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JCAHPO Regional Meetings

2017

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Vikas Chopra, M.D.Health Sciences Associate Professor, Department of Ophthalmology

David Geffen School of Medicine at UCLA

Medical Director, UCLA Doheny Eye Centers – Pasadena

Associate Director, Doheny Image Reading Center, Doheny Eye Institute

pearls and pitfalls of ophthalmic imagingASCRS JCHAPO 2017 Conference

Vikas Chopra, M.D.Financial Disclosure: None

pearls and pitfalls of ophthalmic imagingASCRS JCHAPO 2017 Conference

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Corneal ImagingFor diagnosis and relevance to refractive and cataract surgery outcomes

• If significant irregularity:

Refractive surgery is contraindicated

Astigmatic keratectomy (AK) may be unpredictable and unstable

Limbal relaxing incisions (LRI) may be unpredictable and unstable

Toric IOLs may be unpredictable

Presbyopia-correcting IOLs will NOT perform well

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Corneal Imaging Essential to rule-out Irregular AstigmatismCorneal irregularity may lead to poor refractive and cataract surgery outcomes,

thus proper imaging output critical

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Types of Corneal AstigmatismRegular WTR vs. Regular ATR vs. Irregular

with-the-rule (WTR) regular astigmatism

against-the-rule (ATR) regular astigmatism

Non-symmetric steepeningIrregular astigmatism

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1. Is astigmatism regular or irregular?

2. How many diopters of astigmatism?

3. How steep is the cornea and in which axis?

4. How does the pachymetry map look?

5. Does posterior corneal surface appear normal and symmetric?

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Refractive (and Refractive-Cataract) Surgery ScreeningSystematic Approach for Corneal Tomography Interpretation

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Symmetric anterior and posterior maps?

Symmetric above and below? Centered pachymetry?

Irregularity index @ 3mm

Refractive Surgery Screening with Corneal TomographySymmetric & regular astigmatism, normal pachymetry = Good candidate

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Symmetric anterior and posterior maps?

Symmetric above and below? Centered pachymetry?

Irregularity index @

3mm

Refractive Surgery Screening with Corneal TomographyAsymmetric and irregular astigmatism, thin pachy = poor candidate ( keratoconus)

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Astigmatism Correction in Cataract SurgeryAstigmatic Keratotomy (AK) and Limbal Relaxing Incisions (LRIs)

can correct low levels of corneal astigmatism

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Refractive Cataract Surgery with Acrysof TORIC LensData from Corneal Topography determines Surgical Lens Placement

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Refractive Cataract Surgery with Tecnis TORIC LensData from Corneal Topography determines Surgical Lens Placement

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• Ensure accurate topography to determine candidacy for

astigmatism management

• Identify steep axis for AKs/LRIs and Toric IOL planning

• Assess post-op astigmatism in unhappy patients

• Investigate causes of decreased final vision

•Residual astigmatism

•Rotated Toric IOL

•Cystoid macular edema

Astigmatism management essential for Refractive Cataract SurgeryProper data acquisition and interpretation improve odds of successful outcome

Poor corneal reflex before artificial tears

Sharp corneal reflex after artificial tears

Instill artificial tears pre-testing to improve image quality

Dry eyes (punctate keratopathy) may affect scan qualityLook at the “sharpness” of the corneal reflex to evaluate corneal surface

Re-scanafter

artificialtears

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Eyelid & Tear Film ErrorDry eyes can create artifactual corneal flattening &

Tear lake can create artifactual corneal steepening (example below)

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Retinal ImagingFor diagnosis and management

Evolution of OCT

TD OCT

SD-OCT

SS-OCT

(8-10 µm)

(2-4 µm)

(5-7 µm)

• Changed our understanding of retinal dz

• Allows detection of glaucoma up to 8 years

before perimetric visual field defects seen

• Changed the normal flow in clinic

• Easier for both patient & technician

Optical Coherence Tomography (OCT)Most important imaging technique in Retina (and possibly Ophthalmology)

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Macular OCTexample: Normal

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Retinal layers as seen on retinal biopsy (or autopsy) specimenExample: Normal

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OCT provides a non-invasive in-vivo Retinal BiopsyDistinct retinal layers visualized to distinguish normal from pathologic

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OCT provides very high resolution retinal imagesEven discrete areas of Rods & Cones visualized with high-resolution OCT

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OCT Retinal Layer Segmentation and LabelingInternationally agreed nomenclature

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Macular OCT (Cube scan)Allows assessment of multiple scan areas instead of just single printed scan

Pathology (Ellipsoid zone disruption: CSR)

only identified on additional scans

Pathology may be missed (? Normal scan)

if only single scan seen

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Macular OCTEpiretinal Membrane (ERM)

Normal

ERM

ERM (“retinal wrinkling”) ERM

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Macular OCT“Pseudo”-Macular Hole (due to ERM)

Normal

“Pseudo”-Macular hole ERM

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Macular OCTVitreo-Macular Traction (VMT)

VMT

Normal

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Macular OCTMacular Hole (due to vitreo-macular traction [VMT])

VMT pulled off a strip of retinal tissue (= macular hole)

Normal

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Macular OCTOpen Macular Hole BEFORE surgical repair

and Closed Macular Hole AFTER surgical repair (at Doheny UCLA )

Before repair After repair

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Macular OCTCystoid Macular Edema (CME) with intra-retinal fluid

(can cause “swelling of retina”)

collections of fluid INSIDE retinal layers

Normal

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Macular OCTSub-Retinal Fluid (SRF)

can cause “swelling of retina”

collection of fluid UNDER retinal layers

Normal

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Macular OCTGeographic Atrophy (GA)

in dry Age Related Macular Degeneration (ARMD)

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Macular OCTDrusen/Drusenoid Pigment Epithelial Detachments (PED)

in dry ARMD

Drusen/Drusenoid

PEDs

Normal

Normal

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Macular OCTSub-retinal fluid (SRF)

+ hemorrhagic Pigment Epithelial Detachment (PED)- in wet ARMD

SRF PED

Normal

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Quantitative Macular OCT AssessmentsAllows numerical evaluation for comparison between eyes

OD OS

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Quantitative Macular OCT AssessmentsAllows numerical evaluation for progression vs. resolution

Re-scan4 weeks

aftertreatment

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Retinal OCT ImagingImportance of Good Signal Strength

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Evaluating OCT Images: Signal StrengthHigh Signal to Noise Ratio (SNR) essential in improving visualization of retinal layers

Low SNR High SNR

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Evaluating OCT Images: Anatomical ConstraintsMove focus to area around anatomical constraints (ie corneal opacities)

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OCT ImagingOld records important

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Getting previous images can be useful to evaluate for “change”Digital copies (via CD,USB) are ideal

Color printouts of original scans are 2nd best“Faxed” OCTs (ie. example below) are not useful

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Glaucoma ImagingFor diagnosis and management

Beware of potential obstacles in obtaining ‘interpretable’ OCT scans

Scan Interpretation

• High quality scan?

• Any artifacts?

• Test-retest variability?

• Reproducible?

• vs. normative database?

• Clinical correlation?

Scan Acquisition

• Media opacities

• Punctate keratopathy / corneal edema / scarring

• Dense cataract

• Retinal myopic degeneration

• peripapillary atrophy (PPA)

• Miotic pupil

• Poor vision loss of fixation

• Unable to fixate on target

• Optic disc or retinal abnormalityWu Z, Vazeen M, Varma R, Chopra V, Walsh AC, LaBree LD, Sadda SR. Factors associated with variability in retinal nerve fiber layer thickness

measurements obtained by optical coherence tomography. Ophthalmology 114:1505-1512, 2007.

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OCT scan Signal Strength (SS)Adequate SS is necessary for an ‘interpretable’ OCT scan

• SS: intensity level of the signal & uniformity of signal within a scan

• Scale 110

• 1 = poor image quality

• 10 = excellent image quality

• “good” signal strength score : ≥ 7

Wu Z, Vazeen M, Varma R, Chopra V, Walsh AC, LaBree LD, Sadda SR. Factors associated with variability in retinal nerve fiber layer thickness measurements obtained by optical coherence tomography. Ophthalmology 114:1505-1512, 2007.

Zeiss Cirrus® SD-OCT

RNFL and ONH OCT scan analysis

Evaluate3 important

scan parametersbefore interpreting

scan

1. Signal strength2. Centration3. Scan alignment

RNFL & ONHscan

interpretation

OCT Scan Signal PatternScan display should be evenly strong with solid red line extending across the entire scan

Strong OCT scan signal patternallows proper retinal layer segmentation to accurately calculate RNFL thickness

OCT retinal layer Segmentation Errors

Poor differentiation of retinal layerscan lead to erroneous RNFLT measurements

poor Signal Strength (SS) negatively affects RNFLT

Scans with low SS may have falsely low RNFLT

OD: SS=4/10 Avg RNFLT = 77m

OS: SS=6/10 Avg RNFLT = 64m

Re-scan with higher SS yields greater RNFLT

OD: SS=8/10 Avg RNFLT = 87m

OS: SS=9/10 Avg RNFLT = 81m

Wu Z, Vazeen M, Varma R, Chopra V, Walsh AC, LaBree LD, Sadda SR. Factors associated with variability in retinal nerve fiber layer thickness measurements obtained by optical coherence tomography. Ophthalmology 114:1505-1512, 2007.

Re-scan

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Pupil size may affect scan quality

Pre-Dilation SS = 5/10 Post-Dilation SS = 8/10

Re-scan

Proper centration of scan circle is important for accurate RNFLT measurements with good repeatability and reproducibility

Well-centered scanDe-centered scan

Decentered Scan OS

Same scan OS with proper centration

Poor centration

Centration Errors can lead to “false localized RNFLT defects”

RNFLT decreases withincreasing distance from disc

Good centration

Irregular OCT scan signal pattern can lead to erroneous RNFL thickness measurements

Possible causes of signal dropout or uneven scan

– blinking / eye movement

– PVD / floaters / vitreous debris

– Peripapillary atrophy (PPA)

Eye movement may affect scan quality

Eye Blink Eyes Open

Re-scan

OCT Retinal Layer Segmentation Error due to incomplete scan

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Re-scan

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Scan misalignment can lead to a poor quality scandespite “good” signal strength Posterior vitreous detachment (PVD) can interfere with OCT RNFL measurements

Scan circle

over PVD

PVD can lead to OCT signal dropout with “missing data”

Strategies to Improve Scanning

• eye movement to displace floater

• head repositioning

Peripapillary Atrophy (PPA)

• Measurement error due to scanning over area of PPA

• Very difficult to interpret such scans

OCT-based longitudinal glaucoma progression detection

Progression software availablewith serial overlay scanning

Anterior Segment OCT (AS-OCT)

• Excellent resolution of anterior segment

• Technically easy to use and quick

• Requires no contact or immersion

• Provides light and dark measurements

Scleral spur

Cornea

Angle recess

Lens

Anterior chamber

Iris root

Radhakrishnan S, Goldsmith J, Huang D, et al. Arch Ophthalmol 2005;123:1053-9.

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Anterior Segment OCT (ASOCT): Evaluating treatment outcomes

• Critical to analyze the quality of data from imaging devices

before interpreting the data

•An abnormality on imaging always

requires clinical correlation for correct interpretation

Ocular imaging is now an integral part of ophthalmologyImaging can augment, but does not replace an excellent clinical work-up and exam

by astute technicians and physicians

‘Normal RNFL’ thickness per Normative Databasedoes not always mean normal (non-glaucomatous) optic disc

OD

OS

No cupping with high-normal RNFL

high-normal RNFL low-normal RNFLOS

OS

OD

OD

Vertical cupping with low-normal RNFL

ASYMMETRIC RNFL values

Disc pallor > cupping

Disc pallor > cupping

‘Abnormal RNFL’ thickness per Normative Databasedoes not always correspond with a glaucomatous optic disc

OD

OS

OD - RNFL loss OS - RNFL loss

OPTIC ATROPHY

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THANK YOU.