBOOK.pdf
 
Digital Artefact 1 - Tiny Home Environmental Design
Digital Artefact 1 - Tiny Home Environmental DesignDigital Artefact 1 - Tiny Home Environmental Design
Digital Artefact 1 - Tiny Home Environmental Design
 

Astigmatism

  • 1. ASTIGMATISM PRESENTED BY, MR.SUBHAM KUMAR BACHELOR OF OPTOMETRY 2ND YEAR 2017 RIDLEY COLLEGE OF OPTOMETRY, JORHAT,ASSAM.
  • 2. CONTENTS  DEFINITION  OCCURANCE  STURM’S CONOIDS  ETIOLOGY  TYPES  ETIOLOGY OF REGULAR ASTIGMATISM  REGULAR ASTIGMATISM  TYPES OF REGULAR ASTIGMATISM
  • 3. CONTENTS WITH THE RULE ASTIGMATISM AGAINST THE RULE ASTIGMATISM OBLIQUE ASTIGMATISM BI-OBLIQUE ASTIGMATISM REFRACTIVE TYPES SIGN AND SYMPTOMS
  • 4. CONTENTS  INVESTIGATION  TREATMENT  IRREGULAR ASTIGMATISM  ETIOLOGY OF IRREGULAR ASTIGMATISM  DIFFERENCE BETWEEN REGULAR AND IRREGULAR ASTIGMATISM  SYMPTOMS  TREATMENT  REFERENCES  THANK YOU
  • 5. DEFINITION A refractive condition that is the result of two principal meridians of the eye having different refractive power
  • 6. OCCURRENCE Astigmatism occurs when the cornea or the lens ,has a slightly different surface curvature in one direction from the other There is a steep meridian and a flat meridian Varying refractive index
  • 7. STURM’S CONOID – In a toric surface, one principle meridian is more curved than the second principle meridian. The principle meridian with minimum curvature,and therefore with minimum power is called base curve of a toric lens. The configuration of rays refracted through a toric surface is called strum’s conoid . The shape of bundle of the light rays at different levels in strum’s conoid is as follows:-
  • 8. 1. At point A, the vertical rays(V) are converging more than the horizontal rays (H). So ,the selection here is horizontal oval or an oblate ellipse 2. At point B (first focus) the vertical rays have come to a focus while the horizontal rays are still converging and so they form a horizontal line 3. At point C the vertical rays are diverging and their divergence is less than the convergence of the horizontal rays so a horizontal oval is formed here 4. At point D , the divergence of vertical rays is exactly equal to the convergence of the horizontal rays form the axis . So here the section is a circle , which is called the circle of least diffusion
  • 9. 5. At point E , the divergence of vertical rays is more than the convergence of horizontal rays, so the section here is a vertical oval. 6. At point F (second focus) the horizontal rays have come to a focus while the vertical rays are divergent and so a vertical line is formed here. 7. Beyond F (as point G ) both horizontal and vertical rays are divergent and so the section will always be a vertical oval or prolate ellipse The distance between two foci(B and F) is called the focal interval of sturm.
  • 10. ETIOLOGY Asymmetry of the cornea, or the lens or the posterior retina Any variation in refractive index Tilting of the lens Any eye mass lesion The weight of the upper eyelid resting on the eyeball Any healed aberration or injury of the cornea which can be due to any infection or trauma
  • 12. ETIOLOGY OF REGULAR ASTIGMATISM Corneal Astigmatism Lenticular astigmatism a. Curvatural b. Positional c. Index Retinal astigmatism
  • 13. TYPES OF REGULAR ASTIGMATISM With the rule astigmatism Against the rule astigmatism Oblique astigmatism Bi-oblique astigmatism
  • 15. NOTES-Vertical meridian is more myopic than horizontal Near vertical is usually defined as between 70˚-110˚ i.e ±20˚ of the vertical The axis of the negative cylindrical correction in with the rule astigmatism will be between 0˚-20˚ or 160˚-180˚ i.e ±20˚ of the horizontal
  • 16. AGAINST THE RULE ASTIGMATISM The horizontal curvature is greater than the vertical curvature i.e the correction of astigmatism will require the prescription of a concave cyl at 90˚ or a convex cyl at 180˚
  • 17. NOTE:-Horizontal meridian is more myopic than vertical The axis of the correcting negative cylinder will be between70˚-110˚ i.e within ±20 of the vertical
  • 18. OBLIQUE ASTIGMATISM The power meridian is neither horizontal nor vertical
  • 19. The principal meridian are more than 30˚ from vertical or horizontal The axis of the negative correcting cylindrical axis will be between 20˚-70˚and 110˚-160˚
  • 20. BI-OBLIQUE ASTIGMATISM The two principle meridian are not at right angle to each other i.e one may be at 30˚ and the other at 100˚
  • 21. REFRACTIVE TYPES Simple astigmatism Compound astigmatism Mixed astigmatism
  • 22.
  • 23. SIGNS AND SYMPTOMS Blurring of vertical , horizontal or diagonal lines Eyestrain or fatigue Headaches Distortion in portions of the visual field Squinting NOTES:- The astigmatic patients tend to squeeze the eyes producing a narrow stenopic slit effect
  • 25. TREATMENT – Spectacles (spherocyl.) – Contact lenses(toric lens) SURGICAL TREATMENT – Lasik – PRK
  • 26. IRREGULAR ASTIGMATISM It can defined as if the parallel rays of light coming from infinity is focused in more than two points is called Irregular Astigmatism.
  • 27. ETIOLOGY OF IRREGULAR ASTIGMATISM corneal irregular astigmatism Lenticular irregular astigmatism Retinal irregular astigmatism
  • 28. DIFFERENCE BETWEEN REGULAR AND IRREGULAR REGULAR It is the condition in which there are two principle meridians separated by 90 degree This is the most common form of astigmatism IRREGULAR It is the condition in which there are more than two principle meridians which are not separated by 90 degree This is less common form of astigmatism
  • 29. REGULAR It can be corrected by a cylinder or spherocylindrical lens IRREGULAR  Irregular astigmatism will not be corrected by spherocylindrical lens, Rather it is correct by special contact lens ie RGP, Miniscleral lens etc.
  • 30. SYMPTOMS Defective vision Distortion of object Polyopia Aberration
  • 31. TREATMENT  Special contact lens such as RGP, Rose-K and Miniscleral contact lenses etc Penetrating keratoplasty
  • 32. REFERENCE – Optic and refraction …….. BY A.K KHURANNA Page no 24,79-83 – Refraction and lens prescription ….. BY MONICA CHAUDHARY