Course Title: Choroidal OCT Imaging: Current Concepts & Clinical Applications.
Author: Scott Anthony, OD, FAAO
Abstract:
Choroidal OCT using enhanced depth imaging is quickly gaining importance in the clinical arena
for its ability to reveal in vivo changes beyond the retina. This course reviews the fundamentals
of enhanced depth OCT and its application for detecting and managing a variety of choroidal and
retinal diseases.
1)BACKGROUND
a) Choroid anatomy review
(1) Unique physiological properties of the choroid.
(a) Highly vascularized/pigmented tissue extending form ora serrata to optic
nerve.
(b) Major source of blood supply to the eye and only source for the avascular
foveola.
(c) Composition: blood vessels, connective tissue, melanocytes, intrinsic
neurons.
b) The unexplored choroid
(1)Choroid accounts for a majority of the blood supply to the eye, yet we have an
incomplete understanding of its role in retinal/choroidal disease.
(2)Difficult to assess in vivo due to RPE barrier and densely pigmented choroid.
(3)Evolution of choroidal imaging: choroidal casting, light microscopy, funduscopy,
fluorescein angiography (FA), indocyanine green (ICG) angiography, spectral
domain OCT (SD-OCT), enhanced depth imaging OCT (EDI-OCT), swept-source
OCT (SS-OCT)
(4)EDI-OCT is the current standard for choroidal OCT imaging.
1) SD-OCT IMAGING BASICS
(1) OCT imaging of the retina and choroid go hand-in-hand.
(2) OCT analysis requires thorough knowledge of retinal/choroidal structural
landmarks as depicted by SD-OCT.
(a) Vitreous, internal limiting membrane, nerve fiber layer, ganglion cell
layer, inner plexiform layer, inner nuclear layer, outer plexiform layer,
outer nuclear layer, inner photoreceptor layer, inner segment/outer
segment (IS/OS) junction, outer photoreceptor layer, retinal pigment
epithelium, Bruch’s membrane, choroid, sclera.
(3) Review features of EDI-OCT and highlight the improved visualization of the
outer retina and choroid using this modality.
(a) EDI-OCT utilizes SD-OCT technology but moves the objective lens closer
to the eye to provide improved imaging posterior to the RPE.
(4) Potential limitations of EDI-OCT for imaging choroid.
(a) Ocular media, mid-peripheral/peripheral imaging, limited ability to image
heavily pigmented lesions within the choroid.
1) CHOROIDAL OCT USING EDI-OCT
a) Measuring choroidal thickness (CT) with EDI-OCT.
(1) Average CT values in healthy eyes.
(2) CT in healthy eyes varies throughout the posterior pole:
(a) Posterior>anterior
(b)
(c)
(d)
(e)
Macula: Fovea thickest
Macula: Temporal>Nasal
Macula: Superior>Inferior
Peripapillary: Inferior thinnest
b) Identifying the suprachoroidal layer (SCL)
c) Factors that produce measurement variability in CT: age, time of day, axial length.
d) What is the accuracy/reproducibility of measuring CT using EDI OCT?
(1) Discuss method for measuring CT: plotting segmentation line.
(2) Discuss reproducibility of EDI-OCT CT measurements.
(3) Define the choroid/sclera junction line.
(4) Discuss manual vs. auto-segmentation of choroid/sclera junction.
4) CLINICAL APPLICATIONS FOR CHOROIDAL OCT (Case examples for each
category will be provided)
a) Suspicious choroidal nevus
(1) Review clinical characteristics of suspicious choroidal nevi that should prompt
EDI-OCT imaging.
(a) > 5mm basal diameter
(b) > 2mm thickness
(c) Subretinal fluid (SRF)
(d) Change in size/color
(e) Orange pigment
(f) Absent drusen
(g) Margin continuous with optic disc margin
(h) Visual disturbance
(2) How can EDI-OCT contribute to the clinical assessment of suspicious choroidal
nevus?
(a)
EDI-OCT may provide more accurate thickness measurements of elevated
choroidal nevi.
(i) Ultrasonography (US) mean nevus thickness: 1.5mm
(ii) EDI-OCT mean nevus thickness: 0.685mm
(iii)US overestimated by 126%
(b) Intrinsic EDI-OCT reflectivity of choroidal nevus.
(i) Small choroidal vessel spaces typically present within the lesion.
1. Feature can be used to help differentiate from small choroidal
melanoma.
(ii) Variable intrinsic signal intensity
1. Hyper-reflective band at anterior border of choroidal nevus with
hypo-reflective posterior shadowing.
2. Homogenous hyper-reflective signal with visible choroidal vessels.
3. Isoreflective, less common.
(c) EDI-OCT imaging of choroidal nevus also provides important information
on extrinsic effects of overlying retinal layers.
(i) Abnormal retinal SD-OCT findings are common in benign choroidal
nevus.
(ii) EDI-OCT findings in a case series of 51 choroidal nevi.
1. Only 49% had optimal scan quality.
2.
3.
4.
5.
6.
7.
Choriocapillaris thinning + shadowing: 94%
RPE atrophy: 42%
RPE hypertrophy: 9%
Absent PR layer: 43%
Irregular IS/OS junction: 43%
Sub-retinal fluid: 16%
a. Clinically, only detected in 8% (OCT more sensitive)
b. Not detected in any patients using ultrasonography
8. Drusen: 45%
9. Bruch’s membrane intact: 100%
(d) OCT signs of choroidal nevus that may suggest chronicity (surrogate for
stability)
(i) Retinal edema/thickening not associated with SRF.
(ii) Retinal pigment epitheliopathy (i.e. RPE atrophy/thinning)
(iii)PR loss
(iv) RPE detachment (PED)
(v) Drusen
(e) Advantages over funduscopic evaluation.
(i) SD-OCT shown to be more sensitive for identifying retinal edema, SRF,
and PED.
(ii)
b) Small choroidal melanoma
(1) EDI-OCT not clinically useful for medium/large choroidal melanoma.
(a) Typically outside OCT imaging field (1mm height, 9mm width)
(b) COMS demonstrated 99% diagnostic accuracy using B-scan
ultrasonography, fluorescein angiography, and clinical evaluation.
(2) Review clinical features of small choroidal melanoma.
(a) Small choroidal melanoma can mimic choroidal nevus.
(b) EDI-OCT can help make this critical distinction.
(3) EDI-OCT indicated for small choroidal melanoma
(a) Ultrasonography not sensitive for detecting subretinal fluid.
(i) Resolution approximately 100 µm
(b) SRF is an important clinical finding.
(i) Associated with increased risk for tumor growth and metastasis.
(ii) May be seen in both choroidal nevus and choroidal melanoma.
1. However, less common in choroidal nevi (91% vs. 25%)
(4) EDI-OCT patterns in small choroidal melanoma
(a) Melanocytic tumors: highly reflective band at the anterior choroid with
posterior shadowing.
(b) Amelanocytic tumors: absence of choroidal vascular spaces.
(c) May see an enlarged suprachoroidal layer.
(d) Active tumors tend to exhibit increased overlying retinal thickness
associated with SRF.
(e) Chronic tumors tend to exhibit overlying thinning of the retina, intraretinal
cystic changes, and RPE thickening.
c) Choroidal nevus and small choroidal melanoma may have overlapping OCT
abnormalities.
(1) In small choroidal melanoma, EDI-OCT tends to show abnormalities at all levels
of the retina, RPE, Bruch’s, and choroid.
(2) EDI-OCT images showing visible choroidal vascular spaces are suggestive of
benign choroidal nevus and are not typically seen in choroidal melanoma.
(3) SD-OCT findings in a review of 54 eyes with small choroidal melanoma.
(i) Compared with choroidal nevus, small choroidal melanoma had a higher
prevalence of subretinal fluid, subretinal deposits, and RPE atrophy.
(ii) “Shaggy” photoreceptors (e.g.. hyper-intense spots seen in the PR layer
in areas of SR and not seen in benign choroidal nevus), loss of ELM, loss
of IS/OS junction, irregular IPL, intraretinal edema, and irregular GCL
were found to be statistically more common in melanoma than nevus.
d) Choroidal neovascularization
(1) Exudative age-related macular degeneration
(a) Choroidal thickness shown to be thinner in wet AMD compared to CSC
and PCV.
(b) Potential for identifying occult, subclinical choroidal neovascularization in
asymptomatic AMD patients.
(c) Presently limited role using EDI-OCT to actively manage wet AMD
receiving anti-VEGF therapy.
(i) Potential for improved RPE visualization for RPE auto-segmentation and
more accurate retinal thickness measurements?
(2) Polypoidal choroidal vasculopathy (PCV)
(a) Definition:
(i) First described in 1980’s.
(ii) Abnormal inner choroidal vascular network with exudative aneurysmal
terminal ends
(iii)Best diagnosed using indocyanine green angiography.
(b) Clinical phenotype:
(i) Onset typically 60-70 years old, earlier than exudative ARMD.
(ii) Affects Asians and blacks more than whites
(iii)Subretinal reddish orange polyps may be seen funduscopically.
(iv) Polypoidal lesions in whites tend to have a peripapillary location.
(v) Choroidal polyps result in exaggerated exudation with overlying
neurosensory retinal detachment with heavy lipid deposition and blood
(serosanguineous).
(c) EDI-OCT findings:
(i) Choroidal thickness may help differentiate PCV from wet ARMD.
1. PCV > normal > exudative/dry AMD.
2. Potential for identifying subset of patients with PCV
(ii) Chung et al.
1. PCV eyes: 438 µm
2. Fellow eyes: 372 µm
3. Normal controls: 224 µm
4. Exudative AMD eyes: 171 µm
5. Early dry AMD eyes: 177 µm
(iii)Cystic retinal changes
1. PCV < AMD
(d)
Treatment:
(i) Differs from exudative AMD.
(ii) Use photodynamic therapy with verteporfin.
(iii)Tends to be recalcitrant to anti-VEGF treatments.
e) Central serous chorioretinopathy(CSC)
(1) Clinical phenotype: Macular neurosensory retina detachment in young males.
(2) Etiology: Choroidal hyper-permeability thought to be underlying cause.
(3) EDI-OCT CT is increased throughout posterior pole.
(4) EDI-OCT findings:
(a) Increased subfoveal CT.
(b) Double-layer sign (visible splitting of RPE/Bruch’s): seen in chronic >
acute CSC.
(i) Differs from PCV double-layer sign in that area in between is more often
hypo-reflective vs. hyper-reflective in PCV.
(c) Dilated choroidal vessels in areas of ICG hyperfluorescence.
(d) Inner choroidal layer thinning in area of dilated choroidal vessels.
(e) RPE detachment
(f) RPE rips
f) Age-related choroidal atrophy
(1) Clinical phenotype: Reduced BCVA, mean age 80 years, tessellated fundus, up to
30% with concurrent AMD, up to 30% with concurrent glaucoma.
(2) Pathogenesis: hypothesized that this is a small-vessel disease secondary to agerelated choroidal sclerosis.
(3) Average subfoveal CT: 70µm
5)CONCLUSIONS
a) Choroidal OCT imaging is quickly gaining importance in the clinical arena and will
likely become an integral imaging modality in future OCT devices.
b) EDI-OCT imaging provides superior in vivo imaging beyond the retina, enabling
clinicians to identify disease specific OCT patterns in both the retina and choroid that
facilitate their management.
6)REFERENCES
i. Sayanagi K, Pelayes D, Kaiser P, Singh A. 3D Spectral domain optical coherence tomography
findings in choroidal tumors. Eur J Ophthalmol 2011; 21:271-275.
ii.
The Collaborative Ocular Melanoma Study Group. Accuracy of diagnosis of choroidal
melanomas in the Collaborative Ocular Melanoma Study: COMS Report No. 1. Arch
Ophthalmol 1990; 108:1268-1273.
iii.
Holz F, Spaide R. Medical retina: Focus on retinal imaging. London, UK: Springer; 2010.
iv.
Rogers A, Duker J. Rapid diagnosis in ophthalmology: Retina. US: Elsevier, 2008.
v.
Shah S, Swathi K, Shields C, et al. Enhanced depth imaging optical coherence tomography of
choroidal nevus in 104 cases. Ophthalmolol 2012; 119:1066-1072.
vi.
Shields C, Materin M, Shields J. Review of optical coherence tomography for intraocular
tumors. Curr Opin Ophthalmol 2005; 16:141-154.
vii. Alexander L. Primary Care of the Posterior Segment, 2d ed. Norwalk, Appleton & Lange;
2002: 25-74.
viii. Robertson D. Changing concepts in the management of choroidal melanoma. Am J
Ophthalmol 2003; 136:161-170.
ix.
Shields C, Swathi K, Duangnate R, Ferenzy S, Shields J. Enhanced depth imaging optical
coherence tomography of small choroidal melanoma: Comparison with choroidal nevus. Arch
Ophthalmolol 2012; 130:850-856.
x.
Singh A, Belfort R, Sayanagi K, Kaiser P. Fourier domain optical coherence tomographic and
auto-fluorescence findings in indeterminate choroidal melanocytic lesions. Br J Ophthalmol
2010; 94:474-478.
xi.
Krema H, Habal S, Gonzalez J, Pavlin C. Role of optical coherence tomography in verifying
the specificity of ultrasonography in detecting subtle subretinal fluid associated with small
choroidal melanocytic tumors. Retina 201: June 25, 2013; Epub ahead of print.
xii. Tian J, Marziliano P,Baskaran M, et al. Automatic segmentation of the choroid in enhanced
depth imaging optical coherence tomography images. Biomed Opt Express 2013; 4:397-411.
xiii. Shah S, Mashayekhi A, Shields C, et al. Uveal metastasis from lung cancer. Ophthalmol
2013: Article in press.
xiv. Frenkel S, Pe’er J. Choroidal metastasis of adenocarcinoma of the lung presenting as
pigmented choroidal tumor. Case Rep Ophthalmolol 2012;3:311-316.
xv.
Diener-West M, Reynolds SM, Aguglilaro DJ, et al. Collaborative Ocular Melanoma Study
Group: Second primary cancers after enrollment in the COMS trials for treatment of choroidal
melanoma: COMS Report NO. 25. Arch Ophthalmol 2005; 123:601–604.
xvi. Say E, Shah S, Ferenzy S, Shields C. Optical coherence tomography of retinal and choroidal
tumors. J Ophthalmol 2012; 2012:385058.
xvii. Redmond K, Wharam M, Schachat A. Choroidal Metastases. In: Ryan S, ed. Retina, 5th ed.
Elsevier; 2013: 2325-2329.
xviii. Thomas J, Green W, Maumenee A. Small choroidal melanomas. A long-term follow-up
study. Arch Ophthalmol 1979; 97:861-864.
xix. Li H, Shields C, Mashayekhi A, et al. Giant choroidal nevus. Ophthalmolol 2010;117:324333.
xx.
Newman H, Chin K, Finger P. Subfoveal choroidal melanoma. Arch Ophthalmolol
2011;129:892-898.
xxi. Torres V, Brugnoni N, Kaiser P, Singh A. Optical coherence tomography enhanced depth
imaging of choroidal tumors. Am J Ophthalmolol 2011;151:586-593.
xxii. Shields C, Kaliki S, Rojanaporn D, et al. Enhanced depth imaging optic coherence
tomography of small choroidal melanoma: Comparison with choroidal nevus. Arch
Ophthalmolol 2012;130:850-856.
xxiii. Sheilds C, Furuta M, Berman E, et al. Choroidal nevus transformation into melanoma. Arch
Ophthalmolol 2009;127:981-987.
xxiv. Yang L, Jonas J, Wei W. Optical coherence tomography-assisted enhanced depth imaging of
central serous chorioretinopathy. Invest Ophthalmol Vis Sci 2013;54:4659-4665.
xxv. Spaide R. Age-related choroidal atrophy. Am J Ophthalmol 2009;147:801-810.