OBJECTIVE: The purpose of this study is to determine whether 3-mm computed tomography (CT) cuts are equivalent to 1-mm CT cuts for detecting small intraocular foreign bodies (IOFBs). DESIGN: Experimental instrument validation study. PARTICIPANTS: Seventy-two porcine eyes were divided into three groups. Each group had 0.5 ml of human blood injected into the vitreous cavity and were surgically implanted with IOFBs. INTERVENTION: Each eye was surgically implanted with 0.5-mm metallic, 0.5-mm glass, or 0.5-mm stone IOFBs. Two additional eyes were left without IOFBs to serve as negative controls. MAIN OUTCOME MEASURES: Axial CT images of both 3-mm and 1-mm thickness were obtained and analyzed in masked fashion by two separate neuroradiologists. RESULTS: The sensitivity for detecting 0.5-mm metallic, 0.5-mm glass, and 0.5-mm stone IOFBs with 3-mm CT images was 100%. The sensitivity for detecting 0.5-mm metallic, 0.5-mm glass, and 0.5-mm stone IOFBs with 1-mm CT images was also 100% (confidence interval, 95%; range, 0.88-1.00). Two negative control eyes without IOFBs were also correctly evaluated by the neuroradiologists. CONCLUSIONS: With modern spiral CT scanning, 3-mm cuts are as sensitive as 1-mm cuts for detecting small metallic, glass, and stone IOFBs.