Terminology and Classification
An international classification of ROP was developed so that the disease could be consistently described, staged, and studied. Four classification concepts have prognostic and pathophysiologic importance: the location, or zone, of involvement; the disease severity, or stage; the extent of disease in clock-hours of involvement; and whether or not plus disease is present. Table 8-1 goes into further detail about this important terminology.
Table 8-1 Descriptive Terminology for Acute Retinopathy of Prematurity
Based on this terminology, ROP can be classified into several disease stages and severities to aid clinicians in making management and treatment decisions (Table 8-2). Aggressive posterior ROP (also referred to as rush disease) is characterized by the presence of vascularization that ends in zone I or very posterior zone II and is accompanied by plus disease. Threshold disease is characterized by more than 5 contiguous clock-hours of extraretinal neovascularization or 8 cumulative clock-hours of extraretinal neovascularization in association with plus disease and location of the retinal vessels within zone I or II (Fig 8-7). Prethreshold disease is a term created by the Early Treatment for Retinopathy of Prematurity (ETROP) study; it encompasses all zone I and zone II ROP changes that do not meet threshold treatment criteria, except for zone II stage 1 and zone II stage 2 without plus disease. Prethreshold disease can be further divided into high-risk prethreshold ROP, or type 1 ROP, and lower-risk prethreshold ROP, or type 2 ROP (see Table 8-2).
Table 8-2 Classification of Acute Retinopathy of Prematurity (ROP)
An eye is classified according to the most advanced disease noted; however, documentation should reflect all zones and stages observed, including their relative extent. Eyes with ROP in zone III typically have a good visual prognosis. The more posterior the zone at the time of recognition of the disease, the more nonperfused retina there is and thus the more worrisome the prognosis.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.