Glaucoma is chronic progressive optic neuropathy in which structural damage( Optic Nerve Head and Retinal Nerve Fiber Layer) proceeds the functional deterioration( Visual Field loss). Hence structural imaging plays an important role in early diagnosis and follow up of a patient of glaucoma

1. ROLE OF IMAGING IN GLAUCOMA
MANAGEMENT
DR GUNJAN CHADHA
OPHTHALMOLOGY
RESIDENT
DR S.N.MEDICAL

2. GLAUCOMA CONTINUUM

3.  In glaucoma structural damage( ONH AND RNFL)
proceeds functional deterioration ( VISUAL FIELD
DEFECTS).
 Clinically detected when 40-45% of retinal ganglion cells
are lost.
 Optic nerve head (ONH) and nerve fibre layer(RNFL)
damage is irreversible, early diagnosis is important.
 Structural evaluations of ONH and RNFL are key for:
early diagnosis.
follow up of glaucoma patient.

4. IMAGING TECHNOLOGIES
1. Scanning laser polarimetry- GDx.
2. Confocal scanning laser ophthalmoscopy-
Heidelberg Retina Tomograph(HRT)
3. Optical coherence tomography

5. SCANNING LASER POLARIMETRY
-Gdx

6.  Objective imaging technique of retinal nerve fiber
layer.
EVOLUTION:
 earlier version: fixed corneal compensator
 New generation: variable corneal compensator
(GDxVCC)
 Latest : enhanced corneal compensation
(GDx ECC)

7. PRINCIPLE
 BIREFRENGENCE.
 Birefrengent
intraocular tissues
are:
Cornea, lens and
retina.
• Retardation value
proportionate to the
thickness of the
RNFL.

8. GDx PRINT OUT
. PATIENT DATA
 FUNDUS IMAGE
 RFNL THICKNESS MAP
 DEVIATION MAP
 TSNIT PLOT
PARAMETERS TABLE
 TSNIT AVGERAGE
 SUPERIOR AVERAGE
 INFERIOR AVERAGE
 TSNIT Std.DEVIATION
 INTER EYE SYMMETRY
 NERVE FIBRE INDEX

10. STRENGTH :
.easy ,rapid and simple to operate.
.can be done in undilated pupil
.good reproducibility.
LIMITATIONS:
.only provide RNFL thickness
.doesn’t measure actual RNFL value, but an inferred
one.
.limited use in moderate or advanced glaucoma.
.affected by anterior and posterior segment pathology.

11. CONFOCAL SCANNING LASER
OPHTHALMOSCOPE - HRT

12.  Provides quantitative analysis of optic disc parameters
and RNFL.
EVOLUTION:
 Developed 30 yrs ago: optical sectioning of biological and
industrial specimen.
 Modified techniques : corneal, retinal ,optic disc imaging.
 Since 1992, has been used for glaucoma diagnosis.
 Currently: HRT II and HRT III.

13. PRINCIPLE
 CONFOCALITY
 670nm diode laser
beam.

14. INTERPRETATION
A. Patient details
B. Topography
C. Horizontal height
profile
D. Vertical height
profile.
E. Reflection image
F. Mean contour height
graph.
G. Stereometric
analysis.
H. Moorfield’s

15. HRT III
 Latest software.
 Operator
independent.
 Automatically fits
ONH and RNFL to a
model optic disc.
 Data analysis by –
GLAUCOMA
PROBABILITY
SCORE

16. STRENGTH:
 Low level illumination
 Undilated pupil
 Sophisticated analysis software for glaucoma
detection and progress.
LIMITATIONS:
 Relies on user defined contour line for reference
plane.
 Data outside normal range are not reliable.
 Stereometric measurements influenced by
changes in IOP.

17. OPTICAL COHERENCE
TOMOGRAPHY

18.  Non contact, Non invasive, micron resolution cross-
sectional study of retina which correlates very well
with the retinal histology.
 Scan 3 distinctive ocular structure:
peripapillary retinal nerve fiber layer.
optic nerve head.
macular region.

19. EVOLUTION:
 OCT first described : HUANG (1991)
 2002 – Time domain OCT became popular
 2006- Spectral Domain OCT.
 Future:
SPEED SWEPT SOURCE OCT
ULTRA HIGH RESOLUTION OCT
POLARIZATION SENSITIVE OCT

20. PRINCIPLE
 LOW COHERENCE INTERFEROMETRY.
 TIME DOMAIN: discriminate retinal layers on
basis of time delay of reflections.
 SPECTRAL DOMAIN: detector break optical
beam of different wavelength.
 analysis done on basis of interference signal
based on wavelength of light.

21. OCT PRINT OUT
 PATIENT DATA
 RETINAL NERVE
FIBER LAYER
ANALYSIS
 OPTIC NERVE HEAD
ANALYSIS
 GANGLION CELL
COMPLEX
ANALYSIS.

22. LIMITATIONS:
• Results less reliable when signal strength is poor.
• RNFL thickness values are affected by age, axial
length, disc size.
• Eye blinking or saccade – alignment is poor –
unreliable RNFL measurement.
• Age related loss confound with identification of
glaucoma.

23. DIAGNOSTIC ACCURACY
GDX HRT OCT
SPECIFICITY
72%to78%
86% > 90%
SENSTIVITY 56%to
92%
84% 67% to 84%

24. 3 D OCT
 the 3D OCT-automatically scans both eyes.
 Produces simultaneously an OCT scan and a
true color fundus image.
 More detailed and quantitative analysis of RNFL.

25. MICRO PERIMETRY
 called Fundus related perimetry.
 type of visual field test.
 create a "retinal sensitivity map" of the quantity of
light perceived in specific part of retina.
 Reliable results in patient unable to fixate on an
object or light source.

26. FUTURE DEVELOPMENTS IN
GLAUCOMA IMAGING
 SWEPT –SOURCE OCT
 LONGER WAVELENGTH OCT
 ADAPTIVE OPTIC OCT
 POLARIZATION SENSITIVE OCT
 OCT ANGIOGRAPHY: ANGIOVUE

27. CONCLUSION
 Early detection has great potential value in
delaying and avoiding progression of the disease
.
 Imaging should not be regarded as replacing the
skilled ophthalmologist’s capacity.
 But they can definitely aid in the complicated
decision-making process

28. THANK YOU !!!