This document covers astigmatism, a type of refractive error characterized by unequal light refraction in different meridians, leading to visual distortion. It details the types, causes, symptoms, diagnostics, and treatment options for astigmatism, including optical and surgical methods. Various investigations and their applications, along with the management strategies for post-keratoplasty astigmatism, are also discussed.

1. ASTIGMATISM
MAJ ABHISHEK SINGLA
RESIDENT OPHTHALMOLOGY
CHAF BANGALORE

2. BIBLIOGRAPHY
1. Parson’s Diseases of the Eye 23rd
edition
2. Duke-Elder’s Practice of Refraction 10th
edition
3. A.K Khurana Theory & Practice of Optics & Refraction 5th
edition
4. American Academy of Ophthalmology Vol 3 – Clinical Optics and
Vision Rehabilitation

3. Sl No. Topic
I. WHAT IS ASTIGMATISM ?
II. HISTORY
III. AETIOLOGY
IV. TYPES OF ASTIGMATISM
V. STRUM CONOID
VI. INVESTIGATIONS
VII. SYMPTOMS
VIII. TREATMENT OF ASTIGMATISM
INDEX

4. I. WHAT IS ASTIGMATISM ?
 Type of refractive error with
unequal refraction of light in
different meridian
 A point focus of light cannot
be formed upon the retina
instead a focal line is
formed.

5. III. AETIOLOGY
 Curvatural astigmatism of cornea –
 Curvatural astigmatism occurs more frequently in
cornea
 Usually congenital
 Physiological – direct astigmatism with up to
0.25D due to constant pressure of upper lid

6. III. AETIOLOGY
 Acquired astigmatism due
to corneal pathologies –
 Keratoconus
 Inflammation
 Ulceration
 Trauma
 Acquired astigmatism due
to external pressure -
 Chalazion
 Lid neoplasm
 Finger pressure on eye
 Contraction of lids
 Extra ocular muscle
action

7. III. AETIOLOGY
 Lenticular Astigmatism
 Curvatural: Marked astigmatism in
Lenticonus
 Positional: Decentering of IOL,
traumatic subluxation
 Index astigmatism: due to variable
refractive indices like in nuclear sclerosis
and cataract

8. STURM CONOID-
 Compound hypermetropic astigmatism
 Simple hypermetropic astigmatism
 Mixed astigmatism – distant vision is good
 Simple myopic astigmatism
 Compound myopic astigmatism

9. IV. TYPES OF ASTIGMATISM
1.Regular astigmatism :
Depending upon the axis and angle between the two meridian
can be classified as following types:
(a) With the rule : the two principle meridia are placed at right
angles to each other but the vertical meridian is curved more
than the horizontal ( Incidence – 38 %)

10. IV. TYPES OF
ASTIGMATISM
(b) Against the rule : in which the horizontal meridian is
more curved than the vertical meridian ( Incidence – 30%)
(c) Oblique Astigmatism : two principle meridia are not
horizontal and vertical but at right angles to each other
(32%)
(d) Bi-oblique Astigmatism- the two principle meridia are
not at right angles to each other

11. IV. TYPES OF
ASTIGMATISM
1. Regular Astigmatism
Depending upon the position of
two focal lines in relation to
retina , it can be further
classified into :
(a) Simple Astigmatism – where
one meridian falls on retina and
another either in front ( simple
myopic) or behind (simple
hypermetropic)

12. IV. TYPES OF
ASTIGMATISM
(b) Compound Astigmatism – the
rays of light in both the meridian
either focus in front (compound
myopic) or behind the retina
(compound hypermetropic)
(c) Mixed Astigmatism – the light
rays in one meridian are focused
in front and in other meridian
behind the retina

13. IV. TYPES OF ASTIGMATISM
2. Irregular astigmatism – irregular change of refractive
power in different meridian.
Corneal – Corneal ulceration, scars or
keratoconus
Lenticular – During maturation of cataract

14. CYLINDRICAL LENS
 Cut off from a cylinder
 Axis of a cylindrical lens - AB

15. CYLINDRICAL LENS
 Plano-convex vs plano-
concave lens
 Focal line is formed
 Refract rays of light in one
plane & leaves the rays in
the plane perpendicular to
this unaltered

16. IDENTIFICATION OF
CYLINDRICAL LENS
1. Lens Shape: Cylindrical lenses are not
spherical; they have a curvature in one
direction only (like a section of a cylinder). This
means that when you look at the lens from the
side, it may appear flat in one direction and
curved in another
2. Prescription Markings: The prescription for
cylindrical lenses usually includes a notation
for the cylinder power (indicated by "Cyl" or
"CYL") and the axis (measured in degrees from
0° to 180°)
3. Visual Distortion: When wearing cylindrical
glasses, individuals may notice that objects
appear distorted or blurred in certain

17. POWER CROSS
The rule is that the power meridian of a cylinder is
perpendicular to the axis of cylinder.

18. SPHERICAL EQUIVALENT
 It is the average power of spherocylinder(toric
lens) – Sum of sphere and half of cylinder
power
 Used to calculate the circle of least diffusion
 Used in fitting of contact lens

19. VI. INVESTIGATIONS
 Retinoscopy
 Keratometry- A Keratometer / Ophthalmometer is
a diagnostic instrument for measuring curvature
of anterior surface of the cornea
 Corneal topography

20. VI. INVESTIGATIONS
 Jackson Cross Cylinder
Applications:
• To discover Astigmatism
present or not
• To refine axis of cylinder
• To refine power of cylinder

22. VI. INVESTIGATIONS
 Astigmatism Fan Test

24. SYMPTOMS
 Appreciable degree of astigmatism causes
considerable diminution of vision
 Patient attempts to focus on one or the other
focal line
 Peculiarities of vision –
 Circles appear as oval
 Point of light tailed off
 Line appears as succession of strokes fused
into blurred image

25. SYMPTOMS

26. SYMPTOMS
 If the axis is oblique, head is tilted to one side to
reduce distortion
 Half close the lid to make stenopaeic slit, cutting out
rays in one meridian
 Asthenopic Symptoms like tiredness of eyes and
headaches
Most severe in hypermetropic astigmatism (due to more
accommodative effort)

27. OPTICAL TREATMENT
 Smaller astigmatic errors upto 0.5D with no
deterioration of visual acuity and asthenopia
Do not require optical correction
 If symptomatic – full cylindrical correction

28. OPTICAL TREATMENT
 Contact lens –
• Rigid spherical contact lens : lower to moderate degrees of
astigmatism ( 2 to 3D of astigmatism)
• Toric lens : high degrees of astigmatism

29. SURGICAL CORRECTION OF
ASTIGMATISM
 Incisional refractive procedures –
(a) Astigmatic Keratotomy

30.  Astigmatic keratotomy
 Transverse and arcuate incision in mid-
periphery (around 5 to 7 mm from pupil
centre ) perpendicular to the steepest
corneal meridian
 Correct astigmatism up to 4-6D
 Deeper, longer & more centrally located
incision give greater effect
 Risk of irregular astigmatism , micro
perforations , overcorrection

31. (b) Limbal relaxing incision
 To correct -1.0 to -2.0D astigmatism
 Incision made at limbus
 Advantages vs astigmatic keratectomy
Less glare
Incision heals faster
Optical quality of cornea preserved
Easier to incorporate with cataract
extraction

32. SURGICAL CORRECTION OF
ASTIGMATISM
Laser ablation corneal refractive
procedures –
 Photoastigmatic refractive
keratectomy
 Astigmatic LASIK – up to 0.5-
10.0D
 Astigmatic C-LASIK ( best
technique)

33. MANAGEMENT OF POST
KERATOPLASTY ASTIGMATISM
 Suture removal ( should be tried first of all other
procedures)
• In steep meridians
• Interrupted sutures after 03 months
• Continuous sutures after 01 year
 Relaxing incision
• Along steeper meridian in donor cornea
• Relaxing incision with compression sutures

35. MANAGEMENT OF POST
KERATOPLASTY ASTIGMATISM
 Astigmatic LASIK
 Wavefront guided
 Correct up to 6-8D

36. MANAGEMENT OF POST
KERATOPLASTY ASTIGMATISM
 Corneal wedge resection

37. MANAGEMENT OF POST
KERATOPLASTY ASTIGMATISM
 Ruiz procedure

38. THANK YOU