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The Retina
A Guide to Self-Assessment
Melvin J. Gouder
The Retina
Melvin J. Gouder
The Retina
A Guide to Self-Assessment
13
Melvin J. Gouder
Department of Ophthalmology
Mater Dei Hospital
Msida, Malta
ISBN 978-3-030-48590-0 ISBN 978-3-030-48591-7 (eBook)
https://doi.org/10.1007/978-3-030-48591-7
© Springer Nature Switzerland AG 2020
This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part
of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,
recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or
information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar
methodology now known or hereafter developed.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication
does not imply, even in the absence of a specific statement, that such names are exempt from the relevant
protective laws and regulations and therefore free for general use.
The publisher, the authors and the editors are safe to assume that the advice and information in this book
are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or
the editors give a warranty, express or implied, with respect to the material contained herein or for any
errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional
claims in published maps and institutional affiliations.
This Springer imprint is published by the registered company Springer Nature Switzerland AG
The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland
Dedicated to Floyd Dylan Gouder, my son.
Preface
This book is aimed to assist and help the examinee. The idea behind this book was
born decades ago when I was in my trainee years and always looking for books to
help me succeed in my post-graduate exams in ophthalmic surgery. Then, the
internet was in its infancy and learning was mainly through reading and revis-
ing and finding a source for self-testing in preparation for the exam. Those kinds
of books were scanty. Though exam styles evolved and changed throughout the
years, I still believed that multiple choice questions were a reliable source of test-
ing one’s knowledge. What I noticed then is that such books mostly offered a
quick answer with no or minimal explanation related to the questions.
The idea behind this book is not to serve as a reference but to complement the
equation and answer with detail about the subject matter being tested. This book
provides 100+ questions on the retina mostly medical retina, but coming from
the vitreoretinal field, I made sure to include a thorough chapter on the surgical
aspect. Each question and answer should serve as an inspiration to stimulate the
reader to seek further detail if it needs to be—perhaps in a reference text. MCQs
help in problem solving and provide some form of reassurance in the pre-exam
time hence increasing the chance of success. The final chapter is adorned with
clinical photos of common and less common retinal disease one might expect to
meet during an ophthalmological career.
Though RCOphth exams are still popular we have seen the emergence of the
FEBO exam and many countries now provide their own post-graduate ophthal-
mic exams. This book is ideal for all these kinds of exams. Questions vary from
simple straightforward ones to more complex subjects. Mixing the traditional with
the modern is always more exciting and one can find this featured prominently
throughout the whole book.
MCQs are always challenging and one has to accept that some may be contro-
versial and ambiguous and a degree of misinterpretation is always expected.
Conceiving this book was not easy and hence I am indebted to certain people
and colleagues who made all this possible. I am limitlessly indebted to Ms. Karen
Grech, a talented book and paper conservator/restorer by profession whose ideas,
vii
viii Preface
though coming outside the medical field, have always been helpful and reassuring.
Karen was crucial in helping me finish the book.
I am also indebted to Andrei Camenzuli, clinic manager and technical nurse at
Saint James Eye Clinic in Malta, a private institution always at the forefront in
providing the best medical and surgical ophthalmic care in Malta. And lastly but
not least, I am indebted to my dad Joseph Gouder and my mum Angele Gouder
who always believed in me and will do so ad infinitum.
Msida, Malta Melvin J. Gouder
Contents
1 Basic Anatomy, Embryology and Physiology of the Retina . . . . . . . 1
1 Answers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Answers in Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2 Retinal Testing and Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1 Answers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2 Answers in Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3 Retinal Vascular Disease. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
1 Answers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2 Answers in Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4 Retinal Degeneration and Dystrophies. . . . . . . . . . . . . . . . . . . . . . . . . 31
1 Answers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2 Answers in Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5 Disorders of the Macula. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
1 Answers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2 Answers in Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
6 Vitreous and Vitreoretinal Interface Pathology. . . . . . . . . . . . . . . . . . 49
1 Answers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
2 Answers in Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
ix
x Contents
7 Drug-Induced Retinopathies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
1 Answers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
2 Answers in Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
8 Vitreoretinal Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
1 Answers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
2 Answers in Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
9 Choroidal and Retinal Tumours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
1 Answers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
2 Answers in Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
10 Retinal Imaging. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Abbreviations
AD Autosomal dominant
AION Anterior ischaemic optic neuropathy
AMN Acute macular neuroretinopathy
AMPPE Acute multifocal posterior pigment epitheliopathy
AR Autosomal recessive
AV Arteriovenous
BCVA Best corrected visual acuity
BM Bruch’s membrane
CAR Cancer-associated retinopathy
CC Choriocapillaris
CHRPE Congenital hypertrophy of the RPE
CNV Choroidal neovascular membrane
CRAO Central retinal artery obstruction
CRVO Central retinal vein obstruction
CSR Central serous retinopathy
DMO Diabetic macular oedema
DR Diabetic retinopathy
ELM External limiting membrane
EOG Electrooculogram
EOM Extraocular muscle
FAF Fundus autofluorescence
FAP Familial adenomatous polyposis
FAZ Foveal avascular zone
FEVR Familial exudative vitreoretinopathy
FTMH Full-thickness macular hole
GAG Glycosaminoglycans
GCL Ganglion cell layer
GRT Giant retinal tear
HCQ Hydroxychloroquin
i.v. Intravenous
ICG Indocyanine green
xi
xii Abbreviations
ILM Inner limiting membrane
IOP Intraocular pressure
IPL Inner plexiform layer
IVFA Intravenous fluorescein angiography
MEWDS Multiple evanescent white dot syndrome
NAION Non-Arteritic anterior ischaemic optic neuropathy
NFL Nerve fibre layer
NVD Neovascularisation at the disc
NVE Neovascularisation elsewhere
NVI Neovascularisation at the iris
OA Ophthalmic artery
OCTA Optical coherence tomography angiogram
ONL Outer nuclear layer
OPL Outer plexiform layer
PAMM Paracentral acute middle maculopathy
PCV Polypoidal choroidal vasculopathy
PDR Proliferative diabetic retinopathy
PED Posterior epithelial detachment
PHM Posterior hyaloid membrane
PR Photoreceptors
prn Pro re nata
PXE Pseudoxanthoma elasticum
RAPD Relative afferent pupillary defect
ROP Retinopathy of prematurity
RP Retinitis pigmentosa
RPE Retinal pigment epithelium
SLO Scanning laser ophthalmoscopy
SPCA Short posterior ciliary artery
VEGF Vascular endothelial growth factor
VHL Von Hippel–Lindau disease
WWOP White without pressure
WWP White with pressure
XLJR X-linked juvenile retinoschisis
Chapter 1
Basic Anatomy, Embryology and Physiology
of the Retina
1. Retinal histology:
(a) its thickness does not vary
(b) the innermost layer is the retinal ganglion cell layer
(c) the outermost layer is also the outermost layer of the neuroretina
(d) bruch’s membrane is associated with the RPE
(e) the Umbo is in the centre of the fovea.
2. Retina and vitreous embryology [1]:
(a) The retina is derived from the optic vesicle
(b) It is an out-pouching of the embryonic midbrain
(c) The vitreous is mainly composed of GAG and collagen
(d) Vitreous and choroid are derived from mesenchyme
(e) Mittendorf dot and Bergmeister papilla are remnants of the hyaloid artery.
3. Retina and vitreous embryology:
(a) Retina forms from neuroectoderm
(b) the hyaloid artery is derived from the vascular mesoderm
(c) sensory retina forms from the inner layer of the optic cup
(d) RPE is formed from the outer layer of optic cup
(e) the hyaloid artery is derived from the ophthalmic artery.
4. The vitreous [2]:
(a) Is composed of two main areas: the vitreous core and cortical vitreous.
(b) Forms 80% of the eye volume
(c) The anterior retrolental vitreous is condensed
© Springer Nature Switzerland AG 2020 1
M. J. Gouder, The Retina, https://doi.org/10.1007/978-3-030-48591-7_1
2 1 Basic Anatomy, Embryology and Physiology of the Retina
(d) The vitreous base is closely associated with the zonular fibres of the lens
(e) It is high in ascorbate levels.
5. The ora serrata:
(a) It is the border between the peripheral retina and pars plana
(b) It is a very smooth transition of the periphery of the retina
(c) Retinal tears are associated with meridional folds
(d) Dentate processes are teeth-like extensions of retina onto the pars plana
(e) Tears in the ora serrata area may be associated with pigmentary changes.
6. The fovea [3]:
(a) The fovea has no rods
(b) The central fovea is called the foveola
(c) In the fovea the inner cellular layers of the retina are displaced laterally
(d) RPE is densest at this region
(e) Cones in the fovea are predominately yellow- and blue-sensitive.
7. RPE histology [4];
(a) It is sometimes multilayered
(b) Melanosomes are spread evenly in the cell
(c) The cell base is firmly associated with the choroidal vasculature
(d) Their apices are in contact with the outer segments of the photoreceptors
(e) Melanosomes are abundant in the cells lying beneath the fovea.
8. RPE physiology [6, 7];
(a) RPE forms the outer blood-retinal layer
(b) RPE, being a monolayer, rarely heals by scarring
(c) Integral in recycling visual pigment
(d) Phagocytosis is continuous
(e) Is able to regenerate.
9. Bruch’s membrane;
(a) Is pentalaminar
(b) Prone to calcify in pathologic processes
(c) Essential in keeping the retina healthy
(d) Suppresses the formation of choroidal neovascular membranes
(e) Is fractured in Angioid streaks.
1 Basic Anatomy, Embryology and Physiology of the Retina 3
10. Choroid;
(a) Is supplied mainly by the anterior ciliary arteries
(b) The choriocapillaris circulation is high pressure
(c) Gets thinner away from the macular area
(d) Is highly pigmented
(e) Thickness changes are associated with ocular disease.
11. Choroidal anatomy [5];
(a) Choroid is tightly adhered to the sclera
(b) Up to ten vortex veins provide choroidal drainage
(c) Innervated by the long and short ciliary nerves
(d) Haller’s and Sattler’s layer are vascular
(e) There is a low pressure blood flow in the choriocapillaris.
12. Choroidal physiology;
(a) Choroidal vasculature supplies the outer retina
(b) The photoreceptors of the retina are highly active
(c) The choroid has a high blood flow
(d) Venous blood exiting the choroid has a low oxygen tension
(e) The choroid is a heat sink.
13. Sclera;
(a) Uniform thickness throughout
(b) Is permeable to drugs injected around the eye
(c) Derived from neural crest
(d) Composed of collagen, elastic fibres and proteoglycans
(e) Pigmentation is common.
1 Answers
1. FFFTT
2. TFFTT
3. TTTTT
4. TTTFT
5. TFFTT
6. FTTTF
7. FFFTT
8. TFTTF
4 1 Basic Anatomy, Embryology and Physiology of the Retina
9. TTTTT
10. FFTTT
11. FFTTT
12. TTTFT
13. FTTTT.
2 Answers in Detail
1. FFFTT
Retinal thickness varies throughout but it shows greatest variation centrally i.e.
around the macula. It is thinnest at the foveal floor (<60 microns) than gets thicker
immediately around the macula (~330 microns). Away from the macula it rapidly
thins until the equator (~150 microns) and at the ora serrata it is ~160 microns.
Retinal layers from inside out—ILM-RNFL-GCL-IPL-INL-OPL-ONL-ELM-
PR-RPE hence the RPE is the outermost layer and the ILM is the innermost layer.
The RPE is attached to BM. The Umbo is the central part of the fovea.
2. TFFTT
The retina is derived from the optic vesicle which is an out-pouching of the
embryonic forebrain. The mature vitreous is mainly composed of water (99%).
The rest is made up of hyaluronic acid collagen type 2, hyalocytes, inorganic
salts and ascorbic acid and has a pH of 7.5. The vitreous and choroid are derived
from mesenchyme, the retina from the neuroectoderm and the cornea from sur-
face ectoderm (corneal epithelium) and mesenchyme (corneal stroma). Mittendorf
dot is a small opacity on the posterior aspect of the lens whereas a Bergmeister
papilla is a tuft of fibrous tissue on the optic nerve head—all remnants of the hya-
loid artery.
3. TTTTT
The retina forms from neuroectoderm. The hyaloid artery is derived from the vas-
cular mesoderm.
Sensory retina forms from the inner layer of the optic cup whereas the RPE is
formed from the outer layer of the optic cup.
The hyaloid artery is derived from the ophthalmic artery which in adults is a
branch of the internal carotid artery. When the hyaloid artery regresses it leaves
a clear central zone in the vitreous called Cloquet’s canal. If the artery does not
regress it can remain in the vitreous as a persistent hyaloid artery.
4. TTTFT
The vitreous is made up of the central (or core) and the peripheral (cortical) vit-
reous. It forms 80 percent of the eye volume and made up of hydrated hyaluronic
acid with suspended collagen fibrils. The anterior vitreous behind the lens is made
2 Answers in Detail 5
up of condensed collagen fibres that are attached to the posterior capsule of the
lens—ligament of Weiger. Berger space is the potential space bordering this lig-
ament. The vitreous is particularly attached firmly at the vitreous base, lens cap-
sule, retinal vessels, optic nerve and macula. Ascorbic acid, which is very high in
the lens, has a protective role in the lens. Vitrectomy—which removes most of the
vitreous from the eye—increases the chance of lenticular opacities in the post-op
period (typically nuclear sclerosis).
5. TFFTT
The peripheral retina extends anteriorly and ends in the ora serrata. It is an irreg-
ular, ‘serrated’ area of transition with specific anatomic features. Meridional folds
are areas of excess retina bulging slightly into the vitreous where at its base can
be weak and retinal tears occur. A dentate process (dentate means tooth) is an area
of real parts of the retina jutting into the pars plana like a spear. At the ora serrata
region the pigmented epithelium of the retina transitions into the outer pigmented
epithelium of the ciliary body and the inner portion of the retina transitions into
the non-pigmented epithelium of the ciliary body.
Retinal RPE → outer pigment epithelium of the ciliary body and iris
Neurosensory Retina. → inner non-pigmented epithelium of the ciliary body.
6. FTTTF
Actually it is the foveola, or the central fovea that is devoid of rods. Rods reach
maximal density around 4 mm from the foveal centre. The fovea is rich in red- and
green-sensitive cones and cones density decrease away from the fovea explaining
the decrease in the visual acuity away from fixation. In the fovea the inner cellular
layers of the retina are displaced laterally so as light scatter is reduced. Beneath
the fovea, RPE density is very high as this is a very active metabolic region.
The foveola is the thinnest part of the retina. Apart from cones there are also
Muller cells and their processes.
7. FFFTT
The RPE cell is a hexagonal cell which is very metabolically active. It is derived
from the outer layer of the optic cup. The RPE cell layer is a monolayer and
beneath the fovea it is not only the density that changes (increases) but also the
shape, becoming taller and thinner so more of them fit per unit area. Melanosomes
are denser towards the cell’s apex next to the photoreceptors. The nucleus of the
cell is more commonly found at the outer area next to the Bruch’s membrane.
8. TFTTF
Functions and features of the RPE:
I. Forms the outer blood-retina layer (tight junctions between cells are called
zonulae occludens—most densely situated near the apex).
II. Development of photoreceptors during embryogenesis.
6 1 Basic Anatomy, Embryology and Physiology of the Retina
III. This outer blood-retina layer prevents extracellular fluid leaking into
the sub-retinal space from the choriocapillaris found beneath the Bruch
membrane.
IV. Actively pumps water and ions out of the sub-retinal space (provided
there are no tears in the neurosensory retina a lot of sub-retinal fluid can
be resorbed in a couple of hours. In normal situations the RPE keeps the
sub-retinal space free from water.
V. The RPE is intimately attached to the Bruch’s membrane beneath by the
help of osmotic and hydrostatic pressure and hemidesmosomes.
VI. Continuous phagocytosis and re-cycling of the outer photoreceptor layer.
Intra-RPE lysosomes degrade the engulfed outer PR disc fragments hence
maintaining turn over of PR. The rods shed discs at night and the cones shed
them at dusk.
VII. Promotes a health retina by taking care of waste products and allowing
transport of healthy metabolites towards the neuroretina.
VIII. Uptake, transport, storage, metabolism and isomerization of vitamin A.
IX. Absorption of stray light by melanin to control light scatter.
9. TTTTT
Basically, the Bruch’s membrane, as seen through the electron microscope is made
up of 5 layers. It is enveloped between the RPE and the choroid choriocapillaris.
Histopathological changes to the basic Bruch’s membrane leads to the pathogene-
sis of many diseases. For example calcification of the Bruch’s membrane can lead
to fractures and CNV formation such as what happens in angioid streaks.
Bruch’s Membrane Layers Thickness (microns)
RPE basal lamina 0.3
Inner collagenous layer 1.5
Band of elastic fibres 0.8
Outer collagenous layer 0.7
Choriocapillaris basal lamina 0.1
10. FFTTT
The choroid, is the vascular layer of the eye, containing connective tissues, and is
sandwiched between the retina and sclera. The choroid is thickest at the submacu-
lar area (at 0.2 mm), while near the ora serrata it narrows to 0.1 mm where it is the
thinnest. The choroid provides oxygen and nourishment to the outer layers of the
retina. Along with the ciliary body and iris, the choroid forms the uveal tract.
The choroid receives its blood supply primarily from the posterior ciliary
branches of the ophthalmic artery but there is also some supply from the recurrent
anterior ciliary arteries. Pachychoroid means thick choroid where leptochoroid
means thin choroid and both can be signs of disease.
2 Answers in Detail 7
11. FFTTT
The choroid adheres only loosely to the sclera over most of its area, and as a con-
sequence, the choroid is easily separated from the sclera by either haemorrhage
or serous fluid. The only points at which the choroid is fixed are the optic nerve
and at the vortex veins. Attachment of the choroid to the sclera at the vortex veins
explains the classic quadrantic appearance of choroidal detachments. Four or five
vortex veins provide the choroid’s venous drainage. The nerve supply of the cho-
roid is derived from the long and short ciliary nerves.
Trigeminal nerve (CN V1) — > Nasociliary nerves — > long ciliary nerves.
(sensory + sympathetic)
Oculomotor nerve (CNIII) — > ciliary ganglion — > short ciliary nerves (sym-
pathetic and parasympathetic fibres)
Haller’s layer—the outer large caliber choroidal vessels
Sattler’s layer—smaller diameter vessels and pre-capillary arterioles
There is a low pressure blood flow in the choriocapillaris.
Interspersed with the blood vessels are melanocytes, nevus cells, and nerves.
These blood vessels possess an outer adventitial layer, an intermediate smooth
muscle layer, and an internal elastic lamina. They are not fenestrated and as a
result do not leak dye during fluorescein angiography.
Sattler’s layer is deep to Haller’s layer and is composed of medium-sized blood
vessels, melanocytes, fibroblasts, lymphocytes, mast cells, and supporting colla-
gen fibres. Within Sattler’s layer, arteries gradually decrease in caliber and form
arterioles. In the process, the arteries lose their muscularis layer and their internal
elastic laminae. Like the vessels of Haller’s layer, the vessels of Sattler’s layer are
not fenestrated and do not leak fluorescein.
The choriocapillaris is a layer of capillaries that is immediately adjacent to
Bruch’s membrane. The diameter of the capillaries is relatively large and measures
between 25 and 50 µm. These capillaries are fenestrated and therefore are permea-
ble to large molecules, including fluorescein. On fluorescein angiography, the dif-
fuse fluorescence of the choroid is primarily due to the leakage of fluorescein from
the choriocapillaris. The choriocapillaris extends from the edge of the optic disc to
the ora serrata.
12. TTTFT
The choroidal vasculature supplies the retina and is responsible for supplying 90%
of retinal oxygen needs—the photoreceptors being one of the most metabolically
active cells of the retina. The oxygen tension in the venous outflow of the choroid
still has a high oxygen tension hence prone to oxidative damage. Since blood flow
is fast, the choroid tends to ‘cool’ the retina by acting as a heat sink in removing
thermal energy accumulating by light absorption.
13. FTTTT
The sclera forms the posterior 5/6 of the eye with the remainder made up of
the cornea. It is white and opaque but its colour is determined by pigmentation,
8 1 Basic Anatomy, Embryology and Physiology of the Retina
deposits and circulation status. It is hydrophilic and permeable to certain drugs
injected in the subtenon space as a form of local medication. Embryologically
derived from neural crest and composed mainly of collagen, a few elastic fibres
embedded in proteoglycans. Dark skinned individuals may have a darker sclera.
Thin sclera in kids give it a greyish tone from the choroid.
References
1. Cassin B, Solomon S. Dictionary of eye terminology. Gainesville, Florida: Triad Publishing
Company; 1990.
2. Romer AS, Parsons TS. The vertebrate body. Philadelphia, PA: Holt-Saunders International;
1977. p. 461. ISBN 978-0-03-910284-5.
3. Development of the eye by Victoria Ort, Ph.D and David Howard, M.D. http://education.med.
nyu.edu/courses/macrostructure/lectures/lec_images/eye.html.
4. LifeMap Science, Inc. Embryonic and postnatal development of the eye. https://discovery.life-
mapsc.com/in-vivo-development/eye.
5. Gilbert SF. Developmental Biology. 6th edition. Sunderland (MA): Sinauer Associates; 2000.
Development of the Vertebrate Eye. Available from: https://www.ncbi.nlm.nih.gov/books/
NBK10024/.
6. Sensory reception: human vision: structure and function of the human eye, vol. 27.
Encyclopaedia Britannica; 1987. p. 174.
7. Strauss O. The retinal pigment epithelium in visual function. Physiol Rev. 2005;85:845–81.
Chapter 2
Retinal Testing and Imaging
1. Direct Ophthalmoscopy [1];
(a) is better than indirect ophthalmoscopy
(b) is a monocular test
(c) high-magnification up to ×15
(d) small field of view
(e) it is great for the periphery.
2. Indirect Ophthalmoscopy;
(a) provides a low magnification and an inverted image
(b) provides a stereoscopic image
(c) optimum field of view
(d) easy to master
(e) is a non-contact test.
3. The three-mirror lens;
(a) provides high-resolution images
(b) gives high magnification view of the retina
(c) non-inverted images
(d) the apical smallest mirror is used for the equatorial retina
(e) since the contact lens touches the cornea, total internal reflection issues are
obliterated.
4. Fundus photos:
(a) mydriasis is always needed
(b) gives information only to central retina
© Springer Nature Switzerland AG 2020 9
M. J. Gouder, The Retina, https://doi.org/10.1007/978-3-030-48591-7_2
10 2 Retinal Testing and Imaging
(c) cataracts do not hinder photo capture
(d) different filters can be used
(e) is a cheap test.
5. IVFA [3]:
(a) fluorescein enters the ocular circulation from the internal carotid artery via
the ophthalmic artery
(b) venous stage at 1 min
(c) choroidal flush occurs before retinal filling
(d) involves the injection of 25 cm3 of sodium fluorescein into a vein in the
arm or hand.
(e) patient may feel nauseous once the dye is injected.
6. Physics of IVFA:
(a) the retina is illuminated by blue light
(b) the camera allows yellow-green light from the retina
(c) the filters used are called interference bandpass filters
(d) autofluorescence is fluorescence from the eye which occurs without injec-
tion of the dye
(e) pseudofluorescence means non-fluorescent light is imaged.
7. Causes of hyperfluorescence in IVFA:
(a) leakage of fluid
(b) staining of tissues
(c) blocking in ischaemia
(d) transmission, or window, defect
(e) autofluorescence.
8. Causes of hypofluorescence in IVFA [4]:
(a) ischaemia
(b) retinal embolism
(c) macroaneurysms
(d) optic disc drusen
(e) myopic chorioretinal degeneration.
9. Indocyanine green (ICG) [8, 9]:
(a) is fat-soluble
(b) almost completely protein-bound after injection
(c) leaks profusely through the choriocapillaris
(d) ICG is metabolised in the liver and excreted via bile.
(e) fluoresces very efficiently.
2 Retinal Testing and Imaging 11
10. Indications for ICG angiography include the following:
(a) CNV
(b) pigment epithelial detachment (PED)
(c) polypoidal choroidal vasculopathy (PCV)
(d) central serous chorioretinopathy
(e) choroidal inflammatory conditions.
11. Advantages of OCT Angiography over IVFA [2]:
(a) no dye is used
(b) cheaper test
(c) can identify different layers of the retina
(d) higher definition images
(e) non-invasive.
12. B-Scan ultrasonography [5, 6]:
(a) B stands for “brightness”
(b) no need to use topical anaesthesia
(c) useful in detecting retinal detachment in the presence of dense vitreous
haemorrhage
(d) increasing the gain setting increases the resolution
(e) only useful in intraocular pathology.
13. The following are true about electroretinogram [7]:
(a) the a-wave is produced by the photoreceptors
(b) the b-wave is produced by the ganglion cells
(c) c-wave is produced by the retinal pigment epithelium
(d) different light frequencies can be used to separate rod and cone response
(e) it is useful for detecting early Best’s disease.
14. The electrooculogram (EOG):
(a) measures the electrical potential between the front and the back of the eye
(b) has a resting potential of 40 mV
(c) is abnormal in optic nerve disease
(d) is abnormal in Best’s disease even before the onset of visual symptoms
(e) can be measured using the Arden Index which is the ratio of dark trough to
light rise.
15. The following statements are true:
(a) ERG is diagnostic of Stargardt’s disease
(b) amplitude of ERG is reduced in carriers of choroideremia
12 2 Retinal Testing and Imaging
(c) EOG light peak to dark trough ratio is normal in adult-onset foveomacular
dystrophy
(d) ERG is diagnostic of Leber’s congenital amaurosis
(e) ERG is useful in detecting carrier of X-linked retinitis pigmentosa.
16. The following are true in relation to full-field ERG [7]:
(a) in carotid artery occlusion (CRAO) there is a reduced b-wave greater than
a-wave amplitudes
(b) in hypertension and arteriosclerosis there is initially reduced oscillatory
potentials followed by reduced a- and b-wave amplitudes
(c) in thioridazine toxicity there is decreased photopic and scotopic a- and
b-wave responses
(d) in hydroxychloroquine toxicity there is normal ERG responses unless pres-
ence of advanced retinopathy; cone function initially more affected than
rod function
(e) in Cone dystrophy there is markedly depressed photopic response and less
affected scotopic response.
1 Answers
1. FTTTF
2. TTTTF
3. TFTFT
4. FFFTF
5. TFTTT
6. TTTTT
7. TTFTT
8. TTTFF
9. FTFTF
10. TTTTT
11. TFTTT
12. TFTFF
13. TFTTF
14. TFFTF
15. FFTTT
16. TTTTT.
2 Answers in Detail 13
2 Answers in Detail
1. FTTTF
Direct ophthalmoscopy also sometimes known as fundoscopy provides a vertical,
monocular high magnification image mostly used to examine the central retina, optic
disc and nearby vessels (the eye grounds). However, it provides a very small field
of view ranging from 5–8 degrees—similar to the image obtained using a telephoto
lens in photography. So, this requires a lot of ocular steering to view peripheral areas
but as such is not used to examine the retinal periphery. It is popular with medics and
other non-ophthalmic specialists mainly to assess the eye from a systemic point of
view (such as to rule out an optic disc swelling, obtain some macular information in
diabetic macular oedema or even used as light source to elicit pupillary reflexes).
2. TTTTF
Indirect Ophthalmoscopy can be carried out with a head mounted instrument or
incorporated during slit-lamp analysis using a 90D, 90D wide field, 78D or a 60D
lens. The following table shows the main differences between direct and indirect
ophthalmoscopy (Table 1).
In indirect ophthalmoscopy various condensing lenses can be used typically
and commonly the 20D and 28D in the head mounted type instrument and the 90D
(wide-field option available) and 78D, the latter more for macular assessment as it
gives a more magnified view of the macula. A 20D lens gives a magnification of
−60/20D = − 3 (see Table 2) with the minus sign indicating it is an inverted image.
Hence a 28D lens which is typically used in paediatric fundus examinations gives a
better field of view but a smaller magnification. In slit-lamp indirect ophthalmoscopy
there is the advantage that magnification can be changed from the slit-lamp itself.
3. TFTFF
The three-mirror lens (like the Goldmann three-mirror lens) is a form of con-
tact direct ophthalmoscopy that is essential to examine in detail the central and
Table 1 Comparison between direct and indirect ophthalmoscopy
Direct ophthalmoscopy Indirect ophthalmoscopy
High magnification (×15) Low magnification (×3 with 20D condensing lens)
Low field of view High field of view
Monocular Binocular
2D image 3D image (stereoscopic image)
Erect image Inverted image (and reversed)
Limited peripheral retina view Full peripheral retina view up to ora errata (can be
combined with scleral depressor for a better view)
No need to darken room Better if room is darkened
Clinician has to be very near the patient Clinician some distance away (arms length)
14 2 Retinal Testing and Imaging
Table 2 Comparison of various condensing lenses
Lens Magnification Field of view (degrees) Notes
20D ×3 45 Most commonly used
28D ×2.27 53 Used in paediatrics and through
a small pupil
40D ×1.5 65 Used in uncooperative patients
to obtain a quick fundus
overview
Panretinal 2.2 ×2.68 56 Combines magnification nearly
that of the 20D lens with a field
of view approaching that of the
30D lens.
Table 3 The Goldmann three-mirror lens
1. Central lens Round 30 degree upright view
2. Equatorial mirror Largest mirror From 30 degrees to equator
3. Peripheral mirror Intermediate sized From equator to ora serrata
4. Gonioscopy mirror Smallest and dome—shaped Extreme retinal periphery, Pars
plana, gonioscopy
peripheral retina. It provides high-resolution images with no magnification (image
can be magnified by using slit-lamp magnification). A huge advantage is that it
provides non inverted images and the central portion of the lens gives a field of
view of up to 20 degrees. The other three mirrors can be used to evaluate the mid
periphery and the peripheral retina with the apical smallest mirror ideal also for
gonioscopic analysis (Table 3).
4. FFFTF
Fundus photography involves photographing the fundus. Specialised fundus cam-
eras consisting of an intricate microscope attached to a flash enabled camera are
used in fundus photography. The main structures that can be visualised on a fun-
dus photo are the central and peripheral retina, optic disc and macula. Fundus
photography can be performed with coloured filters, or with specialised dyes
including fluorescein (IVFA) and indocyanine green (ICG angiography)
Advantages of using a fundus camera:
– quick and easy to use and master
– observes a larger retinal field at any one time compares to ophthalmoscopy
– modern cameras are non-mydriatic
– image can be saved and used for monitoring of disease and teaching
– spectrum of filters can be used to obtain more detail and contrast
– the use of dyes such as fluorescein and ICG can be used to get physiological
information about the retina
– different magnification options to focus on a particular area
2 Answers in Detail 15
– composite images possible to access peripheral retina
– 3-D imaging possible with modern cameras.
Disadvantages of using a fundus camera:
• difficulty observing and assessing abnormalities such a cotton wool spots due
to lack of depth appreciation on images
• less image clarity than indirect ophthalmoscopy
• cataracts, vitreous opacities can hinder photographic access of the fundus
• artefact error may produce unusual images
• lack of portability
• expensive machine.
5. TFTTT
Fluorescein enters the ocular circulation from the internal carotid artery via the
ophthalmic artery. The ophthalmic artery (OA) is the first branch of the internal
carotid artery distal to the cavernous sinus. The ophthalmic artery supplies the
choroid via the short posterior ciliary arteries (SPCA) and the retina via the central
retinal artery (CRA), however, the route to the choroid is typically less circuitous
than the route to the retina. This accounts for the short delay between the “choroi-
dal flush” and retinal filling.
Approximate normal circuitry filling time:
• 0 seconds—injection of fluorescein
• 9.5 seconds—posterior ciliary arteries
• 10 seconds—choroidal flush (or “pre-arterial phase”)
• 10–12 seconds—retinal arterial stage
• 13 seconds—capillary transition stage
• 14–15 seconds—early venous stage (or “laminar stage”, “arterial-venous
stage”)
• 16–17 seconds—venous stage
• 18–20 seconds—late venous stage
• 5 minutes—late staining.
Nausea is a common sensation as the dye reaches the midbrain. It is benign.
6. TTTTT
In IVFA:
Equipment-
• Exciter filter: Allows only blue light to illuminate the retina. Depending on the
specific filter, the excitation wavelength hitting the retina will be between 465
and 490 nm. Most filters only allow light through at a wavelength of 490 nm.
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