The document discusses optical coherence tomography (OCT), a non-invasive imaging technique used to obtain high-resolution cross-sectional images of the retina and anterior segment. OCT provides advantages like high resolution, ability to quantitatively monitor disease, and potential to detect glaucoma and other conditions earlier by identifying nerve fiber layer thinning. The document also examines OCT's use in interpreting and diagnosing various ophthalmic conditions by visualizing different layers of the retina, optic nerve, and anterior segment structures.

1. ‫الرحی‬‫الرحمن‬‫هللا‬ ‫بسم‬
‫م‬

2. OCT & VF
PRESENTER : PROFESSOR DR ABDUL BASIR SAFI
HEAD OF DEPARTMENT OPHTHALMOLOGY
NANGRAHAR UNIVERSITY TEACHING HOSPITAL

3. introduction
Optical coherence tomography, or OCT is a noncontact, noninvasive
imaging technique used to obtain high resolution 10 micron cross
sectional images of the retina and anterior segment.

5. Color coding in OCT
Highly reflective structures are shown in bright colures (white and
red) .
Those with low reflectivity are represented by dark colors (black and
blue).
Intermediate reflectivity is shown Green

7. Advantages
1. Non-contact , Non-invasive
2. Easy to operate
3. Minimal cooperation needed , short scaning time
4. Resolution ~ 10 μm
5. Pick up earliest signs of disease
6. Quantitatively monitor disease/staging

8. Disadvantages
1. Best for optically transparent tissues
2. Diminished penetration through
3. Retinal/subretinal hemorrhage
4. Requires pupil diameter > 4 mm

9. INTERPRETATION & CLINICAL
APPLICATION
Spectrialis anterior segment module
New dimension to anterior segment imaging
1. Cornea
2. Angle structure
3. Iris details
A study comparing AS-OCT with Goniscopy , AS-OCT detected more
closed angles than gonioscopy

10. OCT- Posterior segment module
1. Glaucoma
2. ONH analysis
3. Retina
4. Choroid

11. Glaucoma
Diagnosis of glaucoma difficult in early stage
Infrequency of episodes of rise in the IOP
Visual field tests not being sensitive enough
Glaucoma diagnosis traditionally performed by examining
optic nerve cupping
width of the neuroretinal rim

12. Limitations of Visual Field Tests
1. Visual field loss late clinical findings
2. Detected only after significant loss of retinal nerve Fibers
3. Difficult to differentiate early glaucoma from normal

13. ROLE OF OCT IN GLAUCOMA-RECENT
ADVANCES
Any decrease in the overall retinal thickness
an indicator of a loss of the ganglion cell layer and RNFL
OCT detect nerve fiber layer thinning before the onset of

14. visual changes
Potential of diagnosing glaucoma early
examining the retinal thickness in the macular area
Nerve fiber layer thickness, as measured by OCT, has been
shown to correspond to visual function

15. Circle Scan
Differences betweeen average thickness in sectors
(along the calculation circle) in each eye
OCT Scan with automatic segmentation of RNFL
TSNIT RNFL thickness compared to normative
database
RNFL Thickness in quadrants
& sectors compared to
normative database

16. Posterior Pole Retinal Thickness Map with
Compressed Color Scale in
8x8 Analysis Grid
OCT scan of macular region
Hemisphere Analysis with
Asymmetry Gray Scale
Mean Thickness

18. Retina
OCT image display,
Highest reflectivity - red
nerve fiber layer
retinal pigment epithelium and
choriocapillaris
Minimal reflectivity appear blue or black
photoreceptor layer
choroid
vitreous fluid or blood

19. consist of two layer :
1. Retina pigment epithelium
2. Sensory retina or neuro retina
Sub retinal space ( sub retinal fluid )

20. LAYERS OF RETINA
1. Layer of pigment epithelium
2. layer of rods and cones
3. External limiting membrane
4. outer nuclear layer
5. outer plexiform layer
6. inner nuclear layer
7. inner plexiform layer
8. layer of ganglion cells
9. Nerve fiber layer
10. Internal limiting membrane

22. Ganglion cells
(Optic nerve)
3 - Transmitter cells

25. Drusens of the retina

26. Disciform scar

27. Macular hole

28. Limitations of OCT
 Penetration depth of OCT is limited by media opacities , Dense
cataracts , Vitreous hemorrhage , Lead to errors in RNFL and retinal
layer segmentation
 Each scan much be taken in range and in focus , must be examined
for blinks and motion artifacts
 Axial motion is corrected with computer software ,transverse
motion cannot be corrected

29. Visual Field

30. Visual Field
Is 3D area of a subject’s surrounding that can be seen at a time
around a point of fixiation .
The normal extent of vision
 60 degree superiorly
 60 degree nasally
 75 degree inferiorly
 100 degree temporally

31. Visual field divided into central and peripheral field
1. Central : area feom fixiation to a circle 30 degree
physiologic blind spot on temporal side
1. peripheral : rest of area

32. Scotoma
Area of depressed or lost vision surrounded by area of normal vision
• positive and negative
• absolute and relative

33. Common causes of visual field defect
Central field loss
1. Optic neuropathy
2. Macular degeneration
3. Macular hole
4. Cone dystrophies

34. Peripheral field loss
1. Glaucoma
2. Retinal detachment
3. Retinitis pigmintosa
4. chorioretinitis

35. Advantages
1. Localizing the site of the lesion
2. Detecting scotomas
3. Assessment of visual function

36. Interpretations
Scotoma in one eye – lesion in either
1. Optic nerve
2. Retina

39. Optic nerve lesion
 central scotoma
 field defect more marked to red
 VF normal in early papilloedema

40. Glaucoma
Damage to nerve fiber in optic disc
Arcuate fibers are more prone to damage
Macular fibers most resistant

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