Optical coherence tomography: Posterior segment applications

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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