This document discusses the application of anterior segment optical coherence tomography (AS-OCT) in diagnosing various ocular conditions. It provides an overview of AS-OCT imaging principles and compares it to ultrasound biomicroscopy. The document then examines the use of AS-OCT in diagnosing and monitoring conditions of the cornea, conjunctiva, and anterior chamber angle/glaucoma. Examples of pathologies that can be identified include corneal scars, Fuchs' dystrophy, graft rejection, angle closure, and bleb assessment after glaucoma surgery.

1. Application of AS-OCT in
diagnosing Ocular Conditions
Swetha Ravichandran

2. “
2
▸ C
• Introduction
• Imaging Modes
• Advantage over UBM
• Corneal diagnostics
• Conjunctival diagnostics
• Glaucoma diagnostics
CONTENTS

3. Introduction
▸ Optical coherence tomography (OCT) which was first developed by Huang et al. is
a non-contact imaging technology that produces detailed cross-sectional images
(tomography) using low-coherence interferometer in the biological tissues.
▸ Anterior segment OCT in 1994
▸ It is used for imaging the
▪ Cornea
▪ Conjunctiva
▪ Sclera
▪ Anterior chamber
▪ Adjacent anterior segment structures
3

4. “ Low-Coherence
Interferometry
Principle
Picture courtesy: https://www.routledgehandbooks.com/doi/10.1201/9781315373027-4/

5. “
5
Low-Coherence
Interferometry
Principle
Picture courtesy: https://www.routledgehandbooks.com/doi/10.1201/9781315373027-4/

6. “ Low-Coherence
Interferometry
Principle
Picture courtesy: https://www.leica-microsystems.com/science-lab/what-is-oct-and-how-can-it-help-ophthalmologists-acquire-high-
resolution-information-on-ocular-tissue/; https://www.slideshare.net/sealdioftal/oct-presentation

7. “
7
Low-Coherence
Interferometry
Principle
Picture courtesy: https://www.leica-microsystems.com/science-lab/what-is-oct-and-how-can-it-help-ophthalmologists-acquire-high-
resolution-information-on-ocular-tissue/; https://www.slideshare.net/sealdioftal/oct-presentation

8. TD-OCT and SD-OCT
▸ Reference mirror – Varied
▸ Compares time delay
▸ Visante OCT
▸ Hiedelberg Slit Lamp OCT
▸ Wavelength – 1310nm
▸ Scan width – 16mm
▸ Scan depth – 6mm
▸ Resolution – 18 μm in the axial
plane and 60 μm in the lateral
plane
▸ Reference mirror – Stationary
▸ Spectrometer – Employed
▸ Spectralis – OCT
▸ Cirrus OCT
▸ Wavelength – 830nm
▸ Scan width – 3-6mm
▸ Scan depth – Less than TD-OCT
▸ Resolution – 4-7 μm in the axial
plane
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9. Axial and Lateral Resolution
9
Axial
Resolution
Lateral Resolution

10. “ Visante
OCT
Picture courtesy: https://www.insighteye2020.com/product/zeiss-visante-oct/10

11. SS-OCT and UHR-OCT
▸ Wavelength – 1310nm
▸ Casia SS-1000 OCT
▸ Scan width – 16mm
▸ Axial resolution – 10µm
▸ Bioptigen Envisu
▸ SOCT Copernicus HR
▸ Scan width – 5-12mm
▸ Axial resolution – 1-4µm
▸ Light source with a broad bandwidth of
more than 100µm
▸ A Spectrometer that can detect the
fringes reflected from both reference and
sample arms
11

12. “
12
Casia
OCT
Picture courtesy: https://www.ophthalmicmart.com/product/tomey-casia-2/

13. Imaging Modes
▸ High-Resolution Cornea Single – Single image will be obtained at the desired
angle.
▸ High-Resolution Cornea Quad – 4 cross-sectional images are taken at 0 to 180,
45 to 225, 90 to 270, and 135 to 315 degrees, respectively
▸ Pachymetry
▸ Anterior Segment Single
▸ Anterior Segment Double – Images at pre-set angles of 20 to 200 and 160 to 340
▸ Anterior Segment Quad
13

14. Normal AS-OCT Image
14
Picture courtesy: https://www.opsweb.org/page/ASOCT; Su-Ho Lim et al.

15. 15
Normal AS-OCT Image
Picture courtesy: https://www.opsweb.org/page/ASOCT; Su-Ho Lim et al.

16. Differences between UBM and OCT
UBM
▸ Advantage: Precise
visualization of the ciliary
body and retroiridial
structures.
▸ Possible corneal
compression
▸ Lying supine position
OCT
▸ Easy and rapid
▸ No contact
▸ Repeatable
▸ Better resolution
▸ Dynamic
▸ Seated position
16

17. Corneal Diagnostics
▸ Corneal scar
▸ Keratopathy
▸ Pre and post Lamellar transplantation procedures
▸ Keratoconus – Acute Hydrops, INTACS
▸ Pre-operative measurement for refractive surgeries
▸ Boston type-1 Keratoprostheses (K-Pro)
▸ Pathological conditions - Ocular surface squamous neoplasia and
Salzmann nodular degeneration
17

18. Scar
18

19. Poll 1
19
What is the type of
keratoplasty preferred in
case of endothelial
dystrophies?
Picture courtesy: https://aao.org

20. Fuch’s Dystrophy
▸ Guttata
▸ Intrastromal fluid
▸ Thickened Descemet’s membrane
▸ Bullae
20 Picture courtesy: Kaluzny et al.

21. Corneal Grafts
▸ Penetrating Keratoplasty
▸ Deep anterior lamellar keratoplasty
▸ Descemet’s stripping endothelial
keratoplasty
▸ Descemet membrane endothelial
keratoplasty
21
Picture courtesy:
https://www.clspectrum.com/issues/2014/august-2014/contact-
lenses-after-keratoplasty

22. Deep Anterior Lamellar Keratoplasty
22

23. Descemet Stripping Endothelial Keratoplasty
23

24. Descemet Membrane Detachment
24

25. Graft Host Rejection
25
Picture courtesy: https://www.optometricmanagement.com

26. DM Folds and Corneal Bullae
26
Picture Courtesy: https://www.msdmanuals.com/professional/eye-disorders/corneal-disorders/bullous-keratopathy
https://www.ijo.in/viewimage.asp?img=IndianJOphthalmol_2009_57_3_232_49402_u3.jpg

27. DM Folds and Corneal Bullae
27
Picture Courtesy: https://www.msdmanuals.com/professional/eye-disorders/corneal-disorders/bullous-keratopathy
https://www.ijo.in/viewimage.asp?img=IndianJOphthalmol_2009_57_3_232_49402_u3.jpg

28. Interstitial space
28

29. Poll 2
29
What do you see in this
image?
Picture Courtesy: https://www.nvisioncenters.com/keratoconus/intacs/

30. Intrastromal Corneal Ring Segments
30 Picture Courtesy: https://www.allaboutvision.com/conditions/inserts.htm

31. INTACS
31

32. Acute Corneal Hydrops
32
Picture Courtesy: http://www.djo.harvard.edu/print.php?url=/physicians/kr/451&print=1

33. Acute Corneal Hydrops
33
Picture Courtesy: http://www.djo.harvard.edu/print.php?url=/physicians/kr/451&print=1

34. Ulcer
34
Picture Courtesy: https://www.msdmanuals.com/home/eye-disorders/corneal-
disorders/corneal-ulcer

35. Ulcer
35

36. LASIK Flap
36

37. Boston Type I Keratoprosthesis
37 Picture Courtesy: Qian et al; https://webeye.ophth.uiowa.edu/eyeforum/tutorials/cornea-transplant-intro/6-kprosth.htm

38. Poll 3
38
A 22-year old female prefers
to have refractive surgery
with -18.50DS in her right
eye. What would be your
suggestion for the type of
surgery?
Picture Courtesy: https://groups.hyvor.com/EyeHealthBlog/322/myopia-nearsightedness

39. Implantable Collamer lens
39

40. Implantable Collamer lens
40

41. Phakic IOL
41 Picture Courtesy: http://www.askdrash.com/refractive/verisyse-phakic-iol/visante-verisyse-for-professionals/

42. Phakic IOL
42 Picture Courtesy: http://www.askdrash.com/refractive/verisyse-phakic-iol/visante-verisyse-for-professionals/

43. Adherent Leukoma
43

44. Ocular Surface Squamous Neoplasia
44
Picture Courtesy: Nanji et al

45. Salzmann Nodular Degeneration
45
Picture Courtesy: Nanji et al

46. Conjunctiva Diagnostics
▸ Pinguecula or Pterygium
▸ Melanoma or a nevi
▸ Conjunctival lymphoma
46

47. Pterygium
47
Picture Courtesy: Nanji et al

48. Melanoma
48
Shadowing below
the lesion
Picture Courtesy: Nanji et al

49. Conjunctival Lymphoma
49
Picture Courtesy: Nanji et al

50. Poll 4
50
What is the method of
treatment for an severely
diseased cornea with
chemical injury?
It is bilateral
Picture Courtesy: https://www.pinterest.com/pin/542543086337849476/

51. Modified Osteo-Odonto-Keratoprosthesis (OOKP)
51

52. Glaucoma Diagnostics
▸ Important parameters of AC angle such as angle opening distance
and trabecular iris angle
▸ Observation of anterior chamber angle after glaucoma surgery and
bleb assessment
▸ Aqueous shunts
52

53. Picture Courtesy: Lin et al
AS-OCT by Swetha Ravichandran

54. 54
How is the angle and anterior chamber? 5

55. Open and Closed Angles
Picture Courtesy: Kim et al

56. Open Angle – Different AC Depth
▸ Deep Anterior Chamber ▸ Shallow Anterior Chamber
56

57. Closed Angle
▸ Iridotrabecular apposition
▸ Peripheral anterior synechiae
57

58. Pupillary Block – Narrow Angle
▸ Narrow iridocorneal angle related to pupillary block, with convexity and
anterior displacement of the iris, inducing iridocorneal angle closure with
iridotrabecular apposition.
58

59. Plateau Iris Configuration
▸ Closed iridocorneal angle related to a plateau iris mechanism associated
with a pupillary block mechanism on a large lens
59

60. Peripheral Iridotomy
60

61. Bleb
61

62. Poll 6
62
What is the treatment
modality for patients not
responding to maximal
medical therapy, with
previous failed filtering
surgery in case of glaucoma?
Picture Courtesy: https://www.researchgate.net/figure/Ahmed-
glaucoma-valve-tube-exposure-due-to-conjunctival-
erosion_fig2_313850161

63. Ahmed Glaucoma Valve
63

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Ahmed Glaucoma Valve
Picture Courtesy: https://www.semanticscholar.org/paper/Coupling-of-HRT-II-and-AS-OCT-to-evaluate-corneal-
Mendrinos-Dosso/ac95d75c3de7aef883906b8c9bd2188a1078f768/figure/0

65. References
▸ Nanji, A. A., Sayyad, F. E., Galor, A., Dubovy, S., & Karp, C. L. (2015). High-resolution optical coherence tomography as an adjunctive
tool in the diagnosis of corneal and conjunctival pathology. The ocular surface, 13(3), 226-235.
▸ Lim, L. S., Aung, H. T., Aung, T., & Tan, D. T. (2008). Corneal imaging with anterior segment optical coherence tomography for lamellar
keratoplasty procedures. American journal of ophthalmology, 145(1), 81-90.
▸ Han, S. B., Liu, Y. C., Noriega, K. M., & Mehta, J. S. (2016). Applications of anterior segment optical coherence tomographyin cornea
and ocular surface diseases. Journal of Ophthalmology, 2016.
▸ Filipe, H. P., Carvalho, M., da Luz Freitas, M., & Corrêa, Z. M. (2016). Ultrasound biomicroscopy and anterior segment optical
coherence tomography in the diagnosis and management of glaucoma. Vision Pan-America, The Pan-American Journal of
Ophthalmology, 15(2), 37-42.
▸ Lim, S. H. (2015). Clinical applications of anterior segment optical coherence tomography. Journal of ophthalmology, 2015.
▸ Lin, J., Wang, Z., Chung, C., Xu, J., Dai, M., & Huang, J. (2017). Dynamic changes of anterior segment in patients with different stages of
primary angle-closure in both eyes and normal subjects. PloS one, 12(5), e0177769.
▸ Kaluzny, B. J., Szkulmowska, A., Szkulmowski, M., Bajraszewski, T., Kowalczyk, A., & Wojtkowski, M. (2009). Fuchs’ endothelial
dystrophy in 830-nm spectral domain optical coherence tomography. Ophthalmic Surgery, Lasers and Imaging Retina, 40(2), 198-200.
▸ Kang, J. J., Allemann, N., Vajaranant, T., de la Cruz, J., & Cortina, M. S. (2013). Anterior segment optical coherence tomography for the
quantitative evaluation of the anterior segment following Boston keratoprosthesis. PloS one, 8(8), e70673.
▸ OCT and Glaucoma Textbook by Jean Paul Renard; Antoinne Labbѐ and Christopher Baudouin65

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Acknowledgements:
• Elite School of Optometry, Sankara Nethralaya
• Online Optom Learning Series
• Mr. Fakhruddin S. Barodawala
• SlidesCarnival.com and PresentationGo.com

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THANK YOU
For any other queries:
swetha.chandran304@gmail.com