Download Unusual retinal vessels and vessel formations

P E T E R
G .
S WA N N
B S c
( H o n s ) ,
M A p p S c ,
F C O p t o m ,
FA A O
Unusual retinal vessels
and vessel formations
As optometrists, we constantly scrutinise the retinal vasculature and so we are well aware
of its normal characteristics. Retinal arterioles and veins steadily ramify to nourish and
drain each quadrant of the fundus. They branch as curving rather than acute bifurcations
and arterioles usually cross veins. There is an arteriolar-to-vein size relationship of 2:3
and a spontaneous venous pulse is present at most optic discs. Retinal vessels rarely
‘invade’ the macula. These are all routine observations. Occasionally, however, we see
vessels or vessel formations that are unusual and may impact significantly on the patient’s
vision. This paper will seek to clarify some of these situations.
REMNANTS OF THE HYALOID SYSTEM
The hyaloid artery and its ramifications are
derived from the ophthalmic branch of the
internal carotid artery, and form during the
internal eye’s most active period of growth
and differentiation. It enters the developing
globe via the inferior foetal fissure around
the fourth week of gestation, and forms a
group of vessels which nourish the primary
vitreous, and a second group which become
the posterior vascular tunic of the lens. The
system normally atrophies late in the foetal
period but may persist as a Mittendorf dot,
Bergmeister’s papilla, a vessel at the disc,
Vogt’s arcuate line or, very occasionally, the
whole vessel being preserved from disc to
lens. Potential associations include
persistence of the primary vitreous,
coloboma and optic nerve head hypoplasia.
The patient shown in Figure 1
presented for a cosmetic contact lens
assessment as she had a uveal coloboma in
one eye. A Mittendorf dot with a small
vascular tag was present on the posterior
lens surface. The patient in Figure 2 has a
triangular, white area of thin tissue
protruding from the optic disc. This is a
typical Bergmeister’s papilla and is quite
innocuous. Figure 3 depicts a white
hyaloid vessel remnant at the optic disc.
The disc itself may be slightly
colobomatous.
CILIORETINAL ARTERIOLES
These vessels are a variant of the normal
vascular tree and are present in 30-40% of
eyes. They are derived from the posterior
ciliary arteries and usually arise from the
temporal optic disc in a hook-like manner,
often traversing the papillomacular area.
They are said to be more common in cases
of optic disc pit, situs inversus, pre-papillary
loops and optic disc drusen. In occlusion of
the central retinal artery, the presence of a
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cilioretinal arteriole may enable some
degree of central vision to be retained.
Occasionally, cilioretinal arterioles may
themselves become occluded.
The patient in Figure 4 has a well
developed cilioretinal arteriole coursing
above the left macula. Figure 5 shows the
fundus of a patient who presented to the
optometrist with a sudden, painless loss of
vision in the left eye. She had a central
retinal arterial occlusion with some
preservation of central vision due to the
cilioretinal vessel.
CONGENITAL TORTUOSITY
This condition more commonly involves
retinal arterioles than veins. It is usually
non-progressive with all other findings
being normal, although there is a
progressive form which is inherited as an
autosomal dominant trait and may be
associated with retinal haemorrhages.
Congenital
tortuosity
should
be
differentiated from that secondary to other
problems, such as epiretinal membrane,
vein occlusion and diabetes.
Figures 6 and 7 show the fundi of a
patient with congenital tortuosity of the
retinal veins. All other findings were
normal and she was placed on regular
review.
SITUS INVERSUS
Here, the retinal vessels emerge from the
optic disc in an anomalous direction. It is
typically seen in tilted disc syndrome and
also in myopic eyes. A dragged disc and
vessels can have a similar appearance and
occurs in retinopathy of prematurity.
The patient in Figure 8 has a classic
tilted disc. The vessels emerge or exit from
an inferio-nasal direction. The inferio-nasal
fundus is ectatic and depigmented. There
was reduced sensitivity in the superio-
NOVEMBER 19 • 1999 OPTOMETRY TODAY
temporal visual field that, most importantly,
did not respect the vertical midline.
CONGENITAL RETINAL MACROVESSEL
This is an uncommon situation where a
retinal vessel, usually the inferio-temporal
retinal vein, is enlarged and drains an area
superior to the macula. Vision may be
slightly reduced by the large vessel crossing
the macula. There has been a suggestion
that macular cysts are more common in
these patients.
This patient in Figure 9 presented for a
routine eye examination. The macrovessel,
a branch of the inferio-temporal vein,
crosses the macular area. Vision was 6/5 in
each eye.
PRE-PAPILLARY LOOPS
Ninety-five percent of these vessels are
arterioles, and usually originate from and
return to an arteriole on or near the disc.
The loops may be small and simple or large
and corkscrewed. Many are surrounded by
the white remnants of Bergmeister’s papilla.
Most cases are unilateral with associated
cilioretinal arterioles. They fill before or
with other retinal arteries on fluorescein
angiography and do not leak. Vitreous
haemorrhage and occlusion of the loop
have been reported.
The patient in Figure 10 has a typical
pre-papillary arteriolar loop. It projects
forward into the vitreous for a short
distance from the left optic disc.
ARTERIO-VENOUS MALFORMATIONS
In this condition, arterioles and veins
communicate without an intervening
capillary bed. It may be isolated to a small
arteriole and venule or be widespread
involving the entire vascular tree.
Intracranial
and
facial
vascular
malformations may be associated and
constitute the Wyburn-Mason syndrome.
Similar vascular anomalies can involve the
orbit, conjunctiva, sclera and iris, and
neovascular glaucoma can be a
complication. The condition should be
differentiated from the phakomatosis von
Hippel-Lindau’s disease. These patients
should be referred for neurological
assessment.
U N U S U A L
Figure 1
Typical uveal coloboma with a Mittendorf dot
and small hyaloid remnant attached
R E T I N A L
V E S S E L S
A N D
V E S S E L
Figure 2
A small triangular area of white tissue
protrudes from the optic disc representing
Bergmeister’s papilla
F O R M AT I O N S
Figure 3
A white hyaloid vessel courses from the
inferior part of the optic disc
Figure 5
The patient suffered a
central retinal artery
occlusion in the left
eye; some vision was
preserved due to a
patent cilioretinal
artery
Figure 4
A large cilioretinal
artery traverses the
retina above the left
macula
Figures 6 and 7 (right and left)
Congenital tortuosity of the retinal veins in the right and left eyes; there is a small choroidal
naevus in the superio-temporal fundus of the left eye
Figure 8
A tilted disc with situs inversus and
depigmentation of the inferio-nasal fundus
Figure 9
Congenital retinal
macrovessel in the
inferior fundus of the
patient’s left eye
Figure 10
A pre-papillary
arteriolar loop
projects from the left
optic disc
(reprinted with permission
from Practical Optometry
1992; 3 (1): 49-50)
NOVEMBER 19 • 1999 OPTOMETRY TODAY
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U N U S U A L
The patient shown in Figures 11 and
12 came to our clinic for a routine
examination. The enlarged, tortuous
retinal vein and arteriole were noted
running to and from the left optic disc in
the nasal fundus. When the pupil was
dilated, it was clear that they were directly
joined in the nasal periphery. A CT scan
was normal.
COLLATERAL VESSELS
These vessels are preformed capillaries
connecting retinal, and retino-choroidal
circulations. They indicate a preceding
vascular disorder which may point to a
significant ocular and/or systemic disease.
Unlike new vessels, they do not leak on
fluorescein angiography. Potential causes
include retinal vein thrombosis and
glaucoma. If the patient, especially a
middle-aged female, has a chronic,
progressive vision loss, together with a
pale, swollen optic disc and a disc
collateral, then optic nerve sheath
meningioma is a likely cause. It is
important to observe these vessels through
a dilated pupil with the fundus lens and
slit-lamp. Red-free illumination is often
helpful.
The patient in Figure 13 had an
inferio-temporal branch vein occlusion in
the right eye several years ago. A small
collateral vessel is present on the temporal
aspect of the right optic disc. Figure 14 is
of a patient who had a superio-temporal
branch vein occlusion. There are small
collaterals on the disc and another
collateral vessel near the site of the
occlusion.
R E T I N A L
V E S S E L S
A N D
V E S S E L
NEW VESSELS
New vessels proliferate following ischaemia
in conditions such as diabetic retinopathy
and central retinal vein thrombosis. They
may form on the optic disc, elsewhere in
the fundus and in the anterior segment.
They have a delicate feathery appearance
and leak fluorescein. Bleeding from new
vessels may seriously threaten vision in
these patients and referral needs to be most
expedient.
The patient shown in Figure 15 came
in for a routine eye examination. There was
a history of vein thrombosis in the eye.
Ophthalmoscopy revealed a large frond of
new vessels stretching into the vitreous.
This patient was referred to the
ophthalmologist without delay, and laser
photocoagulation was undertaken.
ABOUT THE AUTHOR
Peter Swann is Associate Professor in the
School of Optometry at the University of
Technology in Brisbane, Australia.
F O R M AT I O N S
BIBLIOGRAPHY
Paton, D., Hyman, B.N. and Justice,
J. (1979) ‘Introduction to
ophthalmoscopy’. Upjohn, Michigan.
Kritzinger, E.E. and Beaumont, H.M.
(1987) ‘A colour atlas of optic disc
abnormalities’. Wolfe Medical
Publications, London.
Wood, J. and Swann, P. (1996)
“Cilioretinal artery occlusion”.
Br. J. Optom. Disp. 4: 137-138.
Sears, J., Gilman, J. and Sternberg, P.
(1998) “Inherited retinal arteriolar
tortuosity with retinal
haemorrhages”. Arch. Ophthalmol.
116: 1185-1188.
Swann, P.G. and Da Rin, J. (1992)
“A congenital retinal macrovessel”.
Practical Optometry 3: 49-50.
Figures 11 and 12
The left fundus of a patient with an arteriovenous malformation
Figure 13
A small collateral vessel is present on the right
optic disc following an inferior branch vein
occlusion
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Figure 14
Another patient who had a branch vein
occlusion; collaterals are present on the optic
disc together with another collateral vessel
superior to the macula, near the site of the
occlusion
NOVEMBER 19 • 1999 OPTOMETRY TODAY
Figure 15
A patient with a history of vein occlusion, who
presented for routine eye examination; a large
frond of new vessels stretches forward into the
vitreous