Substance P in proliferative vitreoretinopathy: the significance of aqueous humor levels for evolution of the disease

Purpose: We detected aqueous humor levels of substance P in patients with v arious grades of proliferative vitreoretinopathy and with uncomplicated rhe gmatogenous retinal detachment. To evaluate the significance of the concent ration of substance P at the time of surgery for retinal detachment for sub sequent development of proliferative vitreoretinopathy, the latter patients also underwent fundoscopic control examination. Methods: Using a highly sp ecific and sensitive radioimmunoassay, the content of substance P in fresh samples of aqueous humor obtained by paracentesis was determined both in ca taract controls and in patients with uncomplicated rhegmatogenous retinal d etachment and with various grades of proliferative vitreoretinopathy. Retin al detachment patients underwent fundoscopic control examination 6 months a fter surgical reattachment. Results: The mean concentration of substance P in cataract controls was 40.3 (+22.4) fmol/mg protein, in the retinal detac hment group 61.9 (+/-13.9) fmol/mg protein and in proliferative vitreoretin opathy 335.2 (+/-24.8) fmol/mg protein, but no correlation between levels o f the peptide and various grades of the disease was observed. Already at su rgery for retinal detachment three in four patients who developed prolifera tive vitreoretinopathy presented with levels of substance P in the range of the disease. Conclusion: The concentration of substance P in aqueous humor is significantly high in patients with proliferative vitreoretinopathy in whom surgery is indicated. Furthermore, elevation of the peptide in retinal detachment that originates most obviously from a neurogenic mechanism may indicate initiation of processes associated with proliferative vitreoretino pathy, thus representing an indicator of significant risk for evolution of the disease at a very early time.