FOURIER DOMAIN OPTICAL COHERENCE TOMOGRAPHY IN THE

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FOURIER DOMAIN OPTICAL
COHERENCE TOMOGRAPHY IN THE
MANAGEMENT OF POSTERIOR
SEGMENT DISORDERS: A REVEALING
CASE SERIES
OLUFEMI ODERINLO FRCSEd FWACS DRCOphth
Consultant Ophthalmologist and Vitreoretina
Surgeon
EYE FOUNDATION HOSPITAL GROUP
INTRODUCTION
• There are two principles of image acquisition
and data processing in OCT:
• Time domain and Fourier domain algorithms.
• In time domain OCT, there is a mechanical
moving part that performs the A-scan, and the
information along the longitudinal direction is
accumulated over the course of the
longitudinal scan time. Thus, the rate of the
scan is limited by the movement of the part.
• In Fourier domain OCT, the information in an entire A-scan
is acquired by a charge-coupled device (CCD) camera
simultaneously.
• The A-scan acquisition rate is limited by the CCD camera
frame transfer rate and the computer calculation time to
perform the Fourier transform of the CCD acquired raw
data into A scan information.
• As there is no mechanical movement, the scan time in
Fourier domain OCT is faster. This is an important
advancement because faster acquisition time means lesser
variability in the result due to the patient’s eye movements.
This device has a higher resolution than time domain OCT.
OPTOVUE
• The Fourier domain OCT, RTVue
has been approved by the U.S.
Food and Drug Administration.
• It takes 26,000 A-scans per
second, with a frame rate of 256
to 4,096 A-scans per frame. It has
a depth resolution of 5 μm and a
transverse resolution of 15 μm.
• The scan range is 2 mm to 2.3
mm in depth and 2 mm to 12 mm
in transverse direction. The scan
beam wavelength is 840 ± 10 nm,
and the exposure power at the
pupil is 750 μW.
• Decision making in macula hole
CASE 1
• 36 year old security
guard referred for
macula hole surgery
OD.
• In good general health.
• VA 6/12 OD , 6/5 OS
• Normal anterior
segments, pupillary
reaction and IOP.
• Fundus OS normal
PSEUDOHOLE
• Idiopathic Serous
Retinal Pigment
Epithelial Detachment.
• Seen in patients much
younger than ARMD
definition.
• Few case reports mostly
males 20 – 45 years
Pathophysiology
• a non-specific anatomical alteration that may result from
any number of choroidal disorders that disrupt the normal
junction between the basement membrane of the RPE and
the inner collagenous layer of Bruch’s membrane.
• Idiopathic cases are sometimes associated with ICSC; some
believe these two conditions to represent a continuum of a
similar underlying pathology.
• Uncomplicated idiopathic serous detachments of the RPE
often resolve spontaneously, however, those associated
with more generalized damage to the choriocapillaris may
be complicated by hemorrhage, choroidal neovascular
membrane formation, and disciform scarring.
MORPHOLOGY: to the fundus photo a
hole is a hole
HOLE MORPHOLOGY
MEASUREMENTS
(a) base diameter,
(b) minimum linear dimension
(c) and (d) arms for measuring
hole form factor
(e) hole height
(f) macular hole inner
opening.
Hole form factor ¼ (c+d)/a;
Macular hole index ¼ e/a;
Tractional hole index ¼ e/b.
stage
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Modified Gass classification system of macular holes.
Stage
Description
Stage 1a
Yellow spot with loss of foveal depression, no vitreous separation
Stage 1b
Yellow ring with loss of foveal depression, no vitreous separation
Stage 2
Small full-thickness macular hole < 400 microns
Stage 3
Full-thickness macular hole > 400 microns, no vitreous separation
Stage 4
Full-thickness macular hole > 400 microns, complete vitreous separation
HFF
• In all patients (100%) with HFF >0.9 the
macular hole was closed following one
surgical procedure, whereas in eyes with HFF
<0.5 anatomical success rate was 67%.
• Better postoperative visual outcome
correlated with higher HFF .
GCC
Hole closure type
• Closed macular holes
are categorised into two
patterns based on OCT;
• type 1 closure (closed
without foveal
neurosensory retinal
defect)
• type 2 closure (closed
with foveal
neurosensory retinal
defect).
CASE 2
• 49 year old diabetic
with PDR who has had
extensive PRP laser.
CME/VMT
• Reason for poor vision in heriditary disorders
CASE 3
• 14 year old girl with
nyctalopia and
difficulty with
reading
• Suspicious macula,
more of an atrophic
picture.
Fundus
FFA
Definite CME on FD OCT
FFM
FD OCT
• To evaluate unsatisfactory vision after surgery.
CASE 4
• 41 year old phakic
myope with a 5 day
history of an inferior
retinal detachment OS.
• Round hole at 6 o ‘clock
with foveal affectation
• Had scleral buckle with
drainage of subretinal
fluid.
• Retina reattached
• Vision improved from
6/60 to 6/18, significant
improvement in CVF
FD OCT
• Non reflective subfoveal
cavity representing
subfoveal SRF.
CASE 5
FD-OCT
Fd-OCT CLASSIFICATION FOR CNV
• Type 1> 90% sub-RPE.
• Type 2 > 90% sub-retinal.
• * Minor type 1 component (10% lesion)
visualized.
• † Fibrovascular PED.
• ‡ Minor type 2 component (10% lesion)
visualized.
• Combined
• Indeterminate
• showing a mostly
subretinal growth
pattern of CNVM in an
eye with a minimally
classic angiographic
lesion composition.
• the hyperreflective
lesion (cnvm)is outlined
in gray with the sub-RPE
component of the lesion
in a lighter shade.
• WITH FD OCT FOR MACULA LESIONS I CAN SEE
CLEARLY NOW.
THANK YOU
REFERENCES
• Desai VN, Hee MR, Puliafito CA. Optical
coherence tomography of macular holes. In:
Madreperla SA, McCuen BW, eds. Macular
hole: pathogenesis, diagnosis and treatment.
Oxford: Butterworth-Heinemann 1999:37–47