Behavior Change Among HIV-Negative Men Who Have Sex with Men Not Using PrEP in the United States.

This study measures changes in condomless anal sex (CAS) among HIV-negative men who have sex with men (MSM) who are not taking pre-exposure prophylaxis (PrEP). It considers the 2014-2019 cycles of the American Men's Internet Survey, a serial, cross-sectional web-based survey of US cisgender MSM aged ≥ 15 years, in which ~ 10% of each year's sample is drawn from the previous year. Among those surveyed for 2 years who remained HIV-negative and off PrEP, reports of having any CAS and of CAS partner number were compared across years. We disaggregated by partner HIV status, and considered demographic predictors. The overall population saw a significant 2.2 percentage-point (pp) increase in reports of any CAS year-over-year. Sub-populations with the largest year-on-year increases were 15-24-year-olds (5.0-pp) and Hispanic respondents (5.1-pp), with interaction (young Hispanic respondents = 12.8-pp). On the relative scale, these numbers correspond to 3.2%, 7.2%, 7.3% and 18.7%, respectively. Absolute increases were concentrated among partners reported as HIV-negative. Multivariable analyses for CAS initiation found effects concentrated among Hispanic and White youth and residents of fringe counties of large metropolitan areas. CAS partner number increases were similarly predicted by Hispanic identity and young age. Although condom use remains more common than PrEP use, increasing CAS among MSM not on PrEP suggests potential new HIV transmission pathways. Concentration of increases among 18-24-year-old MSM portends future increases in the proportion of newly diagnosed HIV that occur among youth. Concentration among young Hispanic MSM will likely expand existing disparities. Although reducing barriers to PrEP remains vital, condom promotion for MSM remains a key public health practice and appears to be missing key audiences. LGBTQ+-inclusive sex education is one avenue for enhancing these efforts.

Benefits of thermal and distance-filtered imaging for wayfinding with prosthetic vision.

Visual prostheses such as the Argus II provide partial vision for individuals with limited or no light perception. However, their effectiveness in daily life situations is limited by scene complexity and variability. We investigated whether additional image processing techniques could improve mobility performance in everyday indoor environments. A mobile system connected to the Argus II provided thermal or distance-filtered video stimulation. Four participants used the thermal camera to locate a person and the distance filter to navigate a hallway with obstacles. The thermal camera allowed for finding a target person in 99% of trials, while unfiltered video led to confusion with other objects and a success rate of only 55% ([Formula: see text]). Similarly, the distance filter enabled participants to detect and avoid 88% of obstacles by removing background clutter, whereas unfiltered video resulted in a detection rate of only 10% ([Formula: see text]). For any given elapsed time, the success rate with filtered video was higher than with unfiltered video. After 90 s, participants' success rate reached above 50% with filtered video and 24% and 3% with normal camera in the first and second tasks, respectively. Despite individual variations, all participants showed significant improvement when using the thermal and distance filters compared to unfiltered video. Adding a thermal and distance filter to a visual prosthesis system can enhance the performance of mobility activities by removing clutter in the background, showing people and warm objects with the thermal camera, or nearby obstacles with the distance filter.

High Seroprevalence of Hepatitis C Virus Among Cisgender Women Who Exchange Sex in the Seattle, Washington Area.

BACKGROUND: Injection drug use (IDU) is a risk factor for hepatitis C virus (HCV) acquisition and occurs disproportionately among women who exchange sex (WES). However, little is known about HCV epidemiology in this population. We estimated HCV seroprevalence, identified correlates of HCV seropositivity, and characterized social networks by HCV serostatus and IDU history among WES in the Seattle, Washington, area. METHODS: This was a secondary analysis of data from the 2016 National HIV Behavioral Surveillance survey in the Seattle, Washington area, a cross-sectional survey that used respondent-driven sampling (RDS) to enroll WES for money or drugs (N = 291). All participants were offered rapid HCV-antibody testing. We estimated HCV seropositivity and used log regression methods to estimate crude and adjusted prevalence ratios (PRs) for correlates of HCV seropositivity among WES. Using RDS recruitment chain data, we computed homophily indices to estimate the extent to which participants were likely to recruit another participant with the same HCV serostatus and IDU history. RESULTS: In the study sample of WES in the Seattle, Washington area, 79% reported lifetime IDU and 60% were HCV seropositive. HCV seropositivity was strongly associated with ever injecting drugs (PRadj: 7.7 [3.3, 18.0]). The RDS homophily scores for HCV seropositivity (0.07) and ever injecting drugs (0.02) suggested that participants did not tend to recruit others with the same characteristics beyond what would be expected by chance. CONCLUSION: Among this sample of WES in Seattle, Washington area, HCV seroprevalence was high and strongly associated with a history of IDU. The high burden of HCV among WES suggests this marginalized group would benefit from additional harm reduction services and targeted HCV treatment campaigns to reduce forward transmission. We saw little evidence of preferential recruitment among WES who were HCV seropositive or reported a history of IDU, suggesting the potential futility of peer-based referrals for HCV treatment.

Previous Sexually Transmitted Infections and Partner Services Interviews as Predictors of Subsequent Interview Completion Among Cisgender MSM: Partner Services Fatigue?

BACKGROUND: Anecdotal reports suggest that partner services (PS) are less successful among people with repeat sexually transmitted infection (STI) diagnoses and/or previous PS interactions. We examine whether having repeated STI diagnoses and/or PS interactions is associated with PS outcomes among men who have sex with men (MSM). METHODS: With STI surveillance and PS data for MSM diagnosed with gonorrhea, chlamydia, and/or syphilis from 2007 to 2018, in King County, WA, we used Poisson regression models to examine the relationships between PS outcomes (e.g., completing a PS interview and providing identifying information for a contact) with (1) number of previous STI case episodes and (2) number of previous PS interviews completed. RESULTS: Of the 18,501 MSM STI case patients initiated for interview in the analytic period (2011-2018), 13,232 (72%) completed a PS interview, and 8,030 (43%) had at least 1 prior PS interview. The proportion of initiated cases successfully interviewed declined from 71% among those with no previous PS interview to 66% among those with ≥3 prior interviews. Similarly, the proportion of interviews with ≥1 partner identified declined with greater numbers of previous PS interviews (from 46% [0 interviews] to 35% [≥3 interviews]). In multivariate models, having ≥1 prior PS interview was negatively associated with completing a subsequent interview and providing partner locating information. CONCLUSIONS: Having a history of STI PS interviews is associated with less PS engagement among MSM. New approaches to PS should be explored to address the growing epidemic of STIs among MSM.

The Pre-exposure Prophylaxis (PrEP) Care Continuum Among English-Speaking Latino Sexual Minority Men in the United States (2014-2020).

BACKGROUND: There is limited understanding of the pre-exposure prophylaxis (PrEP) care continuum specific to Latino/x gay, bisexual, and other sexual minority men (SMM) that encompasses the population residing outside of large metropolitan or urban areas. SETTING: We examined trends and characteristics associated with the PrEP care continuum with data from the 2014-2020 cycles of the American Men's Internet Survey, an annual online cross-sectional behavioral survey of cisgender SMM in the United States. METHODS: We calculated PrEP continuum outcomes overall and by year among Hispanic/Latino SMM (n = 9010). We used generalized estimating equations with Poisson links to examine (1) temporal trends (2014-2020) in each step of the PrEP continuum and PrEP use in the past year stratified by PrEP eligibility and (2) correlates of each step of the PrEP continuum in 2020 using multivariable models. RESULTS: Among 2283 Latino SMM in 2020, 84% reported PrEP awareness, 30% discussed PrEP with a provider, 15% used PrEP in the past year, and 12% were currently using PrEP. PrEP awareness increased from 52% in 2014 to 84% in 2020; and PrEP use in the past year increased from 4% in 2014 to 15% in 2020. In the multivariable models, age and PrEP eligibility were associated with PrEP use in the past year, and urban-rural classification was associated with current PrEP use. CONCLUSIONS: While most of the Latino SMM are aware of PrEP, significant gaps remain in this population in discussing PrEP with a provider and using PrEP that require tailored strategies to enhance access to HIV prevention services.

Qualitative inquiry into perceptions of HIV pre-exposure prophylaxis among people who inject drugs living with hepatitis C in Seattle, WA, USA.

BACKGROUND: The incidence of HIV among persons who inject drugs (PWID) in the USA has been increasing since 2014, signaling the need to identify effective ways to engage PWID in HIV prevention services, namely pre-exposure prophylaxis (PrEP). Yet, the uptake of PrEP in this population is minimal compared to other populations at risk of HIV acquisition. In this work, we sought to explore knowledge, attitudes, and perspectives of PrEP acceptability among PWID. METHODS: In the context of a pilot study to explore the acceptability of pharmacy-based hepatitis C virus (HCV) treatment, we conducted semi-structured interviews (n = 24) and focus groups (n = 4, 16 participants) with people who were living with HCV and reported active injection drug use (≤ 90 days since last use). Participants were asked open-ended questions about their familiarity with and motivation to use PrEP. As part of a sub-analysis focused on PrEP, qualitative data were analyzed using a Rapid Assessment Process, where three coders used structured templates to summarize qualitative data and iteratively reviewed coded templates to identify themes. Participants also completed short quantitative questionnaires regarding drug use history and attitudes toward health concerns. RESULTS: Forty-seven percent of participants expressed having little or no concern regarding HIV acquisition. Targeted analyses focused on HIV prevention identified three themes, which help characterize behavioral determinants of nonadoption. First, knowledge of PrEP was limited among PWID and influenced by infrequent open community discussions around HIV risk. Second, PWID perceived sexual behaviors-but not injection drug use-as a motivator for HIV risk prevention. Finally, PWID identified many individual and environmental barriers that hinder PrEP uptake. CONCLUSION: Among PWID, PrEP is rarely discussed and concerns about the feasibility of using daily PrEP are common. Taken with the prevalent perception that drug use is not a high risk for HIV acquisition, our findings point to opportunities for public health work to target PrEP education to PWID and to leverage other successful interventions for PWID as an opportunity to provide PrEP to this vulnerable population.

Considerations Before Selecting a Stepped-Wedge Cluster Randomized Trial Design for a Practice Improvement Study.

PURPOSE: Despite the growing popularity of stepped-wedge cluster randomized trials (SW-CRTs) for practice-based research, the design's advantages and challenges are not well documented. The objective of this study was to identify the advantages and challenges of the SW-CRT design for large-scale intervention implementations in primary care settings. METHODS: The EvidenceNOW: Advancing Heart Health initiative, funded by the Agency for Healthcare Research and Quality, included a large collection of SW-CRTs. We conducted qualitative interviews with 17 key informants from EvidenceNOW grantees to identify the advantages and challenges of using SW-CRT design. RESULTS: All interviewees reported that SW-CRT can be an effective study design for large-scale intervention implementations. Advantages included (1) incentivized recruitment, (2) staggered resource allocation, and (3) statistical power. Challenges included (1) time-sensitive recruitment, (2) retention, (3) randomization requirements and practice preferences, (4) achieving treatment schedule fidelity, (5) intensive data collection, (6) the Hawthorne effect, and (7) temporal trends. CONCLUSIONS: The challenges experienced by EvidenceNOW grantees suggest that certain favorable real-world conditions constitute a context that increases the odds of a successful SW-CRT. An existing infrastructure can support the recruitment of many practices. Strong retention plans are needed to continue to engage sites waiting to start the intervention. Finally, study outcomes should be ones already captured in routine practice; otherwise, funders and investigators should assess the feasibility and cost of data collection.VISUAL ABSTRACT.

Health care-seeking experiences for people who inject drugs with hepatitis C: Qualitative explorations of stigma.

INTRODUCTION: People who inject drugs (PWID) have complex health needs and often experience poor health outcomes. For PWID, intersectional experiences of stigma and other social vulnerabilities may influence their experiences navigating medical care. We conducted a targeted subanalysis of qualitative interview data collected to inform development of a community-pharmacist care model for hepatitis C (HCV) among PWID to explore intersectional influences on health care-seeking experiences. METHODS: The study recruited participants from community organizations in Seattle, Washington, and participants were eligible if they reported injection drug use within 3 months and having HCV. Study staff conducted semi-structured interviews and two independent coders transcribed and initially analyzed them using a Rapid Assessment Process, guided by the Consolidated Framework for Implementation Research. Themes emerged regarding intersections of stigma and social vulnerabilities; thus, we conducted a targeted subanalysis guided by Fundamental Cause Theory and Earnshaw et al.'s Stigma Framework. RESULTS: Forty participants (65% male; 47% non-white) reported multiple social vulnerabilities (e.g., regarding unstable housing and food insecurity). Qualitative analysis identified that receiving health care in the context of social vulnerability is challenging and burdensome (Theme 1); health care interactions are fraught with stigma stemming from intersectional vulnerabilities (Theme 2); and the belief that abstaining from drug use is needed to prove worthiness for care (Theme 3). PWID described experiencing multiple social vulnerabilities (e.g., unmet basic needs) that made seeking health care burdensome. Interactions with health care teams further reinforced participants' feelings of shame about their drug use, which influenced how participants expressed their care preferences and felt heard by providers. And as PWID navigated health care, they felt that their status as an active drug user was used to control and sometimes coerce their access to services, discouraging PWID from seeking needed care. CONCLUSIONS: Stigma and social vulnerabilities play a pervasive and intersecting role in the health care-seeking experiences of PWID and negatively impact their ability to navigate and receive care they need. Evidence-based stigma reduction interventions at multiple levels, coupled with person-centered approaches to care delivery, may help to mitigate negative impacts.

Detection and Response to an HIV Cluster: People Living Homeless and Using Drugs in Seattle, Washington.

INTRODUCTION: The HIV epidemic in King County, Washington has traditionally been highly concentrated among men who have sex with men, and incidence has gradually declined over 2 decades. In 2018, King County experienced a geographically concentrated outbreak of HIV among heterosexual people who inject drugs. METHODS: Data sources to describe the 2018 outbreak and King County's response were partner services interview data, HIV case reports, syringe service program client surveys, hospital data, and data from a rapid needs assessment of homeless individuals and people who inject drugs. In 2020, the authors examined the impact of delays in molecular sequence analyses and cluster member size thresholds, for identifying genetically similar clusters, on the timing of outbreak identification. RESULTS: In 2018, the health department identified a North Seattle cluster, growing to 30 people with related HIV infections diagnosed in 2008-2019. In total, 70% of cluster members were female, 77% were people who inject drugs, 87% were homeless, and 27% reported exchanging sex. Intervention activities included a rapid needs assessment, 2,485 HIV screening tests in a jail and other outreach settings, provision of 87,488 clean syringes in the outbreak area, and public communications. A lower cluster size threshold and more rapid receipt and analyses of data would have identified this outbreak 4-16 months earlier. CONCLUSIONS: This outbreak shows the vulnerability of people who inject drugs to HIV infection, even in areas with robust syringe service programs and declining HIV epidemics. Although molecular HIV surveillance did not identify this outbreak, it may have done so with a lower threshold for defining clusters and more rapid receipt and analyses of HIV genetic sequences.

'Treat my whole person, not just my condition': qualitative explorations of hepatitis C care delivery preferences among people who inject drugs.

BACKGROUND: The advent of direct-acting antivirals (DAAs)-a form of hepatitis C (HCV) treatment associated with shorter treatment course and greater efficacy-offers an unprecedented opportunity to eliminate HCV, but only if care delivery systems are developed to extend treatment to people who inject drugs (PWID). To support the design of a community-pharmacy program, we explored perspectives of PWID with chronic HCV with regard to barriers, motivators, preferences, and prior experiences related to HCV treatment and pharmacists. METHODS: We conducted semi-structured interviews with people living with HCV who reported active injection drug use. Participants were recruited from local community service and clinical organizations in the Seattle, Washington region, and focus groups and interviews were conducted in-person or via phone/video-conference. Rapid Assessment Process was used to analyze qualitative data. Dual coders used structured templates to summarize findings and engaged in iterative review to identify themes. RESULTS: Among the 40 participants, 65% were male, 52.5% were white, and 80% were not stably housed. On average, participants had been injecting drugs for 14 years and living with HCV for 6 years. Analyses revealed 3 themes: (1) limited knowledge regarding HCV and DAA treatments; (2) barriers/motivators for receiving treatment included fear of side effects, prior stigmatizing behaviors from physicians, and desire to protect relatives and the PWID community from HCV transmission; and (3) preferences for HCV care delivery, including a need for person-centered, low-barrier, and collaborative treatment integrated with other care (e.g. primary care and addiction treatment) for PWID. Participants were generally receptive to a community-pharmacy model for HCV treatment, but prior interactions with pharmacists were mixed and there were some concerns expressed that care delivered by pharmacists would not be equivalent to that of physicians. CONCLUSIONS: Even in the direct-acting antivirals era, people who inject drugs still face major barriers to hepatitis C treatment which may be reduced by providing low-barrier points of access for care through pharmacists. Key recommendations for community-pharmacy design included providing care team training to reduce stigma and ensuring care team structures and culture target PWID-specific needs for education and engagement.

Eye movements and the perceived location of phosphenes generated by intracranial primary visual cortex stimulation in the blind.

BACKGROUND: Restoring sight for the blind using electrical stimulation of the visual pathways is feasible but demands an understanding of the spatial mapping of the visual world at the site of targeted stimulation, whether in the retina, thalamus, or cortex. While a visual cortex stimulator can bypass the eye and create visual percepts, there is an inherent dissociation between this stimulation and eye movements. It is unknown whether and how robustly the brain maintains the oculomotor circuitry in patients with bare- or no-light perception. OBJECTIVE: To critically and quantitatively evaluate the effect of eye movements have on phosphene locations elicited by cortical stimulation that bypasses the eyes in order to restore sight in blind subjects. METHODS: The NeuroPace Responsive Neurostimulator (RNS) and the Orion visual cortical prosthesis devices were used to electrically stimulate the visual cortex of blind subjects with bare or no light perception. Eye positions were recorded synchronized with stimulation and the location of the percepts were measured using a handheld marker. RESULTS: The locations of cortical stimulation-evoked percepts are shifted based on the eye position at the time of stimulation. Measured responses can be remapped based on measured eye positions to determine the retinotopic locations associated with the implanted electrodes, with remapped responses having variance limited by pointing error. CONCLUSIONS: Eye movements dominate the perceived location of cortical stimulation-evoked phosphenes, even after years of blindness. By accounting for eye positions, we can mimic retinal mapping as in natural sight.

Glow in the dark: Using a heat-sensitive camera for blind individuals with prosthetic vision.

To date, retinal implants are the only available treatment for blind individuals with retinal degenerations such as retinitis pigmentosa. Argus II is the only visual implant with FDA approval, with more than 300 users worldwide. Argus II stimulation is based on a grayscale image coming from a head-mounted visible-light camera. Normally, the 11°×19° field of view of the Argus II user is full of objects that may elicit similar phosphenes. The prosthesis cannot meaningfully convey so much visual information, and the percept is reduced to an ambiguous impression of light. This study is aimed at investigating the efficacy of simplifying the video input in real-time using a heat-sensitive camera. Data were acquired from four Argus II users in 5 stationary tasks with either hot objects or human targets as stimuli. All tasks were of m-alternative forced choice design where precisely one of the m≥2 response alternatives was defined to be "correct" by the experimenter. To compare performance with heat-sensitive and normal cameras across all tasks, regardless of m, we used an extension of signal detection theory to latent variables, estimating person ability and item difficulty in d' units. Results demonstrate that subject performance was significantly better across all tasks with the thermal camera compared to the regular Argus II camera. The future addition of thermal imaging to devices with very poor spatial resolution may have significant real-life benefits for orientation, personal safety, and social interactions, thereby improving quality of life.

Prosthetic Visual Performance Using a Disparity-Based Distance-Filtering System.

Purpose: At present, Argus II is the only retinal prosthesis approved by the US Food and Drug Administration that induces visual percepts in people who are blind from end-stage outer retinal degenerations such as retinitis pigmentosa. It has been shown to work well in sparse, high-contrast settings, but in daily practice visual performance with the device is likely to be hampered by the cognitive load presented by a cluttered real-world environment. In this study, we investigated the effect of a stereo-disparity-based distance-filtering system on four experienced Argus II users for a range of tasks: object localization, depth discrimination, orientation and size discrimination, and people detection and direction of motion. Methods: Functional vision was assessed in a semicontrolled setup using unfiltered (normal camera) and distance-filtered (stereo camera) imagery. All tasks were forced choice designs and an extension of signal detection theory to latent (unobservable) variables was used to analyze the data, allowing estimation of person ability (person measures) and task difficulty (item measures) on the same axis. Results: All subjects performed better with the distance filter compared with the unfiltered image (P  < 0.001 on all tasks except localization). Conclusions: Our results show that depth filtering using a disparity-based algorithm has significant benefits for people with Argus II implants. Translational Relevance: The improvement in functional vision with the distance filter found in this study may have an important impact on vision rehabilitation and quality of life for people with visual prostheses and ultra low vision.

The use of handheld marker to calibrate a field-programmable gate array based eye tracker for artificial vision system.

Tracking the eye of a blind patient can enhance the usability of an artificial vision system. In systems where the sensing element, i.e. the scene camera that captures the visual information, is mounted on the patient's head, the user must use head scanning in order to steer the line of sight of the implant to the region of interest. Integrating an eye tracker in the prosthesis will enable scanning using eye movements. The eye position will set the region of interest within the wide field-of-view of the scene camera. An essential requirement of an eye tracker is the need to calibrate it. Obviously, off-the-shelf calibration methods that require looking at known points in space cannot be used with blind users.Here we tested the feasibility of calibrating the eye-tracker based on pupil position and the location of the percept reported by the implant recipient, using a handheld marker. Pupil positions were extracted using custom image processing in a field-programmable-gate-array built into a glasses-mounted eye tracker. In the calibration process, electrodes were directly stimulated and the subject reported the location of the percept using a handheld marker. Linear regression was used to extract the transfer function from pupil position to gaze direction in the coordinates of the scene camera.In using the eye tracker with the proposed calibration method, patients demonstrated improved precision on a localization task with corresponding reduction of head movements.

Eye Movement Control in the Argus II Retinal-Prosthesis Enables Reduced Head Movement and Better Localization Precision.

Purpose: Visual scanning by sighted individuals is done using eye and head movements. In contrast, scanning using the Argus II is solely done by head movement, since eye movements can introduce localization errors. Here, we tested if a scanning mode utilizing eye movements increases visual stability and reduces head movements in Argus II users. Methods: Eye positions were measured in real-time and were used to shift the region of interest (ROI) that is sent to the implant within the wide field of view (FOV) of the scene camera. Participants were able to use combined eye-head scanning: shifting the camera by moving their head and shifting the ROI within the FOV by eye movement. Eight blind individuals implanted with the Argus II retinal prosthesis participated in the study. A white target appeared on a touchscreen monitor and the participants were instructed to report the location of the target by touching the monitor. We compared the spread of the responses, the time to complete the task, and the amount of head movements between combined eye-head and head-only scanning. Results: All participants benefited from the combined eye-head scanning mode. Better precision (i.e., narrower spread of the perceived location) was observed in six out of eight participants. Seven of eight participants were able to adopt a scanning strategy that enabled them to perform the task with significantly less head movement. Conclusions: Integrating an eye tracker into the Argus II is feasible, reduces head movements in a seated localization task, and improves pointing precision.

Hand-Camera Coordination Varies over Time in Users of the Argus(®) II Retinal Prosthesis System.

INTRODUCTION: Most visual neuroprostheses use an external camera for image acquisition. This adds two complications to phosphene perception: (1) stimulation locus will not change with eye movements; and (2) external cameras can be aimed in directions different from the user's intended direction of gaze. Little is known about the stability of where users perceive light sources to be or whether they will adapt to changes in camera orientation. METHODS: Three end-stage retinitis pigmentosa patients implanted with the Argus II participated in this study. This prosthesis stimulated the retina based on an 18° × 11° area selected within the camera's 66° × 49° field of view. The center of the electrode array's field of view mapped within the camera's field of view is the camera alignment position (CAP). Proper camera alignments minimize errors in localizing visual percepts in space. Subjects touched single white squares in random locations on a darkened touchscreen 40 or more times. To study adaptation, subjects were given intentional CAP misalignments of 15-40° for 5-6 months. Subjects performed this test with auditory feedback during (bi-)weekly lab sessions. Misaligned CAPs were maintained for another 5-6 months without auditory feedback. Touch alignment was tracked to detect any adaptation. To estimate localization stability, data for when CAPs were set to minimize errors were tracked. The same localization test as above was used. Localization errors were tracked every 1-2 weeks for up to 40 months. RESULTS: Two of three subjects used auditory feedback to improve accuracy with misaligned CAPs at an average rate of 0.02°/day (p < 0.05, bootstrap analysis of linear regression). The rates observed here were ~4000 times slower than those seen in normally-sighted subjects adapting to prism glasses. Removal of auditory feedback precipitated error increases for all subjects. Optimal CAPs varied significantly across test sessions (p < 10(-4), bootstrap multivariate analysis of variance (MANOVA)), up to 21-29° within subjects over the observed period. Across subjects, optimal CAPs showed an average rate of change of 0.39°/day (SD 0.36°/day). CONCLUSIONS: Optimal CAPs varied dramatically over time for all subjects. Subjects displayed no adaptation to misaligned CAPs without feedback. Regular recalibration of CAPs may be required to maintain hand-camera coordination.

Variability and Errors of Manually Digitized Goldmann Visual Fields.

PURPOSE: Goldmann visual fields (GVFs) are useful for tracking changes in areas of functional retina, including the periphery, in inherited retinal degeneration patients. Quantitative GVF analysis requires digitization of the chart coordinates for the main axes and isopter points marked by the GVF operator during testing. This study investigated inter- and intra-digitizer variability among users of a manual GVF digitization program. METHODS: Ten digitizers were trained for 1 hour, then digitized 23 different GVFs from inherited retinal degeneration patients in each of three testing blocks. Digitizers labeled each isopter as seeing or non-seeing, and its target size. Isopters with the same test target within each GVF were grouped to create isopter groups. RESULTS: The standard deviation of isopter group area showed an approximate square-root relationship with total isopter group area. Accordingly, the coefficient of variation for isopter group area decreased from 68% to 0.2% with increasing isopter group area. A bootstrap version of ANOVA did not reveal a significant effect of digitizers on isopter group area. Simulations involving random sampling of digitizers showed that five to seven digitizers would be required to catch 95% to 99% of labeling errors and isopter misses, on the basis of data discrepancies, with 99% probability. CONCLUSIONS: These data suggest that any minimally trained digitizer would be capable of reliably determining any isopter area, regardless of size. Studies using this software could either use five to seven minimally trained digitizers for each GVF, three digitizers who demonstrate low frequencies of errors on a practice set of GVFs, or two digitizers with an expert reader to adjudicate discrepancies and catch errors.

Electrically evoked electroretinograms and pupil responses in Argus II retinal implant wearers.

PURPOSE: We have recorded the electrically evoked electroretinogram (eERG) and flash ERG in Argus II retinal prosthesis wearers with end-stage retinitis pigmentosa to estimate response properties of the degenerated inner retina to local electrical stimulation. In addition, we have recorded pupil diameters during electrical stimulation. METHODS: Raw corneal eERGs were recorded at multiple stimulus levels in three subjects. eERG signals were heavily contaminated with various artifacts, including switching artifacts generated by the implant electronics, stimulus, blink, and eye-movement artifacts. Pupil responses were recorded in one subject using a pupil tracker. RESULTS: eERGs were decontaminated by a variety of techniques, including wavelet transformation and response averaging. The dominant component was a negative wave peaking at approximately 200 ms. eERG amplitudes correlated significantly with stimulus level, but peak latencies did not correlate with stimulus level. Pupil constriction correlated significantly with stimulus level and pupil responses could be accurately used to estimate subjective threshold. CONCLUSION: eERG recordings hold the potential to be developed further for use as a diagnostic tool for retinal implants. A straightforward approach to increase eERG amplitudes would be the development of intraocular recording methods based on reverse telemetry. The robust pupil response to electrical stimulation in one subject indicates that pupillography can be exploited to assess implant functionality, but reliable pupil recordings could not be obtained in all subjects.

Intra-session test-retest reliability of magnitude and structure of center of pressure from the Nintendo Wii Balance Board™ for a visually impaired and normally sighted population.

Individuals with visual impairment (VI) have irreparable damage to one of the input streams contributing to postural stability. Here, we evaluated the intra-session test-retest reliability of the Wii Balance Board (WBB) for measuring Center of Pressure (COP) magnitude and structure, i.e. approximate entropy (ApEn) in fourteen legally blind participants and 21 participants with corrected-to-normal vision. Participants completed a validated balance protocol which included four sensory conditions: double-leg standing on a firm surface with eyes open (EO-firm); a firm surface with eyes closed (EC-firm); a foam surface with EO (EO-foam); and a foam surface with EC (EC-foam). Participants performed the full balance protocol twice during the session, separated by a period of 15min, to determine the intraclass correlation coefficient (ICC). Absolute reliability was determined by the standard error of measurement (SEM). The minimal difference (MD) was estimated to determine clinical significance for future studies. COP measures were derived from data sent by the WBB to a laptop via Bluetooth. COP scores increased with the difficulty of sensory condition indicating WBB sensitivity (all p<0.01). ICCs in the VI group ranged from 0.73 to 0.95, indicating high to very high correlations, and the normal group showed moderate to very high ICCs (0.62-0.94). The SEM was comparable between groups regardless of between-subject variability. The reliability of the WBB makes it practical to screen for balance impairment among VI persons.