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Nov 2011

Proportionate Topographic Areas of Retinal Zones 1, 2, and 3 for Use in Describing Infectious Retinitis

Author Affiliations

Author Affiliations: Department of Ophthalmology, California Pacific Medical Center, San Francisco, and Department of Ophthalmology, Stanford University School of Medicine, Stanford (Dr Cunningham), and Ocular Inflammatory Disease Center, Jules Stein Eye Institute, David Geffen School of Medicine at University of California, Los Angeles (Dr Holland); and Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison (Mr Hubbard and Dr Danis).

Arch Ophthalmol. 2011;129(11):1507-1508. doi:10.1001/archophthalmol.2011.331

Holland and colleagues1introduced the technique of localizing infectious retinitis lesions to 1 or more of 3 contiguous retinal zones in 1989, an approach first applied to the study of cytomegalovirus retinitis in patients with AIDS. As defined in the original study, zone 1 corresponded to an area comprising both 2 disc diameters (3600 μm) from the foveal center and 1 disc diameter (1800 μm) from the margins of the optic disc, an area wherein most immediately sight-threatening lesions reside2; zone 2 was defined as the area extending from zone 1 to the clinical equator of the eye, identified by the anterior borders of the ampullae of the vortex veins; and zone 3 extended from zone 2 to the ora serrata, an area underlying the vitreous base and associated with an increased risk of retinal detachment (Figure 1). Studies of retinitis location, size, and progression are often done photographically in collaboration with a certified reading center using standardized protocols, photographs, and measuring techniques.3 In general, there is good agreement both between individual reading center graders and between separate reading centers,4 whereas clinicians tend to consistently overestimate retinitis lesion size by about a factor of 2.5 The zonal system, as originally developed for cytomegalovirus retinitis, was adopted for the National Institutes of Health–sponsored Studies of the Ocular Complications of AIDS4 and has since been applied to other forms of retinitis, most notably ocular toxoplasmosis,6 but is distinct from the zonal classification (I, II, III) used in the study of retinopathy of prematurity.7