Astigmatism occurs when parallel rays of light focus at multiple points rather than a single point due to differences in curvature along the eye's meridians. There are two types: regular astigmatism where curvature changes uniformly between meridians, and irregular astigmatism with non-uniform changes. Regular astigmatism is further classified as with-the-rule, against-the-rule, or oblique based on meridian angles. Symptoms include blurred vision, eye strain, and headaches. Treatment options include optical correction with glasses or contacts, or refractive surgery.

1. ASTIGMATISM
BAIDHNATH DAS
B. OPTOM

2. WHAT IS ASTIGMASTISM ?
 When parallel rays of light come from infinity and create
multiple focal point with accomodation at rest is called
astigmatism.

4. THERE ARE TWO TYPES OF ASTIGMATISM :
1. REGULAR ASTIGMATISM:
The refractive power changes uniformly from one meridian to
another ( there are two principal meridian).

6. TYPES OF REGULAR ASTIGMATISM:
 WITH-THE-RULE ASTIGMATISM:
- In This Type , The Two Principal Meridia Are Placed At Right Angles To
One Another But The Vertical Meridian Is More Curved Than The
Horizontal .
90
- RANGE : 120 60
60 TO 120 DEGREE
180 0

7.  AGAINST-THE-RULE ASTIGMATISM
- Horizontal meridian is more curved than vertical
meridian.
90
- Range : 150 30
0 to 30 degree, 180 0
150 to 180 degree.

8.  OBLIQUE ASTIGMATISM:
where the two principal meridian are not
horizontal or vertical but these are perpendicular
to one another.
- Range : 30 to 60 degree, 120 to 150 degree.
90
120 60
150 30
180 0

9. OPTICS OF REGULAR ASTIGMATISM
 The parallel rays of light are not focused on a point but
from two focal lines.
 The configuration of rays refracted through the
astigmatic surface (Toric surface ) is called strum’s
conoid and distance between the two focal lines is
known as focal interval of strum.
 The length of this focal interval is measure of the
degree of astigmatism.

11. REFRACTIVE TYPRS OF REGULAR
ASTIGMATISM
 Depending upon the position of the two focal lines in
relation to retina, Regular astigmatism is classified
into three types:
1. SIMPLE ASTIGMATISM
The rays focused on the retina in one meridian
and either in front (SMA) or behind (SHA) the retina in the
other meridian.

12.  SIMPLE MYOPIC ASTIGMATISM.
 SIMPLE HYPERMETROPIC ASTIGMATISM.

13. 2. COMPOUND ASTIGMATISM.
The rays of light in the both the meridia
are focused either infront or behind the retina.
compound myopic astigmatism.

14.  COMPOUND HYPERMETROPIC ASTIGMATISM

15. 3. MIXED ASTIGMATISM
The light rays in one meridian are focused in
front and in other meridian behind the retina.
MIXED ASTIGMATISM

16. SYMPTOMS SIGNS
 DISCOMFORT
 EYE STRAIN
 HEADACHE
 DRY EYE
 SENSITIVITY TO LIGHT
 BLURRED VISION
 FREQUENT BLINKING
 READING MATERIAL HOLD
CLOSE TO EYES.
 HEAD TILT
 HALF CLOSER OF THE LID
 OVAL OR TILT OPTIC DISC
 DIFFERENT POWER IN
DIFFERENT MERIDIAN

17. INVESTIGATION
 RETINOSCOPY
 KERATOMETRY
 ASTIGMATIC FAN TEST
 JACKSON CROSS CYLINDER
 STENOPAEIC SLIT

18. 2. IRREGULAR ASTIGMATISM
It is characterized by an irregular changes of refractive
power in different meridia. There are multiple meridia
which admit no geometrical analysis.

19. ATIOLOGICAL TYPES
1.CORNEAL IRREGULAR ASTIGMATISM
Found in patient with extensive corneal scars
or keratoconus.
2.LENTICULAR IRREGULAR ASTIGMATISM
Occur during maturation of cataract and
seen due to variable refractive index in different parts
of crystalline lens.
3. RETINAL IRREGULAR ASTIGMATISM
Seen due to distortion of macular area.

20. SYMPTOMS SIGNS
 Defective vision
 Distortion of objects
 polyopia
 Irregular pupillary reflex.
 Corneal irregularity of
keratoconus.
 Plano disc test reveals
distorted circles.

21. TREATMENT
1. Optical treatment
2. Surgical treatment