<p>Recent advancements have led to the emergence of a few block-based programming environments that are accessible to individuals with visual impairments, featuring both touchscreen-based and keyboard-based modalities. However, there remains a shortage of empirical evidence concerning the usability of these systems, particularly the keyboard-based versions. This paper details the design and evaluation of Accessible Blockly, a block-based programming library that supports keyboard inputs and screen reader output as alternative interaction modalities. We also present empirical data showing that persons who are blind can effectively navigate, comprehend, create, and edit block-based code using only a keyboard and screen reader within reasonable time constraints. Accessible Blockly was developed iteratively, guided by two empirical studies. In the first empirical study, the initial prototype of Accessible Blockly was evaluated for block-based code navigation and comprehension in a study involving twelve blind programmers. Insights from the first study were used to refine the keyboard and screen reader interactions. A subsequent study with eleven blind programmers tested the enhanced version, focusing on the usability of the keyboard and screen reader for code creation and editing tasks. This research contributes to the ongoing efforts to design and develop accessible block-based programming environments by introducing a functional prototype of an accessible block-based programming library that uses the keyboard and the screen reader for interaction, and by offering foundational empirical data that can serve to establish guidelines and design considerations for building accessible block-based programming environments.</p>