Multidisciplinary Ophthalmic Imaging
Construction of an Inexpensive, Hand-Held Fundus
Camera through Modification of a Consumer ‘‘Point-and-
Kenneth Tran,1Thomas A. Mendel,2,3Kristina L. Holbrook,2and Paul A. Yates1,2
PURPOSE. To construct a low-cost, easy-to-use, high-image-
quality mydriatic fundus camera with ‘‘point-and-shoot’’
operation, and to evaluate the efficacy of this camera to
accurately document retinal disease.
METHODS. A prototype portable fundus camera was designed by
interfacing a novel optical module with a Panasonic Lumix G2
consumer camera. Low-cost, commercially available optics
were used to create even illumination of the fundus, providing
a 508 retinal field of view. A comparative study assessing the
image quality of the prototype camera against a traditional
tabletop fundus camera was conducted under an Institutional
Review Board (IRB)-approved study.
RESULTS. A stand-alone, mydriatic camera prototype was
successfully developed at a parts cost of less than $1000.
The prototype camera was capable of operating in a point-and-
shoot manner with automated image focusing and exposure,
and the image quality of fundus photos was comparable to that
of existing commercial cameras. Pathology related to both
nonproliferative and proliferative diabetic retinopathy and age-
related macular degeneration was easily identified from fundus
images obtained from the low-cost camera.
CONCLUSIONS. Early prototype development and clinical testing
have shown that a consumer digital camera can be inexpen-
sively modified to image the fundus with professional
diagnostic quality. The combination of low cost, portability,
point-and-shoot operation, and high image quality provides a
foundational platform on which one can design an accessible
fundus camera to screen for eye disease. (Invest Ophthalmol
Vis Sci. 2012;53:7600–7607) DOI:10.1167/iovs.12-10449
field and required manual exposure using flash powder and
color film.1,2Since then, the capabilities of fundus cameras
have improved dramatically to include nonmydriatic imaging,
electronic illumination control, automated eye alignment, and
high-resolution digital image capture. These improvements
n 1926, Carl Zeiss Company introduced the first commer-
cially available fundus camera, which offered a 108 retinal
have helped make modern fundus photography a standard
ophthalmic practice for detecting and documenting retinal
Although current fundus cameras have advanced signifi-
cantly since their introduction, the traditional tabletop optical
design has remained largely unchanged.4,5Complex optical
assemblies in current devices provide high-resolution imaging
of the fundus but also require dedicated clinical space and high
manufacturing costs. Portable cameras have recently become
commercially available, but most remain difficult to use in a
hand-held manner and often have substandard image quality,
compared to their tabletop counterparts.6,7
The commercial field of fundus camera equipment stands in
unique contrast to consumer digital camera technology, where
to use. Although other ophthalmic equipment manufacturers
have recently incorporated consumer digital single-lens reflex
(DSLR) cameras into their fundus camera designs, they do not
make full use of the consumer camera’s built-in functions or
space-saving design. Traditional fundus camera designs are thus
ill suited to leverage the significant cost reductions and
technologic advancements of consumer camera technology.
Within the past decade, retinal screening programs for
macular degeneration, have experienced rapid growth.7–10The
expansion of these screening programs into rural, nurse-
operated, highly distributed primary care facilities highlights
to-operate, and high-image-quality fundus camera.11–13
Our goal was to create a device capable of imaging the
human fundus and documenting retinal pathology with
components that cost less than $1000. We also aimed to
improve dramatically the ease of use of the device by
incorporating common ‘‘point-and-shoot’’ consumer camera
technology. A secondary objective was to reduce the design to
a portable form factor that would enable remote use of the
device in settings such as hospital bed consultations and
nursing home facilities. This design would provide a means of
acquiring fundus photographs in clinical settings previously
inaccessible to tabletop cameras.
In this article, we present the technical modifications needed
to transform a consumer digital camera into a mydriatic fundus
camera. We also demonstrate the functional feasibility of using
such a camera in a variety of clinical settings to produce images
of the posterior pole of the eye with pathology detail resolution
comparable to that of existing fundus cameras.
MATERIALS AND METHODS
General Design Description
Human fundus photography is based upon the principle of indirect
ophthalmoscopy. A front objective lens is positioned at a working
distance of 5 to 50 mm from the front of the eye. This lens is used to
From the1Departments of Biomedical Engineering,2Ophthal-
3Pathology, University of Virginia, Charlottesville,
Supported by the UVa-Coulter Translational Partnership Grant
(GF11938), Ivy Foundation of Charlottesville Research Grant (DR-
02314), and National Institutes of Health (NIH) Grants T32
GM08715 (TAM) and K08 GC11897 (PAY).
Submitted for publication June 22, 2012; revised September 2,
2012; accepted October 2, 2012.
Disclosure: K. Tran, RetiVue, LLC (I, E, S), P; T.A. Mendel,
None; K.L. Holbrook, None; P.A. Yates, RetiVue, LLC (I, E, S), P
Corresponding author: Paul A. Yates, Department of Ophthal-
mology, PO Box 801375, Charlottesville, VA
Investigative Ophthalmology & Visual Science, November 2012, Vol. 53, No. 12
Copyright 2012 The Association for Research in Vision and Ophthalmology, Inc.
simultaneously relay light rays toward the eye, collect the reflected
light, and also provide a magnified view of the fundus.
We designed an optical system based upon this imaging principle
that comprised a two-part modular system: an optical attachment that
integrates all of the optical components necessary to produce an image
of the fundus (Fig. 1, module 1), and a camera that was used to
compose, capture, and store an image of the fundus (Fig. 1, module 2).
A schematic diagram of the components within the optical attachment
module is shown in Figure 2. All camera components were integrated
within a custom housing designed by using Rhino3D software
(McNeel, Seattle, WA) and built by using rapid stereolithography
prototyping techniques (Metro Rapid Prototyping, Noblesville, IN).
The final prototype of the fundus camera measures approximately
245395375 mm. Detailed descriptions of the fundus camera compo-
nents are provided in subsequent sections (see Supplementary Material
and Supplementary Table S1 for detailed component list and cost
The primary function of the optical attachment is to provide the
imaging path (Fig. 2, module 1) necessary for the consumer camera to
capture an image of the fundus. A 22-diopter (D) indirect ophthalmic
lens (Ocular Instruments, Bellevue, WA) (Fig. 2, module 4) was used as
the front objective lens of the fundus camera. This lens was selected
owing to a number of favorable characteristics including: a 608 field of
view, a large clear aperture of 52 mm for improved light transmission,
and advanced antireflection coatings. A Panasonic Lumix G2 (Pana-
sonic Corporation, Kadoma, Osaka, Japan) was selected as the camera
back (Fig. 1, module 2). This camera has a number of desirable features
including large 12-megapixel (MP) complementary metal-oxide-semi-
conductor (CMOS) sensor, rapid automatic focus and exposure
capabilities, hot-shoe adapter, Live-View imaging, interchangeable
lensing, and built-in image stabilization.
The front objective lens, which operates with a working distance of
39 mm, was placed co-axially from the front lens of the consumer
optical components and (2) an off-the-shelf consumer digital camera.
General diagram of the prototype low-cost portable fundus camera. The design is separated into two modules: (1) an attachment housing
(2) illumination path was used by coupling with a (5) beam splitter. Diagram components are specified as follows: (3) human eye, (4) front
objective lens, (5) beam splitter, (6) condensing lens, (7) mirror, (8) image mask, (9) holographic diffuser, (10) UV filter, (11) beam splitter, (12)
visible LED unit, (13) xenon flash tube, (14) macro lens, (15) linear polarizer, and (16) analyzer polarizer. This configuration allows a reflection-free,
508 field of view of the fundus in an external housing that can be attached to a consumer digital camera that maintains hand-held, point-and-shoot
Optical configuration of the prototype camera (distances between components are approximated). A shared, (1) co-axial imaging and
IOVS, November 2012, Vol. 53, No. 12
Point-and-Shoot Hand-Held Fundus Camera7601
camera. In our prototype, the distance between the objective lens and
the Panasonic lens was 125 mm. Screw-in macro lenses (Schneider
Optics, Hauppauge, NY) (Fig. 2, module 14) were attached to the
Panasonic camera’s front lens to increase close focusing ability, with
the zoom set to 35 mm. This configuration allows a focused image of
the retina formed by the front objective lens to fill the entire image
sensor of the camera. In addition, an internal circular image baffle was
designed as part of the housing, which functioned to crop the field of
view to 508.
Proper illumination of the retinal field was obtained by focusing an
annular illumination pattern co-axially onto the corneal surface of the
eye (Fig. 3). An annular-patterned illumination scheme is commonly
used in existing fundus camera design and provides the camera with a
clear central imaging aperture. In our camera, an annulus of light was
created by placing a donut-shaped image mask with an optically
opaque central aperture (Fig. 2, module 8).4,5The dimensions of the
annulus were optimized with an inner diameter (ID) of 5.0 mm and an
outer diameter (OD) of 7.0 mm, corresponding to the average range of
pupil diameters of a fully dilated human eye.14The annulus is focused
52 mm from the front objective lens with a beam angle of 448 and beam
waist of 7.0/5.0 mm (OD/ID). We have found that this configuration
provides a bright, near-lambertian illumination pattern on the retina
that is free of corneal reflections.
A continuous illumination source for image composition and
focusing was provided by a light emitting diode (LED) with a color
temperature of 27008K (Luxeon Star, Brantford, Ontario, Canada) (Fig.
2, module 12). The LED was prebuilt with a 108 condensing lens and
was powered by a 1000-mA BuckPuck current driver (Luxeon Star)
using four AA batteries. Although this LED source could be used for
final image capture, the low optical power would necessitate slow
exposure settings. Therefore, an external xenon flash (YongNuo,
Futian District, Shenzhen, China) (Fig. 2, module 13) was incorporated
into the design to allow high shutter speed exposures. This feature
decreases image noise and eliminates artifacts from subject eye drift or
A brief description of the illumination ray path (Fig. 2, module 2)
from source origin to the eye is as follows: light originating from the
LED and xenon flash are combined by using a 50/50 beam splitter
(Edmund Optics, Barrington, NJ) (Fig. 2, module 11), passed through a
UV-blocking film (Edmund Optics) (Fig. 2, module 10), and projected
toward a holographic diffuser (Luminit, Torrance, CA) (Fig. 2, module
9). The near-lambertian emergent light is then directed toward the
annular image mask to produce an annular bundle of light. This light is
vertically reflected by a 458 mirror (Edmund Optics) (Fig. 2, module 7),
passed through a condensing lens (Edmund Optics) (Fig. 2, module 6),
and projected to a second 50/50 beam splitter (Fig. 2, module 5). The
image of the illuminated annulus, now co-axial with the imaging path
(Fig. 2, module 1), is relayed through the front objective lens (Fig. 2,
module 4) and focused on the corneal surface.
Image Artifact Reduction
Although the two-lens optical system described above can capture
properly focused and composed fundus images, a significant conse-
quence of a simplified optical train is the existence of optical
aberrations. As a result, fundus images from the present camera suffer
from image artifacts, primarily lens reflections off the center of the
front objective lens. To reduce these reflections, a method of cross-
polarization was adapted. Cross-polarization is a commonly used
macrophotography technique and has also seen limited use in the
A pair of perpendicularly crossed linear polarizers (Edmund Optics)
(Fig. 2, modules 15, 16) was introduced at two locations in the optical
path. The first polarizer was placed between the condensing lens (Fig.
2, module 6) and the imaging beam splitter (Fig. 2, module 5). This
polarizer absorbs incoming light from the illumination source and only
transmits light that is parallel to its polarization axis. The second
polarizer is placed before the camera’s zoom lens and acts as an
analyzing filter, only transmitting light to the camera sensor, which has
a polarization axis perpendicular to the illumination rays emerging
from the first polarizer. Polarized light rays reflected from the retinal
surface become randomized and are thus able to pass through the
analyzing polarizer. However, light reflected off hard manufactured
surfaces, such as glass, retains the original polarization state and
therefore is eliminated by the analyzing polarizer.
Operation of the constructed fundus camera is similar to the operation
of a common consumer camera. Focal length, shutter speed, aperture,
and International Organization for Standardization (ISO) were preset to
35 mm, 1/160 s, f/9, and 400, respectively. The user turns on the
observation illumination source on the optical attachment. The front
objective lens is then aimed at the eye. Image composition and
autofocusing is performed on the camera’s built-in LCD screen. We
found that proper focus on the retina can be obtained most readily by
moving the focusing area of the camera over the optic nerve. The
image contrast resulting from the optic disc and surrounding
vasculature allows the camera’s contrast-based autofocusing algorithms
to lock accurate focus. A fundus image is then acquired by depressing
the shutter button. As such, a point-and-shoot operation sequence was
Ocular Safety Assessment
Preliminary light hazard assessment consisted of measuring total
radiant energy and effective blue-light and UV-A radiant exposure.
Primary radiometric measurements of both LED and xenon light
sources were made with a calibrated Gentec Ultra-UP Radiometer and
XLP12-1S-H2-D0 detector (GenTec-EO, Quebec, QC, Canada) with a
spectral range between 190 nm and 11 lm. These measurements were
checked by using a calibrated ILT 1400A radiometer/photometer with
SEL240, SEL033-F No. 14,299, and SEL033-UVA No. 28,246 detectors
(International Light Technologies, Peabody, MA) to measure UV, 380- to
1000-nm, and 315- to 400-nm irradiance, respectively. All measure-
ments were taken where the beam diameter filled the circular entrance
aperture of the detector. In most cases, the detector was placed 10 to
15 mm from the focal point of the annulus. Lamp safety was
determined by applying standard criteria for photobiological safety of
lamps and ophthalmic instruments.20–23
5.1-mm clear central aperture allows for corneal reflection-free imaging
of the fundus.
Annular illumination pattern used by the fundus camera. A
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IOVS, November 2012, Vol. 53, No. 12
Clinical Testing Protocol
Clinical testing of the prototype fundus camera was carried out under
an Institutional Review Board (IRB)-approved clinical study at the
University of Virginia Medical Center and in full compliance with the
Declaration of Helsinki. Informed consent was obtained from each
subject (n¼6 eyes in 6 patients) after explanation of the nature of the
camera study and all risks associated with participation. Mydriatic
fundus photography was carried out with pharmacologic pupil dilation
by using 1% tropicamide and 2.5% phenylephrine. The study method
consisted of taking successive unilateral photographs with the
prototype camera and a TRC-50EX mydriatic camera (TopCon Medical
Systems, Tokyo, Japan). Subjects were randomized to the order in
which photos were taken from each camera. This allowed for direct
pathology identification comparisons between the two fundus cameras
under subject-replicated refractive errors and media opacities. An
additional IRB-approved study was conducted for fundus photography
in clinical hospital consultation settings (n ¼ 2 eyes in 2 patients),
where tabletop TopCon fundus photos were impossible to obtain. All
images acquired were equivalently postprocessed by using Adobe
Photoshop (Adobe, San Jose, CA), with uniform adjustments to image
contrast, levels, brightness, and sharpness filtering applied across the
Beam and Light Exposure Characteristics
The subject, when properly positioned for fundus photogra-
phy, experiences uniform retinal illumination over a 468 to 508
field. The exact angular field of illumination varies as a function
of pupil entrance diameter. The spread of the emitted beam of
light was fixed at 508 for a 19-mm-diameter beam. This
illuminates a 14- to 16-mm-diameter area of the retina.
Total radiant power for the LED source was calculated to be
0.25 mW, corresponding to a radiant exposure of 0.13 mJ/cm2.
The total radiant exposure of the xenon flash lamp was found
to be 0.43 mJ per pulse with a pulse duration of between 33
and 125 ls, corresponding to a radiant exposure of approx-
imately 1.0 uJ/cm2. According to the American Conference of
Governmental Industrial Hygienists (ACGIH)/International
Commission on Non-Ionizing Radiation Protection (ICNRIP)
exposure guideline of 3 mJ/cm2, more than 3000 flashes would
be required during an 8-hour period to exceed the daily limit.20
UV-B exposure totaled no greater than 0.01 lW/cm2for the
LED source, and less than 1 lJ/cm2for the xenon flash. UV-A
irradiance values were calculated to be on the order of 1 lW/
cm2for the LED and less than 5 lJ/cm2for the xenon flash.
Similarly, these values are at least 100-fold below safety limits.
These measurements did not exceed the long-term total
irradiance limit of 10 mW/(cm2?sr) as specified in American
National Standards Institute (ANSI) code RP-27.3-07, and
accordingly, the LED and xenon flash sources can be classified
as in exempt risk group (values summarized in Supplementary
Table S2; see Supplementary Material and Supplementary Table
10449/-/DCSupplemental).20Anecdotally, a number of subjects
commented on the relative decrease in brightness from the
portable camera compared to other tabletop cameras, which
significantly improved subject comfort during photography
Portable Fundus Imaging
The finished fundus camera prototype (Fig. 4) was able to be
used in a hand-held and portable manner with the subject
sitting down in a reclined head position. We found that the
camera was most stable when operated while the user was
standing. Both hands were used to stabilize the camera, with
the first holding the Panasonic camera’s built-in rubber grip
and the other grasping the front lens with the index finger and
thumb, while using other fingers to stabilize across the
subject’s forehead. This hand provided a stable pivoting point
to vary axial, horizontal, and vertical distances from the
subject’s eye from which proper alignment could be easily
achieved with practice. In most cases, the front lens of the
camera was positioned between 40 to 45 mm away from the
subject’s eye, depending upon variances in refractive power.
We found that both optic nerve and macula-centered images
could be obtained, but this requires a certain degree of subject
co-operation. Image acquisition times ranged from 10 to 25
seconds for each photo. Subject variability in media opacities,
dilated pupil size, and reflectivity of the fundus were found to
significantly affect the ability to quickly and successfully
acquire fundus images, often resulting in low, partial, or
vignette exposure of the fundus. For these reasons, an average
of two to four photos were taken per eye to ensure satisfactory
quality for clinical diagnosis. Overall, 22 of 26 photos (85%)
taken were judged sufficient for clinical diagnosis.
Preliminary laboratory testing with the constructed fundus
camera demonstrated the importance of image artifact and
reflection elimination. Fundus photographs obtained with
nonpolarized illumination resulted in a central lens reflection
located over the foveal region in a macular-centered image,
potentially obscuring details in this important anatomic region
(Fig. 5A). This can be attributed to internal reflections from the
image mask reflecting off of the front lens surface and is a
fundamental consequence of many standard fundus camera
A number of optical and digital methods may be used for
reducing the central lens reflection, including placing a small
black dot in the center of the front condensing lens (Fig. 2,
module 4), using a light baffle, placing the illumination system
(Fig. 2, modules 5–12) outside of the camera between the eye
(Fig. 2, module 3) and front condensing lens, or taking two
photos with overlapping fields of view and digitally subtracting
the reflection. We found that the most straightforward
approach with best photographic result was to introduce
polarizing filters (Fig. 2, modules 15, 16) into the optical path,
with the filters oriented at 908 to one another to achieve cross
polarization. The addition of polarizing filters into the optical
system results in a dramatically reduced central lens reflection
to a size and brightness equivalent to that of other commercial
camera. The design uses a consumer camera for intuitive, point-and-
Front and rear depictions of the prototype low-cost fundus
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Point-and-Shoot Hand-Held Fundus Camera 7603
fundus cameras (Fig. 5B). Polarizing the retinal field also results
in reduction in corneal haze from media opacities and, as a
result, improves image detail definition and contrast.
A consequence of image polarization is a loss of reflectivity
from highly refractive surfaces such as the internal limiting
membrane and nerve fiber layer (Figs. 5C, 5D). These findings
were supportive of prior studies using cross-polarization for
viewing the fundus, including ophthalmoscopy; specular
reflection biomicroscopy; and optic disc, anterior segment,
and nerve fiver layer fundus photography. These studies have
shown that cross-polarization enhances the ability to image
eyes with cataract or vitreous haze, and accentuates defects in
the nerve fiber layer.15–18Cross-polarization also improves
visualization of subretinal details, including exudates and
drusen. Given the intended use of this camera for retinal
screening of diabetic retinopathy and macular degeneration,
we believe this is a favorable compromise.
Of note, the employed polarization scheme resulted in a
theoretical 75% reduction in available light reaching the
camera sensor. However, we found that this can be compen-
sated by increasing output from the flash lamp and doubling
the exposure ISO from 200 to 400.
Image Analysis and Clinical Documentation
The point-and-shoot fundus camera was capable of obtaining
co-axial images of the fundus with a field of view of
approximately 508. The consumer camera captured a 7.8-MP
image as measured by the total pixel area contained within the
circular retinal area. Total image dimensions measured 3158 3
3158 pixels, corresponding to 57 pixels per retinal field
degree. These measurements exceed the image resolution
benchmarks of 6 MP and 30 pixels per degree set forth by the
United Kingdom’s National Health Service for effective
retinopathy screening and detection of diabetic retinopathy
A unilateral clinical comparison photograph obtained by
using the prototype fundus camera and a commercial tabletop
camera validated the ability of the camera to accurately
document retinal pathology. As demonstrated in this image,
the prototype camera was capable of imaging the retina with
comparable quality to the commercial equivalent (Fig. 6).
Indeed, all of retinal pathology, including micro-aneurysms, dot
blot hemorrhages, soft drusen, and laser scarring, could be
equally visualized and identified with the hand-held prototype.
As with commercial fundus cameras, stereo pair photography
is also possible, which can facilitate identification of optic
nerve cupping as well as retinal and subretinal pathology (Fig.
7). Similar results were obtained from each of the eight
subjects involved with the study, wherein an accurate
diagnosis of retinal disease (or lack thereof) was made across
replicate unilateral comparison photographs. The camera was
Unpolarized fundus image with prominent central lens reflection (teal
arrow). (B) Polarized fundus image and dramatic reduction of central
lens reflection (teal arrow). (C) Unpolarized fundus image with
visualization of reflectivity sheen from the blood vessels (green arrow)
and nerve fiber layer. (D) Polarized fundus image demonstrating
marked reduction in blood vessel sheen reflectivity (green arrow). All
images were obtained as optic nerve–centered images on the same
Effect of image polarization on fundus image quality. (A)
Right eye images show a subject suffering from diabetic retinopathy, with significant dot blot hemorrhaging (green arrows), exudates (teal arrows),
and laser scarring post ablation therapy. One-hundred percent of the retinal pathology identified with the commercial camera could be equally
identified with the low-cost portable camera.
Unilateral comparison photographs taken with (A) the hand-held prototype camera and (B) a commercial TopCon TRC-50EX camera.
7604 Tran et al.
IOVS, November 2012, Vol. 53, No. 12
also able to visualize regions of geographic atrophy, vitreo-
macular traction, and signs of wet AMD (Fig. 8).
We reported that a point-and-shoot retinal camera can be
inexpensively built around a consumer digital camera and that
such a camera is capable of performing high-resolution 508
mydriatic retinal imaging in a compact and portable form
factor. We believe that the described system offers specific
practical advantages over currently available tabletop fundus
cameras and other portable ophthalmic imaging devices.
First, our camera leverages recent advancements in
consumer camera technology, including, but not limited to,
Stereo pair images obtained with the prototype camera, demonstrating exudative AMD with subretinal fibrosis.
study participants show a variety of retinal pathology, including (A) geographic atrophy, (B) a healthy fundus, (C) background diabetic retinopathy
with exudates and vitreomacular traction, (D) geographic atrophy with drusen, (E) diabetic retinopathy with exudate and dot blot hemorrhage, and
(F) geographic atrophy.
Right and left eye fundus photographs obtained with the low-cost, point-and-shoot camera. The unilateral fundus photographs of the
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Point-and-Shoot Hand-Held Fundus Camera 7605
large low-noise image sensors, live view imaging, image
stabilization, and secure digital (SD)-card storage. In addition,
retinal pathology can be immediately identified after image
capture by using the camera’s LCD display. The independent
modular design also allows one to upgrade the camera back as
consumer camera technology continues to evolve. Indeed, we
have successfully retrofitted the front-end optical module
onto other consumer cameras, including the Canon G12
(Canon, Lake Success, NY) and Kodak M750 (Kodak, Ro-
chester, NY). However, the smaller charge coupled device
(CCD) sensors found on these cameras result in loss of image
detail and increased noise as compared to the larger CMOS
sensor found in the Panasonic Lumix G2 camera.
Second, cost-conscious efforts were made throughout the
design and construction of the point-and-shoot camera, with a
total component parts cost of less than $1000. We significantly
reduced hardware costs by foregoing a compound front
objective lens and custom multistage optical train, instead
using a 22-D ophthalmic indirect lens and simpler, commer-
cially available optics. However, the prototype build cost does
not necessarily imply the retail price for a commercial version
of this device, as many variables are involved in determining
this. Choice of a less expensive camera back and production of
the camera in larger volumes would both serve to substantially
decrease parts costs, while the traditional medical device
markup of 2 to 3 times production costs would serve to
increase the final retail price.
While the camera has exceeded our initial expectations in
limited use, we make no formal claims of equivalency or
efficacy to commercial tabletop fundus cameras, as a formal
clinical study has yet to be performed. It is important to note
that the present study excluded subjects with significant ocular
opacities. A subsequent study should consist of a larger, more
variable subject cohort with image evaluation performed by
blinded, independent graders. In addition, other parameters,
such as image acquisition time and percentage of gradable
images, must be compared to existing commercial cameras.
Such a study would be necessary to truly demonstrate clinical
equivalency with commercial fundus cameras. Nonetheless,
we hope that in the future this camera platform can be a
suitable replacement for traditional tabletop photography in
the primary care setting, particularly for use in screening for
common eye diseases such as diabetic retinopathy.
Although the prototype camera may be sufficient as is for
screening photography, a number of improvements could be
made to improve usability in the clinic. Currently, the user is
required to place the ‘‘focus box’’ of the camera directly over
the high-contrast area of the optic nerve and surrounding trunk
vessels in order to obtain accurate focus. After using this
method, most images obtained in the clinical study were found
to be properly in focus. A small percentage of photos, however,
were affected by slight image blur and soft focus. This was
likely due to individual variations in media opacity. It may be
possible to improve the focusing method to account for these
subject variations by fine-tuning image contrast and focus point
settings in camera. There is also currently no method of eye
fixation on the camera. We found that patients with cognitive
impairments had difficultly keeping their eye steady without a
fixation target, often resulting in out-of-focus and misaligned
fundus images. To address this issue, a flexible external fixation
target can be affixed to the exterior housing. Finally, alignment
of the camera with the eye to obtain suitable retinal
photographs relies on operator expertise, and this could be
improved with some means to better determine proper
alignment with the eye, as found on commercial tabletop
Perhaps the most important limitation of the current
camera is the need for pharmacologic mydriasis. To conduct
efficient screening programs, one must provide the ability to
image the retina nonmydriatically.7,12,13The current camera
cannot be used effectively without pharmacologic dilation, as
the brightness of the alignment LED is significant enough to
cause virtually all pupils to constrict below 3 mm. It may be
possible to modify the camera and underlying optics of the
optical attachment to image in the infrared spectrum, and
therefore enable nonmydriatic use. This would involve
modifying the image sensor to visualize infrared wavelengths,
as well as replacing the existing visible spectrum LED with an
850-nm LED. Such an arrangement would allow the user to
view the external eye and fundus in infrared in a similar
manner as other commercial nonmydriatic fundus cameras.
The image quality of the camera may be further improved
by coupling a highly sensitive scientific-grade imaging sensor to
a front objective lens with shorter working distances to the
eye. These changes would substantially improve light gathering
capability while decreasing the size and weight of the current
prototype fundus camera. However, this approach has several
disadvantages. First, using a separate imaging sensor would
require much higher design complexity involving custom user
interface integration and software, instead of directly leverag-
ing a consumer product platform. Second, shorter working
distances in close proximity to the patient’s eye would result in
patient discomfort as well as greater potential for operator
error during alignment.
In conclusion, a portable, point-and-shoot retinal camera
can be constructed by using a novel combination of
commercial optics and a consumer digital camera with a
component cost inferior to $1000. The constructed prototype
camera was able to compose, capture, and store images all in a
single compact, hand-held device. Most importantly, non-
ophthalmic medical personnel, such as nurses and administra-
tive staff, should be able to easily use this camera after only
minimal training. The combination of these three features in a
retinal camera—low cost, portability, and ease of use—
provides a foundational platform from which a revolutionary
screening camera can potentially be designed.
The authors thank Shayn Peirce-Cottler, Brendan Zotter, and David
Kao (University of Virginia, Charlottesville, Virginia) for reviewing
this manuscript; David Sliney for assisting with retinal hazard
assessment; and Alan Lyon of the University of Virginia Department
of Ophthalmology for technical assistance.
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