The document provides an overview of astigmatism, including its definition, etiology, classification, signs and symptoms, clinical tests, and management options. It explains the condition as irregular focusing of light due to variations in corneal curvature, with types classified based on etiology, orientation of meridians, and focal points relative to the retina. Various clinical tests for diagnosis and management strategies, including corrective lenses and surgical procedures, are also discussed.

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ASTIGMATISM
BY: Komal Yaseen

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Content:
• Introduction
• Etiology
• Classification
• Signs and symptoms
• Clinical tests
• Management

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Astigmatism:
• The term astigmatism (from a, meaning
"lacking," and stigma, meaning "a point")
• Astigmatism by definition is a condition where
the parallel beam of light rays incident on the
cornea after refraction are not focused to form a
point image near or on the retina.

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Spherical Vs Astigmatic cornea

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Image in Astigmatism:

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Etiology:
• Irregular curvature or RI of anterior
corneal surface/posterior corneal surface.
• Irregular surface, RI and position of
lens/IOL.
• The refracting power is not uniform in all
meridians of both lens or cornea.

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Classification:
• Based on Etiology.
• Based on Orientation of meridians
• Based on Focal points relative to
retina

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Based on Etiology:
Curvature of
cornea
Irregular
regular
Axis not
perpendicular
Irregular surface
of cornea
Axis
perpendicular

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Orientation of meridians:

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Principle meridian:
• WTR- with the rule astigmatism.
-vertical meridian of cornea is more power
• Greatest power is with in 30 degree of vertical
meridian. (60deg- 120 deg).
• ATR- against the rule astigmatism.
- horizontal meridian of cornea is more power
• Greatest power is with in 30 degree of
horizontal meridian(30deg-150deg).

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Axis Orientation of WTR and ATR
astigmatism

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Based on Orientation of meridians:
• Oblique astigmatism:
- Axis position is not near to 90 and 180.
-Range of axis will be in 30-60deg and 120
and 150deg.

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Focal point relative to retina.
1. Simple astigmatism
- One of the focus falls on retina and the other one
may fall in front of retina or behind retina
- Two condition.
- Simple Myopic astigmatism
- Simple Hypermatropic astigmatism

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Continue…
• Compound astigmatism:
- Both(2) the focal point lies in front of retina or
behind the retina.
-Compound Myopia
- Compound Hypermetropia

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Continue…
• Mixed astigmatism:
- One focus lies in front of retina and other
lies behind the retina.
- one meridian is Myopic
- other one Hypermetropic

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Irregular astigmatism:
• Irregular differences in curvature or
refractive index of the optic components or
misalignment of any optical component may
lead to irregularity.
• Pterygium,
• corneal scars/healed ulcers
• Complication of refractive surgery.
• keratoconous

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Signs and Symptoms:
• Visual acuity↓
• Difficulty in both near and distance
• Letter confusion
• Eyestrain
• Headache
• squinting

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Vision with Astigmatism:

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Clinical tests:
-Objective tests:
• Autorefraction
• Keratometry
• Retinoscopy
• Corneal topography
- Subjective tests
• JCC- Jacson’s cross cylinder
• Astigmatic Fan
• Stenopaeic slit

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Management:
• Conservative management:
• Sphero-cylindrical lens
• Spherical soft contact lenses
• Spherical RGP contact lenses
• Toric soft contact lenses
• Surgical laser procedure:
• Photorefractive keratectomy(PRK)
• Laser in-situ keratomileusis(LASIK)

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