Remote sighted assistance (RSA) has emerged as a conversational assistive technology for people with visual impairments (VI), where remote sighted agents provide realtime navigational assistance to users with visual impairments via video-chat-like communication. In this paper, we conducted a literature review and interviewed 12 RSA users to comprehensively understand technical and navigational challenges in RSA for both the agents and users. Technical challenges are organized into four categories: agents' difficulties in orienting and localizing the users; acquiring the users' surroundings and detecting obstacles; delivering information and understanding user-specific situations; and coping with a poor network connection. Navigational challenges are presented in 15 real-world scenarios (8 outdoor, 7 indoor) for the users. Prior work indicates that computer vision (CV) technologies, especially interactive 3D maps and realtime localization, can address a subset of these challenges. However, we argue that addressing the full spectrum of these challenges warrants new development in Human-CV collaboration, which we formalize as five emerging problems: making object recognition and obstacle avoidance algorithms blind-aware; localizing users under poor networks; recognizing digital content on LCD screens; recognizing texts on irregular surfaces; and predicting the trajectory of out-of-frame pedestrians or objects. Addressing these problems can advance computer vision research and usher into the next generation of RSA service.