Edward Chang, MD · Ultrasound testing in 1930’s A-mode and B-mode scanning 1960’s 10 MHz to 50...
Transcript of Edward Chang, MD · Ultrasound testing in 1930’s A-mode and B-mode scanning 1960’s 10 MHz to 50...
Edward Chang, MD Everett & Hurite Ophth Assoc
1887 – Photo of human retina on a live subject
1898 – Fundus camera developed allowing better fundus photography – Zeiss Jena
1909 – First stereo photograph - Thorner
Ultrasound testing in 1930’s
A-mode and B-mode scanning 1960’s 10 MHz to 50 MHz Ocular contents present a challenge Millimeters vs micrometers
IOL’s become available
Refractive surgery
Anterior Segment Anatomic evaluations Narrow angle Plateau Iris Tumors, cystic structures
Cataracts Biometry
Refractive
Trauma
Posterior Segment Retina Diabetic disease – rx and follow-up Cystoid macular edema Macular degeneration and similar Tumors
Glaucoma Nerve fiber layer Ganglion cell
Armament A-scan, B-scan
Ultrasound Biomicroscopy – UBM
CT/MRI
Confocal microscopy
Anterior Segment OCT – (AS-OCT)
IOL Master, Lenstar, Pentacam
Posterior segment OCT, GDx, Optovue
HD Photography
Cataracts Still the most commonly performed surgery within
Medicare
Population median age continues to rise
High expectations
Reimbursement stagnant
Technology advancements
A-scan, B-scan
IOL Master, Lenstar & Pentacam
AS-OCT
Posterior segment OCT
A-scan Immersion vs Applanation
Technology has improved over time
Portable
Accurate
Cost efficient
Comparative to other testing
Tech dependent;
IOL Master Approved in 2000
Non-contact optical device; measures distance from corneal vertex to retinal pigment epithelium by partial coherence interferometry
Accuracy to 0.02mm or better A-scan resolution 0.10mm to 0.12mm
500 version most commonly used
700v now available; swept source OCT
Lenstar Available in 2000
First biometer that can measure thickness of crystalline lens
Integrated formulas; easier data input
Dual zone keratometry; pachymetry, pupillometry, W to W, ACD
Pentacam Introduced in 2002
Rotating Scheimplug camera
Biometry added last year with AXL edition
Offers improved corneal data
Integration of data with IOL formulas
If you have one of the others, do you really needs this also??
Corneal rx uses such as crosslinking
B-scan
Glaucoma
Glaucoma - facts u 2.4 million people develop glaucoma throughout
world annually; 50% are unaware
u 2.6 million Americans with POAG
u >10 million with elevated IOP in U.S.
u Second leading cause of blindness overall in U.S. 80,000 to 116,000 blind from glaucoma
u Black pts. are 3X more likely to have glaucoma; 6-8x more likely to be blind from it
What is Glaucoma Family of ocular diseases characterized by
progressive optic neuropathy and visual field loss Gradual optic disk cupping Associated visual field deficits Progressive retinal ganglion cell loss
No longer defined alone by elevated intraocular pressure (IOP)
Disc Photography Fundus photography 1920’s
35mm disc photography starting in 1960’s
Digital photography
Stereo disc photos
Allowed baseline and ability for extended analysis of disc
Red-free nerve fiber layer photography
Quantitative Imaging Confocal Scanning Laser Ophthalmoscopy HRT
Scanning Laser Polarimetry GDx
Optical Coherence Tomography OCT
Heidelberg - HRT Developed in 1955
670-nm diode laser produces up to 64 transaxial scans of ONH
3-D topographical image
C/D ratio, rim area, disc parameters
HRT II and III versions available
?reproducibility
What do you do with data?
GDx measures peripapillary RNFL thickness by sending a
laser beam to the posterior retina and assessing the change in polarization (retardation) of the reflected beam. This retardation of the scanning beam results from the birefringent properties of the neurotubules contained within the ganglion cell axons.
780nm
Initial devices suffered from data affected by corneal birefringence; updated devices have variable corneal compensation
OCT Low-coherence interferometry, near infra-red light.
High resolution scanning within micrometers
Limited to 1-2 mm
Time domain, Frequency domain, Spectral domain, Swept source OCT
Becoming standard of care
Ultrahigh speed swept source OCT, ultrahigh resolution OCT, polarization sensitive OCT, and adaptive optics OCT are all on the horizon
Time vs Fourier domain OCT Time domain OCT
A scan generated sequentially, one pixel at a time of 1.6 seconds
Moving reference mirror
400 scans/sec
Resolution – 10 micron
Slower than eye movement
Fourier domain OCT Entire A scan is generated at
once based on Fourier transformation of spectrometer analysis
Stationary reference mirror
26,000 scans/sec
Resolution – 5 micron
Faster than eye movement
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OCT image display,
Highest reflectivity - red nerve fiber layer retinal pigment epithelium and Choriocapillaris
Minimal reflectivity appear blue or black photoreceptor layer choroid vitreous fluid or blood
A 53 year old female patient : glaucoma suspect due to borderline IOP of 23 mm Hg
Right optic nerve: 0.5 cup with an infero-temporal RNFL loss (arrows)
The visual fields normal in both eyes along with the rest of the eye examination.
Circle Scan
Differences betweeen average thickness in sectors (along the calculation circle) in each eye
OCT Scan with automatic segmentation of RNFL
TSNIT RNFL thickness compared to normative database
RNFL Thickness in quadrants & sectors compared to normative database
Ultrasound Biomicroscopy UBM
Compared to regular ultrasound (A & B-scan 10Mhz), it uses higher frequency (35-100Mhz)
Resolution to 25 microns
Anterior segment pathology
Trauma Multiple modalities of imaging to be used for diagnosis
and follow-up
B-scan
Photography
AS-OCT
UBM
Post-segment imaging
Thank You