Influence of ocular volume and lens status on pharmacokinetics and duration of action of intravitreal vascular endothelial growth factor inhibitors.

PURPOSE: To assess the effects of ocular axial length, refraction, and lens status on pharmacokinetics and duration of action of the vascular endothelial growth factor (VEGF) inhibitors ranibizumab and bevacizumab after intravitreal injection in humans. METHODS: In 119 eyes of 119 patients, aqueous humor was sampled at different time points after intravitreal injection of ranibizumab or bevacizumab, and either drug or VEGF concentrations were measured by enzyme-linked immunosorbent assays and Luminex multiplex bead technology, respectively. Relative deviation of the measured drug concentrations from the time-corrected mean values was calculated (n = 41). Repetitive VEGF measurements were preformed to identify the duration of complete suppression of ocular VEGF activity for individual eyes (n = 78). In addition, axial length, spherical equivalent refraction, and lens status were determined. RESULTS: For neither ranibizumab nor bevacizumab, a correlation between ocular pharmacokinetics (as measured by relative deviation of drug concentration from the mean) and axial length was detected in phakic eyes (Spearman's correlation coefficient, r = 0.084; P = 0.600). Similarly, the duration of action of intravitreal ranibizumab (as measured by VEGF suppression time) did not correlate with spherical equivalent refraction in phakic eyes (Spearman's correlation coefficient, r = 0.164; P = 0.301) and was not different between phakic and pseudophakic eyes (P = 0.694; Mann-Whitney U test). CONCLUSION: The results indicate that ocular volume and lens status have no relevant impact on ocular pharmacokinetics and duration of action of VEGF-inhibitory drugs and may, thus, be excluded as factors accounting for the high interindividual variability in morphologic and functional responses to intravitreal anti-VEGF therapy.

Semiautomated image processing method for identification and quantification of geographic atrophy in age-related macular degeneration.

PURPOSE: To determine intraobserver and interobserver longitudinal measurement variability of novel semiautomated software for quantification of age-related macular degeneration-associated geographic atrophy (GA) based on confocal scanning laser ophthalmoscopy fundus autofluorescence (FAF) imaging. METHODS: Three-field FAF (excitation 488 nm, emission 500-700 nm), near-infrared reflectance (820 nm), and blue reflectance (488 nm) images of 30 GA subjects were recorded according to a standardized protocol at baseline after 6 and 12 months. At all visits, the GA area was analyzed on central FAF images by seven independent readers using semiautomated software. The software allows direct export of FAF images from the database and semiautomated detection of atrophic areas by shadow correction, vessel detection, and selection of seed points. RESULTS: The mean size of atrophy at baseline and the mean progression rate were 5.96 mm² (range, 1.80-15.87) and 1.25 mm²/year (0.42-2.93), respectively. Mean difference of interobserver agreement (Bland-Altman statistics) ranged from -0.25 to 0.30 mm² for the baseline visit and from -0.14 to 0.11 mm²/year for the atrophy progression rate. Corresponding reflectance images were helpful for lesion boundary discrimination, particularly for evaluation of foveal GA involvement and when image quality was poor. CONCLUSIONS: The new image processing software offers an accurate, reproducible, and time-efficient identification and quantification of outer retinal atrophy and its progression over time. It facilitates measurements both in natural history studies and in interventional trials to evaluate new pharmacologic agents designed to limit GA enlargement.

Effects of lipid peroxidation products on lipofuscinogenesis and autophagy in human retinal pigment epithelial cells.

Several lines of evidence suggest that progressive dysfunction of the retinal pigment epithelium (RPE) is central to the pathogenesis of age-related macular degeneration (AMD). We previously demonstrated that protein modifications with lipid peroxidation products, such as 4-hydroxynonenal (HNE) and malondialdehyde (MDA), induce lysosomal dysfunction in RPE cells in vitro. Here, we investigated whether phagocytosis of modified photoreceptor outer segments (POS) affects lipofuscinogenesis and autophagy, two interrelated processes directly connected to lysosomal function. Incubation of human RPE cells with HNE- and MDA-modified POS resulted in pronounced intracellular accumulation of granular material with lipofuscin-like autofluorescence. After daily treatment with modified POS for 7 days, cellular autofluorescence increased 8.2-fold as quantified by flow cytometry. In the presence of the lysosomal inhibitor ammonium chloride, unmodified POS likewise induced an 8.0-fold increase in autofluorescence. Spectral profiles of cellular autofluorescence after incubation with modified POS were unchanged compared to incubation with native POS. Autophagy activity, measured as turnover of metabolically radiolabeled endogenous proteins, was reduced by both HNE- and MDA-modified POS by 40%. Autophagy inhibition by 3-methyladenine and lysosomal inhibition by ammonium chloride induced lipofuscinogenesis even in the absence of POS. In summary, our results demonstrate that induction of lysosomal dysfunction by lipid peroxidation-derived protein modifications results in increased lipofuscinogenesis and reduced autophagy activity in RPE cells in vitro. These mechanisms may contribute to RPE cell dysfunction and degeneration in AMD.