ASTIGAMATISM presentation dhir hospital.pptx

1. ASTIGMATISM
Is the D Line Really Straight ???
PRESENTER - Dr Nikhil Agrawal
MODERATOR – Dr Parikshit Dhir
DHIR HOSPITAL & POST GRADUATE INSTITUTE OF OPHTHALMOLOGY

2. ASTIGMATISM
ASTIGMATIC VISION NORMAL VISION

3. ASTIGMATISM
Parallel beam of light rays after refraction are not
focused to form a point image .
VERTICAL MERIDIAN

4. ASTIGMATISM
Same curvature on all meridians .
There is a flat and a steep meridian .
Principal meridians are the meridians of the greatest and the
smallest refracting powers .

5. STURM’S CONOID

6. TYPES OF ASTIGMATISM
ETIOLOGY
CORNEAL LENTICULAR RETINAL
Curvatural Positional Index

7. TYPES OF ASTIGMATISM
ASTIGMATISM
REGULAR IRREGULAR

8. TYPES OF ASTIGMATISM
SIMPLE MYOPIC
-2*180
SIMPLE HYPERMETROPIC
+2*180
COMPOUND MYOPIC
-2/-4*180
COMPOUND
HYPERMETROPIC
+1/+2*180
MIXED
+3/-7*90
Based on relation of focal points to the retina

9. TYPES OF ASTIGMATISM
Based on relation between
principal meridian .
• With the rule
• Against the rule

11. TYPES OF ASTIGMATISM
• Oblique Astigmatism :Principal meridian are not
horizontal and vertical , though are at right
angles to one another .
• Bi-Oblique Astigmatism : Principal meridian are
not at right angle to each other.
Based on the orientation of the meridians

12. ASTIGMATISM
Clinical Features:
1. Blurring of Vision
2. Asthenopic Symptoms
3. Tilting of the Head : To reduce
image distortion .
4. Squinting i.e. half closure of the
lids : to cut out rays in one
meridian .
5. Letter confusion

13. ASTIGMATISM
Investigations :
1. Visual Acuity
2. Retinoscopy
3. Keratometry and Corneal Topography
4. Astigmatic fan test
5. Jackson Cross Cylinder Test : To find out power
and axis of cylindrical lens .

14. ASTIGMATISM
Retinoscopy
Jackson Cross Cylinder Test Keratometry

15. ASTIGMATISM
Regular Astigmatism

16. ASTIGMATISM
Treatment :
Optical Treatment : High degree of
astigmatism require toric contact
lens.
• Small astigmatism :0.5D or less
should be treated if producing
asthenopic symptoms .
• High astigmatism always needs
to be treated . A adult patient
may not accept full correction
for the first time.

17. ASTIGMATISM
Surgical Correction:
• Astigmatic Keratotomy: Transverse or arcuate cuts at
mid periphery perpendicular to the steepest meridian.
• Limbal Relaxing Incision
• Photoastigmatic Refractive Keratotomy: Cylindrical
ablation pattern to remove tissue from a particular
meridian .
• Astigmatic LASIK

18. ASTIGMATISM
Irregular Astigmatism : Irregular change of refractory
power in different meridian .
1. Corneal Irregular Astigmatism : Corneal scars ,
Keratoconus
2. Lenticular Irregular Astigmatism : During maturation of
cataract.
3. Retinal Irregular Astigmatism :Scarring or tumours of
coroid and retina pushing the macular area .

19. ASTIGMATISM
Irregular Astigmatism - Keratoconus

20. ASTIGMATISM
Treatment
1. Optical : Contact lens
2. Orthokeratology
3. Phototherapeutic keratectomy
4. Surgical : Penetrating Keratoplasty

21. REFERENCE
• Optometry , Journal of American optometric
association
• Theory and practice of Optics and Refraction , AK
Khurana
• https://eyesoneyecare.com/resources/optometrist
s-treating-astigmatism-2020/
• https://www.aao.org/image/types-of-astigmatism