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Optical Coherence Tomography
(OCT)
Optical Coherence Tomography, or OCT, is a noncontact,
noninvasive imaging technique used to obtain high resolution cross-sectional
images of the retina. OCT was developed through a collaborative
effort between the New England Eye Center, Tufts University School
of Medicine, the Department of Electrical Engineering and Computer
Science at MIT, and Lincoln Laboratory, MIT.
OCT is analogous to ultrasound B-scan imaging except
that light rather than sound waves are used in order to obtain a
much higher longitudinal resolution of approximately 10µm
in the retina. OCT has been shown to be clinically useful for imaging
selected macular diseases including macular holes, macular edema,
age-related macular degeneration, central serous chorioretinopathy,
epiretinal membranes, schisis cavities associated with optic disc
pits, and retinal inflammatory diseases. In addition, OCT has the
capability of measuring the retinal nerve fiber layer thickness
in glaucoma and other diseases of the optic nerve.
Learn more about OCT in:
The topographic mapping protocol is useful for
longitudinally monitoring patients for the development of macular
edema and for following the resolution of edema after laser treatment.
The false-color map of retinal thickness provides an intuitive and
efficient method of comparing retinal thickness over several visits
which could be directly compared with slit-lamp observation.
Development and resolution of diabetic macular
edema. A 50-year-old man with NPDR and CSME in the right eye was
examined (fundus below).
His visual acuity OD was 20/25. OCT at the initial
visit showed foveal and juxtafoveal macular thickening which
was most significant temporally and corresponded with areas of
hard exudate. Eight months later, the patient's visual acuity
OD had decreased to 20/40. OCT at the second
visit displayed a substantial increase macular thickness centrally.
Focal laser photocoagulation was performed and the patient returned
five months later. On follow-up examination, the visual acuity
OD had returned to 20/20. OCT at the final
visit showed resolution of the edema with a normal foveal
and central macular thickness. A remaining area of minimal retinal
thickening was evident nasal to the fovea.
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Fundus
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Initial Visit
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Second Visit
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Final Visit
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Lamellar or partial thickness macular holes, most
often due to rupture of macular cysts, may also ophthalmoscopically
resemble full-thickness holes. The visual acuity, which is often
worse in eyes with a true macular hole due to the complete loss
of photoreceptors, may not accurately indicate the diagnosis.
Macular hole and lamellar macular hole. A 69-year-old
woman had a full-thickness macular hole in her right eye and a lamellar
macular hole in the left. The visual acuity (20/100 OD and 20/200
OS) was worse in the eye with the partial thickness hole compared
to the eye with a full-thickness hole.
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Full Thickness
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Lamellar
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Fundus
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Fundus
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OCT
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OCT
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Glaucoma
Features
Vitreoretinal
Disease Features
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