We have conducted a prospective crossover randomized controlled trial to compare SO with DO in teaching final-year medical students to view the fundus. All students could equip the SO using their own models of smartphone, and were capable to view the fundus. Objective comparison between SO and DO revealed that students' performance of ophthalmoscopy was better overall when SO was used over DO.
There are reasons for the superiority of SO over DO. Smartphones are attractive to users in the convenience and effectiveness of image capture, screen display, and real-time sharing. Accordingly, SO is highly applicable in clinical practice and medical education, especially in ophthalmology, in which fine morphological features play an important role in diagnosis.[8] DO has one single inspection window and more difficult working distance in comparison with the SO. With excellent screen display and comfortable doctor-patient distance, users, especially students first learning to use SO, could easily keep the device and image stable. Also, the long doctor-patient distance avoids closed contact with the patients, especially in the era of COVID-19. These advantages explain why medical students preferred the SO over the DO. The students also thought that using SO could provide more help for non-ophthalmologists and expected popularization of SO in clinical service.
There are two different types of SO. One is based on the principle of direct ophthalmoscope,[11] and the other on the principle of indirect ophthalmoscope[12]. Although the smartphone indirect ophthalmoscope has the advantage of a wide field of view, it requires a condensing lens that has to be hand held. Also, the images are inverted and the examination needs fine bimanual coordination. Therefore, it needs more time of practice and is not as easy as the smartphone direct ophthalmoscope to teach medical students. Smartphone direct ophthalmoscope doesn't require a lens attachment, so it provides an erect magnifying image, with a field of view of 20° for a dilated pupil.[6]
Several studies have investigated the utility of SO in medical education.[1, 6, 9, 13–15] Uses of subjective questionnaire gave indications on the competency of the medical students in visualizing the fundus. In the current study, we used a verified eye model to objectively investigated competency as the major outcome. Besides, as reported, D-EYE, one of the most frequently used SO[1, 6, 9, 13, 14], works specifically with iPhone 5s/SE/6/6s/6Plus/6s/7/8, but not other smartphone models. The new SO designed in the current study could work with any model of smartphone. And the smartphone app was available for both Android and iPhone. The Ullman Indirect app is an app with the function of the manual focus, ensuring that fundus images can be captured easily with any refractive status. The students used their own smartphones to equip the SO, install the app, and perform the ophthalmoscopy, followed by viewing, capturing, and storing the fundus images on their own phones. This do-it-yourself approach aroused great interest and enthusiasm in the students.
On the period effect in crossover design, the overall score after the first training session (6.1 in average) was lower than that after the second session of training (7.0 in average). The difference, though not statistically significant, could be due to cumulative learning effects. Actually, in the setting of a half-day clinical skills training course, there was limited time for students to keep practicing until the skill was mastered, so the difference between these two periods was not obvious in the present study.
Notably, when analyzing the sequence effect, we found that the students beginning with the SO (Group B) had a significantly higher score compared with those beginning with the DO (Group A). Given the randomization grouping design and the matched demographic information, this finding indicated that using the SO first may improve the student's ability of ophthalmoscopy overall, suggesting that the SO may be more helpful to understand the fundus examination and may serve as an adjunctive tool to help teach direct ophthalmoscopy. Even so, in further study, the base-line information about the skill of ophthalmoscopy should be more perfectly matched.
We recognize some limitations in the current study. Firstly, this is a short-term study based on a single skills session in accordance to the established teaching curriculum. Further longitudinal studies are needed to determine whether the SO can improve medical students' competency of ophthalmoscopy in future careers. Secondly, the questionnaire used in the current study has not been previously validated. There may be biases, such as recall bias. We had tried to minimize biases by the crossover study design, randomization of participants and anonymity in data analysis. Thirdly, the position of LED was not standardized because it was fixed with a tape. A better design with a fixed location of the LED should help to improve the performance of the SO.
In conclusion, we utilized crossover design, prospective randomization, and the use of both objective and subjective measures to compare students' use of SO and DO. Students were more able to view the fundus using the SO, and expected more popularization and application of SO. The smartphone ophthalmoscope has the potential to be a useful alternative in ophthalmic fundus examination. Further research is needed to assess SO in various clinical and educational settings.