Trends and challenges in microfluidic methods for protein manipulation-A review.

Proteins are important molecules involved in an immensely large number of biological processes. Being capable of manipulating proteins is critical for developing reliable and affordable techniques to analyze and/or detect them. Such techniques would enable the production of therapeutic agents for the treatment of diseases or other biotechnological applications (e.g., bioreactors or biocatalysis). Microfluidic technology represents a potential solution to protein manipulation challenges because of the diverse phenomena that can be exploited to achieve micro- and nanoparticle manipulation. In this review, we discuss recent contributions made in the field of protein manipulation in microfluidic systems using different physicochemical principles and techniques, some of which are miniaturized versions of already established macro-scale techniques.

Manipulating the insulating post arrangement in DC-biased AC-iEK devices to improve microparticle separations.

There is a growing interest in the advancement of microscale electrokinetic (EK) systems for biomedical and clinical applications, as these systems offer attractive characteristics such as portability, robustness, low sample requirements and short response time. The present work is focused on manipulating the characteristics of the insulating post arrangement in insulator-based EK (iEK) systems for separating a binary mixture of spherical microparticles with same diameter (5.1 µm), same shape, made from the same substrate material and only differing in their zeta potential by ∼14 mV. This study presents a combination of mathematical modeling and experimental separations performed by applying a low-frequency alternating current (AC) voltage in iEK systems with 12 distinct post arrangements. These iEK devices were used to systematically study the effect of three spatial characteristics of the insulating post array on particle separations: the horizontal separation and the vertical separation between posts, and introducing an offset to the posts arrangement. Through normalization of the spatial separation between the insulating posts with respect to particle diameter, guidelines to improve separation resolution for different particle mixtures possessing similar characteristics were successfully identified. The results indicated that by carefully designing the spatial arrangement of the post array, separation resolution values in the range of 1.4-2.8 can be obtained, illustrating the importance and effect of the arrangement of insulating posts on improving particle separations. This study demonstrates that iEK devices, with effectively designed spatial arrangement of the insulating post arrays, have the capabilities to perform discriminatory separations of microparticles of similar characteristics.

Enabling the characterization of the nonlinear electrokinetic properties of particles using low voltage.

Insulator-based electrokinetically driven microfluidic devices stimulated with direct current (DC) voltages are an attractive solution for particle separation, concentration, or isolation. However, to design successful particle manipulation protocols, it is mandatory to know the mobilities of electroosmosis, and linear and nonlinear electrophoresis of the microchannel/liquid/particle system. Several techniques exist to characterize the mobilities of electroosmosis and linear electrophoresis. However, only one method to characterize the mobility of nonlinear electrophoresis has been thoroughly assessed, which generally requires DC voltages larger than 1000 V and measuring particle velocity in a straight microchannel. Under such conditions, Joule heating, electrolysis, and the DC power source cost become a concern. Also, measuring particle velocity at high voltages is noisy, limiting characterization quality. Here we present a protocol-tested on 2 µm polystyrene particles-for characterizing the mobility of nonlinear electrophoresis of the liquid/particle system using a DC voltage of only 30 V and visual inspection of particle dynamics in a microchannel featuring insulating obstacles. Multiphysics numerical modelling was used to guide microchannel design and to correlate particle location during an experiment with electric field intensity. The method was validated against the conventional characterization protocol, exhibiting excellent agreement while significantly reducing measurement noise and experimental complexity.

Fine-Tuning the Characteristic of the Applied Potential To Improve AC-iEK Separations of Microparticles.

There is an immediate need for the development of rapid and reliable methods for microparticle and cell assessments, and electrokinetic (EK) phenomena can be exploited to meet that need in a low cost and label-free fashion. The present study combines modeling and experimentation to separate a binary mixture of microparticles of the same size (5.1 µm), shape (spherical), and substrate material (polystyrene), but with a difference in particle zeta potentials of only ∼14 mV, by applying direct current (DC)-biased low-frequency alternating current (AC) voltages in an insulator-based-EK (iEK) system. Four distinct separations were carried out to systematically study the effect of fine-tuning each of the three main characteristics of the applied voltage: frequency, amplitude, and DC bias. The results indicate that fine-tuning each parameter improved the separation from an initial separation resolution Rs = 0.5 to a final resolution Rs = 3.1 of the fully fine-tuned separation. The separation method exhibited fair reproducibility in retention time with variations ranging from 6 to 26% between experimental repetitions. The present study demonstrates the potential to extend the limits of iEK systems coupled with carefully fine-tuned DC-biased low-frequency AC voltages to perform discriminatory micron-sized particle separations.

Recent advances and challenges in temperature monitoring and control in microfluidic devices.

Temperature is a critical-yet sometimes overlooked-parameter in microfluidics. Microfluidic devices can experience heating inside their channels during operation due to underlying physicochemical phenomena occurring therein. Such heating, whether required or not, must be monitored to ensure adequate device operation. Therefore, different techniques have been developed to measure and control temperature in microfluidic devices. In this contribution, the operating principles and applications of these techniques are reviewed. Temperature-monitoring instruments revised herein include thermocouples, thermistors, and custom-built temperature sensors. Of these, thermocouples exhibit the widest operating range; thermistors feature the highest accuracy; and custom-built temperature sensors demonstrate the best transduction. On the other hand, temperature control methods can be classified as external- or integrated-methods. Within the external methods, microheaters are shown to be the most adequate when working with biological samples, whereas Peltier elements are most useful in applications that require the development of temperature gradients. In contrast, integrated methods are based on chemical and physical properties, structural arrangements, which are characterized by their low fabrication cost and a wide range of applications. The potential integration of these platforms with the Internet of Things technology is discussed as a potential new trend in the field.

BETTER BASELINE VISION LEADS TO BETTER OUTCOMES AFTER THE 0.19-mg FLUOCINOLONE ACETONIDE INTRAVITREAL IMPLANT IN DIABETIC MACULAR EDEMA.

PURPOSE: Analysis of a 3-year, Phase 4, open-label, observational study evaluating the association of baseline best-corrected visual acuity (BCVA) with visual, treatment burden, and retinal thickness variability (RTV) outcomes and intraocular pressure (IOP)-related events after the 0.19-mg fluocinolone acetonide (FAc) intravitreal implant. METHODS: Data from patients with diabetic macular edema (DME) who did not have a clinically significant rise in IOP after previous corticosteroid treatment (N = 202 eyes from 159 patients) were segregated by baseline BCVA of ≥20/40 or <20/40 and analyzed for BCVA, number of yearly supplemental DME treatments, RTV, and incidence of IOP-related events. RESULTS: At 36 months post-FAc, eyes with better baseline BCVA (≥20/40) maintained baseline BCVA, whereas vision in eyes with worse baseline BCVA (<20/40) increased by approximately 7 letters to 61.34 letters (Snellen equivalent approximately 20/60; P < 0.05). Treatment burden and RTV decreased post-FAc regardless of baseline BCVA. Eyes with better baseline BCVA (≥20/40) had numerically fewer IOP-related events post-FAc versus eyes with worse baseline BCVA (<20/40), including a lower incidence of incisional IOP-lowering surgery. CONCLUSION: The 0.19-mg FAc implant improved RTV and treatment burden regardless of baseline BCVA. Better baseline BCVA (≥20/40) was associated with long-term BCVA maintenance. Although eyes with worse baseline BCVA (<20/40) experienced significantly improved BCVA, it never rose to the level of those with better baseline BCVA. These data indicate that early, effective intervention in DME, before significant vision loss occurs, is key to maintaining visual outcomes.

Three-Year Safety and Efficacy of the 0.19-mg Fluocinolone Acetonide Intravitreal Implant for Diabetic Macular Edema: The PALADIN Study.

PURPOSE: To assess the long-term safety and efficacy of the 0.19-mg fluocinolone acetonide (FAc) intravitreal implant (Iluvien; Alimera Sciences, Inc) in patients with diabetic macular edema (DME). DESIGN: Three-year, phase 4, nonrandomized, open-label observational study. PARTICIPANTS: Patients with DME who previously received corticosteroid treatment without a clinically significant rise in intraocular pressure (IOP; all eyes, n = 202 eyes of 159 patients; 36-month completion, n = 94 eyes). METHODS: A prospective, observational study in which patients received a 0.19-mg FAc intravitreal implant at baseline and then were observed for safety-, visual-, anatomic-, and treatment burden-related outcomes for up to 36 months. MAIN OUTCOME MEASURES: Primary safety outcomes included changes in IOP and interventions to manage IOP elevations. Secondary outcomes included changes in best-corrected visual acuity (BCVA), central subfield thickness (CST), and adjunctive DME treatment frequency RESULTS: At 36 months after FAc implantation, study eyes showed a mean CST change of -60.69 µm (P < 0.0001) and a mean BCVA change of +3.61 letters (P = 0.0222) compared with baseline. Overall median treatment frequency decreased from 3.4 treatments/year in the 36 months before FAc implantation to 1 treatment/year in the 36 months after FAc implant, a treatment burden reduction of 70.5%. Furthermore, among the group that completed 36 months of treatment (n = 94 eyes), 25.53% of eyes remained rescue free through 36 months. Mean IOP remained stable throughout the study, and IOP increases to more than 30 mmHg occurred in 10.89% of eyes. Intraocular pressure-related procedures were infrequent, with a surgical rate of 2.97%, with 1.49% attributable to steroid use (vs. surgeries attributable primarily to neovascular glaucoma). In addition, an IOP response of < 25 mmHg after the steroid challenge predicted that 96.92% of eyes would have a similar outcome to 0.19-mg FAc implant at the last visit. Intraocular pressure increases that did occur were manageable with standard treatments (n = 202 eyes). CONCLUSIONS: In patients with DME, the 0.19-mg FAc implant provided improved visual outcomes and reduced treatment burden compared with previous treatments while maintaining a favorable safety profile.

Electrically driven microfluidic platforms for exosome manipulation and characterization.

Exosomes are small extracellular vesicles that can be obtained from several body fluids such as blood and urine. Since these vesicles can carry biomarkers and other cargo, they have application in healthcare diagnostics and therapeutics, such as liquid biopsies and drug delivery. Yet, their identification and separation from a sample remain challenging due to their high degree of heterogeneity and their co-existence with other bioparticles. In this contribution, we review the state-of-the-art on electrical techniques and methods to displace, selectively trap/isolate, and detect/characterize exosomes in microfluidic devices. Although there are many reviews focused on exosome separation using benchtop equipment, such as ultracentrifugation, there are limited reviews focusing on the use of electrical phenomena in microfluidic devices for exosome manipulation and detection. Here, we highlight contributions published during the past decade and present perspectives for this research field for the near future, outlining challenges to address in years to come.

Nanomaterials for electrochemical detection of pollutants in water: A review.

The survival of living beings, including humanity, depends on a continuous supply of clean water. However, due to the development of industry, agriculture, and population growth, an increasing number of wastewaters is discarded, and the negative effects of such actions are clear. The first step in solving this situation is the collection and monitoring of pollutants in water bodies to subsequently facilitate their treatment. Nonetheless, traditional sensing techniques are typically laboratory-based, leading to potential diminishment in analysis quality. In this paper, the most recent developments in micro- and nano-electrochemical devices for pollutant detection in wastewater are reviewed. The devices reviewed are based on a variety of electrodes and the sensing of three different categories of pollutants: nutrients and phenolic compounds, heavy metals, and organic matter. From these electrodes, Cu, Co, and Bi showed promise as versatile materials to detect a grand variety of contaminants. Also, the most commonly used material is glassy carbon, present in the detection of all reviewed analytes.

Thermal limits of Africanized honey bees are influenced by temperature ramping rate but not by other experimental conditions.

Interest in assessing the critical thermal limits of bees is rapidly increasing, as these physiological traits are good predictors of bees' potential responses to extreme temperature changes, which is relevant in the context of global climate change. However, estimates of thermal limits may be influenced by several factors and published studies differ in experimental methods and conditions, such as the rate of temperature change (ramping rate) and feeding status, which might yield inaccurate predictions and limit comparisons across taxa and regions. Using Africanized honey bees as a model organism, we assessed the effect of ramping rate (0.25, 0.5, 0.75, 1.0 and 1.5 °C min-1) and length of starvation (recently fed vs. fasted for 6, 12, and 18 h) on foragers' lower (CTMin) and upper (CTMax) thermal limits, as well as the effect of cold stress on CTMax. In addition, we evaluated the two approaches currently used to assess CTMax with a water bath: floating or submerging the testing vials in the bath. We found that critical thermal limits were influenced by ramping rates but not by the other assessed experimental conditions. On average, at ramping rates faster than 0.5 °C min-1, bees displayed a CTMin 1.1-2.6 °C lower and a CTMax 5.3-6.9 °C higher than those of the slowest ramping rate. We discuss the implications of these results and provide suggestions for future thermal studies on bees.

Panretinal Photocoagulation for Diabetic Retinopathy in the RIDE and RISE Trials: Not "1 and Done".

PURPOSE: To evaluate panretinal photocoagulation (PRP) treatment and re-treatment patterns in patients with diabetic retinopathy (DR) and diabetic macular edema (DME). DESIGN: Post hoc analysis of the phase 3 RIDE (clinicaltrials.gov identifier, NCT00473382) and RISE (clinicaltrials.gov identifier, NCT00473330) clinical trials of ranibizumab for the treatment of DME. PARTICIPANTS: Seven hundred fifty-nine patients were randomized for treatment. METHODS: Panretinal photocoagulation treatment patterns and clinical experiences were assessed by baseline PRP treatment status. MAIN OUTCOME MEASURES: Number and timing of on-study PRP treatment sessions undergone through month 24. Time to new proliferative event (composite end point) was also assessed. RESULTS: At baseline, approximately 25% of patients in RIDE and RISE had undergone PRP treatment before enrollment (22.2%, 24.4%, and 25.4% of patients in the sham, ranibizumab 0.3 mg, and ranibizumab 0.5 mg arms, respectively). In patients without prior PRP at baseline (n = 577), 9.5% of sham-treated patients underwent 1 or more PRP treatments through month 24, compared with 1.1% and 1.6% of patients receiving ranibizumab 0.3 mg and ranibizumab 0.5 mg, respectively (P < 0.001 for both ranibizumab arms vs. sham). In patients with prior PRP at baseline (n = 182), 19.3% of sham-treated patients underwent 1 or more PRP treatments through month 24. No ranibizumab-treated patients with prior PRP at baseline required additional on-study PRP through month 24 (P < 0.001 for both ranibizumab arms vs. sham). Ranibizumab treatment also significantly reduced clinical DR progression among patients who underwent prior PRP. By month 24 in patients with prior PRP at baseline, the probability of experiencing a new proliferative event was 10.3% and 9.9% in patients receiving ranibizumab 0.3 mg and ranibizumab 0.5 mg treatment, respectively, compared with 39.4% in sham-treated patients (P < 0.0001). Overall, sham-treated patients, including those patients who were PRP naïve at baseline who went on to require PRP, experienced more clinical events than ranibizumab-treated patients. CONCLUSIONS: In RIDE and RISE, PRP treatment was not a "1 and done" procedure, with on-study PRP re-treatment occurring in patients both with and without prior PRP treatment at baseline. Ranibizumab treatment reduced on-study PRP treatment and DR progression regardless of prior PRP treatment status at baseline.

Particle trapping in electrically driven insulator-based microfluidics: Dielectrophoresis and induced-charge electrokinetics.

Electrokinetically driven insulator-based microfluidic devices represent an attractive option to manipulate particle suspensions. These devices can filtrate, concentrate, separate, or characterize micro and nanoparticles of interest. Two decades ago, inspired by electrode-based dielectrophoresis, the concept of insulator-based dielectrophoresis (iDEP) was born. In these microfluidic devices, insulating structures (i.e., posts, membranes, obstacles, or constrictions) built within the channel are used to deform the spatial distribution of an externally generated electric field. As a result, particles suspended in solution experience dielectrophoresis (DEP). Since then, it has been assumed that DEP is responsible for particle trapping in these devices, regardless of the type of voltage being applied to generate the electric field-direct current (DC) or alternating current. Recent findings challenge this assumption by demonstrating particle trapping and even particle flow reversal in devices that prevent DEP from occurring (i.e., unobstructed long straight channels stimulated with a DC voltage and featuring a uniform electric field). The theory introduced to explain those unexpected observations was then applied to conventional "DC-iDEP" devices, demonstrating better prediction accuracy than that achieved with the conventional DEP-centered theory. This contribution summarizes contributions made during the last two decades, comparing both theories to explain particle trapping and highlighting challenges to address in the near future.

Toward low-voltage dielectrophoresis-based microfluidic systems: A review.

Dielectrophoretically driven microfluidic devices have demonstrated great applicability in biomedical engineering, diagnostic medicine, and biological research. One of the potential fields of application for this technology is in point-of-care (POC) devices, ideally allowing for portable, fully integrated, easy to use, low-cost diagnostic platforms. Two main approaches exist to induce dielectrophoresis (DEP) on suspended particles, that is, electrode-based DEP and insulator-based DEP, each featuring different advantages and disadvantages. However, a shared concern lies in the input voltage used to generate the electric field necessary for DEP to take place. Therefore, input voltage can determine portability of a microfluidic device. This review outlines the recent advances in reducing stimulation voltage requirements in DEP-driven microfluidics.

A survey of electrokinetically-driven microfluidics for cancer cells manipulation.

Cancer is one of the leading causes of annual deaths worldwide, accounting for nearly 10 million deaths each year. Metastasis, the process by which cancer spreads across the patient's body, is the main cause of death in cancer patients. Because the rising trend observed in statistics of new cancer cases and cancer-related deaths does not allow for an optimistic viewpoint on the future-in relation to this terrible disease-the scientific community has sought methods to enable early detection of cancer and prevent the apparition of metastatic tumors. One such method is known as liquid biopsy, wherein a sample is taken from a bodily fluid and analyzed for the presence of CTCs or other cancer biomarkers (e.g., growth factors). With this objective, interest is growing by year in electrokinetically-driven microfluidics applied for the concentration, capture, filtration, transportation, and characterization of CTCs. Electrokinetic techniques-electrophoresis, dielectrophoresis, electrorotation, and electrothermal and EOF-have great potential for miniaturization and integration with electronic instrumentation for the development of point-of-care devices, which can become a tool for early cancer diagnostics and for the design of personalized therapeutics. In this contribution, we review the state of the art of electrokinetically-driven microfluidics for cancer cells manipulation.

Simultaneous Determination of Linear and Nonlinear Electrophoretic Mobilities of Cells and Microparticles.

Direct-current insulator-based electrokinetics (DC-iEK) is a branch of microfluidics that has demonstrated to be an attractive and efficient technique for manipulating micro- and nano- particles, including microorganisms. A unique feature of DC-iEK devices is that nonlinear EK effects are enhanced by the presence of regions of higher field intensity between the insulating structures. Accurate computational models, describing particle and cell behavior, are crucial to optimize the design and improve the performance of DC-iEK devices. The electrokinetic equilibrium condition (EEEC) is a recently introduced fundamental concept that has radically shifted the perspective behind the analysis of particle manipulation in these microfluidic devices. The EEEC takes into consideration previously neglected nonlinear effects on particle migration and indicates that these effects are central to control particle motion in DC-iEK devices. In this study, we present a simultaneous experimental characterization of linear and nonlinear electrokinetic (EK) parameters, that is, the electrophoretic mobility (µEP(1)), the particle zeta potential (ζP), the EEEC, and the electrophoretic mobility of the second kind (µEP(3)), for four types of polystyrene microparticles and four cell strains. For this, we studied the electromigration of polystyrene microparticles ranging in size from 2 to 6.8 µm, three bacteria strains (B. cereus, E. coli, and S. enterica) and a yeast cell (S. cerevisiae), ranging in size from 1 to 6.3 µm, in a polydimethylsiloxane (PDMS) microfluidic channel with a rectangular cross-section. The results illustrated that electrokinetic particle trapping can occur by linear and nonlinear electrophoresis and electroosmosis reaching an equilibrium, without the presence of insulating posts. The experimentally measured parameters reported herein will allow optimizing the design of future DC-iEK devices for a wide range of applications (e.g., to separate multiple kinds of particles and microorganisms) and for developing computational models that better represent reality.

Direct Current Electrokinetic Particle Trapping in Insulator-Based Microfluidics: Theory and Experiments.

The classic theory of direct-current (DC) insulator-based dielectrophoresis (iDEP) considers that, in order to elicit particle trapping, dielectrophoretic (DEP) velocity counterbalances electrokinetic (EK) motion, that is, electrophoresis (EP) and electro-osmotic flow (EOF). However, the particle velocity DEP component requires empirical correction factors (sometimes as high as 600) to account for experimental observations, suggesting the need for a refined model. Here, we show that, when applied to particle suspensions, a high-magnitude DC uniform electric field induces nonlinear particle velocities, leading to particle flow reversal beyond a critical field magnitude, referred to as the EK equilibrium condition. We further demonstrate that this particle motion can be described through an exploratory induced-charge EP nonlinear model. The model predictions were validated under an insulator-based microfluidic platform demonstrating predictive particle trapping for three different particle sizes (with an estimation error < 10%, not using correction factors). Our findings suggest that particle motion and trapping in "DC-iDEP" devices are dominated by EP and EOF, rather than by DEP effects.

Electrokinetically Driven Exosome Separation and Concentration Using Dielectrophoretic-Enhanced PDMS-Based Microfluidics.

Exosomes are a specific subpopulation of extracellular vesicles that have gained interest because of their many potential biomedical applications. However, exosome isolation and characterization are the first steps toward designing novel applications. This work presents a direct current-insulator-based dielectrophoretic (DC-iDEP) approach to simultaneously capture and separate exosomes by size. To do so, a microdevice consisting of a channel with two electrically insulating post sections was designed. Each section was tailored to generate different nonuniform spatial distributions of the electric field and, therefore, different dielectrophoretic forces acting on exosomes suspended in solution. Side channels were placed adjacent to each section to allow sample recovery. By applying an electric potential difference of 2000 V across the length of the main channel, dielectrophoretic size-based separation of exosomes was observed in the device. Analysis of particle size in each recovered fraction served to assess exosome separation efficiency. These findings show that iDEP can represent a first step toward designing a high-throughput, fast, and robust microdevice capable of capturing and discriminating different subpopulations of exosomes based on their size.

Recent advances and challenges in the recovery and purification of cellular exosomes.

Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome-based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed.

Joule heating effects in optimized insulator-based dielectrophoretic devices: An interplay between post geometry and temperature rise.

Insulator-based dielectrophoresis (iDEP) is the electrokinetic migration of polarized particles when subjected to a non-uniform electric field generated by the inclusion of insulating structures between two remote electrodes. Electrode spacing is considerable in iDEP systems when compared to electrode-based DEP systems, therefore, iDEP systems require high voltages to achieve efficient particle manipulation. A consequence of this is the temperature increase within the channel due to Joule heating effects, which, in some cases, can be detrimental when manipulating biological samples. This work presents an experimental and modeling study on the increase in temperature inside iDEP devices. For this, we studied seven distinct channel designs that mainly differ from each other in their post array characteristics: post shape, post size and spacing between posts. Experimental results obtained using a custom-built copper Resistance Temperature Detector, based on resistance changes, show that the influence of the insulators produces a difference in temperature rise of approximately 4°C between the designs studied. Furthermore, a 3D COMSOL model is also introduced to evaluate heat generation and dissipation, which is in good agreement with the experiments. The model allowed relating the difference in average temperature for the geometries under study to the electric resistance posed by the post array in each design.

THE OASIS MP-1 SUBSTUDY: Characterization of the Effect of Ocriplasmin on Microperimetry Parameters.

PURPOSE: To evaluate the effects of ocriplasmin and symptomatic vitreomacular adhesion resolution on visual fixation and macular sensitivity using microperimetry. METHODS: MP-1 parameters were analyzed from 3 OASIS sites after the use of standardized instruments and testing procedures over 24 months. RESULTS: A total of 27 patients (19 ocriplasmin, 8 sham) were evaluated. Mean distance of the preferred fixation locus to the anatomical center was farther in the sham group at baseline and farther in the sham versus ocriplasmin group throughout the study. Retinal sensitivity values were consistently higher in the ocriplasmin versus sham group after Month 3. Fewer patients in the ocriplasmin group had predominantly eccentric fixation at study end compared with the sham group, which also had an increased number of patients with unstable fixation. Patients with vitreomacular adhesion resolution had lower bivariate contour area, fewer relative scotomas, and higher retinal sensitivity parameters at baseline than those with unresolved vitreomacular adhesion. CONCLUSION: Substudy results suggest that fixation and sensitivity parameters tended to be better in the ocriplasmin group than in the sham group over time. The substudy identified parameters that were distinct between patients with and without vitreomacular adhesion resolution, suggesting that microperimetry warrants further study as a relevant biomarker for visual function.