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pearls and pitfalls of ophthalmic imaging JCHAPO 2016 Conference Vikas Chopra, M.D. Medical Director, UCLA Doheny Eye Centers Pasadena Principal Investigator, Doheny Image Reading Center, Doheny Eye Institute Health Sciences Associate Professor, Department of Ophthalmology David Geffen School of Medicine at UCLA NaMee Donan, C.O.T. Imaging and Technician Manager UCLA Doheny Eye Centers - Pasadena Department of Ophthalmology David Geffen School of Medicine at UCLA pearls and pitfalls of ophthalmic imaging JCHAPO 2016 Conference Vikas Chopra, M.D. Financial Disclosure: None Corneal Imaging For diagnosis and relevance to refractive and cataract surgery outcomes NaMee Donan, C.O.T. Financial Disclosure: None 4 Corneal Imaging Essential to rule-out Irregular Astigmatism Corneal irregularity may lead to poor refractive and cataract surgery outcomes, thus proper imaging output critical Types of Corneal Astigmatism Regular WTR vs. Regular ATR vs. Irregular 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 with-the-rule (WTR) regular astigmatism against-the-rule (ATR) regular astigmatism Non-symmetric steepening Irregular astigmatism 5 10 1
Refractive (and Refractive-Cataract) Surgery Screening Systematic Approach for Corneal Tomography Interpretation 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? Refractive Surgery Screening with Corneal Tomography Symmetric & regular astigmatism, normal pachymetry = Good candidate Symmetric anterior and posterior maps? Irregularity index @ 3mm Symmetric above and below? Centered pachymetry? 11 12 Refractive Surgery Screening with Corneal Tomography Asymmetric and irregular astigmatism, thin pachy = poor candidate ( keratoconus) Symmetric anterior and posterior maps? Astigmatism Correction in Cataract Surgery Astigmatic Keratotomy (AK) and Limbal Relaxing Incisions (LRIs) can correct low levels of corneal astigmatism Irregularity index @ 3mm Symmetric above and below? Centered pachymetry? 13 14 Refractive Cataract Surgery with Acrysof TORIC Lens Data from Corneal Topography determines Surgical Lens Placement Refractive Cataract Surgery with Tecnis TORIC Lens Data from Corneal Topography determines Surgical Lens Placement 15 16 2
Astigmatism management essential for Refractive Cataract Surgery Proper data acquisition and interpretation improve odds of successful outcome Dry eyes (punctate keratopathy) may affect scan quality Look at the sharpness of the corneal reflex to evaluate corneal surface 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 Poor corneal reflex before artificial tears Sharp corneal reflex after artificial tears Instill artificial tears pre-testing to improve image quality 18 Eyelid & Tear Film Error Contact Lens Wear Error K 39.96/42.89 Astig: 2.94 D K 40.43/44.78 Astig: 4.35 D 21 22 Optical Coherence Tomography (OCT) Most important imaging technique in Retina (and possibly Ophthalmology) Evolution of OCT Retinal Imaging For diagnosis and management Changed our understanding of retinal dz Allows detection of glaucoma up to 8 years before perimetric visual field defects seen TD OCT (8-10 µm) SD-OCT (5-7 µm) Changed the normal flow in clinic Easier for both patient & technician SS-OCT (2-4 µm) 24 3
example: Normal Retinal layers as seen on retinal biopsy (or autopsy) specimen Example: Normal 26 27 OCT provides a non-invasive in-vivo Retinal Biopsy Distinct retinal layers visualized to distinguish normal from pathologic OCT provides very high resolution retinal images Even discrete areas of Rods & Cones visualized with high-resolution OCT 28 29 OCT Retinal Layer Segmentation and Labeling Internationally agreed nomenclature (Cube scan) Allows assessment of multiple scan areas instead of just single printed scan Pathology may be missed (? Normal scan) if only single scan seen Pathology (Ellipsoid zone disruption: CSR) only identified on additional scans 30 31 4
Epiretinal Membrane (ERM) Pseudo -Macular Hole (due to ERM) ERM Pseudo -Macular hole ERM ERM ( retinal wrinkling ) ERM Normal Normal 32 33 Vitreo-Macular Traction (VMT) Macular Hole (due to vitreo-macular traction [VMT]) VMT pulled off a strip of retinal tissue (= macular hole) VMT Normal Normal 34 35 Open Macular Hole BEFORE surgical repair and Closed Macular Hole AFTER surgical repair (at Doheny UCLA ) Cystoid Macular Edema (CME) with intra-retinal fluid (can cause swelling of retina ) Before repair After repair collections of fluid INSIDE retinal layers Normal 36 37 5
Sub-Retinal Fluid (SRF) can cause swelling of retina Geographic Atrophy (GA) in dry Age Related Macular Degeneration (ARMD) Normal collection of fluid UNDER retinal layers 38 39 Drusen/Drusenoid Pigment Epithelial Detachments (PED) in dry ARMD Sub-retinal fluid (SRF) + hemorrhagic Pigment Epithelial Detachment (PED) - in wet ARMD Normal Drusen/Drusenoid PEDs SRF PED 40 41 Quantitative Assessments Allows numerical evaluation for comparison between eyes Quantitative Assessments Allows numerical evaluation for progression vs. resolution 42 43 6
Quantitative Choroidal Evaluation with OCT Central Serous Chorioretinopathy (CSR) with Thicker Choroid Quantitative Choroidal Evaluation with OCT High Myopia (Myopic Retinal Degeneration) with Thinner Choroid Normals: 280-290 microns vs CSR patients: 400-500 microns Normals: 280-290 microns vs High Myopes: 93 microns 44 45 Evaluating OCT Images: Signal Strength High Signal to Noise Ratio (SNR) essential in improving visualization of retinal layers Retinal OCT Imaging Importance of Good Signal Strength Low SNR High SNR 46 48 Evaluating OCT Images: Anatomical Constraints Move focus to area around anatomical constraints ie corneal opacities OCT Imaging Old records important 49 50 7
Getting previous images can be useful to evaluate for change Digital copies (via CD,USB) are ideal Color printouts of original scans are 2 nd best Faxed OCTs (ie. example below) are not useful Before accepting the imaging output as valid and ready for interpretation, we need to assess the quality of the data by doing a quick but careful scan analysis 51 AAO s Preferred Practice Pattern (PPP) guidelines for glaucoma Glaucoma Imaging For diagnosis and management Evaluation of optic nerve head and retinal nerve fiber layer, with stereoscopic visualization AND Documentation of optic disc morphology, best performed by color photos or imaging 54 AAO s Ophthalmic Technology Assessment Committee Glaucoma Panel on-going advances in imaging and related software as well as impracticalities associated with obtaining and assessing optic nerve stereo-photos have made imaging increasingly important in many practice settings. Before accepting the imaging output as valid and ready for interpretation, we need to assess the quality of the data by doing a quick but careful scan analysis Lin SC, Singh K, Jampel HD, Hodapp EA, Smith SD, Francis BA, Dueker DK, Fechtner RD, Samples JS, Schuman JS, Minckler DS; American Academy of Ophthalmology; Ophthalmic Technology Assessment Committee Glaucoma Panel. Ophthalmology. 2007 Oct;114(10):1937-49. Erratum in: Ophthalmology. 2008 Mar;115(3):472. 8
Beware of potential obstacles in obtaining interpretable OCT scans 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 abnormality Scan Interpretation High quality scan? Any artifacts? Test-retest variability? Reproducible? vs. normative database? Clinical correlation? 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. 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 1 10 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 OCT Scan Signal Pattern Scan display should be evenly strong with solid red line extending across the entire scan Evaluate 3 important scan parameters before interpreting scan RNFL & ONH scan interpretation 1. Signal strength 2. Centration 3. Scan alignment Strong OCT scan signal pattern allows proper retinal layer segmentation to accurately calculate RNFL thickness OCT retinal layer Segmentation Errors Poor differentiation of retinal layers can lead to erroneous RNFLT measurements 9
OCT retinal layer Segmentation Errors Irregular OCT scan signal pattern can lead to erroneous RNFL thickness measurements Examine retinal layer segmentation pattern to assess accuracy before interpreting RNFLT Possible causes of signal dropout or uneven scan blinking / eye movement PVD / floaters / vitreous debris Peripapillary atrophy (PPA) poor Signal Strength (SS) negatively affects RNFLT Scans with low SS may have falsely low RNFLT Re-scan with higher SS yields greater RNFLT OD: SS=4/10 Avg RNFLT = 77m OD: SS=8/10 Avg RNFLT = 87m Re-scan OS: SS=6/10 Avg RNFLT = 64m OS: SS=9/10 Avg RNFLT = 81m OCT Retinal Layer Segmentation Error due to incomplete scan Re-scan 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. 68 Pupil size may affect scan quality Pre-Dilation SS = 5/10 Post-Dilation SS = 8/10 Re-scan Glaucoma Imaging Importance of Pupil Size (undilated vs. dilated) 69 10
Proper centration of scan circle is important for accurate RNFLT measurements with good repeatability and reproducibility Glaucoma Imaging Proper Centration (manual vs. autotracking) De-centered scan Well-centered scan 71 Centration Errors can lead to false localized RNFLT defects Eye movement may affect scan quality Poor centration Decentered Scan OS Eye Blink Re-scan Eyes Open RNFLT decreases with increasing distance from disc Good centration Same scan OS with proper centration Poor scan alignment during scan acquisition may miss data points Glaucoma Imaging Scan Alignment 75 11
Scan misalignment can lead to a poor quality scan despite good signal strength Glaucoma OCT Imaging Effect of Vitreous Floaters 78 Posterior vitreous detachment (PVD) can interfere with OCT RNFL measurements PVD can lead to OCT signal dropout with missing data Scan circle over PVD Strategies to Improve Scanning eye movement to displace floater head repositioning Vitreous Floater Within Scan Circle causing Error Re-scan OCT-based longitudinal glaucoma progression detection 81 Progression software available with serial overlay scanning 12
Anterior Segment OCT (AS-OCT) Anterior Segment OCT (ASOCT): Evaluating treatment outcomes Excellent resolution of anterior segment Technically easy to use and quick Requires no contact or immersion Provides light and dark measurements Cornea Anterior chamber Scleral spur Angle recess Lens Iris root Radhakrishnan S, Goldsmith J, Huang D, et al. Arch Ophthalmol 2005;123:1053-9. Ocular imaging is now an integral part of ophthalmology Imaging can augment, but does not replace an excellent clinical work-up and exam by astute technicians and physicians Good imaging can make a difference for diagnosis and management in eye care practices Critical to analyze the quality of data from imaging devices before interpreting the data THANK YOU. An abnormality on imaging always requires clinical correlation for correct interpretation 94 pearls and pitfalls of ophthalmic imaging JCHAPO 2016 Conference Vikas Chopra, M.D. Medical Director, UCLA Doheny Eye Centers Pasadena Principal Investigator, Doheny Image Reading Center, Doheny Eye Institute Health Sciences Associate Professor, Department of Ophthalmology David Geffen School of Medicine at UCLA NaMee Donan, C.O.T. Imaging and Technician Manager UCLA Doheny Eye Centers - Pasadena Department of Ophthalmology David Geffen School of Medicine at UCLA 13