Optic coherence tomography

Optic Coherence
Tomography
DR BHAVIN J PATEL
SR NEUROLOGY
MBS HOSPITAL AND GMC, KOTA

Introduction
Imaging technique use to screen various superficial structures…
Noncontact & Non invasive
Nonradiation
Fast, Efficient and Safe
Micron resolution
Reproducible diagnostic imaging
Bhende M,Optical coherence tomography: A guide to interpretation of common macular diseases.
Indian J Ophthalmol 2018;66:20-35

History

Principle of OCT

Types of oct
Time domain Spectral domain
Reference mirror moves Reference mirror stationary
1 pixel at a time 2048 pixel at a time
Slow Rapid
Motion artifacts present No motion artifacts
Less sharp images Sharper and clear images

Generations of OCT
Curr Opin Ophthalmol. 2013 May ; 24(3): 213–221.

Analysis of OCT
Qualitative analysis
Morphology and anomalous structures
Reflectivity: hyper, hypo and shadowing
Quantitative analysis
 Thickness
 Volume
 Area

Qualitative analysis
High reflectivity:-
 Nerve Fiber Layer, RPE
ERM, hemorrhage, cotton‐wool spots, hemorrhage, hard exudates, drusen, RPE
hyperplasia
Medium reflectivity:- Plexiform layers Nuclear layers
Low reflectivity:- Photoreceptors, fluid, cysts

Anatomy of Retina on OCT

Type of Scan
POSTERIOR SEGMENT SCAN
 MACULAR SCAN
 OPTIC DISC SCAN
 RNFL THICKNESS ANALYSIS SCAN
ANTERIOR SEGMENT SCAN

Uses
Neurological
Ophthalmological
Other uses

Multiple Sclerosis
Multiple sclerosis (MS) causes both demyelination and axonal loss
pRNFL thickness can be used to assess axonal loss
MS patients who have not experienced a clinical episode of optic neuritis, the
average pRNFL thickness has been shown to be thinner than in healthy controls
Neurol Clin Pract 2015;5:460–469

Multiple Sclerosis
Microcystic retinal edema without a clinically identifiable cause can
be seen in the inner nuclear layer (INL) in patients with MS
GCL and inner plexiform layer (IPL) are preferentially affected.
Combined GCL and IPL thickness has been shown to be superior to
RNFL thickness in correlation to severity of disease.

Multiple Sclerosis
The progressive thinning of retinal layers as measured by OCT varies
depending on the subtype Of MS.
RNFL thickness correlates with T1 or T2 lesion volume, grey matter atrophy,
MTR, and diffusion tensor imaging measures (DTI).

Multiple Sclerosis

NMO
Neuromyelitis optica (NMO) typically follows a more aggressive and
debilitating course.
After at least 3 months, the peripapillary RNFL is typically thinner
following NMO optic neuritis compared to MS optic Neuritis……

NMO
In NMO optic neuritis, RNFL loss is more severe, diffuse, and
involves the superior and inferior quadrants.
In MS optic neuritis, RNFL loss is less severe and predominantly
affects the temporal quadrant that contains the papillomacular bundle

Demyelinating optic neuritis
Combined GCL - IPL thickness decreases before RNFL thinning in eyes
with optic neuritis
Optic neuritis have diffuse thinning of the pRNFL with preferential
involvement of the temporal quadrant.
 RNFL thickness below 75 mm are more likely to have persistent visual
field defects

Leber Hereditary Optic Neuropathy
As papillomacular bundle thickens at the presymptomatic stage, pRNFL
thickness (pRNFLT) increases.
mGCC thickness decreases at presentation as atrophy of the macular retinal
ganglion cells (RGC) sets in
mGCC damage begins as early as 6 weeks before the onset of visual loss in
LHON
Curr Opin Ophthalmol 2017, 28:000–000

Papilledema
OCT can also aid in differentiation of optic nerve head drusen (i.e.,
pseudo papilledema) from papilledema
Degree of pRNFL thickening of more than 127 microns gave a 73%
sensitivity and specificity
OCT volumetric measurements correlate well with clinical grading
of optic nerve head photographs,

Optic pathway glioma
Patients with neurofibromatosis-1 (NF1) with OPGs were found to have
thinner peripapillary RNFL and maculae than healthy controls
Similarly, combined macular GCL-IPL thickness was thinner in children
with OPGs and vision loss

Compressive optic neuropathy
Enlargement of the optic cup and thinning of the RNFL
More thinning nasally and temporally in compressive optic neuropathy
OCT can be used to predict the likelihood of postoperative visual recovery
Patients with thinning (less than 97.5%of normal) of the RNFL were less
likely to show any improvement in visual acuity or visual fields

NAION
Ganglion cell complex measurements have shown to correlate well with the
severity and location of visual field loss.
NAION eyes showed significant thinning of macular ganglion cell inner
plexiform layer (GCIPL) as early as 2.2 days after symptoms onset.
Degree of initial pRNFL swelling correlated with the severity of atrophy, as
well as the level of functional impairment,…

Alzheimer disease
Decreased macular thickness and RNFL thinning are associated with
abnormalities on electroretinogram.
There is decreased choroidal thickness in patients with AD compared
to healthy controls
Rev Neurol Dis. 2009;6(4):E105-E120 doi: 10.3909/rind0243

Parkinson disease
Ophthalmologic manifestations of Parkinson disease (PD) include:-
Decreased visual acuity,
Decreased contrast sensitivity,
Hallucinations,
Altered color perception,
Prolonged visual evoked potential latency
The meta-analysis found a higher prevalence of RNFL thinning at the
temporal quadrant compared to other quadrants.

Parkinson disease
GCL thickness was inversely correlated with disease duration and severity.
The differential thicknesses of the outer nuclear layer and outer plexiform
layer could help distinguish PSP from MSA.

Amyotrophic lateral sclerosis
In a study of 24 patients with ALS, there were significantly lower
measures of average RNFL, INL, and macular thickness compared to
controls.

Drug Toxicity
Vigabatrin-attributed visual field loss is asymptomatic at early stage
with normal fundoscopy or subtle retinal changes only.
Fingolimod asso macular edema(FAME) can be diagnosed by
macular OCT.

Opthalmological uses
For purposes of analysis, the OCT image of the retina can be
subdivided vertically into four regions
Pre-retina
Epi-retina
Intra-retina
Sub-retina

Pre retinal pathology
Anomalous structures
 pre-retinal membrane
 epi-retinal membrane
 vitreo-retinal strands
 vitreo-retinal traction
 pre-retinal neovascular membrane
 pre-papillary neovascular membrane

Intra retinal pathology
 Choroidal neovascular membrane
 Diffuse intra-retinal edema
 Cystoid macular edema
 Drusen
 Hard exudates
 Scar tissue
 RPE tear

OCT IN GLAUCOMA
Diagnosing and monitoring the glaucomatous change.
 Evaluating the RNFL for early (pre- perimetric) glaucoma detection.
 Evaluation of cystoid macular edema after combined cataract and
glaucoma surgery.

ANTERIOR SEGMENT OCT
Corneal thickness and keratoconus evaluation
Anterior chamber angle
 Assessing the fit of intraocular lens implants
Results of corneal implants

Other Uses
Imaging of non transparent tissue.
Neoplasia, vol 2, jan-apr, 2000 pp 9-25

Other Uses
Optical biopsy and detecting early neoplastic changes

Other Uses
Cathater and endoscopic oct imaging  Cellular level oct imaging

NEWER OCT’s
 OCT- SLO
 3D OCT
OCT-angiography
Enhanced depth imaging
Retinal single-layer imaging

Artifacts
Misidentification of inner or outer retinal layer
Off center artifact
Off register artifact
Motion artifact
Blink artifact

Limitations
Quality of OCT depends on the transparency of the ocular media
OCT is operator dependent
The statistical analysis is based on a control population, which may not be
accurate depending on the population studied

Conclusion
Helps in diagnosis, treatment monitoring and deciding prognosis of
neurological illness.
Can replace need of tissue biopsy in future.
Required further research to make it more clinically applicable.
Novel and developing imaging modality.

References
Neoplasia, vol 2, jan-apr, 2000 pp 9-25
Review Neurological Dis. 2009;6(4):E105-E120 doi: 10.3909/rind0243
Curr Opin Ophthalmol 2017, 28:000–000
Neurology Clinical Pract 2015;5:460–469
Curr Opin Ophthalmol. 2013 May ; 24(3): 213–221.
Bhende M,Optical coherence tomography: A guide to interpretation of
common macular diseases. Indian J Ophthalmol 2018;66:20-35
Uptodate.com

Summary

Optic coherence tomography

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