The ISET (Instrument for SElf-Triage) is a validated pen-and-paper instrument for patient self-triage in ophthalmic emergency departments. The aim of the present study is to develop a validated computer-assisted ISET (ca-ISET) with a touch screen.In the emergency department of the Eye Hospital Rotterdam, the Netherlands, successive computer-assisted versions of the ISET were tested by patients visiting the emergency department. The versions were developed by iteratively prototyping, testing, analysing and refining the computer-assisted ISET. In three test cycles, 16, 53 and 75 patients ≥18 years old, visiting the emergency department for the first time with their ophthalmic complaint, were monitored while using the ca-ISET. They were debriefed, and their input was used to adapt the computer-assisted ISET. To validate the ca-ISET, a sensitivity outcome of .80 and a specificity of .70 was required (CI=95%). The ca-ISET sensitivity and specificity were tested by comparing ca-ISET triage outcome to triage outcome as decided by the regular triage assistant.ISET accuracy increased from 0.69 in the first test to 0.79 in the third test. Sensitivity increased from 0.66 (CI 0.13–0.98) to 0.80 (0.51–0.95). Specificity increased from 0.69 (0.39–0.90) to 0.78 (0.65–0.88). To improve validity and usability, several adjustments were made in the text and the flow chart of the computer-assisted ISET.A ca-ISET prototype was developed, with minor textual modification of the pen-and-paper version. The new ca-ISET was validated by comparing against triage decided by the regular triage assistant.