RESUMO
Recently, smartphone-based fundus camera (SBFC) research has been actively conducted in response to the need to expand medical infrastructure in underdeveloped countries and the increased telemedicine since the COVID-19 pandemic. Compared to the conventional table-top system, SBFCs have technical challenges that make it difficult to guarantee uniform illumination and avoid back-reflection because of the design constraints of minimizing the form factor and cost. This paper proposes a novel illumination design methodology using characterized illuminance to obtain high-quality fundus images for SBFCs. Key performance indicators (KPIs), such as retinal uniformity, back-reflection suppression, and optical efficiency, were defined to evaluate the performance of the illumination system. Each KPI was calculated using optical simulation software based on Monte-Carlo ray tracing and mapped into a normalized three-dimensional coordinate, the retinal illumination performance space (RIPS). In RIPS, the KPIs are combined into a single parameter ΔRIPS, which is the quantitative difference evaluated as the Euclidean distance between the ideal and actual design point. A compact SBFC illumination system with five design variables was presented to verify the proposed methodology. The final design values at the minimum ΔRIPS were determined using the Taguchi method and response surface methodology. Finally, a working prototype was built, and fundus images were acquired by clinical testing under institutional review board approval. The fundus image had sufficient brightness and resolution to diagnose the lesion with a viewing angle of approximately 50° in one shot.
RESUMO
OBJECTIVE: This study assessed the feasibility of smartphone-based colposcopy (SBC) for visual inspection of the cervix by community healthcare workers in low-resource areas. METHODS: This was a retrospective study conducted in community villages in rural Vietnam, where 177 participants were enrolled for a cervical cancer screening. Cervical images were obtained by pre-trained community healthcare workers using a portable, upcycled SBC (Samsung Galaxy Note 20). Images were taken before and after the visual inspection after acetic acid (VIA) examination. Captured images were stored on a web server through an Android-based application and later reviewed independently by two experienced gynecologists. Image quality was assessed, and kappa statistics were calculated for the measurement of agreement in VIA findings. RESULTS: Cervical images of 177 women obtained between July and August 2020 were analyzed. The mean age of women was 42 ± 9.1 years, and 20.3% were postmenopausal. The percentage of adequate visibility of the squamocolumnar junction (SCJ) in the captured images was 83.1%. The kappa value for interobserver reliability was 0.61 for VIA positivity agreement between the two gynecologists. Image clarity was rated as average or above in 77.3%. The reasons for suboptimal clarity were poor focusing (15.3%), inadequate SCJ visibility (18%), and obscuring of the transformation zone due to blood (11.3%), discharge (14.7%), or artifacts such as intrauterine devices or polyps (5.1%). CONCLUSION: Upcycled SBC was feasible when performed by pre-trained healthcare workers in a low-resource setting. VIA findings by SBC showed adequate agreement between two independent assessments, suggesting its potential as a method to aid cervical cancer screening.