Optical coherence tomography (OCT) is a non-invasive imaging technique that uses light waves to capture high-resolution cross-sectional images of the retina, proving vital for diagnosing and guiding treatment for various eye conditions, particularly glaucoma and retinal diseases like age-related macular degeneration. The technology involves two main types: time-domain OCT and spectral-domain OCT, with the latter offering superior sensitivity and speed. OCT provides critical insights into retinal anatomy and pathology, allowing for effective monitoring and management of eye diseases.

2. Ocular Coherence Tomography

3. Dr Khushmina Khan

4. Contents To Discuss
• OCT
• Eye Conditions
• Findings
• Conclusion

5. Introduction Of OCT
• Optical coherence tomography (OCT) is an imaging
technique which works similar to ultrasound.
• Optical coherence tomography (OCT) is a non-
invasive imaging test.
• OCT uses light waves to take cross-section pictures
(tomograms) of your retina.
• Infrared Ray of 830nm is used for Retina and
1310nm For AS-OCT.

6. Normal Retinal Scan

7. • It shows not only the surface but also the depth
of the structures.
• We can see each of the retina’s distinctive layers.
• This allows to map and measure the thickness.
• OCT measurements help with diagnosis.
• Also provide treatment guidance
for Glaucoma and diseases of the Retina.
• These retinal diseases include age-related
macular degeneration (AMD) and diabetic eye
disease.
Cont…

8. 3D View of Retinal Layer

9. Technology
• There are two main categories of OCT instrumentation:
• Time-Domain OCT (TDOCT) and Spectral-Domain OCT
(SDOCT).
• Time-Domain OCT Gives 400 A-scans/sec with a
resolution of 10 μm.
• Spectral-Domain OCT is rapidly replaced the Time-
Domain technology because it offers significant
advantages in sensitivity and imaging speed.
• Spectral Domain Gives 1-15μm resolution and up to
52,000 A-scans/sec.

10. Principle Of OCT
• Oct is Based on Michelson Interferometry.
• Low Coherence Infra red light Travels through
beam splitter and directed towards Eye and
Reference mirror.
• Distance b/w reference mirror and beam splitter
continuously varies.
• When the distance becomes equal b/w
LS and retinal tissue = LS and reference mirror
• The reflected light and reference mirror interacts
and produce and interference pattern.

12. Reflectivity of Images
• The images are presented in a color (or gray) scale based
on the different reflectivity of the tissue structures.
• More concisely, tissues that are highly reflective are
shown in red and white.
• While Low reflective tissues are shown in blue and
black.
• Tissues that are moderately reflective are shown as
green or yellow.
• Therefore, the image is not real but represents the true
dimensions of the measured structures.

13. Hyper reflectivity
pattern
Nerve fiber layer,
Inner Limiting Membrane
RPE and choriocapillaris (red)
PED, Drusen, ARMD & CNVM Lesions.
Normal
reflectivity
pattern
Inner and outer plexiform layer
(yellow-green), inner and outer
nuclear layers (blue).
Hypo reflectivity
pattern
Photoreceptor layer
Fluid, Retinal Edema & Sub-retinal
Fluid.
Reflectivity Patterns of the Retinal
Structures and Pathology

14. Indications
OCT is Mainly Indicated For
• Retinal Layer e.g. Edema, Atrophy, Traction
• Assess Macula
• Analysis of Optic Nerve thickness & RFNL
• Glaucoma
-Macular Thickness
-RNFL
-Optic Nerve Head
• Anterior Segment
-Cornea
-Ant. Chamber
-Iris
-Lens
-Refractive surgery and Glaucoma
-Angle Evaluation

15. Cont…
• OCT provides important information
• Location and nature of the changes
• Normal anatomy of retina and pathology
• Thickness of the retina
• Epiretinal membrane
• Macular holes
• Cystoid macular edema

16. Cont…
• Subretinal neovascular membranes
• Exudative macular degeneration
• Central serous chorioretinopathy
• Diabetic macular edema
• Serous retinal detachments
• Vitreomacular traction
• Management of age-related
macular degeneration (AMD) and
macular edema

17. Epiretinal Membrane or
Macular Pucker
• Extra layer of tissue forms
on the retinal surface.
• Contracts to distort the
central retina.
• We call it a macular
pucker.
• A macular pucker is
sometimes called an
Epiretinal membrane, a
wrinkle, preretinal fibrosis
or Pseudomacular hole.
• Macular puckers are
present in about 10% of
people over the age of 50.

18. Cystoid Macular Edema
• Cystoid Macular Edema
CME refers to fluid accumulation
and swelling inside the retina in
the macular area.
• Some of the causes of Cystoid
Macular Edema CME are,
• Vitreo-macular traction or
epiretinal membrane traction
• Age-related macular
degeneration
• Ocular diseases or inflammatory
conditions that compromise the
RPE, could lead to CME due to a
breakdown of the blood barrier.

19. Macular Hole
• A macular hole is an
anatomical
Discontinuation of the
neurosensory retina at
the centre of the
macula.
• They are often a result
of pathological
vitreoretinal traction at
the fovea.
• High myopia and blunt
ocular trauma have
also been implicated in
the formation of
macular holes.

20. Central Serous Retinopathy
• Central serous
chorioretinopathy
(CSCR) (also
known as central
serous
retinopathy) is a
relatively common
and often self-
limiting
chorioretinopathy
Characterized by
fluid accumulation
underneath the
retina or RPE.

21. Subretinal Fluid
• Subretinal fluid (SRF) from the choroid enters the Subretinal space
through damaged pigment epithelium Caused by inflammation or
tumour.

22. Age-related Macular
Degeneration
• Age-related macular
degeneration (AMD)
affects the choroid,
RPE and outer retinal
layers.
• Age-related macular
degeneration (AMD),
is defined as the
presence of areas of
hyperpigmentation or
hypopigmentation of
the RPE and/or
confluent or soft
drusen.

23. Vitreomacular Traction
• Vitreomacular traction occurs as the result
of Vitreomacular adhesions in a detaching posterior vitreous.

24. Glaucoma Assessment
• Measurement of the optic nerve, macula and RNFL,
which when used appropriately can aid glaucoma
diagnosis and Treatment.
• A global RNFL thickness classification of “Outside
Normal Limits” is compared to Patient’s data.

25. Macular Thickness
Normative Data

26. Macular Thickness
• The 3D macula protocol was used for macular thickness measurements.
• It reconstructs a false-color topographic image displayed with numeric
averages of thickness Measurement.
• According to ETDRS map, macula is divided into 9 regions with 3
concentric rings measuring 1 mm (innermost ring), 3 mm (inner ring) and
6 mm in diameter (outer ring) centered on the fovea.
• The innermost 1 mm ring is the fovea while the 3 mm inner ring and 6 mm
outer ring are further divided into four equal regions.

27. Retinal Nerve Fiber Layer
• Circular Analysis
around ONH.
• 3 Scans are acquired
and data is averaged
and compared with
normative data base
of aged matched
subjects.
• Scans begins From
temporal side.

28. Optic Nerve Head
• Optic nerve sans are
composed of 6 linear
in a spoke pattern.
• Separated by 30
degree intervals
centered on Optic
nerve head.

29. Anterior Segment
• Anterior segment OCT (AS-OCT) generates in vivo, cross-
sectional scans of the tissue to assist in analyzing the
cornea, anterior chamber angle, iris and lens.
• Exceptional quality images captured, Provides Information
• Angle-width
• Iris Thickness
• Ant-chamber depth
• Corneal Degeneration
• Ulcers
• Scars

30. AS-OCT
• Anterior segment OCT scan of the eye: A, cornea; B, anterior
chamber; C, anterior part of the lens; D, iris; E, ciliary body.

31. Limitation Of OCT
• OCT utilizes light waves (unlike ultrasound which uses
sound waves) and following conditions Can interfere with
optimal imaging.
• Media Opacities
• Vitreous Hemorrhage
• Dense Cataract
• Corneal Opacities
• Patient Cooperation (Motion related artifacts).

32. Conclusion
• OCT has emerged as a useful imaging modality by providing new high-
resolution three-dimensional anatomic information about various features
of macular pathology.
• OCT allows us to investigate and follow the prognosis of clinical pathologies.
• Detect early damage
• Predict the visual outcome.
• Diagnosis and follow-up of optic nerve diseases.
• Objective measurement of nerve swelling or nerve atrophy.
• Monitoring the treatment of macular and optic nerve disease.
• To detect changes in the optic nerve head, retinal nerve fiber layer, and
currently the ganglion cell layer.
• Diagnostic aid to diagnose and monitor the progression of this sight
threatening disease called glaucoma.

33. References
• American Academy Of Ophthalmology
• Diagnostic Procedure in Ophthalmology
• Clinical Ophthalmology: A Systematic Approach Book by
Jack J. Kanski
• Google
• Eyewiki
• Wikipedia