AbstractBackgroundMacular Integrity Assessment microperimetry assesses macular sensitivity to projected point light sources and maps eye movements to assess fixation stability. Although microperimetry is gaining prominence as an assessment tool in clinical and research settings, there is no consensus on whether it should be performed before or after pupil dilation. No studies to date have examined the effect of pupil dilation on results. The aim of this project was to elucidate the effect of pupil dilation on microperimetry outcomes.DesignProspective audit.ParticipantsTwenty healthy patients from postoperative cataract clinic and 10 patients with choroideremia to simulate a disease with peripheral visual field loss.MethodsSubjects underwent 10–2 68‐point field testing using the Macular Integrity Assessment microperimeter on each eye. Subjects then underwent randomized dilation of one eye, and the test was repeated in both eyes.Main Outcome MeasuresWe compared changes in threshold sensitivity and fixation stability pre‐pupil and post‐pupil dilation. The undilated eye was analysed for any learning or fatigue effect caused by test repetition.ResultsDilation produced no significant effect on threshold sensitivity (dilation effect: −0.29 decibels, P = 0.23) or fixation stability in healthy controls or in choroideremia patients (dilation effect: +0.08log bivariate contour ellipse area, P = 0.14). There was also no significant learning effect seen in the undilated eye, with no improvement in threshold sensitivity (order of eye testing: +0.03log bivariate contour ellipse area, P = 0.71).ConclusionsIn the clinical setting, patients may be tested for 10 degree microperimetry with or without pupil dilation, as both scenarios yield consistent and interchangeable results.