Astigmatism is a refractive error where refraction varies in different meridians of the eye. In astigmatism, light rays from one sector focus on one point of the retina while rays from another sector focus on a different point, resulting in blurred vision. Around 60% of refractive error cases involve astigmatism. It is classified as mild, moderate, severe, or extreme depending on the degree of refractive error. Regular astigmatism results from corneal or lenticular shape and irregular astigmatism involves irregular changes in refractive power. Treatment options include optical aids like glasses and contact lenses or refractive surgery procedures.

1. ASTIGMATISM
Nishita afrin
ICO
B.OPTOM

2. What is Astigmatism ?
O one type of refractive error ,where
in refraction varies in different
meridian

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O For example, the image may be
focused on the retina in the
horizontal (sagittal )plane,but not
on the retina in the vertical plane
O Most Astigmatic cornea have two
curves,one is steeper and another
oner a flatter curve

6. OPTICS OF ASTIGMATISM
O In Astigmatism , the rays of light
from one sector fall on one point and
rays from aanother sector fall on
another point.
O The configuration of rays refracted
through the Astigmatic surface (toric
surface) is called sturms conoid

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9. INCIDENCE
O No eye is perfectly stigmatic ,
almost all individuals have a minor
degree of physiological Astigmatism
O About 60 % cases of refractive
error have Astigmatism which
needs to be corrected

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O Occurs with equal frequency in males and
female
O Approximate distributation recording to
degree of Astigmatism
0.25 - 0.50 50%
0.75 - 1.0 25%
1.00 – 4.00 24 %
> 4.00 1%

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O One study report as –
WTR 38%
ATR 30%
Oblique 32%

12. SEVERITY OF
ASTIGMATISM
O Classified as follows –
Mild Astigmatism <1 D
Moderate Astigmatism 1.00 to
2.00 D
Severe Astigmatism 2.00 to 3.00 D
Extreme Astigmatism >3.00 D

13. CLASSIFICATION
O Regular Astigmatism
O Irregular Astigmatism

14. REGULAR ASTIGMATISM
Aeitiology -
1. Corneal Astigmatism
2. Lenticular Astigmatism
Curvatural, Positional,
Index
3. Retinal Astigmatism

15. TYPES OF REGULAR
ASTIGMATISM
O With the rule Astigmatism
O Against the Astigmatism
O Oblique Astigmatism
O Bi-oblique Astigmatism

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20. REFRACTIVE TYPES OF
ASTIGMATISM
O Simple Astigmatism – simple
myopic,simple hyperopic
astigmatism
O Compound Astigmatism –
compound myopic,compound
hyperopic astigmatism
O Mixed Astigmatism

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22. SYMMETRIC ASTIGMATISM
O Regular Astigmatism
O principal meridian of each eye
have similar but opposite axes
O which together add upto 180±15˚

23. SYMPTOMS OF REGULAR
ASTIGMATISM
O DISTORTION OR BLURRING
OF VISION
O ASTHENOPIC SYMPTOM
O TILTING OF HEAD
O SQUINTING OF EYE
O READING MATERIAL MAY BE
HELD CLOSE TO EYES
O BURNING AND ITCHING
SENSATION

24. IRREGULAR ASTIGMATISM
O IRREGULAR CHANGE IN
REFRACTIVE POWER IN
DIFFERENT MERIDIAN
O AEITIOLOGICAL TYPE –
Corneal irregular Astigmatism
Lenticular irregular Astigmatism
Retinal irregular Astigmatism

25. SYMPTOMS OF IRREGULAR
ASTIGMATISM
O DEFECTIVE VISION
O IMAGE DISTORTION
O POLYOPIA

26. RESIDUAL ASTIGMATISM
O The largest element of the Astigmatism is due
to anterior corneal surface
O While the other components like –
Posterior corneal surface
Lens
Refractive indices
Constitute the residual Astigmatism
RESIDUAL ASTIGMATISM = TOTAL –
CORNEAL ASTIGMATISM

27. INVESTIGATION OF
ASTIGMATISM
I. VA with and without correction
monocularly
II. Retinoscopy
III. keratometry
IV. keratometry with placido disc
V. computerized corneal
topography

28. CONTINUE
O SUBJECTIVE REFRACTION –
I. Jacson cross cylinder
II. Astigmatic fan and block
technique
III. stenopic slit
IV. trial and error technique

38. TREATMENT
1. OPTICAL-
SPECTACLES
CONTACT LENS
2. SURGICAL –
LASER
LASIK
3. KERATOPLASTY

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