Assessing Change in Exudative Age-Related Macular Degeneration With Macular Thickness Maps as a Surrogate Strategy for Remote Patient Monitoring.

PURPOSE: To determine if macular thickness maps (MTMs) are sufficient to guide management of eyes with exudative age-related macular degeneration (eAMD), we compared the ability to detect change using MTMs with the ability to detect change using the entire optical coherence tomography (OCT) scan in patients undergoing therapy. DESIGN: Retrospective, comparative diagnostic analysis. METHODS: Patients with eAMD were imaged using macula-centered 6 × 6-mm OCT scans (CIRRUS HD-OCT 5000; Zeiss). In each case, graders were asked to determine if there were changes that warranted a full clinical assessment after viewing 2 consecutive scans using one of 3 different imaging strategies: MTMs alone, individual foveal-centered B scans alone, or 5 macular B scans including the foveal-centered B scan. Graders were told the 2 scans were taken 2 weeks apart. The consensus ground truth was reached by the graders using a CIRRUS review station to evaluate all the information contained within the OCT scans. RESULTS: A total of 53 eyes were included in this study with 1385 imaging sessions. The Fleiss kappa was highest when graders were given MTMs alone compared with the ground truth. When the averages of all 5 graders were compared with the ground truth, the MTMs alone showed the highest level of agreement (90.05%, SD 0.78%) followed by the central B scans (87.87%, SD 1.59%) and the 5-B scan method (86.512%, SD 0.64%). CONCLUSION: MTMs alone provide sufficient information to easily identify recurrent exudation in patients with eAMD, and these maps may be all that is needed for remote monitoring.

Aqueous Humor Dynamics of the Brown-Norway Rat.

Purpose: The study aimed to provide a quantitative description of aqueous humor dynamics in healthy rat eyes. Methods: One eye of 26 anesthetized adult Brown-Norway rats was cannulated with a needle connected to a perfusion pump and pressure transducer. Pressure-flow data were measured in live and dead eyes by varying pump rate (constant-flow technique) or by modulating pump duty cycle to hold intraocular pressure (IOP) at set levels (modified constant-pressure technique). Data were fit by the Goldmann equation to estimate conventional outflow facility (C) and unconventional outflow rate (Fun). Parameter estimates were respectively checked by inserting a shunt of similar conductance into the eye and by varying eye hydration methodology. Results: Rat IOP averaged 14.6 ± 1.9 mm Hg at rest. Pressure-flow data were repeatable and indistinguishable for the two perfusion techniques, yielding C = 0.023 ± 0.002 µL/min/mm Hg and Fun = 0.096 ± 0.024 µL/min. C was similar for live and dead eyes and increased upon shunt insertion by an amount equal to shunt conductance, validating measurement accuracy. At 100% humidity Fun dropped to 0.003 ± 0.030 µL/min. Physiological washout was not observed (-0.35 ± 0.65%/h), and trabecular anatomy looked normal. Conclusions: Rat aqueous humor dynamics are intermediate in magnitude compared to those in mice and humans, consistent with species differences in eye size. C does not change with time or death. Evaporation complicates measurement of Fun even when eyes are not enucleated. Absence of washout is a notable finding seen only in mouse and human eyes to date.

A Wireless Pressure Sensor for Continuous Monitoring of Intraocular Pressure in Conscious Animals.

An important aspect of eye health in humans and animal models of human diseases is intraocular pressure (IOP). IOP is typically measured by hand with a tonometer, so data are sparse and sporadic and round-the-clock variations are not well characterized. Here we present a novel system for continuous wireless IOP and temperature measurement in small animals. The system consists of a cannula implanted in the anterior chamber of the eye connected to pressure sensing electronics that can be worn by rats or implanted in larger mammals. The system can record IOP with 0.3 mmHg accuracy and negligible drift at a rate of 0.25 Hz for 1-2 months on a regulated battery or indefinitely at rates up to 250 Hz via RF energy harvesting. Chronic recordings from conscious rats showed that IOP follows a diurnal rhythm, averaging 16.5 mmHg during the day and 21.7 mmHg at night, and that the IOP rhythm lags a diurnal rhythm in body temperature by 2.1 h. IOP and body temperature fluctuations were positively correlated from moment-to-moment as well. This technology allows researchers to monitor for the first time the precise IOP history of rat eyes, a popular model for glaucoma studies.

Development of a Smart Pump for Monitoring and Controlling Intraocular Pressure.

Animal models of ocular hypertension are important for glaucoma research but come with experimental costs. Available methods of intraocular pressure (IOP) elevation are not always successful, the amplitude and time course of IOP changes are unpredictable and irreversible, and IOP measurement by tonometry is laborious. Here we present a novel system for monitoring and controlling IOP without these limitations. It consists of a cannula implanted in the anterior chamber of the eye, a pressure sensor that continually measures IOP, and a bidirectional pump driven by control circuitry that can infuse or withdraw fluid to hold IOP at user-desired levels. A portable version was developed for tethered use on rats. We show that rat eyes can be cannulated for months without causing significant anatomical or physiological damage although the animal and its eyes freely move. We show that the system measures IOP with <0.7 mmHg resolution and <0.3 mmHg/month drift and can maintain IOP within a user-specified window of desired levels for any duration necessary. We conclude that the system is ready for cage- or bench-side applications. The results lay the foundation for an implantable version that would give glaucoma researchers unprecedented knowledge and control of IOP in rats and potentially larger animals.

Structural and evolutionary basis for the dual substrate selectivity of human KDM4 histone demethylase family.

N(ε)-Methylations of histone lysine residues play critical roles in cell biology by "marking" chromatin for transcriptional activation or repression. Lysine demethylases reverse N(ε)-methylation in a sequence- and methylation-selective manner. The determinants of sequence selectivity for histone demethylases have been unclear. The human JMJD2 (KDM4) H3K9 and H3K36 demethylases can be divided into members that act on both H3K9 and H3K36 and H3K9 alone. Kinetic, crystallographic, and mutagenetic studies in vitro and in cells on KDM4A-E reveal that selectivity is determined by multiple interactions within the catalytic domain but outside the active site. Structurally informed phylogenetic analyses reveal that KDM4A-C orthologues exist in all genome-sequenced vertebrates with earlier animals containing only a single KDM4 enzyme. KDM4D orthologues only exist in eutherians (placental mammals) where they are conserved, including proposed substrate sequence-determining residues. The results will be useful for the identification of inhibitors for specific histone demethylases.

Inhibitor scaffolds for 2-oxoglutarate-dependent histone lysine demethylases.

The dynamic methylation of histone lysyl residues plays an important role in biology by regulating transcription, maintaining genomic integrity, and by contributing to epigenetic effects. Here we describe a variety of inhibitor scaffolds that inhibit the human 2-oxoglutarate-dependent JMJD2 subfamily of histone demethylases. Combined with structural data, these chemical starting points will be useful to generate small-molecule probes to analyze the physiological roles of these enzymes in epigenetic signaling.