optical coherence tomography: posterior segment applications
TRANSCRIPT
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Pinakin Davey OD, PhD, FAAO
Professor and Director of Research
Disclosures Speaker Optovue and Topcon
Research- Topcon
Definitions “Ocular tissue damage at least partially related to
intraocular pressure”
A chronic, bilateral, often asymmetrical disease in adults, featuring acquired loss of optic nerve fibers and abnormality of visual field with an open anterior chamber angle.
Goals Document status of optic nerve structure and function
Target pressure- so damage is unlikely to happen
Maintain IOP below target pressure
Monitor status of the optic nerve and reset target pressure if deterioration occurs.
Minimize side effects of management and impact on vision and general health and quality of life.
Educate and engage the patient in management
Gold standard Simultaneous stereo photography!
Problems?
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Glaucoma evaluation Anterior chamber evaluation
Angle evaluation
Corneal thickness
Macula evaluation
Retinal Nerve fiber layer
Optic disc photography
Anterior segment OCT
Author Difference in OCT and ultrasound values
Kim et al AJO 2008 26 microns
Wang et al J Refract Surg 2008 38 microns
Gunvant & Darner Medical Imaging 2011
13 microns
Difference between optical and ultrasound pachymetrymeasurments
Kim, H.Y., Budenz, D.L., Lee P.S, et al., “ Comparison of central corneal thickness using anterior segment optical coherence tonography vsultrasonic pachymetry, Am J Ophthalmol,; 145:228-232 (2008).Wang, J.C., Bunce, C., and Lee, H.M., “ Intraoperative corneal thickness measurement using optical coherence pachymetry and corneo-gage plus ultrasound pachymetry J Refract Surg. 24(6):610-4 (2008P Gunvant, R Darner: Evaluation of corneal thickness measurements obtained using optical coherence tomography and ultrasound technique and determination of specificity in keratoconus screening Medical Imaging: 79661 B1-B8
Corneal Thickness Maps
Stromal thickness Glaucoma Symptom Scale
Lee B et al. Arch Ophthalmol 1998
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Evaluate the cornea and conjunctiva Look at Epithelium
Pay attention to dry eye and glaucoma –particularly if multiple meds
Even when patient does not complain they may have sub-clinical dry eyes.
Extreme dryness changes in stromal thickness
Erroneous estimates of risk ??
The Scoring Tool for Assessing Risk (S.T.A.R. II) calculator
OHTs and EGPS data
Intended for use only in untreated OHT patients
Age (30-80)
IOP 20-32 mmHg
CCT 475 to 650 microns
PSD 0.50 to 3.00 dB
C/D ratio vertical 0.00 to 0.8
Probability of conversion in
5- years
<5% observe and monitor
5 to 15% consider
treatment
>15% treat
Gonioscopy
Iris insertion
Curvature of periheral iris
Angle approach
A = Above Schwalbe line, totally occluded angle.B = Behind the Schwalbe line, peripheral iris is in contact with TM.C = Scleral spur Iris root at the level of scleral spur
D = Deep anterior ciliary body
seen.
E = extremely deep
Guidelines recommend once a year procedure
Angle Measurement with
Quantification
Anterior segment Angle Analysis
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6 x 6 mm scan, Disc
12x9mm Widefield scan, Report
RNFL Thickness Map
GCL + IPL + RNFL GCL + IPL
Best diagnostic parameter in identifying glaucoma using OCT is- Inferior average thickness
Thickness map
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Deviation Map Tomogram
Global parameters
Axonal facts 700,000 to 1.2 million
Large variation
Count of axons increase with increase in area.
50% of axons to the macula
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Ganglion Cell Complex (GCC) Macula analysis Optovue
NFL+ GCL + IPL
Zeiss Ganglion Cell analysis- GCL+ IPL
Topcon Maestro gives both
NFL+ GCL+ IPL
GCL+IPL
Spectralis gives individual layers.
GCL + IPL + RNFL GCL + IPL
GCC Change
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Hood report
Dr. Donald C Hood
S
I
What is TSNIT ?
cpRNFL Map
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TSNIT graph
Dr. Donald C Hood
NSTIN graph(Hood report)N S T I N
Rauber Kopsch Band2. Abb-633
Dr. Donald C Hood
Slide from Dr. Hood AAO 2016 booth seminar
TSNIT Versus NSTIN
From: A Single Wide-Field OCT Protocol Can Provide
Compelling Information for the Diagnosis of Early
Glaucoma
Trans. Vis. Sci. Tech.. 2016;5(6):4. doi:10.1167/tvst.5.6.4
Figure Legend:
(A) Report for a glaucomatous eye
correctly classified by the
report specialist. (B) Report for a healthy eye
correctly classified by the report specialist.
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Progression Consensus is limited
Visual fields tend to fluctuate in early glaucoma
Reliable and repeatable structural measurements is very valuable
Fourier domain OCT 5 microns accuracy.
CASE MR.X DOB 1951
Asian Male
Medical unremarkable
Family medical Brother Glaucoma
Tmax – 23 OU
On PGA IOPs 15-18 OU
Overall quite regular in care and compliance
During follow-up One year had changed to generics PGA
Seen by 4 different doctors in practice….
Charts …. And observations
OD OS
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OCTRed syndrome Green Syndrome
False positive False neagtive
SD-OCT image quality at varying Z depths
Image quality decreases at deeper Z depths
Image Acceptance Criteria1. Image Quality Score (TopQ Score)
2. Eye Blinks
3. Eye Movement
4. Clipping
5. Fixation/Centration
6. Localized weak signal
Factors influencing OCT images• Dirty objective lens
• Subject’s head and/or chin not in proper position
• B Scan too high or too low in scanning area
• Improper focus
• Pupil too small
• Media opacity
• Reduced tear film on cornea
• These suggested steps should be used in order to
improve the image quality score
Eye Blinks
View on Instrumnt
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Eye Blinks
Blin
ksN
o B
links
Eye Movements- Unacceptable
View on Instrument
Clipping- Unacceptable
View on Instrument
Clipping- Acceptable
View on Instrument
Fixation/Centration- not acceptable
6 mm x 6 mm -Disc
View on PC
6 mm x 6 mm -Macula
Localized Weak Signal
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Summary OCT is a must in clinics that would like to manage any
chronic diseases
Particularly when monitoring change overtime
Good quality data is a must in getting the best clinical outcome