In all blind eye diseases, fundus disease remains the primary cause of irreversible visual loss, significantly impacting visual acuity. In severe scenarios, this results in a higher prevalence of blind fundus disease. Many fundus diseases manifest in the eye periphery. If the lesion does not affect the macular area, patients often overlook early lesions since their visual acuity remains largely unchanged, presenting no symptoms. During examinations, standard fundus-imaging equipment fails to visualize the peripheral area of the fundus due to its limited imaging field of view. Once the lesion impacts the central macular area of the fundus, treatments become challenging, and outcomes are generally unfavorable. As such, early examinations play a crucial role in preventing and treating fundus diseases, underscoring the need to innovate instruments that image the retina, encompassing the fundus periphery. Traditional fundus photography has a field of view limited to 30°?50°. Even utilizing multi-region fundus image stitching only marginally expands the fundus imaging area, concentrating the imaging on the posterior pole. Conversely, laser scanning confocal fundus imaging offers superior clarity and contrast, enabling non-mydriatic fundus imaging even in patients with constricted pupils and facilitating real-time dynamic observations of fundus image changes. Ultrawide-angle fundus imaging rooted in laser scanning confocal imaging emerges as a significant advancement in fundus imaging. We anticipate that our alignment method and study findings will inform the design of cutting-edge ophthalmic examination devices.

To thoroughly image the peripheral area of the fundus, we explore the fundus line-scanning imaging technology and construct an ultra-wide-field confocal laser line-scanning fundus imaging system. Initially, we devise a comprehensive optical pathway for the system. For achieving ultra-wide-angle, high-resolution dual-mode imaging, it is essential to design the geometrical optical parameters of the components within the respective mode, ensuring that the parameters satisfy the dual-mode imaging requirements simultaneously. We commence by establishing the overarching framework of the optical system, which incorporates the parameter design for ultra-wide-field, high-resolution dual-mode imaging. This is followed by Zemax simulations and image quality optimization for the system detection and imaging sections. Components are chosen based on these parameters, leading to the construction of the experimental system. By utilizing the pixel boundaries of the target surface in the area camera, we are able to achieve line scanning dual-mode confocal imaging of fundus through the creation of virtual slits. Once the theoretical design phase concludes, we employ Zemax software to simulate the system detection optical path, optimize this path, and validate the system design metrics and viability. The camera pixel boundary forms a virtual confocal slit, facilitating line scanning dual-mode confocal imaging of the fundus. We then assess the actual field of view of the system, resolution, and imaging capabilities.

The designed laser line-scanning ultrawide-angle confocal fundus imaging system in this study realizes ultrawide-angle, high-resolution dual-mode imaging by simply switching the eyepiece lens (Fig. 1). After parameter design and simulation (Table 1), the commercially available lenses for scanning, lighting, and imaging objectives fully meet the system requirements, reducing the system design cost. In the ultrawide-angle mode, the system actual field of view reaches 136.3°, achieving ultrawide-angle imaging (Table 3). In the high-resolution mode, the system equivalent conversion fundus resolution stands at 8.5 μm, accomplishing high-resolution imaging (Fig. 9). We conduct ultrawide-angle mode imaging, ordinary fundus camera photography, and high-resolution mode imaging on the simulated eye, and the system dual-mode imaging effect proves significant (Fig. 10).

This study offers a method for achieving ultrawide-angle confocal imaging of the fundus based on line scanning. The system employs a Powell prism in conjunction with a cylindrical lens to produce an ultra-long and ultra-fine laser line beam. It utilizes the pixel boundary of the camera target surface to establish virtual slits, achieving confocal fundus imaging. This effectively diminishes the interference of non-focal plane stray light on the fundus image. The system possesses both an ultra-wide-angle fundus imaging mode and a high-resolution imaging mode. Theoretical calculations and experiments indicate that the field of view in the ultrawide-angle mode is 136.3°, and the actual resolution in the high-resolution mode is 8.5 μm. Grounded on the experimental results, the proposed laser line-scanning fundus imaging method proves feasible. It effectively achieves ultrawide-angle fundus imaging and serves as a reference for the development of related instruments.