Introduction 1 2 3 5 3 5 b 6 7 9 3 4 10 11 12 13 14 15 Methods Nine obligate carriers (eight parents, one offspring) of XLRS patients were enrolled in the study. They were selected on the basis of their availability and willingness to participate in the study. Each had at least one male family member who was diagnosed as having characteristic XLRS findings by one of the authors (GAF). Five of the nine XLRS patients were confirmed as having the causative gene RS1. None of the carriers had any other medical or ocular conditions that might have affected their retinal function. After each carrier was counseled regarding the study, they signed a written informed consent approved by the Institutional Review Board at the University of Illinois at Chicago. The examinations were conducted in accordance with Health Insurance Portability and Accountability Act regulations. 16 2 2 2  2 17 Results 1 1 18 Table 1 The age, visual acuity for the right eye (OD) and left eye (OS) and fundus findings for each of the X-linked retinoschisis carriers Carrier Age (years) VA OD VA OS Fundus findings 1 35 20/15 20/15 Mild situs inversus OU 2 47 20/20 20/20 Normal OU 3 23 20/20 −1 Normal OU 4 53 20/20 20/20 Mild situs inversus OU 5 48 20/25 20/20 Situs inversus OU 6 58 20/20 20/20 Situs inversus OU 7 39 20/20 20/20 Mild situs inversus OU 8 43 −2 20/20 Situs inversus inferior vein OS, anomalous branching OS > OD 9 70 −2 −2 Anomalous branching OU, situs inversus superior artery OD, inferior artery OS Fig. 1 Fundus photograph of XLRS carrier #1 demonstrating situs inversus of the retinal veins  2 3 2 3 2 3 Fig. 2 a b c  Fig. 3 a b c  Discussion 19 20