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N. Bothra and S. Rath
Fig. 34.4 A clinical photograph showing an inamed
swelling on the lower eyelid extending lateral to the lacrimal sac position with a pus point along with corneal scar-
a
c
e
ring and exotropia (Panel A). The 3D CT-DCG scan
demonstrates a minimally superiorly displaced sac on the
right side with a postero-lateral sacdiverticulum (Panel B)
b
d
Fig. 34.5 The clinical photograph demonstrates telecanthus on the right side (Panel A) and normal lower and
upper puncta (Panels B and C). The 3D CT-DCG and
maximum intensity projection sequence demonstrate a
canalicular obstruction involving the upper and lower
canaliculus on the right sideand a patent lacrimal drainage system on the left side (Panels D and E)
ab
34 Computed Tomography: Dacryocystography
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469
c
d
e
Fig. 34.6 The 3D CT-DCG scans demonstrated a dilated
sac on the right side and an inferiorly brosed sac on the
left side, in the lacrimal sac fossa (Panels A, B, C, and D),
and the maximum intensity projection sequence showeda
bilateral incomplete, inferior osteotomy indicative of a
previous surgery (Panel E)
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N. Bothra and S. Rath
Patient 6
A 48-year-old female had undergone bilateral
endonasal endoscopic DCR elsewhere 3 years
ago. A month after surgery, she had watering and
discharge from both eyes. Endoscopic
examination revealed complete scarring anterior
to the middle turbinate in the sac-duct junction
(inferior scarring). The CT-DCG scans showed a
dilated sac on the side and a comparatively
shrunken sac on the left side with an underlying
incomplete bony osteotomy (Fig.34.6).
Inference: During the revision DCR surgery,
the osteotomy should be enlarged (Right eye
more than Left eye) to open the sac completely
into the nasal cavity. It also identies that the failure of the previous surgery was due to inadequate
osteotomy, which was mainly inferior. The area
opposite the common canaliculus was still covered with bone and could likely cause failure.
34.6 Conclusion
Dacryocystography can be an adjunct to diagnosing and managing complex and complicated
cases. It cannot be used as a single modality to
understand the case scenarios. It has to be combined with a proper history, clinical examination,
and other corroborative tests. Also, it provides a
clear picture and helps make appropriate decisions on further management.
Funding Hyderabad Eye Research Foundation.
Disclosure Receives royalties from Springer for his trea-
tise The textbook Surgery in Thyroid Eye Disease: A
Conceptual Approach.
References
1. Singh S, Ali MJ, Paulsen F.Dacryocystography: from
theory to current practice. Ann Anat. 2019;224:33–40.
2. Ewing AE.Roentgen ray demonstrations of the lacrimal abscess cavity. Am J Ophthalmol. 1909;26:1–4.
3. Zinreich SI, Miller NR, Freeman LN, et al.
Tomographic dacryocystography using topical contrast media for lacrimal system visualization. Orbit.
1990;9:79–87.
4. Goldberg RA, Heinz GW, Chiu L.Gadolinium MR
imaging dacryocystogra-phy. Am J Ophthalmol.
1993;15:738–41.
5. Munk PL, Burhenne LW, Buffam FV, et al.
Dacryocystography: comparison of watersoluble and oil-based contrast agents. Radiology.
1989;173:827–30.
6. Manseld DC, Zeki SM, Mackenzie JR.Case report:
extravasation of lipiodol—a complication of dacryocystography. Clin Radiol. 1994;49:217–8.
7. Delaney Y, Khooshabeh R.Lipogranuloma following
traumatic dacryocystography in a 4-year-old boy. Eye
(Lond). 2001;15:683–4.
8. Priebe M, Mohr A, Brossman J, etal. Gadobutrol: an
alternative contrast agent for digital subtraction dacryocystography. Eur Radiol. 2002;12:208386.
Home Care
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andTeleophthalmology
TaraprasadDas , DebananadaPadhy ,
KalpaNegiloni , JenilSheth , SanilJospeph ,
SuryasnataRath , andRameshKekunnaya
35
35.1 Introduction
Family medicine comprises comprehensive
health care for people and their families and provides continuing health care to everyone across
all ages, genders, and diseases [1]. Although fam-
T. Das (*)
Anant Bajaj Retina Institute, Srimati Kanuri
Santhamma Centre for Vitreoretinal Diseases, Kallam
Anji Reddy Campus, L V Prasad Eye Institute,
Hyderabad, Telangana, India
e-mail: tpd@lvpei.org
D. Padhy
Gullapalli Pratibha Rao International Centre for
Advancement of Rural Eye Care, L V Prasad Eye
Institute, Hyderabad, India
K. Negiloni
Remidio Innovative Solutions Pvt Ltd,
Bengaluru, India
J. Sheth
Shantilal Shanghvi Eye Institute, Mumbai, India
S. Jospeph
Lions Aravind Institute of Community
Ophthalmology, Aravind Eye Care System,
Madurai, India
S. Rath
Mithu Tulsi Chanrai Campus, L V Prasad Eye
Institute, Bhubaneswar, India
e-mail: suryasnata@lvpei.org
R. Kekunnaya
Child Sight Institute, Jasti V Ramanamma Children’s
Eye Care Center, Kallam Anji Reddy Campus,
L V Prasad Eye Institute, Hyderabad, India
e-mail: rameshak@lvpei.org
ily medicine has been an age-old practice globally and in India, it has slowly given way to
specialist medical care. While it is not practiced
as much in eye care as it is for systemic care, even
in the latter, it is decreasing. Despite its dwindling popularity, one of the key advantages of
family medicine is last-mile access, especially to
vulnerable individuals, due to their age, sickness,
and/or mobility constraints.
Home care emerged as an acute need during
the SARS-CoV-2 pandemic, forcing people to
stay indoors for several months. As a result, various technologies for keeping patients safe and
healthy emerged. Tools that enabled home care
and were a matter of convenience and compliance at one point have now become a critical
need. Moreover, home care has become essential,
with the WHO reafrming the criticality of prioritizing primary health care to ensure that people receive comprehensive promotive, preventive,
curative, rehabilitative, and palliative care as
close to their everyday environments as possible
[2, 3]. However, to be acceptable, home care
must be technologically safe, scientically sound,
socially acceptable, easily accessible, and nancially affordable.
Eye disease and visual impairment are fre-
quently seen in older adults. Although ophthalmic pathology is rarely life-threatening, the
consequences of visual impairment are wideranging. Visual impairment may be associated
with social and functional decline, depression,
© 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_35
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Table 35.1 Teleophthalmology methods
Modality Parameters Description
Store and forward Process Patient information, such as medical images, is acquired and sent to
the specialist as needed.
Advantage Medical practitioners need not meet the patient in person.
It saves time and is convenient for the physician.
Disadvantage Given that it relies on history and documented information or images
rather than a physical examination, it has the potential for
misdiagnosis.
Remote monitoring
(self-testing)
Real-time interactive
asynchronous
Real-time interactive
synchronous
Process Remote monitoring uses various technological devices to remotely
monitor a patient's health and clinical signs.
Advantage It is cost-effective; hence, more frequent monitoring is possible, and
there is greater patient satisfaction.
Disadvantage Given that it is patient-dependent, the tests conducted by the patients
may not always be accurate.
Process It utilizes several different media, including phones, online
consultations, and home visits by technicians of the eld team.
Advantage A video/audio interaction between the patient and physician occurs
after the eld team has visited the individual’s home, either on the
same or another day.
Disadvantage Relatively expensive and time-consuming.
Process While it is similar to the asynchronous modality, the main difference
is the live consultation by an ophthalmologist/an eye care personnel.
Advantage A real-time video/audio interaction between the patient and
physician occurs immediately after the eld team completes the eye
examination.
Disadvantage Relatively expensive and time-consuming; logistic challenge of
coordinating the video call at the time of the home visit. Needs a
reliable network connection.
T. Das et al.
falls, and increased mortality. These could be
partly met with telemedicine and home care.
Telemedicine is an exchange of medical data
by electronic telecommunication technology
that allows a remotely located physician to
evaluate and monitor the patient’s medical
problems. Ophthalmology being highly visual
and image intensive is uniquely suited for telemedicine. There are three main types of telemedicine: (1) store-and-forward, (2) remote
monitoring, and (3) real-time synchronous and
asynchronous interactive services. Each one
has its advantages and disadvantages.
(Table35.1).
This chapter describes the ophthalmic devices
and technology of home eye care and teleophthalmology. Table35.2 lists the eight eye examinations for which teleconsultation and home care
are available for adults.
Table 35.2 Eight eye examinations
Sr. No. Parameter Device
1 Visual acuity Web-based/smartphone-
based (PEEK)
2 Refraction Folding Phoropter,
autoref (e-see; InstaRef)
3 Intraocular
pressure
4 External eye Pocket ashlight
5 Visual eld Head-mounted device,
6 Anterior
segment
7 Pupil Pupillometer
8 Fundus Direct and indirect
Rebound tonometer,
modular slit lamp with
applanation
virtual reality-based
perimetry
Modular slit lamp, an
anterior imaging system
(Grabi ™)
ophthalmoscopy,
non-mydriatic fundus
camera
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35.2 Visual Acuity
Visual acuity (VA) is essential for assessing a
patient’s eye health. It is conventionally measured
using a printed Snellen or ETDRS (Early
Treatment Diabetic Retinopathy Study) chart
placed at a 6-m (20ft) distance under a standard
illumination of 300 lux. With the introduction of
digital charts, the distance for visual acuity measurement is now reduced to 3–4m. Historically,
while VA testing has been done exclusively in a
clinical setting under the guidance of a trained
professional, in recent years, various options have
been created for testing VA outside of the clinic,
using web-based (e.g., www.smart-optometry.
com) or smartphone-based (e.g., PEEK; https://
peakvision.org) tests. These devices are validated
against the standard visual acuity charts [4].
35.2.1 PEEK is one ofthepopular VA
measurement devices.
(Fig.35.1)
Technology: It is a smartphone-based vision
check app that allows anyone to check VA using
an Android smartphone. The advantages of PEEK
include a visual representation of results for easy
explanation to patients, and it provides standard
units of Snellen acuity.
Technique: A “Tumbling E” is used in
PEEK.Only the letter “E” appears on the smartphone, but it has a different orientation each time
it appears. Once this has been explained to the
patient, the smartphone is held at a distance of
1m. One eye is examined at a time, with the other
eye covered.
Clinical Application: PEEK helps screen and
identify people who need further examination. It
is not intended to replace detailed examinations
from a qualied eye health professional.
35.3 Refraction
The global burden of uncorrected refractive error
is high. Refraction is the rst essential step in the
correction of refractive error. The patient can be
refracted at home by traditional retinoscopy
using a streak retinoscope, followed by a subjective correction with a series of trial lenses. While
ideal, this requires an elaborate setup, including a
skilled workforce. De-skilling the refraction process would reduce the cost of training. This will
help increase efciency and improve the quality
of spectacle prescriptions and the cost of care.
Although autorefraction is an alternative option
that can be performed at home, the autorefractometer must be portable, lightweight, reliable
enough to avoid a subjective correction, and able
to transfer data to an eye clinic or optical outlet.
We will describe three such devices in the following section.
Fig. 35.1 Visual acuity testing using PEEK.A new letter
appears when the phone is swiped in the direction the
patient identies the letter. (Photo courtesy: Krishnaveni
& Monika, LV Prasad Eye Institute, Hyderabad, India)
35.3.1 Folding Phoropter (FoFo)
(Fig.35.2)
Technology: The Folding Phoropter is a foldable
paper device comprising two retractable paper
tubes with a converging and diverging lens on
each tube. (Fig. 35.2; Left panel) Like a telescope, the user can move the tubes while looking
through them and stop when the target is viewed
clearly. The target image becomes clear by
adjusting the distance between the lenses. A scale
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T. Das et al.
ab
Fig. 35.2 Left panel: (a) optics; (b) the FoFo device. Right panel: schematic diagram describing how the FoFo is oper-
ated. (Copyrights Padhay D etal., 2023 [5] under Creative Common Attribution License)
embedded into the device approximates the
refractive error when a clear image is obtained
and gives the spherical equivalent of the refractive error. The refractive error range for the FoFo
is +4.00 to–7.00 D.It is user-dependent since it
relies on a subjective assessment of refractive
error.
Technique: The FoFo is held at eye level in the
non-dominant hand. The subject focuses on a distance target of 6/60 level at 3m. The height or
level of the eye is aligned parallel with the distance target. The subject then focuses on the letter/image (Fig. 35.2; right panel). The target
image becomes clear by adjusting the distance
between the lenses. The dominant hand slides the
outer tube to nd the point where the target
appears clear. With one eye, the user looks
through the FoFo and moves the tubes while xating on the distant target. The measurement of
refractive error for each eye is done separately.
When the endpoint for each eye is obtained, the
scale on the FoFo gives the spherical equivalent
of the refractive error.
Clinical Application: The FoFo is useful in
screening during home visits. It could be used for
screening children at schools as well. It is valuable for refractive error assessment in lowresource settings. Its relative advantages and
disadvantages are shown in Table35.3 [5].
35.3.2 QuickSee (e-See)
Technology: The QuickSee is a portable openview wavefront aberrometer capable of conducting binocular autorefraction. There is also a
monocular model of the QuickSee, the
Table 35.3 Advantages and disadvantages of the FoFo
Advantages Disadvantages
Easy to
understand and
use
Requires less
time
Inexpensive Cannot measure astigmatism
Lightweight Breaks easily
Portable Works well with literate people
No need for
electricity/
battery
Difcult to measure the refractive
error in people in extremes of
age—Very elderly and young
children
Findings are not reliable if used
improperly
Cannot determine higher refractive
errors
“QuickSee Flip” or “e-see,” specically designed
to market at a lower price to increase accessibility in low- and middle-income countries [6].
(Fig.35.3).
Technique: The subject holds the autorefractor
to the face and looks through the device at a
back-lit VA chart placed at 3 or 6m. The interpupillary distance wheel on the autorefractor and
the pitch of the instrument are manually adjusted
until one sees a red spot on the autorefractor. A
trained technician is usually required to guide the
subjects using it. The device illuminates the eye
using a low-power laser diode through the pupil,
and the light captured by the inbuilt wavefront
sensor provides an estimate of the magnitude of
various aberrations in the subject’s eye. An
approximately 10-s video of the captured light is
recorded for each eye. The device then uses this
information to estimate the subject’s refraction
and generate the spectacle prescription on a laptop [7, 8].
Clinical Application: The e-see provides glass
prescriptions that satisfy most individuals with-
ed (IR) Laser beam
35 Home Care andTeleophthalmology
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475
out requiring highly trained personnel to perform
subjective refraction.
35.3.3 InstaRef
Technology. InstaRef R20™ is a portable,
Hartmann Shack wavefront aberrometer-based
autorefractometer. It is a monocular handheld
Fig. 35.3 The e-See is used to refract one eye at a time
a
c
device weighing 400 g, allowing monocular
refractive error measurements. (Fig.35.4) A specic point on the retina is illuminated using an
Infrared (IR) beam (Fig.35.4c-red) with a wavelength of 850nm, emitted from a laser module.
The reected IR laser beam (Fig. 35.4c-blue)
passes through the lens system. The wavefront
sensor comprises a micro lenslet array measuring
12.92×8.75mm and 1.55mm thick. This array
connes the reected light to a pattern of spots,
which are detected by an image sensor measuring
4.76×5.61mm. (Fig.35.5) The tilt of the wavefront that enters each lenslet corresponds directly
to the position of each spot on the image sensor.
By determining the positions of the spots, the
phase of the wavefront, which relates to the ocular aberrations, is calculated. Using standard
mathematical calculations, these spot-position
coordinates are used in modal reconstruction to
approximate the three-dimensional wavefront
Beamsplitter-1
Beamsplitter-2
Pupil centering
Camera Module
Lens-1
Lens-2
b
Lenslet Array
Sensory
Board
Fig. 35.4 InstaRef: (a) monocular device capture mode, (b) measurement recordings, and (c) optical components of
the system. (Source: Rao DP, etal. [9])
IR Laser Module
Optical path details
InfraR
Reflected IR laser beam
Anterior Imaging path
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Fig. 35.5 Optics of the InstaRef. (Kalpa-more details)
T. Das et al.
topology for lower order aberrations. The device
also includes a pupil-centering module and an
audible tilt warning system. The refractive error
range is −10.0 D to +10.0D sphere and−5.0D to
+5.0D cylinder.
Technique. Using the non-testing eye, the
subject is instructed to xate on a distant target
(~20feet). This can eliminate the inuence of
accommodation on measurement. The examiner places the device in front of the testing eye
(Fig.35.4a). It is advisable to test under dim
illumination so that the pupil diameter is large
and the wavefront-based measurements are
more reliable. The pupil-centration crosshair in
the device is aligned with the center of the subject’s pupil. The device alerts the examiner if
there is any signicant tilt in the device through
a tilt warning system. Once the crosshair is
centered and after ensuring that the fellow eye
is xed for the distance, the examiner triggers
the measurement button. The device lets the
examiner capture three readings per eye in 3s.
Based on the three readings, the device automatically calculates the average of spherical,
cylindrical, and axial values. It also allows the
negative and positive representations of the
cylindrical values. The same procedure is followed for refractive error measurement in the
other eye. The results can be immediately
printed using Bluetooth-enabled printers or
accessed on an electronic medical record
system.
Clinical Applications. The InstaRef is a good
starting point for subjective refraction in all age
groups and is useful in clinical and community
vision screening as a quick and reliable tool. The
advantages of this tool are: it requires less clinical space, provides a quick reading, requires less
training, and has electronic compatibility.
Compared with the open-eld autorefractometer
(OFAR), the device works well in adults [9], can
be used pre- and post-cycloplegic treatment, and
can be used for subjective refraction in children
older than 8 [10].
35.4 Intraocular Pressure
Glaucoma is one of the leading causes of visual
impairment and blindness globally. Increased
intraocular pressure (IOP) is one of the signs of
glaucoma. The development and progression of
glaucoma can be slowed only by controlling the
IOP. Therefore, accurate measurement of IOP is
of paramount importance. It can be measured at
home by allied ophthalmic personnel using a
handheld device. One such device is described
below.
Generation of a voltage fluctuation in the
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477
35.4.1 Rebound Tonometer
The Goldman applanation tonometer (GAT) is
the current reference standard in IOP measurement. However, it requires a slit lamp, topical
anesthesia, and sodium uorescein dye; it can
only be measured with the patient in a sitting posture. Other ocular tonometers, such as the
rebound tonometer, are comparable to the GAT
[11] while also portable, lightweight, easy to use,
and do not require topical anesthesia.
Technology: The rebound tonometer consists of
a tiny probe (of variable length) made of stainless
steel with a 1.8mm diameter plastic ball. The probe
is held in the device by an electromagnetic eld
powered by a battery. When the button on the
device is pushed, a spring drives the probe with its
plastic ball to hit the corneal surface. The speed of
deceleration of the probe when it hits the corneal
surface is measured and converted into an IOP
measurement. (Fig. 35.6) The speed of deceleration depends on the IOP; it is rapid for high IOPs
and slow for low IOPs. The motion parameter
(probe deceleration) and contact time (when the
probe hits the cornea) are measured by an induction-based coil system and analyzed by an advanced
algorithm in the device. The rebound tonometer
was introduced as the Icare TAO1i (Helsinki,
Finland) device in 2003. Updated versions of the
rebound tonometer, i.e., the Icare Pro, Icare 100,
and Icare 200, were introduced subsequently. It
weighs around 250–400g. It is handheld, rechargeable battery-operated, lightweight, and portable.
Technique: For recording the IOP, the patient
sits upright, looks straight ahead, and keeps his/
her eyes steady (the device can also be used on
the subject in a supine position). The device is
held in front of the eye so that the ball of the
probe is around 4–8mm from the center of the
cornea and is perpendicular to the corneal surface. When the push button of the device is
pressed, the probe touches the center of the cornea rapidly. Six consecutive measurements are
taken, and the result is displayed on an LCD
screen facing the examiner. The IOP measurement in the rebound tonometer does not need any
prior eye preparation and does not need corneal
anesthesia.
Unlike the rst-generation rebound tonometer, the current versions have magnetized probes
and position sensors; these allow IOP measurements only if the probe is perpendicular to the
center of the cornea (in sitting or supine positions), thereby improving the reliability and
repeatability of the IOP recordings.
Clinical Application: The rebound tonometer
is particularly useful for recording IOP in conditions like corneal scarring, active inammatory
and infectious corneal conditions, where other
tonometers cannot record the IOP reliably.
Additionally, in post-refractive surgery, for
patients where an air-puff and/or applanation
tonometer is contraindicated due to the risk of
ap displacement, a rebound tonometer would be
very useful for measuring IOP.However, its reliability decreases with increasing corneal thick-
Fig. 35.6 Rebound tonometer. Left: the device in use;
the green circle indicates correct alignment; Right: the
principle of the rebound tonometer works; (Reprinted
coil ends leads to a movement of the
tonometer probe
tonometer
tonometer probe
Moving direction of the
tonometer probe
with permission from Ruokonen PC etal. [12] Copyright,
2007, Springer Nature)
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