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1500
Time Amplitude (uV)
33 The Clinical Electro-Oculogram
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RE
minimum = 342uV
maximum = 399uV
ARDEN ratio = 117%
LE
minimum = 418uV
maximum = 459uV
ARDEN ratio = 110%
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Fig. 33.8 Best’s vitelliform macular dystrophy. Upper
panel-The EOG recordings for the right and left eyes
show a marked reduction in the Arden or LP:DT ratio of
approximately 1.1; Middle panel-color fundus image with
characteristic central vitelliform lesions; Lower panel-
of the EOG can be abnormally low, resulting in a
paradoxically normal or elevated LP:DT ratio
[52].
Systemic drugs affecting the outer retina or
RPE are also associated with a reduced or absent
light-rise of the EOG [53]. Chloroquine retinopa-
Ocular coherence tomography (OCT) images of the macula show a central pigmented area (with lipofuscin) of the
detached epithelium, which will eventually degenerate.
Images courtesy: Srikanta Padhy, MD
thy is associated with a reduced light-rise but
may not be detected through multi-focal electroretinography or color vision testing [54]. The
iron chelator, deferoxamine, can cause a reduction in the light-rise and dark trough amplitudes
as it can damage the RPE [55]. The anti-epileptic
458
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P. A. Constable
Fig. 33.9 Images and EOG of autosomal recessive
bestrophinopathy (conrmed via genetic tests) in a
25-year-old male. The rst and second panels show a
montage of the fundi with a hyperpigmented ring at the
equator corresponding with hyper-uorescence of the
RPE.The third panel shows OCT scans of the horizontal
and vertical meridians through the macula with a hyporeective region in the right and left eyes corresponding
with a separation of the RPE from the Bruch’s membrane.
The fourth panel shows reduced or absent light-rise in the
EOG, implicating the BEST1 gene in the potential differential diagnosis. Images courtesy: Srikanta Padhy, MD
minimum =
maximum = 392u
ARDEN r
minimum = 230u
maximum = 308u
ARDEN r
28mn
392
301
RE LE
33 The Clinical Electro-Oculogram
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uV
1500
RE
174uV
atio = 226%
LE
atio = 134%
1000
V
V
V
500
0
0510 15 20 25 mn
uV
1500
1000
500
0
0510 15 20 25 mn
Fig. 33.9 (continued)
Time Amplitude (uV)
0mn
5mn
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drug, vigabatrin, is also linked to visual eld loss
and reduced EOGs in children due to its toxicity
to the outer retina [56]. Other drugs that change
the EOG are: digoxin (elevates EOG), cisplatin
(reduces the EOG), ethambutol (elevates the
LP:DT ratio), and isotretinoin (reduces LP:DT
ratios) [53]. A reduced light-rise has also been
reported in tamoxifen retinopathy [57]. EOGs are
not routinely performed to monitor the toxic
effects of drugs since electroretinograms and retinal imaging can identify functional or structural
changes in the retina ahead of any marked
reductions in the EOG.Incidentally, the LP:DT
ratio is reduced in seasonal affective disorder,
which is characterized by depression in the wintertime [58], and Parkinson’s Disease [59].
33.5 Clinical Interpretation
Clinically, the main utility of an EOG is in diagnosing and monitoring conditions caused by
mutations in the BEST1 gene, which lead to a
functional loss of bestrophin in the RPE. The
ratio of the light-rise peak to the dark trough minimum is the main clinical measure. The ratio is
reduced where there is a disruption to the rodRPE interface, when bestrophin function is
affected, and there is a reduction in the basolateral chloride conductance. However, care must
be taken to observe the amplitude of the dark
trough as a reduced dark trough amplitude and a
relatively normal LP:DT ratio may indicate disruptions in the tight junctions. The timing of the
light peak is slower in those aged 55years and
older, and the LP:DT ratio also reduces at a rate
of 0.13units per decade; these measures must be
considered when recording/interpreting the EOG
in older subjects [41]. Typically, the EOG is
interpreted in conjunction with additional imaging and visual electrophysiological tests such as
the electroretinogram; these, combined with
genetic information and family history, are used
to make a clinical diagnosis.
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Computed Tomography:
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Dacryocystography
34
NandiniBothra andSuryasnataRath
34.1 Introduction
A century ago, in 1909, Ewing performed the
rst dacryocystography (DCG) to visualize the
lacrimal abscess cavity and passages using
X-rays. He used bismuth subnitrate as the contrast material. However, the surrounding bone
and soft tissue details were not discernible in this
DCG [1, 2]. A modication of this technique,
namely, digital subtraction, made the lacrimal
passage stand out but failed to show the surrounding details. Nevertheless, details of the
common canaliculus and nasolacrimal duct could
be seen, making it a useful tool in cases with stenosis. Using X-rays was a disadvantage due to
the dangers of radiation exposure [1]. This was
overcome to some extent by the advent of computed tomography dacryocystography (CT-DCG)
in 1990. This allowed the documentation of the
bone and soft tissue anatomy and the lacrimal
drainage system (LDS) [3]. The most important
use of CT-DCG was in complex nasolacrimal
N. Bothra
Govindram Seksaria Institute of Dacryology, Kallam
Anji Reddy Campus L V Prasad Eye Institute,
Hyderabad, India
S. Rath (*)
Mithu Tulsi Chanrai Campus, L V Prasad Eye Institute,
Bhubaneswar, India
e-mail: suryasnata@lvpei.org
duct obstructions (NLDO) in craniofacial trauma.
It is also useful in diagnosing and monitoring
tumors and masquerades involving the LDS [1].
Magnetic resonance dacryocystography
(MR-DCG) was rst performed in 1993 to study
the functional and morphological aspects of the
lacrimal pathways. Although the adverse effects
of radiation exposure were nullied, the high
cost, longer acquisition time, and motion artifacts
were the limitations [4]. CT-DCG is currently the
most used technique because of its distinct advantages in delineating details of the LDS, adjacent
bone and soft tissue anatomy, low acquisition
time, and relatively low radiation exposure.
34.2 Indications
ofDacryocystography
It delineates the following in the lacrimal drainage system:
1. Position and size of the lacrimal sac with
respect to the bony landmarks.
2. Abnormalities like lacrimal sac diverticula.
3. Filling defects caused by mucopeptide
concretions.
4. Functional passage of tears in the lacrimal
system.
5. Lacrimal sac tumours.
6. Partial nasolacrimal duct obstructions.
7. Differentiate masquerading conditions from
LDS abnormalities.
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024
T. Das, P. Satgunam (eds.), Ophthalmic Diagnostics, https://doi.org/10.1007/978-981-97-0138-4_34
463
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N. Bothra and S. Rath
34.3 Dyes Used
inDacryocystography
There are oil-soluble and water-soluble dyes
available for conventional DCG and
CT-DCG. The ideal dye must be radio-opaque,
non-irritant, non-toxic, homogenous, with optimal viscosity, and should not cause adverse reactions [1]. Oil-soluble dyes like lipiodol provide
signicantly better images than water-soluble
dyes like iohexol, iopamidol, sinogran, and
omnipaque; however, these are also very viscous,
immiscible with tears, and carry a risk of tissue
reaction or granuloma formation [5–7]. This
makes water-soluble dyes preferable over oilsoluble counterparts. Water-soluble dyes can
have a high (iohexol, iopamidol 300) or low
(omnipaque) iodine content. Those with high
iodine content provide better images but may
cause more patient discomfort [5–7]. For patients
allergic to iodinated substances, gadobutrol can
be used [8]. MR-DCG uses a gadolinium solution
as a contrast medium [4]. The authors use iohexol
dye in a 50:50 dilution with normal saline for
CT-DCG.
34.4 CT-DCG Scan Requisition
A request for CT-DCG should ideally full a few
prerequisites for optimal information. These
include:
1. Region of interest: computed tomography
scans of the orbit + dacryocystography.
2. Slice thickness: typically, 2 mm cuts (sec-
tions) are preferred for the orbit.
3. Imaging plane: Coronal, axial, three-
dimensional volumetric reconstruction
(3-DR), and parasagittal views are requested.
Coronal and axial views demonstrate the passage of the LDS in the lacrimal sac fossa and
a small portion of the NLD (nasolacrimal
duct) and surrounding bony canal. The 3-DR
scans provide a view of the LDS in three
dimensions and determine the position of the
LDS with respect to the bony structures. The
parasagittal view shows the bony segment of
NLD in its entirety.
4. Tissue windows: The bone windows help
delineate the relationship of a dye-lled LDS
with the surrounding bony structures, and the
soft tissue windows show the position of the
dye-lled LDS within the surrounding soft
tissues.
34.5 Methods
1. Drop method: The dye is instilled in the inferior cul-de-sac, and the passage of the dye is
monitored on serial scans. This technique is
mainly used to assess the functional capacity
of the LDS.
2. Injection method: The dye is directly injected
into the system using an irrigation cannula.
This method is faster and serial scans are not
needed.
34.5.1 Patient Stories
Patient 1
A 27-year-old male presented with complaints of
watering from his left eye and double vision for
2 months. He had sustained a road trafc accident 4months before, followed by a maxillofacial repair of facial fractures. The irrigation of the
left LDS showed complete regurgitation of
mucoid discharge from the opposite punctum,
and the right side was patent. CT-DCG 3-DR
scans showed a large dilated sac on the left side
with a block at the junction of the lacrimal sac
and nasolacrimal duct with minimal spillover of
the dye and patent system on the left side. The
sac was fairly in position on the left side. There
was an inferior rim fracture with plates on the
maxillary bone just short of the expected area of
surgery. Coronal CT scans of the orbit showed an
associated large oor fracture on the left side
involving the strut. The nasal anatomy and cribriform plate position appeared normal (Fig.34.1).
Inference: CT-DCG helped delineate the anatomy of the bones in relation to the lacrimal system, which was relatively preserved. This allowed
the surgical team to decide on an external or
endoscopic dacryocystorhinostomy. An orbital
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abc
465
Fig. 34.1 Clinical photograph showing minimal pigmentation of the medial canthal region with mild telecanthus on the left side (Panel A). Computed tomography
scans with dacryocystography and 3D reconstructed
images demonstrate a dilated sac on the left side with
obstruction at the sac-duct junction; the right side shows
fracture repair could be planned during the same
sitting.
Patient 2
A 30-year-old gentleman with a history of blunt
trauma to the forehead and upper part of his nose
with a cricket bat 4years ago complained of right
eye watering after trauma. A CT-DCG scan and
3-DR images showed a small shrunken lacrimal
sac on the rightside and an obstruction at the lacrimal sac-nasolacrimal duct junction. On rotating
the 3-DR images, the right-side sac position
could be conrmed with respect to the underlying lacrimal sac fossa. The coronal images, bone
windows depicted a normal relationship between
the dye-lled sac with the lacrimal sac fossa and
a shrunken sac compared to the left side. The
parasagittal cuts showed no evidence of any bony
fractures in the bony NLD canal. The remaining
orbital and nasal anatomy appears normal
(Fig.34.2).
Inference: External or endoscopic approach
could be attempted. Expect the sac to be small,
brosed, and slightly higher in position.
Patient 3
A 38-year-old male sustained multiple facial
fractures after a road trafc accident. He complained of epiphora on both sides. He underwent
a maxillofacial repair after the accident. On looking at the CT-DCG scans, gross lacrimal sac malposition was noted (left, more than right). The
right lacrimal sac was almost completely scarred.
The left sac was displaced postero-superiorly in
drainage of the dye to the inferior meatus; left inferior
orbital rim fracture, screws and plates on the maxillary
and zygomatic bones on both sides (Panel B) and coronal
scans showing left-sided orbital oor and medial wall
fracture involving the strut, with the cribriform plate having a normal position and normal nasal anatomy (Panel C)
orbit beneath the ipsilateral frontal sinus. Damage
to the horizontal plate of the cribriform and other
fractures of the orbital walls were also noted
(Fig.34.3).
Inference: An osteotomy at this location could
lead to a signicant risk of injury to the skull
base. In addition, maneuvering the canalicular-lacrimalsac anatomy in such a malposition
would be challenging. In this scenario, DCT
(dacryocystectomy) may be a safer option.
Alternatively, if attempted, a staged approach
with the reconstruction of the naso-ethmoid fracture and correction of the medial canthal dystopia
may need navigation guidance to decrease the
risk of CSF (cerebrospinal uid) leak.
Subsequently, a conjunctival DCR with a Jone’s
tube may be considered for intractable epiphora.
Patient 4
After a road trafc accident, a young male presented with a red, inamed, and tender swelling
below the right lower eyelid medially with complaints of epiphora. Irrigation revealed total
regurgitation of the uid from the opposite punctum, with the swelling becoming more tense and
pronounced. The CT-DCG scans showed a minimally displaced sac with a large postero-lateral
diverticulum, partially lled with diluted dye
(Fig.34.4).
Inference: While trying to do a dacryocystorhinostomy surgery, one has to ensure that the
diverticula are either completely excised or internalized into the ostium created to prevent recurrences of the problem and failure of the procedure.
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N. Bothra and S. Rath
c
d
e
Fig. 34.2 Clinical photograph demonstrating a raised
tear meniscus height and minimal discharge medially in
the right eye (Panel A). The CT-DCG and 3DR images
show a small shrunken sac with obstruction at the sac-duct
junction (Panel B). The 3-DR image, right-sided view, and
maximum intensity projection sequence (MIPS) show the
sac is within the lacrimal sac fossawith theobstruction at
the sac-duct junction (Panels C and D). The parasagittal
cuts demonstrate a normal bony nasolacrimal duct with no
drainage (Panel E)
The position of the diverticula noted on the scans
will help take the appropriate surgical steps. A
posterior diverticulum can be managed to a large
extent during an endoscopic DCR, but a large
anterolateral diverticulum is best approached via
an external approach.
Patient 5
A 10-year-old boy was scratched by a dog in the
medial part of the right eye about a year ago. He
has had complaints of epiphora for the past
10 months. There was scarring in the midcanalicular area. On probing and irrigation, the
ab
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c
d
e
Fig. 34.3 Clinical photograph showing traumatic telecanthus on the left side (Panel A). The 3D CT-DCG
showed a shrunken, brosed sac on the right side and a
postero-superiorly displaced sac on the left side (Panel B).
The CT-DCG scans, coronal cuts demonstrate the orbital
fractures on the right side a displaced, shrunken sac and a
damaged cribriform plate (Panel C) and naso-orbitoethmoid fracture, postero-superior dislocation of the sac,
and damaged cribriform plate on the left side (Panel D).
The CT scan orbit, coronal cuts, bone windows demonstrate the presence of orbital fractures and cribriform plate
damage on both sides (Panel E)
upper and lower canaliculus on the right side
showed a mid-canalicular obstruction, but the
child was certain he could appreciate minimal
uid in the nasal cavity. The CT-DCG scans
conrmed the mid-canalicular obstruction with
no evidence of any trace of dye in the remaining
LDS (Fig.34.5).
Inference: Considering the scarred tissue on
the conjunctival side of the medial eyelid and the
obstruction precisely at the same spot, one can
explore the area with a guarded prognosis or convince the patient to undergo a conjunctivaldacryocystorhinostomy since the remaining
anatomy is unaffected.
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