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Purpose: To investigate the relationship, if any, between vitreous pigment epithelium-derived factor (PEDF) levels and a number of clinical factors used to assess the functional activity of the retina after an intravitreal surgery for complications of proliferative diabetic retinopathy (PDR). Materials and Methods: Seventy PDR patients (70 eyes) were involved into the study. PEDF levels in vitreous samples were quantified by enzyme-linked immunosorbent assay. Results: In vitreous samples from eyes with PDR the mean ± SD PEDF level was 3.26 ng/mL ± 1.57 ng/mL. Vitreous PEDF levels were statistically significantly higher for eyes operated on for vitreous hemorrhage (VH) only than for eyes operated on for VH in the presence of macular traction detachment (t=2.35, р=0.022). The lower was the vitreous PEDF level (lower median value, 3.12 ng/mL), the more severe was retinal ischemia, which was confirmed by electrophysiological examination (namely, the parameters of the oscillatory potentials). It was found that when the level of PEDF in the vitreous is decreased, retinal neurodegeneration develops, with the greatest damage exhibited by bipolar, amacrine, and Muller cells. Conclusions: Parameters of photopic and 30 Hz flicker ERG as well as of oscillatory potentials are surrogate indicators of levels of PEDF in ocular tissues, and may be used in later studies for investigation of the role of PEDF levels in pathological processes in the eye.

Purpose: To determine prospectively whether there is any relationship between a number of clinical factors and the degree of neuropathy of the optic nerve (ON) following intravitreal interventions in proliferative diabetic retinopathy (PDR). Materials and Methods: One hundred and five patients (105 eyes) with good anatomic results after undergoing vitrectomy were followed up and underwent visual evoked potential (VEP) testing at 2 months and 12 months. Results: At 2 months, neuropathy of the ON was observed in 56.1% of cases. Additionally, in 20.5% of these eyes, it was profound and characterized by intensely pale optic nerve head (ONH). At 12 months, the degree of neuropathy of the ON did not change. The functional activity of the visual system revealed by VEP tests (with 12-Hz flash, 1° and 0°15? checks) in study eyes was approximately 2-fold lower than normal values. Additionally, at both follow-up time points, the changes in VEP indices in eyes operated on for macular traction detachment were evidence of statistically significantly more profound degenerative processes in the nerve tissue than in eyes operated on for vitreous hemorrhage only. Conclusions: Progressive proliferative diabetic retinopathy is accompanied by a progressive neurodegenerative process in the retina and in the optic nerve, resulting in the development of a profound neuropathy of the optic nerve. The findings advocate the need for intensive neuroprotective therapy as well for as early as possible intravitreal intervention in this category of patients.