various imaging technique in glaucoma

1. Dr NIKITA
JAISWAL
IMAGING IN
GLAUCOMA

2.  INTRODUCTION
 DIFFERENT MODALITIES
 PRINCIPLES
GLOSSARY

3.  Glaucoma is an optic neuropathy with characteristic optic
nerve appearance and visual field loss for which elevated
intraocular pressure is one of the main risk factors.
 This characteristic optic nerve appearance results from
structural glaucomatous changes which usually precede
functional deterioration (visual field loss).
 KEY TO DIAGNOSIS: OPTIC NERVE HEAD
RETINA
INTRODUCTION:
STRUCTURAL
EVALUATION

4.  ONH IMAGING
 HRT
 GDX
 OCT
 RTA
IMAGING

5. ONHRNFLMACULA

6. IMAGES:

7. OPTIONS:
PRINCIPLE COMMERCIAL APPLICATION
CONFOCAL SCANNING LASER
OPHTHALMOSCOPY{CSLO}
HEIDELBERG RETINAL
TOMOGRAPHY{HRT}
SCANNING LASER POLARIMETRY{SLO} GDX
INTERFERENCE OPTICAL COHERENCE TOMOGRAPHY

8. STRUCTURES TO BE
SCANNED
MODALITIES
ONH HRT + OCT
RNFL GDX + OCT
MACULA OCT
CHOICE OF SCANS

9. CONFOCAL SCANNING LASER
OPHTHALMOSCOPY
HEIDELBERG
ENGINEERING,HEIDELBERG GERMANY
USE THIS PRINCIPLE FOR THE STUDY.
GENERATION:HRT
HRT ||
HRT |||
THIS TECHNIQUE FOR PRECISE
MICROSCOPIC IMAGING WAS PATENTED
BY PROF MARVIN MINSKEY IN
1955.

10.  BASED ON THE PRINCIPLE OF SPOT ILLUMINATION &
SPOT DETECTION.
 A SPOT OF LASER LIGHT IS PROJECTED ONTO THE TISSUE &
THE REFLECTED LIGHT IS DETECTED BY A SENSOR.
DEVICE FUNDAMENTALS
IT uses 670 nm & captures a series of 32 sequential 2D scans in a
total scans in a total acquisition time of 1.6 seconds.
Transverse resolution: 10 µm.
Axial resolution: 300 µm.

11.  CSLO generates up to 64 transaxial laser scans
through the ONH & peripapillary retina to reconstruct
a high resolution 3D image.
 3 options for the field of view: 10×10 degrees
15×15 degrees
20×20 degrees.
 A 670-nm diode laser emits a beam that is focused
in the X & Y axis {horizontal & vertical dimensions}
of the ONH, perpendicular to the Z axis(axis along
the optic nerve).
 It acquires 256×256 measuring points.
PRINCIPLE:

13. PRINCIPLE:

15. COMPONENTS OF HRT:
 Patient data: name, sex, date of birth, patient ID, and date of
exam are provided here.

16. Topography image: It is a false-color image. More superficial areas appear
darker and deeper areas appear of a lighter color. Additional colors
are added to the map: red indicates the cup (area below the reference
plane) and green and blue indicate neuroretinal rim tissue
(above the reference plane). Blue indicates sloping rim.

17. .
Reflectance image: located in the right upper corner of the unilateral
report or below the topography image on the ‘OU report.’
It is also a false-color image and is similar to a photograph with
the brighter areas representing highest reflectance, like the cup. The
reflectance image is overlaid with Moorfields analysis.

18. 4. Retinal surface height variation graph: this appears once the
disc
contour is drawn and accepted. It is the graphical representation
of the retinal height along the contour line and of the thickness of
the nerve fiber layer. A green line represents the retinal height and
a red line represents the reference plane.

20. 1.VERTICAL &
HORIZONTAL
INTERACTIVE
ANALYSIS.
2.STEREOMETRI
C ANALYSIS
3.MOORFIELDS
REGRESSION
ANALYSIS
4.GLAUCOMA
PROBABILITY
SCORE

21. STRENGTH & LIMITATIONS
STRENGTH LIMITATIONS
GIVES A 3 D IMAGE OF ONH OPERATOR DEPENDEND FOR MARKING
OF CONTOURS.
NO NEED OF PUPIL DILATATION BLOOD VESSELS CAN GIVE FALSE
IMPRESSSION.
LARGE NUMBER OF NORMATIVE DATAS
ARE AVAILABLE
ONLY FOR ONH

22. SCANNING LASER POLARIMETRY{GDX}
Scanning laser polarimetry is an imaging
technology that is utilized
to measure peripapillary RNFL thickness. It
is based on the principle
of birefringence.
Currently it is in its 4th generation
GDX VCC (variable corneal compensation)
(CARL ZEISS MEDITEC: JENA
,GERMANY,DUBLIN,CALIFORNIA)

23. PRINCIPLE:-
In the retina, the parallel arrangement
of the microtubules in retinal ganglion cell
axons causes a change
in the polarization of light passing through
them. The change in
the polarization of light is called retardation,
which can be quantified.
The retardation value is proportionate to the
thickness of the
RNFL. GDX is the device that utilizes this
technology.

24.  These devices uses a diode laser (780nm) for the illumination
& measurement of a 15×15 degree area of retina.
 Acquisition time :0.7 sec
 Scanned datas are displayed as a 256×256 pixels colour
coded grid.
PRINCIPLE:-

25. COMPONENTS OF THE
GDX REPORTS

26.  Patient data and quality score: The patient’s name, date of
birth,gender and ethnicity are reported at the top of the
printout. An ideal quality score is from 7 to 10.

27.  Fundus image: it is a reflectance image of the posterior pole
that measures 20° by 20°. GDX VCC obtains more than 16
000 data points to construct this image. During the scanning
process, this image serves to evaluate the quality of the scan
before moving forward.

28. RNFL thickness map: this is a color map depicting the
Different thicknesses of peripapillary RNFL .
It represents the retardation level of the different scanned points.
Hot colors like red and yellow mean high retardation or thicker
RNFL and cool colors like blue and green mean low retardation or
thinner areas. A typical scan pattern is that one with thicker RNFL
superiorly and inferiorly, like a vertical bow-tie.

29. TSNIT graph: this graph demonstrates the patient’s RNFL
thickness as a black line drawn over a shaded area of normality
based on a normative database of over 500 eyes. This graph is based
on data points within the calculation circle.
TSNIT symmetry graph: this graph overlays the individual
TSNIT graphs for the right and left eye.
TSNIT comparison graph and serial analysis graph:
these graphs
compare two or more scans of the same eye obtained on different
visits. These graphs do not appear on the regular printout.

30. NERVE FIBER INDICATOR: IT IS INDICATOR OF LIKELIHOOD THAT THE EYE HAS
GLAUCOMA.
It is a number
between 0 and 100.
The higher the NFI, the more likely the
patient has glaucoma.
The GDX manufacturer offers the following
as a guideline on the NFI interpretation:
< 30: low likelihood of glaucoma
30–50: glaucoma suspect
>50: high likelihood of glaucoma.

34. STRENGTH & LIMITATIONS
STRENGTH LIMITATIONS
RAPID ASSESSMENT OF PERIPAPILARY
RNFL
ONLY ASSESS RNFL
NO PUPILLARY DILATATION REQUIRED

35. OPTICAL COHERENCE TOMOGRAPHY

37.  A super luminescent 820 or 850 nm diode laser beam is the
light source directed to a partially reflecting mirror that splits
the light into two beams: one is directed towards a mirror
placed at a known distance (reference mirror) and the other is
directed towards the eye, from where it will reflect back. This
back-reflected light will consist of multiple echoes, with
information about the distance and thickness of the different
intraocular tissues. The back-reflected light from the eye is
combined with the back-reflected light from the reference
mirror and coherent light is compared.

40. STRENGTH LIMITATIONS
VERSATILE. Limited normative database
BEST AXIAL RESOLUTION. Limited sampling
IT IMAGES RNFL,ONH & MACULA.
STRENGTH & LIMITATIONS:

41.  USAGE SIMILAR TO SLIT LAMP BIOMICROSCOPY.
 IT PROJECTS A THIN LASER SLIT OBLIQUELY ON RETINA.
OBLIQUE PROJECTION-BACK REFLECTED LIGHT-2 LIGHT PEAKS—
CORRESPONDING TO THE VITERORETINAL & CHORIORETINAL
INTERFACE--.
THE DISTANCE BETWEEN THESE LAYERS REFLECTS THE RETINAL
THICKNESS
RETINAL THICKNESS ANALYSER

42.  LASER:540nm HeNe laser
3 mm in length
10 µm in width.
 The RTA acquires 16 optical cross sections approx 100µm
apart covering a total area of 3×3 mm in 400 msec
 Total acquistion time : 13 scans in 10 mins.
PRINCIPLE:
Strength Limitationssss
Multiple scanning regions Pupil dilatation required
Limited cross sectional view. Highly affected by media
opacity

43. Thank you