Objective: Retinitis pigmentosa (RP) is the most common inherited retinal disease and a major cause of irreversible vision loss. The purpose of this study was to assess peripheral retinal vessels in RP. Design: Cross-sectional study Subjects: Patients with RP and age-matched controls. Methods: Using ultra-wide field fundus images, the retina was divided into three zones: posterior, mid periphery, and far periphery. To evaluate vascularity of the retina, the vessels were counted at the border of posterior and mid peripheral zones (Z1/2) and the border of mid peripheral and far peripheral zones (Z2/3). Main outcome measures: Vessel counts at Z1/2 and Z2/3 Results: 181 eyes of 107 RP patients and 130 eyes of 84 controls were included. In the RP group, the median vessel counts at Z1/2 and Z2/3 were 8 and 3, respectively. These were strikingly lower than the control group with the median vessels of 42 and 43.5 at Z1/2 (p<0.001) and Z2/3 (p<0.001), respectively. 22% of RP eyes were entirely avascular in the far periphery and 7% were avascular in the mid periphery and far periphery. Only 5% of RP eyes had more than 25 vessels at Z2/3. There were significantly fewer vessels in the temporal retina at both Z1/2 (p=0.01) and Z2/3 (p<0.001) in RP eyes. Furthermore, eyes with visual acuity of 20/200 or worse had significantly fewer vessels at Z1/2 (p<0.001) and Z2/3 (p<0.001). There were no significant differences in the number of vessels at Z1/2 and 2/3 between the right and left eyes of RP patients with both eyes included in the study. Conclusions: This study provides compelling evidence of substantial symmetrical peripheral retinal vascular loss in RP. This finding may aid in clinical diagnosis of the disease and have significant therapeutic implications.

The authors have declared no competing interest.

This work was supported by grant UL1TR001855 from the National Center for Advancing Translational Science (NCATS) of the U.S. National Institutes of Health. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The Department of Ophthalmology received an unrestricted grant from Research to Prevent Blindness (New York, NY). The sponsor or funding organization had no role in the design or conduct of this research.

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The study was approved by the Institutional Review Board of the University of Southern California.

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All data produced in the present study are available upon reasonable request to the authors