上原記念生命科学財団研究報告集, 34 (2020)

上原記念生命科学財団研究報告集, 34（2020）

197. 新眼科診療機器 スマートアイカメラの臨床実用化
清水 映輔
慶應義塾大学 医学部 眼科学教室
Key words：Artificial intelligence，telemedicine，Smart Eye Camera，Cataract，Diagnostic AI

緒 言
A slit-lamp microscope is an essential medical instrument in the field of ophthalmology [1]. This device
irradiates the anterior segment of the eyes with a slit-light, and the reflection thereof is observed with its
biomicroscope function [2]. However, most conventional slit-lamp microscopes are not portable, and patients
have to visit the ophthalmologist for these examinations. Therefore, some patients (e.g. bedridden patients,
children, the elderly, and infected patients) have less opportunity to undergo ophthalmology examinations.
Although there are some portable slit-lamp microscopes, these devices are not recordable. External camera isneeded to record the anterior eye images, but it requires to alter the instrument larger and heavier. Moreover,due to the large size and heavy weight of the conventional microscope to be used with one hand, it is difficult
to use the microscope outside of the eye clinic which complicates validation between conventional non-portableand portable slit-lamp microscopes. Blindness is increasing globally. It is estimated that 36 million people are
now blind, and this number will increase to 115 million in the next 30 years [3]. The main cause of global
blindness is cataract. They account for 55% of blindness in adults older than 50 years globally [4]. Cataract isthe most common age-related ophthalmological disease, and it is diagnosed using a reflection of the thin slitlight from the slit-lamp microscope [5]. Blindness caused by cataract is preventable by surgery [6];nevertheless, lack of medical resources especially in undeveloped countries often hamper appropriate
intervention [4，6，7]. An appropriate medical invention to detect cataract could be the solution for thisproblem. To address this issue, we have previously invented a portable and recordable slit-lamp device, the“Smart Eye Camera” (SEC), which convert the smartphone light source to the light needed for theophthalmology diagnosis. In addition, SEC has a recording function using smartphone camera and wasproven to be safe and feasible in an animal model [8]. We added slit-light converter to make a slit-beam thinenough to diagnose the cataract in direct focal illumination method [9]. Here, we verified the performance of
SEC by the clinical trial, in which we evaluated and compared the efficacy and diagnostic performance forcataract diagnosis with those of a conventional slit-lamp microscope.

方 法
1. Study Design
This prospective study was performed according to the steps shown in Figure 1. We screened all patients
who visited the Department of Ophthalmology, Tsurumi University School of Dental Medicine from July to
September 2019. The patients who matched our inclusion criteria were recruited for the study. The inclusion
criteria were (1) Japanese adult males and females (older than 20 years) who had been diagnosed as nuclear
cataract (NUC), (2) cases with good mydriasis (>6 mm) to allow better evaluation of the crystalline lens, and(3) no obvious ocular surface infections and/or inflammations. Patients who had at least one of the following
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上原記念生命科学財団研究報告集, 34（2020）

were excluded: (1) Both pseudophakic or aphakic eyes, (2) Other types of cataract (i.e. cortical cataract[COR], anterior subcapsular cataract [ASC], and posterior subcapsular cataract [PSC]), (3) Severe corneal
disease that adversely affected cataract grading (e.g. bullous keratopathy, band keratopathy, and corneal
opacity), (4) Lack of data or patients who did not provide written informed consent. In total, 124 eyes in 62
cases were enrolled. The NUC grading of these eyes was evaluated with the portable and recordable Smart
Eye Camera (SEC; OUI, Inc., Tokyo, Japan) and with a conventional slit-lamp microscope (SL130, Carl
Zeiss AG, Oberkochen, Germany).

Prospective study in the Department ofOphthalmology, Tsurumi University School of
Dental Medicine. July 2019 ~ September 2019↓
128 eyes of 64 patients
screened for our inclusion criteria→

4 eyes of 2 patients are excluded
according to exclusion criteria↓
124 eyes of 62 patients meet theinclusion/exclusion cirteria.
Nuclear sclerotic grading analysis

Figure 1. Study flowchart
This prospective study adhered to the tenets of the Declaration of Helsinki. All procedures were performedin compliance with the protocol approved by the Institutional Ethics Review Board of Tsurumi University
Dental Hospital (Kanagawa Prefecture, Japan; IRB No. 1634). Patient data were anonymized before accessor analysis.
2. Conventional non-portable slit-lamp microscope and SEC examination
We used the SL130 as the conventional, non-portable slit-lamp microscope. This instrument is widelyused for screening and diagnosis of several ocular diseases. For a comparison, the portable SEC slit-lamp
device was selected. SEC is a smartphone attachment that fits above the light source and camera lens ofa smartphone (Figure 2). It is a Japanese pharmaceuticals and medical devices agency-certified medical
device that is able to convert the light source of the smartphone to a thin slit-light, allowing the light toenter the non-dilated pupil and reach the crystalline lens (Japanese Medical Device approval number:
13B2X10198030101). The slit-light of the SEC is unmovable as it uses the light source of the smartphoneitself. Moreover, the slit-light angle is fixed by 40 degree which commonly used by the direct focal
illumination method9. To convert the light source of the smartphone to the 0.2 to 1.0 mm-width slit-light,
a cylinder lens made from acrylic resin was attached in front of the light source. Above the camera lensof the smartphone, there is a removable convex macro lens to adjust the focus to the anterior segment of
the eye. The frame was produced using a 3D printer (Multi Jet Fusion 3D Model 4210; Hewlett-Packard
Company, Palo Alto, CA, USA) using polyamide 12. For the current study, an iPhone 7 (Apple Inc.,
Cupertino, CA, USA) was used as the camera and the light source. The resolution of the video was set at1080 p and 30 frames per second, which equates to 2.1 megapixels (2,073,600 pixels) per file.

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上原記念生命科学財団研究報告集, 34（2020）

Figure 2. Appearance of (a) the SEC and (b) the conventional slit-lamp microscope
3. Cataract evaluation by the conventional slit-lamp microscope and the SEC
After dilating the pupil, the recruited cases were examined using both conventional slit-lamp
microscope and SEC. To minimize selection bias in terms of the order of the instrument used, we
randomized all cases using a table of random digits. First, three ophthalmologists (H.F., H.Y., and S.O.)
used the conventional slit-lamp microscope to examine the grade of the cataract. Second, a single
orthoptist (T.K.) used the SEC to record a video of the cataract according to an instruction by anophthalmologist (H.Y.). These examinations were all performed under a darkroom as well as an ordinallyenvironment in the ophthalmology department. Third, the images were documented in the medical
records after filming. Finally, on another day, cataract grading was performed by a single ophthalmologist(H.F.) blinded to the patients' information. The grading of the cataract by both the conventional slit-lamp
microscope examination and the SEC examination was based on the NUC grading system by the WHO
Cataract Grading Group [10]. Although the Lens Opacities Classification system III is the most commonlyused criteria, it mainly involves evaluation based on a specialist’s subjective assessment. Moreover, thesubjective grading may change according to the specialists’ environment. When the diagnosis wasdifferent among the ophthalmologists, final diagnose of the NUC grading were decided by the majority
consensus.
4. Data Analysis
Routine examinations, including a refraction test, visual acuity, intraocular pressure measurement
using a non-contact tonometer, and fundus examination, were conducted for all cases, in addition to theclinical ocular evaluation using the SEC and conventional slit-lamp microscope. Visual acuity wasmeasured using a standard Snellen chart, and the BCVA with spectacle correction was recorded. The
results were measured in decimal acuity and converted to the logarithm of the minimal angle of resolution(logMAR) units using a visual acuity conversion chart.
5. Statistical Analysis
All data were analyzed using SPSS software (IBM SPSS statistics ver 25; IBM Corp, New York, NY,
USA) and Prism software (ver. 6.04 for Mac; GraphPad Software Inc, San Diego, CA, USA). It was not
appropriate to pre-define a sample size, as this is a comparison study between a conventional instrument
and a new device. Therefore, we selected all of the patients who matched our inclusion criteria within acertain period of time. Mann‒Whitney's U test was performed to compare the NUC grade differences
between conventional slit-lamp microscope and the SEC. To assess the reproducibility of the cataract
grading by the two devices (conventional slit-lamp microscope and SEC), weighted kappa statistics were3

上原記念生命科学財団研究報告集, 34（2020）

selected31. Moreover, Spearman's correlation coefficient was used to assess the correlation of the cataract
grading evaluated using the 2 devices. Data were presented as adjusted means ± 95% confidence intervals(CI), ± standard deviation (SD), or ranges. P-value < 0.05 was considered to indicate statisticalsignificance.

結 果
1. Demographics of the subjects
In the current study, 128 eyes of 64 individuals (30 males and 34 females) were enrolled. Four eyes
were excluded because the complete data was missing. The mean age of participants was 73.95 ± 9.28
years. In the current study, 110 of 124 eyes were phakic, 14 of 124 eyes were pseudophakic, and noaphakic eye was observed. The mean severity of the NUC grading of the cataract was 1.84 ± 0.82 basedon the evaluation by conventional slit-lamp microscope and 1.92 ± 0.82 by the SEC (P = 0.47, Table 1).
There were no cases with NUC grade 0, which was not significant NUC formation, and grade 9, which
was very advanced cataract that failed to provide adequate posterior illumination for grading cortical
and/or PSC cataracts. The mean duration of the measurement by the SEC was 30.38 ± 6.27 seconds per
2 eyes, and the mean size of the filmed video was 85.96 ± 18.61 MB per 2 eyes (Table 1). Representative
photos taken with the SEC are shown in Figure 3.
Table 1. Demographic of the subjects
P value
Cases
Male/Female
Age
Eyes

64
30/34
73.95 ± 9.28
128

Phakia110

Pseudophakia

14

Lack of data

4

Nuclear Sclerotic grading
Conventional/SEC

1.84 ± 0.82/1.92 ± 0.82

SEC
Examination time, seconds

30.38 ± 6.27

File size, MB

85.96 ± 18.61

Data shown as mean ± SD. SEC: Smart Eye Camera. MB: Megabyte.
*Mann-Whitney's U test.

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0.47*

上原記念生命科学財団研究報告集, 34（2020）

Figure 3．Representative cases imaged with the Smart Eye Camera.
Eyes with (AA) the lens replaced by an intraocular lens (IOL), (B
B) NUC grade 1,(CC) NUC grade 2, and (DD) NUC grade 3 are shown.

2. Correlation of cataract grading evaluation by the two devices
To compare the performance of cataract grading by the conventional slit-lamp microscope and the SEC,
the correlation of the NUC grading was evaluated. The NUC value from the conventional slit-lamp
microscope and the SEC showed a significantly strong correlation in the right eye (r = 0.926 [95%CI: 0.881
to 0.955; P<0.001]; Table 2), left eye (r = 0.836 [95%CI: 0.743 to 0.898; P<0.001]; Table 2), and both eyes(r = 0.871 [95%CI: 0.821 to 0.907; P<0.001]; Table 2).
Table 2. Correlation of the cataract grading evaluated by the two devices
Eye

n

R

P Value*

95% CI

R

62

0.926

< 0.001

0.881

0.955

L

62

0.836

< 0.001

0.743

0.898

Total

124

0.871

< 0.001

0.821

0.907

*Spearman's correlation coefficient
3. Reproducibility of the cataract grading evaluated by the two devices
To assess the reproducibility of the cataract grading by the conventional slit-lamp microscope and by
the SEC, weighted kappa statistics of the NUC grading were evaluated. A high kappa value was observed
between the cataract grading by the conventional slit-lamp microscope and that by the SEC (Kappa =0.807 [95%CI: 0.798 to 0.816; P<0.001]; Table 3).
Table 3. Reproducibility of the cataract grading evaluated by the two devices
Smart Eye Camera
Grade

1

2

3

Conventional

1

4

0

0

microscope

2

5

78

2

3

0

5

16

P Value< 0.001

Weighted kappa

0.807

95%CI

0.798-0.816
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上原記念生命科学財団研究報告集, 34（2020）

考 察
In the current study, we evaluated the cataract diagnosis by the new portable and recordable slit-lamp
device, the “SEC.” The diagnostic accuracy and the performance of this device were compared with thoseof the conventional slit-lamp microscope. When we compared the NUC grading between the conventionalslit-lamp microscope and the SEC, we found no significant differences of the gradings between the two
devices (Table 1). Moreover, there was a significantly strong correlation between the NUC grading of theconventional slit-lamp and SEC evaluations (Table 2). Furthermore, using weighted kappa statistics toassess cataract grading demonstrated a high kappa value, which suggested that the images obtained byboth devices were highly reproducible (Table 3). These results demonstrated that the performance of the
SEC is equivalent to that of the conventional slit-lamp microscope in evaluating cataract. On the other
hand, we did not estimate statistical power due to lack of past references. To address this disadvantage,
we designed our study to screen every patient who visited a single hospital during a certain period
prospectively. Our functional analysis suggested that the slit-light converted by the SEC allows
evaluation of the severity of the NUC grading in cataract eyes, equal to that done using the conventionalslit-lamp microscope.
Currently, few devices that can record anterior segment images by slit-light are available, althoughsimilar technologies have previously been reported. Some studies have reported the usefulness of slitlamp microscope accessories that can attach to a smartphone camera. Chen et al. demonstrated good
reproducibility of cataract grading using the same diagnosis criteria as those used in our study. Moreover,Dubbs et al. reported a good rust ring image on the cornea taken using a smartphone. These devices areattachable to the conventional non-portable slit-lamp microscopes, but not to smartphones.
Mohammadpour et al. demonstrated the effectiveness of images obtained with a smartphone combinedwith a macro lens, using a concept similar to that of the SEC. However, the light source of the smartphone
could release only diffuse white light, which was only capable of illuminating the surface of the eye.
Chiong et al. invented a smartphone-based anterior segment-examining device that could irradiate theeyes with thick slit-light. However, in ophthalmology departments, specialists require narrow slit-lightthat is thinner than the pupil width of 2‒8 mm to ensure that the slit-light reaches the crystalline lens.
To the best of our knowledge, no previous paper has reported that cataract grading was possible with asmartphone slit-lamp device. This may be due to the difficulty in converting the smartphone light source
to a thin slit-light. The SEC has a function to overcome this problem by applying the slit structure above
the light source and the cylinder lens to concentrate the light on the object. Therefore, we believe that
SEC has an advantage over the conventional devices.
In this study, we demonstrated the usefulness of the SEC in cataract grading. The SEC may have thefollowing potential advantages in healthcare: (1) It could be applied to other ophthalmological diseases,
particularly in the anterior segment of the eye. We previously reported that this device could evaluate
tear film breakup time and corneal epithelial disorder in a dry eye disease mouse model [8]. The size ofthe mouse eye is about 3-mm wide and is much smaller than that in humans. Therefore, the SEC has thepotential to be useful for the screening of other anterior segment eye diseases. (2) It could be used outsideof the eye clinic. In the current study, an orthoptist rather than an ophthalmologist filmed the patient's
eye using the SEC. The average recording time was approximately 30 seconds for 2 eyes, which illustrates
that the SEC is user-friendly for healthcare workers. Although the non-specialists can use this portableslit-lamp device, the ophthalmologists may need to evaluate the recorded images to make a cataract
diagnosis. SEC is a smartphone attachment that allows video recording [8], and thus, it may be useful in6

上原記念生命科学財団研究報告集, 34（2020）

telemedicine. Several studies have demonstrated that ophthalmological diagnoses are amenable toremote medicine, as the diagnosis is made based on images of the eye. To the best of our knowledge, there
is no other portable and recording device that can take a distinct eye photo with a thin slit-light.
Therefore, the SEC may allow screening for and remote diagnosis of cataract outside of an eye clinic.
Our study only included NUC and did not include COR, ASC, and PSC. Other cataract variations could
associate with reductions of visual acuity. However, NUC is the most common type especially in theelderly ages. Therefore, we selected NUC for our primary evaluation. Moreover, our study included cases
over 53 years of age and NUC grade 1 to 3 which were similar population to previous report. Our findings
justify conduct of similar trials on a larger number of subjects with other types of cataract which willdefinitely provide invaluable information.
The results of this study suggested that not only the conventional, non-portable slit-lamp microscope,
but also the portable and recordable slit-lamp can diagnose and record cataract images appropriately. An
ophthalmologist successfully evaluated the videos taken by a non-ophthalmologist using the device. It
may hold great potential for the diagnosis of other ophthalmological diseases in the anterior segment of
the eyes, application outside of the eye clinic, and application in telemedicine. The challenge for the future
is to verify whether or not the same results can be obtained when the product is actually used in the
different fields including overseas.

共同研究者・謝辞
Hiroyuki Yazu 1,2,3,*, Eisuke Shimizu 2,3 , Sho Okuyama 1,2 , Takuya Katahira 1 , Naohiko Aketa 2 , Ryota
Yokoiwa 3 , Yasunori Sato 4, Yoko Ogawa 2 and Hiroshi Fujishima 1,2
1

Department of Ophthalmology, Tsurumi University School of Dental Medicine, Kanagawa 230-0063,
Japan; g.h.yazu@gmail.com (H.Y.); go_my_way1987@yahoo.co.jp (S.O.); katahira-t@tsurumi-u.ac.jp(T.K.); fujishima117@gmail.com (H.F.)

2

Department of Ophthalmology, Keio University School of Medicine, Tokyo 160-0016, Japan;
ophthalmolog1st.acek39@gmail.com (E.S.); nao.nao.pao.pao@gmail.com (N.A.); yoko.z7@keio.jp (Y.O.)

3

OUI Inc., Tokyo 160-0022, Japan; ryota.yokoiwa@gmail.com

4

Department of Preventive Medicine and Public Health, Biostatistics at Clinical and Translational
Research Center, Keio University School of Medicine. Tokyo 160-0016, Japan; yasunori.sato@keio.jp

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