AIM: To develop an eye health knowledge, attitude and practice (EH-KAP) field-based assessment tool for use in implementing effective eye health care services. METHODS: An instrument development and validation study. A Vietnam EH-KAP dataset were used to identify and eliminate redundant questions to develop a standardized tool. Face validity was assessed by the KAP survey team. Internal validity (congruency/criterion) was assessed by comparing descriptive analysis of two datasets (n=531; n=38) collected from the same sampling frame at different time points. Weighted scores were calculated for each construct. Kappa values for test-retest and inter-observer agreement were calculated to check the reliability of responses. The modified version was assessed by analysing the raw and ungrouped data. Responses were weighted and agreement was tested by comparing construct scores. RESULTS: Totally 38 respondents were included in this validation process (mean age 58.5y). Mean scores for knowledge were 9.15 (old questionnaire n=531) and 5.05 (modified version). For attitude, the scores were 2.23 and 2.42, and for practice the scores were 3.33 and 2.21. Test-retest agreement was between 62% to 93% (Kappa 0.24 to 0.86) for the ungrouped raw data, and 55% to 72% (Kappa 0.42 to 0.65) for KAP domain. Inter-observer Kappa value for ungrouped data was 0.37 and 0.45 for the weighted scores. CONCLUSION: This standardized tool applied at critical time points can assess trends in KAP within the same population and for comparison across groups. If used alongside a Rapid Assessment of Avoidable Blindness (RAAB), this tool provides a comprehensive perspective on eye-health of a population.