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To assess the effectiveness of an active learning approach to measuring the contrast sensitivity function (CSF) in patients with various degrees of dry age-related macular degeneration (AMD) under multiple luminance conditions.Cross-sectional study.Patients with AMD (26 intermediate AMD, 19 AMD with subretinal drusenoid deposits [SDD], 20 geographic atrophy [GA]) and 23 age-matched controls were tested with the Manifold Contrast Vision Meter (Adaptive Sensory Technology) and the qCSF algorithm, which applies active learning to estimate a model of the CSF's global shape. Testing was performed under conditions of standard and low luminance. For each AMD severity, the area under log CSF (AULCSF) and contrast sensitivities at individual spatial frequencies were calculated for analysis. Low-luminance deficits (LLDs) for visual acuity (VA) and AULCSF were calculated as the difference between standard and low luminance values.Progressive decreases in AULCSF were observed as disease severity increased. For standard luminance, pairwise comparisons revealed significant differences between control/intermediate AMD (P.0005), control/SDD (P.0005), control/GA (P.0005), and intermediate AMD/GA (P.005). Similarly, for low luminance, pairwise comparisons revealed significant differences between the controls and each disease group (all P.0005), in addition to significant differences between intermediate AMD/SDD (P.005), and intermediate AMD/GA (P.005). No correlations were found between LLD VA and LLD AULCSF in any AMD groups.Contrast sensitivity measured via qCSF under both standard- and low-luminance conditions correlates with advancing stages of dry AMD. The interaction between luminance and contrast sensitivity appears to reflect a different aspect of visual function than the interaction between luminance and VA.

Age-related macular degeneration (AMD) is one of the major causes of vision loss in the elderly in most developed countries. Among other causes, oxidative stress in the retinal pigment epithelium (RPE) has been hypothesized to be a major driving force of AMD pathology. Oxidative stress could be treated by antioxidant administration into the RPE cells. However, to achieve high in-vivo efficacy of an antioxidant, it is imperative that the agent be able to penetrate the tissues and cells. Evidence suggests that lipophilicity governs cellular penetrance. Out of many antioxidant candidates, N-acetyl-L-cysteine (a prodrug of L-cysteine) (NAC) is a potent antioxidant as the bioavailability of the parent drug, L-cysteine, determines the production of glutathione; the universal antioxidant that regulates ROS. To increase the lipophilicity, four ester derivatives of N-acetylcysteine: N-acetylcysteine methyl ester, N-acetylcysteine ethyl ester, N-acetylcysteine propyl ester, and N-acetylcysteine butyl ester were synthesized. To mimic in vitro AMD conditions, hydroquinone, a component of cigarette smoke, was used as the oxidative insult. Cytosolic and mitochondrial protection against oxidative stress were tested using cytosolic and mitochondrial specific assays. The results provide evidence that these lipophilic cysteine prodrugs provide increased protection against oxidative stress in human RPE cells compared with NAC.

Purpose This study investigated the effects of esterification and increased lipophilicity on cellular penetration, accumulation and retention in ARPE-19-nic cells using ester functionalized rhodamine B dyes. Methods Rhodamine B was esterified to generate four dyes with increasing lipophilicity. Cellular uptake, retention and mitochondrial localization were investigated in vitro using ARPE-19-nic cells using direct intracellular and extracellular and mitochondrial fluorescence quantitation, confocal and high-resolution live cell imaging and co-localization with Mito-GFP. Results Cellular penetrance, mitochondrial accumulation, and retention of the esterified dyes were increased in ARPE-19-nic cells compared with the nonesterified parent dye by direct fluorescence quantitation. Imaging demonstrated intracellular accumulation was confined to mitochondria as confirmed by colocalization with Mito-GFP. Conclusions Esterification is an effective way to increase lipophilicity of a dye to improve cellular penetration of chemical entities. These observations may be key to improving retinal drug delivery for retinal pigment epithelium-based diseases. Translational relevance Understanding the intracellular distribution of drugs into retinal pigment epithelium cells is a critical component for identifying potential therapies for retinal pigment epithelium-based diseases.