The pathogenesis of retinopathy of prematurity as it relates to surgical treatment.

Our current surgical treatment for threshold retinopathy of prematurity (ROP) is based upon three concepts which emerged from morphologic and biochemical study of 250 pairs of whole eye donations obtained over a ten year period. 1) Spindle cells normally migrate and canalize to form inner retinal vessels, but when stressed, spindle cells secrete angiogenic factors. The clinical implication is that transretinal cryotherapy to the avascular retina is efficacious because it obliterates spindle cells. The number and timing of cryosessions are determined by the migration and kinetics of spindle cells. 2) Myofibroblasts originate from the shunt, are the major cellular component of extraretinal fibrovascular proliferation (EFP), and contract to produce retinal distortion and detachment. The clinical implication is that a second transretinal cryotherapy session should obliterate the shunt and the EFP, and should eliminate the source of retinal traction. 3) Anterior ocular growth occurs exponentially during the period when ROP develops and is treated. The clinical implication is that a prophylactic scleral buckle supports the fixed surface area of the developing retina while the choroid and sclera enlarge anteriorly. Retinal distortion produces misaligned photoreceptors, and retinal detachment results in rapid retinal death.