18th Annual Glaucoma Report
Optic Neuropathies: Glaucomatous vs. Non-glaucomatous
While these conditions have overlapping clinical features, distinguishing one from the other is vital to chart the appropriate treatment and follow-up plan.
Release Date: JULY 2012
Expiration Date: JULY 31, 2014
Glaucomatous optic neuropathy is the most commonly acquired optic neuropathy encountered in clinical practice. While it has clinical features that overlap with non-glaucomatous optic neuropathies—including the presence of vision loss, visual field (VF) loss and optic disc cupping—there are distinct differences. Thus, it is crucial for clinicians to determine the context of a discovered optic neuropathy so that they can consider an appropriate work-up that will lead to suitable intervention and follow-up.
Julie K. Hutchinson, O.D., Andrew S. Gurwood, O.D., and Marc D. Myers, O.D.
This course is COPE-approved for 2 hours of CE credit. COPE ID is 35186-NO. Please check your state licensing board to see if this approval counts toward your CE requirement for relicensure.
This continuing education course is joint-sponsored by the Pennsylvania College of Optometry.
Drs. Hutchinson, Gurwood and Myers have no relationships to disclose.
Glaucomatous optic neuropathy is the most commonly
acquired optic neuropathy
encountered in clinical practice.1 While it has clinical features
that overlap with non-glaucomatous
the presence of vision loss, visual
field (VF) loss and optic disc cupping—there are distinct differences
in conditions. Non-glaucomatous
optic nerve disorders must be differentiated from their glaucomatous
brethren because their underlying
are often part of systemic disease
processes that have the potential to
Characteristic signs of irreversible retinal ganglion cell destruction
include optic nerve cupping, optic
disc sinking, optic disc pallor as well
as focal and diffuse retinal nerve
fiber layer (RNFL) loss. While these
are commonly observed as part of
the disease process in glaucoma,
they are not exclusive signs of the
disease. Other diseases or congenital
conditions may exhibit these findings in either the absence of glaucoma or in tandem with it.
Thus, it is crucial for clinicians to
determine the context of a discovered optic neuropathy so that they
can consider an appropriate workup that will lead to suitable intervention and follow-up. Accurate and
timely management of impending,
worsening or developing conditions
can only be instituted when the
correct diagnosis is uncovered and
the underlying causes are revealed.
Glaucoma is traditionally defined
as a progressive optic neuropathy
with accompanying characteristic
optic nerve and visual field changes.1-8 It is classically diagnosed by the
presence of a progressive optic nerve
cupping with concurrent progressive VF loss.1-8 Diagnosis is aided by
the presence of risk factors such as
elevated intraocular pressure (IOP),
positive family history, predisposed
race, advanced age and thin central
There are three mechanistic theories to explain why glaucomatous optic neuropathy develops:9-29
- The pressure-dependent bio-mechanical mechanism.9-14 Here,
"high" IOP causes the lamina
cribrosa to physically deform and
bow, which results in pinching of the
axons and supportive tissues, leading to ganglion cell death and tissue
remodeling.30-32 "High" IOP also
creates an environment of increased
resistance to perfusion, which can
produce axonal death by inducing poor axoplasmic and vascular
- The vascular/autoregulatory
mechanism.20-26 This process is
defined by vascular insufficiency
or malfunctioning autoregulatory
mechanisms at the level of the optic
nerve.33 Poor perfusion induces
ganglion cell or supportive tissue
death.20-26 This mechanism most
likely explains why glaucomatous
processes are seen at "normal" IOPs.
- Linkage to genetic factors that
coerce preprogrammed cell death
(apoptosis).27-30,34-39 The classic clinical finding seen in most glaucoma
patients is a level of IOP inconsistent
with the health of the optic nerve.
While increased IOP has traditionally been associated with the disease
process, the literature has lobbied
that it be considered a single risk factor among several risk factors, rather
than diagnostic for the disease.40-41
Optic pits are depressions in the optic disc that result from herniation of neuroectoderm
tissue during development. Although they may occur anywhere on the disc, they often are
observed in the temporal quadrant and give the impression of a large disc.
In diagnosing glaucoma, other
clinical features that must be consistently detected with evidence of
repeatability and reliability include
spared central visual acuity in early-stage disease, spared central visual
field with intact color vision in early-and moderate-stage disease, optic
disc elongation with disc notching
and evidence of RNFL atrophy or
dropout providing the anatomic
correlation for the non-vertical-respecting visual field loss. Also, an
afferent pupillary defect (APD) may
be present, depending on the relative
asymmetry of optic nerve damage
between the two eyes in glaucoma.
Glaucomatous VF defects traditionally correlate to the focal areas
of optic nerve compromise. As the
retinal ganglion cell axons undergo
alterations, the regions of photo-receptors they subserve lose their
connection with the visual pathway,
creating the recognizable patterns
of functional deficit seen in glaucoma. Because the lamina cribrosa
is anatomically weaker in its vertical
regions, the nerve tissues that course
those locations often succumb to
the pathology during the beginning
phases, creating pathognomonic
patterns in synchrony with the
distribution of the affected nerve
fibers.50-56 Early glaucomatous VF
defects exhibit classic patterns of loss
corresponding to the specific nerve
bundles affected. In most cases, the
earliest field defects are superior or
inferior arcuate defects occurring
secondary to loss of the optic nerve's
corresponding portions. As a result,
the corresponding VF defects present
as relative, arcuate nasal scotomas
(nasal step and Bjerrum scotoma).
Characteristics often noted when
observing the glaucomatous optic disc
- Neuroretinal rim tissue that does not
respect the “ISNT” rule.
- Notching of the rim.
- Verticalization of the optic cup.
- An acquired optic pit.
- Baring of a circumlinear vessel.
- Vessel bayoneting at the optic rim
(indicating bean-pot cupping).
- Nasalization of vessels.
- Disc hemorrhage (Drance hemorrhage).
- Abnormally large or atypical pattern of
peripapillary atrophy (beta zone atrophy).
- Nerve not exhibiting rim pallor.
With progressive optic disc damage, an arcuate defect will emerge
in the affected eye having no respect
for the virtual vertical field dividing
line, permitting the loss to arc from
the nasal field to the temporal blind
spot.56 The earliest field defects in
glaucoma are small, shallow fluctuating scotomas due to highly variable retinal sensitivity, leading early
field tests to be noisy and difficult to
replicate. Eventually, the field loss
becomes persistent in early and mid-level disease.
In most instances of open-angle
glaucoma, bilateral, advancing disease inevitably presents as relative biarcuate defects. As the disease
progresses, the field defects coalesce,
creating a "tunnel" field in both
eyes.56 In glaucoma, because the
ganglion cell axons lose function
gradually as their injury progresses,
the measurement of the loss can be
variable until the end stage. This,
along with peculiarities created by
automated testing, creates a scenario where ganglion cells may be
taxed in differing patterns, which
gives the appearance of VF defects
that seemingly come and go or
change position from measurement
Inflammatory optic neuropathy
may be caused by a number of
underlying conditions, including
systemic infection, vaccination or
autoimmune disease.57 The most
commonly associated cause of
inflammatory optic neuropathy is
demyelinating optic neuritis secondary to multiple sclerosis.57,58 A complex cascade of inflammatory events
begins peripherally in the body,
induces the activation of T lymphocytes, and serves as the peripheral
trigger.59 The activated cells cross
the blood-brain barrier and gain
access to the central nervous system.59 Antigens cause the activation
of more inflammatory mediators,
microglia, lymphocytes and cytokines.59 The initial inflammatory
cascade leads to phagocytosis of the
myelin sheath.60 As a result, fibrotic
tissue is laid down in place of missing myelin; as this substitutive tissue
lacks the saltatory conduction properties of myelin, the nerve impulse
is interrupted.59-60 As the disease
progresses, further demyelination
occurs, which exaggerates axonal
damage and culminates in retinal
ganglion cell death.60
Patients with optic neuritis
typically present with ocular pain
(exaggerated upon eye movement),
noticeable changes in color vision
in the affected eye and variable unilateral loss of vision, ranging from
20/30 to no light perception.58,61-64 This is often accompanied by an
APD, the magnitude of which
depends on the degree of visual
disability. Light disturbances in
the field of vision known as phosphenes may also be reported during
rapid eye movements (saccades).
Dyschromatopsia as well as color
desaturation and depressed contrast
sensitivity are also often noted in
Affected eyes present with a
depressed field having a variety patterns ranging from cecocentral scotomas to dense central scotomas.61-66 As the eye naturally recovers over
the course of the event, in most cases
VF defects resolve as axonal damage
becomes limited to localized nerve
bundles.65 Interestingly, patients
often exhibit non-specific field deficits in the fellow, unaffected eye.65
In patients presenting with acute
optic neuritis, the optic nerve's clinical appearance ranges from normal
to edematous (papillitis). Only one-
third of patients manifest diffuse
optic disc edema.67 Disc hemorrhages are possible but less common
in optic neuritis.67 Segmental or
diffuse optic disc pallor represents
axonal infarction. Cases that present
without the telltale optic disc signs
are diagnosed based on the patient's
history, demographics (young, typically female, white, age 20 to 40)
and the constellation of clinical signs
and symptoms. The nomenclature
is often referred to as retrobulbar
optic neuritis. Demylinating optic
neuropathy is confirmed definitively
through magnetic resonance imaging (MRI) and cerebrospinal fluid
Optic disc cupping and peripapillary tissue remodeling are plausible
outcomes of demyelinating optic
The Optic Neuritis Treatment
Trial (ONTT), a multicenter study
of optic neuritis patients, delineated
treatment options.58,62,69 The study
helped to point out that the previous treatment of oral steroids alone was contraindicated, recommending intravenous methylprednisone,
administered over the course of
three days followed by an 11-day
course of oral prednisone.58,62,69 The
study also concluded that monitoring—while leading to increased
recovery time—was essentially
equivalent to the intervention arm of
Demyelinating Optic Neuropathy
Demyelinating optic neuropathy can be
distinguished from glaucomatous optic
neuropathy by these characteristics:
- IOP is typically within normal range.
- VF defects occur in the central or
cecocentral portion of the visual field.
- Visual fields often demonstrate a history
of improvement correlating to recovery
from the acute event.
- Consistent with death of ganglion
axons from recurrent episodes, there will
often be dyschromatopsia, red color desaturation defects, brightness desaturation
defects and an APD that is not consistent
with the appearance of the disc's cupping
or severity of the visual field.
- Typically asymmetric.
- Age and demographics do not match
the demographics of the typical glaucoma
Compressive optic neuropathy
results from mechanical mass effect
secondary to tumors and non-neoplastic lesions (i.e., retrobulbar
hemorrhage, aneurysm, mucocele,
orbital apex syndrome), which
impinge on intraorbital or intracranial structures of the visual pathway.70-71 Intracranial tumors such as
sphenoid wing meningioma, pituitary adenoma, craniopharyngioma,
meningioma and masses secondary
to metastases to the orbit or anterior
intracranial cavity may cause unilateral or bilateral optic nerve compression. Optic nerve tumors, such as
optic nerve sheath meningioma and
optic nerve glioma, also may result
in unilateral or bilateral optic nerve
Patients who develop compressive
optic neuropathy have no specific
demographic predilection to age
or gender. In the case of traumatic
orbital apex syndrome or traumatic
retrobulbar hemorrhage, a provocative mechanical force will be
uncovered in the history. In the case
of space-occupying lesions (SOLs),
history reveals a slowly progressive
process with changes or fluctuations
in visual acuity or missing visual
field that occur over several months
to years.70-72 In cases where there is
sudden expansion of an SOL, acute
changes in field and acuity may
occur as a result of novel vascular
compression causing sudden infarction of the optic nerve.
NAION is caused by a lack of optic nerve perfusion or embolic disease that affects the arteries supplying the optic nerve. Fundoscopic examination in the acute phase of cases reveals mild to severe optic nerve swelling.
Along with acuity changes,
patients also may report changes in
color vision and/or diplopia. Double
vision results from interruption of
any of the cranial nerves innervating the extraocular muscles (CN III,
IV, VI). Compression may occur at
the orbital apex, in the cavernous
sinus or via mechanical restriction
of the extraocular muscles (with
or without proptosis) secondary to
orbital tumor expansion or thyroid
VF defects associated with compressive lesions vary depending
on their location.70,71 Retrobulbar optic nerve compression commonly
produces central, cecocentral and
paracentral defects. Compression in
the optic chiasm region can produce
junctional (the affected eye has a
deep central scotoma with an afferent defect and the fellow eye has
a temporal defect) and bitemporal
hemianopsia. Optic tract lesions
produce incongruous homonymous
hemianopias.66,70,71 In cases of unilateral or asymmetric optic nerve
compression, an afferent defect may
be noted. Orbital and eyelid signs
may include proptosis, resistance to
retropulsion, enophthalmos, ptosis
or lid retraction.
Compressive Optic Neuropathy
Compressive optic neuropathy can be distinguished from glaucomatous optic neuropathy by
- Acute vision loss secondary compressive optic neuropathy has the potential to be marked
(20/100 or worse).
- IOP typically is within normal range unless altered by an intraorbital mass (mass effect).
- In cases where the mass effect evolves inside the orbit, there may be proptosis with poor
retropulsion, lid retraction, EOM restriction or choroidal folds.
- VF defects occur in the central or cecocentral portion of the visual field.
- The visual fields often demonstrate a steep depth with respect to virtual vertical hemianopic
- Compressive lesions often induce disc pallor.
- Dyschromatopsia, red color desaturation defects, brightness desaturation defects and an
APD that is inconsistent with the appearance of the disc's cupping or visual field severity.
- Unilateral compressive optic neuropathy is asymmetric compared to open-angle glaucoma
and lesions evolving from the chiasm or behind induce congruous or incongruous homonymous
VF defects that respect the neuroanatomical architecture (quadrant or hemianopic
- The age and demographics of compressive optic neuropathy often do not match the
demographics of the typical glaucoma patient.
The optic disc's appearance
may vary greatly depending on the
lesion's magnitude.70,71 Note that
early in the compressive disease
process, the optic disc may appear
normal. Other optic disc findings
may include atrophic changes (most
often due to chronic compression),
optic disc edema and the presence of
optociliary shunt vessels.70,71
Optic disc cupping and tissue
remodeling are a plausible outcome
of compressive optic neuropathy.73,74
Accurately diagnosing and
promptly treating the underlying
cause of the compression is vital
to preserve the patient's vision and
medical health. Surgical and medical treatments directed at managing
the underlying etiology may result
in recovery of acuity, fields and
Aside from glaucoma, anterior
ischemic optic neuropathy (AION)
is the most common cause of optic
nerve-related permanent vision loss
in adults.75-79 The two forms of
anterior ischemic optic neuropathy
are non-arteritic (NAION) and
arteritic (AAION). The main cause
of AAION is infarction of the short
posterior ciliary arteries due to giant
cell arteritis (GCA), when large
multinucleated monocytes infiltrate
the small- and medium-sized arteries, causing obliteration of their
lumen.75-80 Some research suggests
that transient hypoperfusion or
non-perfusion of the optic nerve is
the predominant cause of NAION,
while atherosclerosis along with
other systemic diseases like diabetes
mellitus or hypertension are merely
AION patients typically are
more than 40 years of age, and the
condition does not demonstrate a
particular bias toward gender (slight
predilection for males over females).
Patients present with sudden unilateral visual acuity and/or visual field
loss that occurred upon awakening.
Patients may present with scalp or
jaw pain, which may be interpreted
by the patient as eye pain or may
result in eye pain that is referred.
Depending upon the anatomical
involvement (cranial nerves III, IV, VI), diplopia is possible; however,
global systemic neurologic symp
toms are absent.75-80
Anterior Ischemic Optic Neuropathy
AION can be distinguished from glaucomatous optic neuropathy by these characteristics:
- IOP typically is either within normal range or lower normal range secondary to reduced
aqueous production because of poor perfusion to the ciliary body.
- Optic disc cupping seen in AAION does not involve the peripapillary zones.
- VF defects seen in ischemic optic neuropathy occur in the central or cecocentral visual
field and usually present with a complete altitudinal pattern respecting the virtual horizontal
meridian because of a propensity to be sectorial rather than diffusely damaging.
- Visual fields in AION cases often present attitudinally and can easily mimic the arcuate
defects seen in glaucoma. The telltale signs of AION fields are that they often demonstrate
a steep depth, they are very repeatable and consistent, they do not worsen or improve, and
because of the anatomy they affect, they have a distinct respect for the horizontal meridian.
- Ischemic optic neuropathy produces disc pallor.
- The cupping in AAION exhibits less cup volume and less cup depth compared to that
seen in open-angle glaucoma upon scanning laser ophthalmoscopy evaluation.84
- Ischemic optic neuropathy often produces dyschromatopsia, red color desaturation
defects, brightness desaturation defects and an APD immediately after its detection that is not
consistent with the disc's cupping or visual field severity.
- Unilateral ischemic optic neuropathy is asymmetric compared to open-angle glaucoma
and in many cases presents with some form of head pain (eye pain, jaw claudication, earache,
scalp tenderness, etc.) and possibly diplopia.
Key diagnostic signs include
acuity that may range from normal to variably decreased, variably
altered color vision, presence of a
relative APD in the setting of no
proptosis, no ptosis, normal ocular
motilities, and normal corneal and
Fundoscopic examination in
the acute phase of AION cases
reveals mild to severe optic nerve
swelling. Depending on the timing
of the observation, the disc may
appear hyperemic or pale, with
sectorial findings in less severe
cases and diffuse characteristics in
a more severely damaged papilla.
Retinal hemorrhages may be present at the optic disc margins with
cotton-wool spots suggesting an
arteritic etiology.75-80 The uninvolved eye commonly presents with
a "crowded" optic nerve head with
an absent or small cup.81,82 Medical
history may include one or more
vasculopathic risk factors such as
hypertension, hypercholesterolemia, diabetes or smoking.75-79
Optic disc cupping and tissue
remodeling are a plausible outcome
of ischemic optic neuropathy.83-86
Acute management for any suspected ischemic optic neuropathy
includes prompt laboratory and
diagnostic studies (erythrocyte
sedimentation rate, C-reactive protein, and platelets) to not only differentiate AAION from NAION,
but to identify systemic etiologies
that warrant immediate medical
The initial treatment for AAION
includes high-dose (80mg to 100mg
p.o. q.d.) prednisone or hospitalization to begin intravenous methyl-prednisolone followed by a course of
There is no one perfect test for
diagnosing GCA. The laboratory
work-up includes complete blood
count with differential and platelets,
liver function studies, erythrocyte
sedimentation rate and C-reactive
protein. Suspicious results are followed up with temporal artery
biopsy (TAB), while management is
While the TAB is not foolproof
(false positives and false negatives
occur), the constellation of signs
and symptoms dictate the treatment
protocols. Occult GCA is subtler,
because its eye problems occur in
the absence of systemic signs and
symptoms. Expert evaluation by
neurology or neuro-ophthalmology
When there is no suspicion
of GCA, the initial treatment of
NAION should focus on medical
management of potential vasculo-pathic etiologies. The main goal of
therapy is to control the suspected
disease process and to ultimately
protect the unaffected eye and reduce
the risk of cerebrovascular accident
and myocardial infarction.75-79
In cases of AAION, recovery of
visual acuity and/or visual field is
rare.75-80 There are reports describing
NAION patients who recover some
visual acuity and some visual field;
however, the recovery is often small
and not approaching the pre-loss
In both AAION and NAION, the
disease's natural course over several
months brings about resolution of
the disc swelling, eventual resultant
disc pallor with the potential for
papillary disc and tissue remodeling
that results in what appears to be
Infiltrative Optic Neuropathy
Infiltrative optic neuropathy
can result from systemic infection,
systemic lupus erythematosus,
blood-borne cancers and metastatic
disease; however, it is most commonly found in association with
While neuroimaging may be used
to confirm the presence of inflammation or an SOL, it is not specific
in cases of infiltrative optic neu-ropathy. Infiltration can be difficult
to confirm without biopsy and the
ability to directly observe the histological characteristics of the pathological cells.87-92
The sequence of events that
occurs in optic nerve infiltration varies. Generally, it is believed that the
bloodstream carries pathologic cells
to the meninges via the perivascular
and subarachnoid space.93 Once
present in meningeal tissue, these
cells have the capability to invade
the cranial nerves.89,93 Infiltration
of optic nerve tissue along with
accompanying impairment to its
blood supply lead to infarction and
loss of axons.93
Infiltrative Optic Neuropathy
Infiltrative optic neuropathy can be distinguished
from glaucomatous optic neuropathy
by these characteristics:
- IOP typically is within normal range,
barring the presence of an accompanying
anterior chamber inflammatory event that
might produce a secondary open-angle
uveitic glaucoma in the acute stages or
secondary synechial angle closure glaucoma
secondary to chronic disease.
- VF defects vary widely and are interpreted
as diffuse, lacking the classic pattern
seen in primary open-angle glaucoma.
- Visual fields can improve with pharmaceutical
- Consistent with optic nerve infarction,
there will often be dyschromatopsia,
red color desaturation defects, brightness
desaturation defects and an APD.
- Infiltrative optic neuropathy is often
unilateral with a unilateral diffusely edematous
optic disc in the acute stages that
inevitably becomes pale over time.
- Discs and nerves with significant
infiltration may create interrupted venous
egress, causing the filling of optociliary
shunt vessels, a clinical sign of pathology
independent of glaucoma.
- The patient's age and demographics
do not match the typical glaucoma patient.
The demographics of infiltrative
neuropathy varies widely by age,
race, gender and is subject to the
particular demographics of underlying disease.87-97 Clinically, these
patients often experience a reduction
in visual acuity, color vision and
contrast sensitivity that is typically
painless, unilateral or asymmetric
and variable in its nadir.87-97 An APD
is often present.88,91,94 Associated
ocular inflammation (iritis, vitritis,
pars planitis, intermediate uveitis)
can be present depending on the
etiology.94 The optic disc is often diffusely edematous.87-97
In cases producing granulomatous
infiltration, such as sarcoidosis, the
optic nerve may accumulate numerous discrete granulomata, creating
a cauliflower-like appearance.88,94 However, because infiltrative
events may occur anywhere along
the length of the optic nerve, it is
not always possible to distinguish infiltrative etiology based on disc
Optociliary shunts may develop
at the optic disc to serve as a second
drainage route in cases where infiltrative, compressive or neoplasmic
compression reduces ocular vascular
egress.88 The presence of optociliary
shunts predicts a poor visual outcome and definitively suggests a
pathological process independent of
The pattern of VF defects seen in
these cases is variable, ranging from
diffuse, non-specific defects to amaurosis.89,91,94 Visual field improvement
is possible in some cases with timely
Congenital Optic Disc Anomalies
Congenital optic nerve anomalies
can appear pseudo-glaucomatous.
Congenital anomalies that may
mimic glaucomatous disease include
megalopapillae, tilted discs and
optic pit. Each of these entities has
distinguishing characteristics that
allow differentiation from glauco-matous nerves.
Megalopapilla is similar to its
glaucomatous disc counterpart in
that it is defined as having a disc
volume greater than 2.5mm2 with
increased cupping.98,99 Two variants
of megalopapillae exist:99
- Type 1, which is bilateral with
large round or oval cupping where
the rim tissue obeys the ISNT rule
but may appear paler than the average healthy nerve.
- Type 2, which is unilateral with
a displaced round cup.
What distinguishes megalopapilla from optic discs that incur
cupping from glaucomatous optic
neuropathy is that megalopapilla
discs display a normal visual field
(some may exhibit an enlarged blind
spot), have a normal rim area, have
a normal cup volume and have
a normal RNFL, as measured by
scanning laser technology.99,100 It
should be noted that skewed findings can result from interpretation
of scanning laser topography, as the
Moorfields regression analysis on
the Heidelberg Retinal Tomograph
is calibrated to discs ranging from 1.2mm2 to 2.8mm2.99
Glaucoma traditionally is defined as a progressive optic neuropathy with accompanying characteristic optic nerve and VF changes. It is classically diagnosed by the presence of a progressive optic nerve cupping with concurrent progressive VF loss.
Tilted optic discs, colobomatous discs and discs exhibiting conus
from axial myopia can also mimic
glaucomatous discs. Scanning laser
tomography (OCT) has shown
tilted discs to have thicker-than-average temporal nerve fiber layer
tissue.101,102 Interestingly, there is no
actual rotation of the disc in tilted
disc cases—the name is a misnomer.
The tilted nature appears secondary
to abnormal scleral canal morphology where there is an absence of
fibers inferiorly and an excess of
Additionally, due to the optic
disc's counterclockwise rotation,
the superior nerve fiber layer tissue's peak thickness appears to be
dislocated temporally.101-102 Helpful
clues to discriminate myopic conus
discs from glaucomatous discs
include high myopia and increased
axial length (detectable on A-scan
Optic disc colobomas also can
mimic glaucomatous optic neuropathy. They appear as enlarged,
excavated discs with reduced nerve
fiber volume in the vertical pole
where the coloboma is present.100 A
distinguishing characteristic of disc
coloboma that can help differentiate
it from a glaucomatous disc is that
there may be other colobomas present in the iris or lens. Involvement
of neighboring tissues (including the
choroid or retina) and the presence
of microphthalmia are also indicators of coloboma.100
Congenital Optic Disc Anomalies
These characteristics distinguish congenital optic disc anomalies from glaucomatous optic
- IOP typically is within normal range.
- VF defects vary widely and may mimic those seen in glaucoma; however, they are often
deep defects that neither show improvement or worsening over time and are consistently
- Visual fields (as well as the disc appearance), for the most part, remain consistent over
time, unless a clinical complication (retinoschisis, serous retinal detachment) develops.
- Anomalies do not have a specific demographic predilection.
Disc cupping with a concomitant
presentation of macular retinoschisis
or serous macular retinal detachment is inconsistent with glaucomatous disease.105 Records indicating
the presence of this anomaly from
birth should provide definitive
proof that the unusual appearance
is not secondary to glaucomatous
Optic pits are depressions in the optic disc that result from herniation of neuroectoderm tissue during
development.100 They may occur
anywhere on the disc but are often
observed in the optic disc's temporal
quadrant and give the impression of
a large disc.100
Optic pits are associated with
variable visual field defects. Associated paracentral arcuate deficits can
mimic those seen in glaucoma.100 Optic pits increase the risk of vision
loss from complications, which
include macular schisis or serous
They can be differentiated from
the glaucomatous cupping process
by their location, depth, lack of
change over time, and associated
complications that are inconsistent
with glaucomatous disease, such
as retinoschisis and serous macular
It is imperative to note that the
presence of an optic disc anomaly
does not preclude the development
of glaucomatous disease. Reliable
and repeatable changes detected in
diagnostic testing may indicate the
development of an optic neuropathy.
optic nerve disorders from glaucomatous disease can save significant
time and money that would have
been spent managing a condition
that is neither there nor developing.
It can also save many lives. In cases
where optic disc changes evolve
secondary to non-glaucomatous pro
cesses, pathophysiological mechanisms may be budding, producing
consequences that are systemic with
the potential to impact other organ
systems or mortality.
Dr. Hutchinson practices in St.
Louis and is an adjunct faculty
member at the University of
Missouri-St. Louis College of
Optometry. Dr. Gurwood is a professor at Salus University in Elkins
Park, Pa. Dr. Myers is the senior
staff optometrist at the Coatesville
VA Medical Center in Pennsylvania.
- O'Neill EC, Danesh-Meyer HV, Kong GX, et al. Optic disc evaluation in optic neuropathies: the optic disc assessment project.
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