You must have a good understanding of the anatomical location of the
peripheral retina structures and their relationship to one another. The
peripheral retina is defined as the zone from the equator to the ora serrata
and is approximately three to four disc diameters (3DD-4DD) in
width.
ANATOMICAL STRUCTURES OF THE RIGHT EYES PERIPHERAL RETINA
The vortex veins and ampullae will serve as very good landmarks
for an examiner. These vortex ampullae and veins represent the equator
of the eye. They are very important when one wants to describe retinal defects
and their relationship to the rest of the retina. Vortex veins and ampullae
are usually very easily seen in fair complexioned, light hair and blue eyed
individuals. However, they might blend in with the rest of the retinal pigment
background making them more difficult to delineate. There is always some
pigment migration, in these cases, toward and around the vortex ampullae
and in these cases the pigment migration is the only clue to the vortex
ampullae location.
The long ciliary nerves are your two horizontal landmarks located
at three and nine o'clock. They have a broad base located at the ora and
taper to a somewhat rounded apex approximately at the equator. The short
ciliary nerves are most visible in the superior and inferior peripheral
retina and usually located very near one of the vortex veins and ampullae.
They may run all the way to the ora or only be seen as a very short
whitish to yellow colored structure that definitely stands out from the
rest of the retina
The ora serrata is the point where the choroid and retina end.
The ora will vary in color from black, brown to a felt soft gray. It is
not uncommon to find the retina near it to have a slightly off colored orange
gray appearance known as chorioretinal degeneration. This can be
broken down in to mild, moderate, and severe degeneration. Regardless how
one classifies the degeneration there is little to worry about and is considered
to be benign with no predisposition to retinal holes or tears
The pars plana, when first seen, is very confusing because in many patients
it looks very much like the rest of the retina in color. It is usually noticed
while looking at the ora serrata and the degeneration near the ora. Suddenly
one finds themselves trying to determine what they have just discovered.
One moment the pigmented ora is seen then what appears to be normal colored
retina jumps into view. It must be pointed out that you will not see this
structure in every patient unless the pupil is dilated maximally.
It is essential that everyone realizes the primary reason for performing
a dilated examination of the peripheral retina is to detect potential retinal
detachments (RD). There are of course other findings
a dilated retinal examination can reveal, but RD are
the primary reason. Retinal detachments constitute a separation of the sensory
retina from the underlying retinal pigment epithelium, (RPE)
due to the accumulation of liquefied vitreous fluid in that potential space.
Most RD are the result of one or more retinal holes
that allow passage of fluid between the sensory retina and the RPE.
The RD may be quite flat or become large and bullous
protruding into the vitreous cavity and undulate with eye movements. The
bullous detachment is an active detachment with sloping visual field margins.
Detachments may occur anywhere in the retina where a hole or tear is located.
Superior detachments are potentially more serious than inferior ones because
of gravity. They may rapidly extend inferior to detach the macula with loss
of central vision which may be permanent, even if surgery is successful
in restoring the retina to its proper position. Older or small incomplete
RD will leave a pigmented line along their borders.
These flat peripheral RD if suspect must be sclerally
indented to differentially them from a flat retinoschisis. Dr. James Hunter
refers to these pigmented (demarcation) lines as danger lines. If not correctly
diagnosed an the patient later develops a RD the doctor
is in danger of being sued.
Symptoms associated with a RD may be minimal to
no symptoms at all. Frequently the patient complains of light flashes, dark
floating specks, and a curtain-like defect in their field of vision. Patients
with these complaints must be seen promptly. Most retinal detachments are
associated with retinal holes and the holes, in turn, are the result of
vitreous traction. Vitreous traction may cause a classic horseshoe tear
or retinal break making the patient more predisposed to developing a retinal
detachment.
BENIGN PERIPHERAL RETINA FINDINGS
1.) It is common to fine cystoidal degeneration near the ora serrata. It
is found in most all adult eyes and increases with age. Though considered
to be benign by itself it is involved with some other conditions that are
not so benign. These will be discussed later (retinoschisis ).
2.) Pavingstone or Cobblestone degeneration is found in about 27% of the
population. It is considered by some not to be a degeneration but a retinal
defect that has been present since birth. Though the retina appears atrophied
the condition is more like that of a coloboma or failure of that part of
the retina to develop. It is most often found in the inferior-temporal part
of the retina between the ora and the equator. Dr. Alexander, however, classifies
this as a degeneration seen in patients over the age of 20 years.
3.) Reticular pigmentary degeneration is a common finding in the peripheral
fundi of older patients. When these areas are indented one usually finds
an area of honeycomb degeneration present deeper in the retina.
4.) Equatorial drusens are another common finding that is very interesting
and are usually only note worthy. They are usually of the soft fluffy type
and as long as they do not involve the macula foveal area they seldom cause
vision problems. What are drusens? The RPE functions in several ways. It
forms an outer blood-retina barrier, works in the transport of metabolites
between the choriocapillaris and the retina, functions to eliminate damaged
and discarded photoreceptor outer segments and works to prevent the development
of choroidal neovascular nets. When the RPE cells are not functioning properly
they produce an extracellular material such as collagen an basement membrane
material, which is deposited onto Bruch's membrane. The resulting deposits
are called drusens which are composed of mucopolysaccharides and lipids.
One might think of drusens as kind of garbage dump resulting from a not
too healthy RPE. Drusens of some form are found in over 70% of patients
over 50 years and do not negatively affect all eyes.
5.) Choroidal or pigmentary degeneration, are one and the same and is located
at or near the ora. Another peripheral retinal condition that is only note
worthy.
RHEGMATOGENOUS PERIPHERAL CONDITIONS
1.) Lattice degeneration, (Non-pigmented & pigmented lattice)
holes within this degeneration are the result of extreme thinning of the
retinal tissue.
Pigmented lattice like degeneration aligned with a peripheral
vessel.
- A.) Retinal erosion (non-pigmented)
- B.) Snail track (non-pigmented) with holes and tears
2.) Retinoschisis - bullous & flat
- A.) Acquired or Reticular schisis
- B.) Congenital or Typical Schisis
3.) White Without Pressure
4.) Vitreoretinal Adhesions (Retinal Tag)
5.) Snowflake Vitreoretinal Degeneration once was thought to be a benign finding.
However, recent findings classify it as an inherited condition which may be related
to retinitis pigmentosa. The retinal layers involved included the inner retinal layers.
The condition progresses through four stages and may develop retinal breaks,
retinal detachments, or neovascularization
of the peripheral retina may occur.
Rhegmatogenous means to tear or break. In these cases it is related to
retinal areas of degeneration that may develop tears, breaks or holes leading
to retinal detachments. The reason dilation and peripheral retinal examinations
are so very important is detecting conditions that may lead to retinal detachments
or patients who have retinal detachments. It is somewhat surprising that
about 50% of all patients with retinal detachments are totally asymptomatic.
Detachments not secondary to a retinal holes tears or breaks are called
nonrhegmatogenous detachments and are caused by primary choroidal tumors,
inflammation, or metastatic lesions. The tumors that commonly produce these
"secondary" detachments are choroidal melanomas or metastatic
carcinomas from the breast, lung, and prostate which migrate to the choroidal
vascular system.
LATTICE DEGENERATION: The clinical appearance is that of circumferentially
oriented, sausage-shaped areas. Located at or between the equator and the
ora serrata, of increased atrophic thinning retina and increased retinal
pigment epithelium (RPE) pigmentation. The vitreous
over lying this area is liquefied and the vitreous membrane is firmly attached.
Radial white (lattice) lines represent sclerosed retinal vessels and along
with these may be overlaying vitreoretinal (glitter). The majority of the
lesion has a grayish white appearance. Holes which occur within lattice
areas are either the result of continued thinning of the retinal tissue
or secondary to vitreoretinal adhesions which are associated with the lesion.
Tears occur as a result of vitreoretinal adhesions and traction at the
borders of the primary lesions. Tears and holes have a deeper reddish color
than the surrounding lesion or retina which helps make a differential diagnosis.
Other atrophic equatorial retinal changes are "retinal erosion"
and "snail tracks" which are grayish in color and most likely
variations of lattice degeneration. They do lack the pigmentation, but
have many of the other characteristics of lattice degeneration. A very
good term for these areas of atrophy is "lattice like" degeneration".
RETINOSCHISIS: There is a congenital "flat"("typical"
according to Dr. Alexander, probably to differentiate it from Congenital
Hereditary Retinoschisis) retinoschisis which is the splitting of the nerve
fiber layer at the outer plexiform layer. Dr. Alexander believes the "flat"
schisis represents an advanced form of cystoid degeneration. Then there
is the acquired "bullous" ("reticular" according to
Dr. Alexander) form of retinoschisis. The acquired form if not the most
common is certainly the most eye-catching looking like a water blister protruding
inwardly toward the inside of the eye. Some believe it is actually a complication
occurring secondary to peripheral cystoid retinal degeneration. Clinically,
degenerative acquired retinoschisis appears as a ballooning "bullous"
retinal elevation with smooth sharp borders. The cavity of "bullous"
schisis is thought to be filled with hyaluronic acid a mucopolysaccharide.
Hyaluronic acid is typically very viscous, a component of the vitreous,
which would explain the taut appearance of the schisis. The condition is
the result of splitting of the inner limiting membrane and the outer nuclear
layer of the retina. The neuroepithelium remains intact, but the inner
layer becomes stretched and thinned because of the vitreous traction. Vitreoretinal
"glitter" which is sometimes referred to as "snowflakes"
and sclerosed whitish colored retinal vessels are found on its inner surface.
These vessels give it a reticular appearance and are common findings on
the inner layer. Retinal holes or breaks may occur in either the inner
or outer layers; holes in just the inner layer are basically note worthy,
while holes in the outer layer are of greater concern, e.g., retinal detachments
are more likely. Superior bullous retinoschisis with inner and outer layer
breaks or a schisis that is already posterior to the equator should be referred
for a second opinion. Because of the splitting of the retina the field
defects are absolute and have steep borders. Bullous retinoschisis do not
undulate (wave) with eye movements like a retinal detachment. Holes in
the inner layer are not treated because they are simply openings into the
cystic cavity, but outer layer holes may require treatment, since they could
facilitate the formation of a retinal detachment. Cases with holes in both
layers should be referred for consultation and possible treatment.
VITREORETINAL ADHESION (RETINAL TAG): These are areas of atypical retinal
tissue to which the vitreous membrane has become firmly attached. The condition
may be either congenital or acquired, in that the atypical retinal tissue
may have been present from birth or resulted from a small area of inflammation
or trauma. With vitreous age changes, the vitreous body liquefies and shrinks,
causing a strong physical tugging on this area of retina. Two things may
happen, either a small plug of retina will pull free releasing the physical
tension or the retina will tear. If a plug of retina pulls free releasing
the tension the likelihood of a retinal detachment is very small. However,
if the retina tears the odds of a retinal detachment then or in the future
are greatly increased. These areas should be monitored every 2 months,
then 4 months and every 6 months, however, tears should either be referred
or monitored more closely. Photographs of these areas are a great aid in
monitoring patients.
Patient education in all rhegmatogenous cases is a must . It is extremely
important and should always be recorded in the patients record that the
patient has been educated regarding symptoms associated with RD.
Also, record when you want to see them again then followed this up with
a recall card. Patients should be told to return anytime they experience
any visual changes; increased number of floaters, spots, flashes of light,
veil like curtain affecting peripheral vision or any change of concern.
In the event of any of these symptoms and negative dilated fundus examination
findings you must always check for "Shafer's Sign". The presence
of pigment granules in Berger's space or anterior vitreous indicates there
is a retinal break or detachment. Pigment granules may be present if the
patient has had previous ocular surgery, but you cannot allow that to influence
the need to go back and take another look.
Dr. James E. Hunter conducted a peripheral retina study on 1000 patients.
All patients were dilated and B.I.O. examinations
performed. The break down of the 1000 patients is as follows:
Caucasians = 692
African Americans = 308
1.) Lattice degeneration (all types)
- Present in 3.5% of the Caucasians
- Present in 7.0% of the African Americans
2.) Retinoschisis (all types)
- Present in 0.5% of the Caucasians
- Present in 1.0% of the African Americans
3.) White without pressure
- Present in 2.5% of the Caucasians
- Present in 23% of the African Americans
In all conditions African Americans had a higher incidence, even though
there were more than twice the number of Caucasians in the study. The condition
of white without pressure might be understandable for it is much easier
seen in a darkly pigmented retinas. However, it is still hard to accept
that African Americans would have such a significantly higher incidence
of white without pressure than Caucasians.
You should be familiar with the following slides and the description
information plus the Manual Handout on peripheral retina.
1.) Histoplasmosis - Presumed Ocular Histoplasmosis Syndrome (POHS) has
a triad of retinal involvement ( a.) peripheral atrophic retinal spots-punched
out lesions (b.) peripapillary choroidal atrophy (c.) exudative maculopathy
secondary to choroidal neovascular membranes. the condition is fungal related
an associated with birds. The condition is a (hypersensitivity reaction)
with the organisms reaching the choroidal circulation during a systemic
involvement. Active histoplasmosis does not produce the massive proliferation
of cells within the vitreous body like toxoplasmosis. See color plates
79 through 82 in Dr. Alexander's book. (Monitor closely, Amsler Grid)
2.) Choroidal nevus (Benign Choroidal Melanoma)- usually a flat, grayish-green
lesion which varies in size. Overlying drusens and increase in size tendency
with age. Red-free, green filter, is used to differentiate choroidal from
retinal. Up to 2DD in size document and follow. 2DD to 5DD be suspicious
with special testing and careful follow-up care. Over 5DD assume malignancy
until proven otherwise. See color plate 98 in Dr. Alexander's book. (Note
those 2 1/2 to 5 disc diameters or larger should be monitored more closely;
more likely to develop into malignant tumors).
3.) Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPE), also know
as a Halo nevus, is a benign condition. However, there is a relative scotoma
which corresponds to the area of hypertrophy when tested with threshold
fields. With increase in age the scotoma becomes more absolute because
of atrophy of the underlying chorioretina and overlying sensory retinal
degeneration. See color plates 95 & 96 and pages 376-377 in Dr. Alexander's
book.
4.) Horseshoe tears - are a direct result of vitreoretinal adhesions.
This break coupled with the liquefied vitreous greatly increases the risk
for a rhegmatogenous retina detachment. See color plate 109 in Dr. Alexander's
book. It is not a horseshoe tear, but is a tear secondary to vitreoretinal
traction. Page 404 has a black and white photograph of a horseshoe tear.
(These tears should be referred).
5.) Toxoplasmosis - is an intracellular protozoan parasite an can be
either congenital or acquired in nature. It is one of the more likely causes
of posterior uveitis in the United States. The most common route of congenital
or maternal toxoplasmosis is exposure of the mother to cat feces, as the
cat is the natural host for the parasite. The protozoa enters the eye via
the circulatory system, then locates within the nerve fiber layer. The
ocular inflammation caused by the parasite and hypersensitivity reaction
is likened to "headlights in the fog" because the inflammation
and lesion has a white central area seen through a very hazy vitreous filled
with cells and debris. See color plates 83 & 84 plus pages 316 &
317 in Dr. Alexander's book.
6.) Branch Retina Vein Occlusion (BRVO) - has been reported to be the
second most prevalent retinal vascular diseases seen in eyecare practice.
Occurs most frequently at arteriovenous crossings and is the result of
a thickened artery pressing on a thin-walled vein. The clinical picture
can vary depending on the site of the occlusion. The superior temporal
veins are affected most often because there are more arteriovenous crossings
in the superior temporal retina then elsewhere. The clinical picture is
that of dilated tortuous veins, dot-blot and flame shape hemorrhages from
the site of obstruction out to the retinal periphery in the sector of the
retina drained by the affected vein. See color plates 34, 38, and 39 in
Dr. Alexander's book.
7.) Metastactic tumors- One cannot determine if a choroidal tumor is
metastatic just by the color, however, they are typically yellowish-white
with deposits of lipofucin. They are usually different in color from the
malignant choroidal melanoma. The prognosis is relatively poor in malignant
choroidal melanomas and metastatic tumors. Regardless of the final outcome,
all suspect uveal melanomas deserve a consultation with a retinal oncologist
for this is a vision and life threating condition. See color plates 99
and 100 in Dr. Alexander's book. (If that's what you think you have, refer).
8.) Disciform macular degeneration (Wet "Exudative"- Age Related
Macular Degeneration (ARM)- has long been associated with drusens even though
the neovascular growth occurs away from the visible drusens, within the
RPE and Bruch's membrane. The presence of soft fluffy drusens, really choroidal
infiltrates or RPE detachments, should increase the doctor's suspicion.
Choroidal neovascularization occurs as the result of disruption in the
RPE and Bruch's barrier. The new vessels from the choriocapillaris grow
up through the disruption in Bruch's. The neovascularization may (1) leak,
creating an RPE detachment or sensory detachment, (2) hemorrhage or (3)
form a disciform scar. All hard exudates (Coat's response) in the macula
area in the absence of retinal vascular disease should alert you to the
possibility of choroidal neovascular nets. Patients with suspected choroidal
neovascular membranes or other signs of wet ARM should have fluorescein
angiography performed within three days. It has been shown that expertly
placed laser photocoagulation applied in a timely manner reduces the risk
of severe vision loss in patients with wet ARM. See color plates 64 through
71 in Dr. Alexander's book.
9.) Drusens of the optic disc (Buried Drusen Of the Optic Nerve Head)-
can create a diagnostic dilemma and does not represent a benign, nonprogressive
condition. They can make the differential diagnosis of papilledema very
difficult. Nerve head drusens are congenital and have no correlation to
retinal drusens. They are calcium-like deposits which are confined anterior
to the lamina cribrosa. The calcific deposits can compromise the nerve
fibers and vascular supply, leading to visual field defects and peripapillary
hemorrhages. Intervention therapy is currently not available to prevent
the associated nerve fiber loss or hemorrhages. See color plates 11 and
12 in Dr. Alexander's book.
10.) Coats' disease is a exudative retinopathy resulting from telangiectasias
of the retinal vessels. Telangiectasia is a Greek term meaning "dilation
of capillaries and sometimes of terminal arteries producing an angioma of
macular appearance." Coats' disease usually occurs unilaterally in
the first to second decades of life. Its seen approximately four times
more often in males than females, yet despite the fact that the telagiectasias
are congenital, the condition usually is not discovered until the first
or second decades. Over time the congenital abnormal vessels become altered
leading to leakage, degeneration and development of hard exudates.
Unless the condition is caught early it usually leads to parafoveal and
perifoveal exudates, retinal hemorrhages, neovascularization and loss of
vision. Dr. Alexander describes the following characteristics: 1.) Occurs
unilaterally in 90 percent of patients 2.) Most often in males under age
20 years 3.) No genetic association 4.) No systemic disease association
5.) Irregular dilatation of retinal vessels with a wide variation in clinical
presentation 6.) May progress to intraretinal and subretinal exudate accumulation
with a poor visual prognosis. Dr. Alexander's suggested management in suspected
patients is fluorescein angiography to determine if the lesions that are
threatening vision are treatable by photocoagulation. The earlier the disease
is detected and appropriate treatment administered, the better the prognosis.
11.) Central Areolar Choroidal Dystrophy (CACD) has been described as
having autosomal dominate and autosomal recessive inheritance patterns and
some are sporadic cases. The earliest fundus changes are bilateral RPE
mottling in and around the macula. There is progressive atrophy of the
RPE and choriocapillaris within a sharply outlined zone around the fovea.
Clinically the appearance is one of atrophy of the choriocapillaris loss
of the RPE and atrophy of the sensory retina.
The main symptom of this condition is reduced vision from age 30 to 40
with a slow progression to 20/200 or worse with aging. Loss of color vision
and central scotomas are related to the degree of impairment. Peripheral
vision remains intact and there is no complaint of night blindness.
12.) Macular holes have a somewhat confusing etiology. It is generally
considered that any condition that precipitates cystoid macular edema may
result in the development of a macular hole. The presence of a posterior
vitreous detachment (PVD) may lead to tugging at the macula causing the
formation of a macular hole has been suggested.
Macular holes are clinically still divided into two categories , full
thickness and lemellar holes. The classic full thickness hole is usually
1/4 to 1/3 disc diameters in size. It has a reddish color surround by a
grayish edematous appearing cuff of retinal tissue and there are yellowish
deposits in the base of the hole. The full thickness hole will cause significant
reduction in visual acuity and a central scotoma. Lamellar holes do not
have the characteristic reddish color of a full thickness hole. The patient
with a lamellar hole will present with slightly reduced vision and metamorphopsia.
For suspected macular holes that appear questionable or uncertain in nature or do
not lend themselves to a clear diagnostic observation, consider the Watzke-Allen test.
A vertical beam of light is presented to the fovea, slit lamp beam with a fundus lens or
a direct ophthalmoscope. Ask the patient if the line is uniform or broken in the
center-patients with macular compromise report a broken line. Those with a pseudohole
might report the line as complete, but centrally distorted.
See color plates 77 & 78 in Dr. Alexander's book.
13.) Papilledema is defined as optic nerve head edema secondary to increased
intracranial pressure. The main cause of optic nerve head swelling is blockage
of the axoplasma transport and the blockage occurs at the lamina cribrosa.
The optic nerve head can swell to the extent where it is extended forward
into the vitreous as well as laterally. This lateral swelling causes the
retina to buckle inward at the temporal aspect of the optic nerve head.
The buckling is know as Paton's folds and results in a enlarged blind spot.
The acute rise of intracranial pressure results in papilledema, sometimes
called a choked disc, flame shape hemorrhages, engorged veins, and cotton-wool
soft exudates. There are most certainly varying degrees of papilledema
depending on the what is causing the rise in intracranial pressure and what
stage in this compromise the clinician sees the patient.
Symptoms will vary depending the degree of optic nerve head swelling
and the how long the condition has been present. Headaches might start
out like any common headache but as the condition reaches the chronic stage
they may be severe enough to cause vomiting. In the chronic stage transient
loss of or blurring of vision may occur lasting 5 to 30 seconds. I must
say it sure seems longer than 30 seconds. There are no signs of optic nerve
conduction defects such as the Marcus Gunn pupil (afferent pupillary defect)
APD or color desaturation until optic atrophy occurs. Papilledema should
be considered a life treating condition and any patient with suspect optic
nerve head edema should be referred to a neurologist who must run either
a CAT scan or MRI or both.
OTHER SLIDES WHICH WERE PRESENTED
14.) Retinitis pigmentosa
15.) Advanced Glaucoma
16.) Drusens of the macula
17.) Melanocytoma
18.) Medullated nerve fibers
19.) Bear tracks
20.) Bergmeister's papilla
21.) Staphyloma
22.) Coloboma of nerve head
23.) Branch artery occlusion
