Evaluation and Optimization of Diabetic Retinopathy Screenings for Uninsured Latinx Patients in a Resource-Limited Student-Run Free Clinic.

Background: Diabetic retinopathy (DR) is a sight-threatening condition that causes progressive retina damage. Student-run free clinics represent a valuable opportunity to provide DR screenings to high-risk populations. We characterized the patient population, evaluated the performance, and conducted a needs assessment of DR screenings at the University of California, San Diego Student-Run Ophthalmology Free Clinic, which provides care to predominantly uninsured, Latino patients. Methods: Retrospective chart review was conducted of all patients seen at the free clinic since 2019 with a diagnosis of type II diabetes. Date and outcome of all DR-related screenings or visits from 2015 onward, demographics information, and DR risk factors such as A1c and insulin dependence were recorded. Predictors of diabetic retinopathy and frequency of DR screenings for each patient were analyzed using multiple logistic regression, t-test for equality of means, and Pearson's correlation. Results: Of 179 uninsured diabetic patients receiving care at the free clinic, 71% were female and average age was 59. 83% had hypertension, 93% had hyperlipidemia, and 79% had metabolic syndrome. Prevalence of non-proliferative DR was 34% and that of proliferative DR was 15% in diabetic patients. The free clinic capacity in recent years plateaued at just under 50% of patients seen for DR screening or visit per year, though average wait time was over 2 years between visits. Patients with higher no-show rates had less frequent DR screenings. Chronic kidney disease and poor glycemic control were the strongest predictors of DR. Conclusion: The student-run free ophthalmology clinic has been effective in providing screening and follow-up care for DR patients. Creation of a protocol to identify which patients are at highest risk of DR and should be seen more urgently, addressing no-shows, and implementation of a tele-retina program are potential avenues for improving clinic efficiency in a resource-limited setting for vulnerable populations.

Usability and Clinician Acceptance of a Deep Learning-Based Clinical Decision Support Tool for Predicting Glaucomatous Visual Field Progression.

PRCIS: We updated a clinical decision support tool integrating predicted visual field (VF) metrics from an artificial intelligence model and assessed clinician perceptions of the predicted VF metric in this usability study. PURPOSE: To evaluate clinician perceptions of a prototyped clinical decision support (CDS) tool that integrates visual field (VF) metric predictions from artificial intelligence (AI) models. METHODS: Ten ophthalmologists and optometrists from the University of California San Diego participated in 6 cases from 6 patients, consisting of 11 eyes, uploaded to a CDS tool ("GLANCE", designed to help clinicians "at a glance"). For each case, clinicians answered questions about management recommendations and attitudes towards GLANCE, particularly regarding the utility and trustworthiness of the AI-predicted VF metrics and willingness to decrease VF testing frequency. MAIN OUTCOMES AND MEASURES: Mean counts of management recommendations and mean Likert scale scores were calculated to assess overall management trends and attitudes towards the CDS tool for each case. In addition, system usability scale scores were calculated. RESULTS: The mean Likert scores for trust in and utility of the predicted VF metric and clinician willingness to decrease VF testing frequency were 3.27, 3.42, and 2.64, respectively (1=strongly disagree, 5=strongly agree). When stratified by glaucoma severity, all mean Likert scores decreased as severity increased. The system usability scale score across all responders was 66.1±16.0 (43rd percentile). CONCLUSIONS: A CDS tool can be designed to present AI model outputs in a useful, trustworthy manner that clinicians are generally willing to integrate into their clinical decision-making. Future work is needed to understand how to best develop explainable and trustworthy CDS tools integrating AI before clinical deployment.

Detection of Nonglaucomatous Macula Findings With Ganglion Cell Analysis Printouts vs Full Macular Cube Scans.

Importance: Ganglion cell analysis (GCA) of ocular coherence tomography (OCT) imaging is routinely used to detect and monitor glaucomatous damage of the ganglion cell complex in the macula. The GCA printout provides qualitative and quantitative data about the macular ganglion cell-inner plexiform layer and a single B-scan of the retina through the fovea. However, the full macular cube scan, including all 128 B-scans, is available for review. The macular cube scan provides considerable information about nonglaucomatous ocular pathology that may be missed if clinicians review only the GCA printout. Objective: To determine the frequency and type of nonglaucomatous macular findings that are observable in the full macular cube scan but not the GCA printout. Design, Setting, and Participants: A retrospective cross-sectional analysis of GCA printouts and full macular cube scans to detect nonglaucomatous macular pathology at a tertiary care academic center. Consecutive patients undergoing ganglion cell complex imaging during routine glaucoma evaluations over a 1-week period in a multi-clinician glaucoma clinic. Main Outcomes and Measures: The prevalence and type of nonglaucomatous macular pathology visible on the GCA printout or macular cube scan. Results: Among 105 patients (mean (SD) age, 67 (15.46) years; 63 [60%] female and 42 [40%] male) 201 eyes were imaged (64 [31.7%] with suspected glaucoma, 126 [62.4%] with open-angle glaucoma, 6 [3.0%] with closed-angle glaucoma, and 6 [3.0%] with other glaucoma). GCA printouts and macular cube scans revealed nonglaucomatous macular pathology in 65 eyes (32.2%). Of these, 25 eyes (38.5%) included findings that were not visible on the GCA printout. Of the cases not visible on the printout, 16 eyes (64.0% ) included macular pathology that required further evaluation. Conclusions and Relevance: The findings indicate that nonglaucomatous macular pathology may be missed based on GCA printouts alone. While it may be beneficial to review the full macular cube to detect potentially vision-threatening disease and ensure proper patient care, this study cannot determine if this missed pathology affects clinical outcomes.

Dry Eye Symptom Severity and Visual Field Reliability Metrics.

PRCIS: Tracking failure frequency (TFF) increases with dry eye symptom severity and in the left eye. PURPOSE: Symptoms of dry eye disease are commonly encountered in glaucoma patients and can be exacerbated by topical glaucoma medications. Dry eye disease may influence the reliability of visual field (VF) tests and impact the accurate interpretation of the results. PATIENTS AND METHODS: Patients at the Veterans Administration Medical Center San Diego completed the 5-item Dry Eye Questionnaire before VF testing between December 2018 and February 2019. VF reliability metrics were recorded for each patient. Standard reliability metrics included fixation losses, false positive, and false negative rates. Gaze tracking (GT) metrics included percent of stimuli with gaze deviations between 1 and 2 degrees, 3 and 5 degrees, 6 degrees or greater, and percent of stimuli with tracking failure (TFF). The use of glaucoma medications and artificial tears was also recorded. RESULTS: A total of 494 patients completed the 5-item Dry Eye Questionnaire and VF testing. There was no association between dry eye symptom severity and standard reliability metrics or most GT metrics. However, TFF increased as dry eye symptom severity increased (P=0.015). TFF was also greater in the left eye, which was tested second (P=0.012); no other reliability metrics were related to laterality. Patients were more likely to use artificial tears with increased dry eye symptom severity (P<0.001), but there was no relationship between symptom severity and glaucoma medication use. DISCUSSION: Dry eye symptom severity may influence the acceptable range or threshold of TFF when using GT metrics to determine VF reliability. Likewise, the acceptable range or threshold for TFF may be different between eyes.

Association of Visual Field Pattern Reversal with Paracentral Visual Field Loss.

PURPOSE: Visual field (VF) results that show more test points outside normal limits on the pattern deviation map than on the total deviation map have been assumed to be evidence of unreliable VF results. We propose the term pattern reversal to describe this VF finding and explore its association with paracentral loss. DESIGN: Retrospective cohort and case-control studies. PARTICIPANTS: Glaucoma and glaucoma suspect patients who completed VF testing in Veteran's Affairs ophthalmology or optometry clinics. METHODS: In the cohort study, VF results were included that demonstrated pattern reversal. The area of pattern reversal was categorized as peripheral, paracentral, or mixed (both peripheral and paracentral). In the case-control study, a group of patients with paracentral loss confirmed on 10-2 VF tests were compared with a control group whose VF results were without paracentral loss. MAIN OUTCOME MEASURES: In the cohort study, the calculated false-positive (FP) error rates were compared among groups categorized by area of pattern reversal. In the case-control study, the rates of pattern reversal were compared between patients with and without paracentral loss. RESULTS: Two hundred seventeen eyes of 145 patients were included in the cohort study. Visual field results with pattern reversal and mixed loss had significantly higher FP rates compared with those with paracentral or peripheral loss only (16.25% vs. 6.26% and 8.15%, respectively; P < 0.001). Fifty-five eyes of 41 patients were included in the case group and 55 eyes of 41 patients were included in the control group. Patients with paracentral loss were more likely to have history of pattern reversal compared with those without paracentral loss (58.2% vs. 29.1%; P = 0.004). Twelve eyes with paracentral loss had 24-2 VF results that showed defects on the pattern deviation map, but not on the total deviation map. CONCLUSIONS: Pattern reversal may be associated with paracentral VF loss and is not always associated with elevated FP rates.

Qualitative Evaluation of the 10-2 and 24-2 Visual Field Tests for Detecting Central Visual Field Abnormalities in Glaucoma.

PURPOSE: To examine whether glaucomatous central visual field abnormalities can be more effectively detected using a qualitative, expert evaluation of the 10-2 test compared with the topographically corresponding central 12 locations of the 24-2 test (C24-2). DESIGN: Cross-sectional study. METHODS: Eyes with a glaucomatous optic nerve appearance or ocular hypertension (n = 523) and healthy eyes (n = 107) were included as cases and control subjects, respectively. The 10-2 and C24-2 visual field results of all eyes were graded by 4 glaucoma specialists for the probability that central visual field abnormalities were present. RESULTS: The sensitivity of the 10-2 and C24-2 tests for detecting the cases at 95% specificity were not significantly different (e.g., 32.2% and 31.4%, respectively, for grader 1, P = .87; all graders P ≥ .25). At 95% specificity, the pattern standard deviation values from these tests had a similar sensitivity to the qualitative evaluation for the C24-2 test for all graders (P ≥ .083), but it had a significantly higher sensitivity than the qualitative evaluation for the 10-2 test for 3 graders (P ≤ .016). CONCLUSIONS: The similarity in performance of the 10-2 and C24-2 test suggests that the increased sampling density of the former does not significantly improve the detection of central visual field abnormalities, even when based on expert assessment. These findings should not be taken to mean that the 10-2 test is not useful, but it underscores the need for its utility to be clearly established before incorporating it as routine glaucoma standard of care.

Promoting Quality Face-to-Face Communication during Ophthalmology Encounters in the Electronic Health Record Era.

OBJECTIVE: To evaluate informatics-enabled quality improvement (QI) strategies for promoting time spent on face-to-face communication between ophthalmologists and patients. METHODS: This prospective study involved deploying QI strategies during implementation of an enterprise-wide vendor electronic health record (EHR) in an outpatient academic ophthalmology department. Strategies included developing single sign-on capabilities, activating mobile- and tablet-based applications, EHR personalization training, creating novel workflows for team-based orders, and promoting problem-based charting to reduce documentation burden. Timing data were collected during 648 outpatient encounters. Outcomes included total time spent by the attending ophthalmologist on the patient, time spent on documentation, time spent on examination, and time spent talking with the patient. Metrics related to documentation efficiency, use of personalization features, use of team-based orders, and note length were also measured from the EHR efficiency portal and compared with averages for ophthalmologists nationwide using the same EHR. RESULTS: Time spent on exclusive face-to-face communication with patients initially decreased with EHR implementation (2.9 to 2.3 minutes, p = 0.005) but returned to the paper baseline by 6 months (2.8 minutes, p = 0.99). Observed participants outperformed national averages of ophthalmologists using the same vendor system on documentation time per appointment, number of customized note templates, number of customized order lists, utilization of team-based orders, note length, and time spent after-hours on EHR use. CONCLUSION: Informatics-enabled QI interventions can promote patient-centeredness and face-to-face communication in high-volume outpatient ophthalmology encounters. By employing an array of interventions, time spent exclusively talking with the patient returned to levels equivalent to paper charts by 6 months after EHR implementation. This was achieved without requiring EHR redesign, use of scribes, or excessive after-hours work. Documentation efficiency can be achieved using interventions promoting personalization and team-based workflows. Given their efficacy in preserving face-to-face physician-patient interactions, these strategies may help alleviate risk of physician burnout.

Review of the measurement and management of 24-hour intraocular pressure in patients with glaucoma.

Elevated intraocular pressure (IOP) is a major, and currently the only, modifiable risk factor that has been shown to reduce the risk of glaucoma onset and progression. Diurnal measurements of IOP, usually during office hours, are commonly used for the assessment of IOP variation and the relative success of medical, laser, or surgical IOP-lowering interventions. Such measurements, however, fail to capture variation in IOP over the day/night cycle, which may be influenced by factors such as body position. We examine current evidence in the field of IOP measurement and control-with a focus on 24-hour (circadian) study design and measurement techniques and the 24-hour efficacy of current treatments-in patients with glaucoma and ocular hypertension. We then provide our recommendations for the design of future studies of circadian IOP with the aim of improving the assessment, management, and treatment of patients with glaucoma and ocular hypertension.

Hypotony Keratopathy Following Trabeculectomy.

PRECIS: Hypotony keratopathy is a potential complication of hypotony following trabeculectomy and successful treatment depends on increasing intraocular pressure (IOP). PURPOSE: To evaluate corneal decompensation in patients following trabeculectomy with adjuvant mitomycin C (MMC). We propose "hypotony keratopathy" as a descriptive term. METHODS: Patients with trabeculectomy and follow-up performed by the authors were included in this retrospective single-center study. Patients were included if they had evidence of corneal decompensation (Descemet membrane folds or corneal edema) the following trabeculectomy with MMC with concurrent hypotony. Outcome measures included best-corrected visual acuity, average IOP at time of diagnosis, and changes in central corneal thickness. Clinical outcomes for the treatment of hypotony keratopathy were noted when performed. RESULTS: A total of 14 eyes from 12 patients were included in the series. Hypotony developed an average of 5 years after trabeculectomy, and hypotony keratopathy was diagnosed 7.5 years after trabeculectomy. Hypotony keratopathy ranged from nonvisually significant Descemet membrane fold without increased corneal thickness to visually significant corneal edema. Best-corrected visual acuity decreased 0 to 6 Snellen lines after diagnosis of hypotony keratopathy. Lower IOP was associated with increased corneal thickness. Vision improved after trabeculectomy revision (6 eyes) and cataract extraction with an intraocular lens implant (1 eye) but did not improve after Descemet stripping automated endothelial keratoplasty (2 eyes). CONCLUSIONS: Hypotony keratopathy is a poorly described but potentially treatable complication of trabeculectomy with MMC. Hypotony keratopathy may be related to endothelial dysfunction secondary to hypotony.

Peripheral Vaso-Occlusive Events Following Trauma in Patients With Sickle Cell Trait.

Sickle cell trait (SCT) is a common hemoglobin variant, particularly in patients of African descent. Patients with SCT have an increased risk of adverse ocular events following trauma with subsequent elevated intraocular pressure (IOP). The authors describe three cases of young males with peripheral vaso-occlusive events following ocular trauma with subsequent elevated IOP. These cases demonstrate the importance of careful peripheral exams in young patients with SCT following trauma. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:e84-e87.].

Time Requirements of Paper-Based Clinical Workflows and After-Hours Documentation in a Multispecialty Academic Ophthalmology Practice.

PURPOSE: To assess time requirements for patient encounters and estimate after-hours demands of paper-based clinical workflows in ophthalmology. DESIGN: Time-and-motion study with a structured survey. METHODS: This study was conducted in a single academic ophthalmology department. A convenience sample consisted of 7 attending ophthalmologists from 6 subspecialties observed during 414 patient encounters for the time-motion analysis and 12 attending ophthalmologists for the survey. Outcome measurements consisted of total time spent by attending ophthalmologists per patient and time spent on documentation, examination, and talking with patients. The survey assessed time requirements of documentation-related activities performed outside of scheduled clinic hours. RESULTS: Among the 7 attending ophthalmologists observed (6 men and 1 woman), mean ± SD age 43.9 ± 7.1 years, during encounters with 414 patients (57.8 ± 24.6 years of age), total time spent per patient was 8.1 ± 4.8 minutes, with 2.8 ± 1.4 minutes (38%) for documentation, 1.2 ± 0.9 minutes (17%) for examination, and 3.3 ± 3.1 minutes (37%) for talking with patients. New patient evaluations required significantly more time than routine follow-up visits and postoperative visits. Higher clinical volumes were associated with less time per patient. Survey results indicated that paper-based documentation was associated with minimal after-hours work on weeknights and weekends. CONCLUSIONS: Paper-based documentation takes up a substantial portion of the total time spent for patient care in outpatient ophthalmology clinics but is associated with minimal after-hours work. Understanding paper-based clinical workflows may help inform targeted strategies for improving electronic health record use in ophthalmology.

Impact of Electronic Health Record Implementation on Ophthalmology Trainee Time Expenditures.

OBJECTIVE: Electronic health records (EHRs) are widely adopted, but the time demands of EHR use on ophthalmology trainees are not well understood. This study evaluated ophthalmology trainee time spent on clinical activities in an outpatient clinic undergoing EHR implementation. DESIGN: Prospective, manual time-motion observations of ophthalmology trainees in 2018. PARTICIPANTS: Eleven ophthalmology residents and fellows observed during 156 patient encounters. METHODS: Prospective time-motion study of ophthalmology trainees 2 weeks before and 6 weeks after EHR implementation in an academic ophthalmology department. Manual time-motion observations were conducted for 11 ophthalmology trainees in 6 subspecialty clinics during 156 patient encounters. Time spent documenting, examining, and talking with patients were recorded. Factors influencing time requirements were evaluated using linear mixed effects models. MAIN OUTCOME MEASURES: Total time spent by ophthalmology residents and fellows per patient, time spent on documentation, examination, and talking with patients. RESULTS: Seven ophthalmology residents and four ophthalmology fellows with mean (standard deviation) postgraduate year of 3.7 (1.2) were observed during 156 patient encounters. Using paper charts, mean total time spent on each patient was 11.6 (6.5) minutes, with 5.4 (3.5) minutes spent documenting (48%). After EHR implementation, mean total time spent on each patient was 11.8 (6.9) minutes, with 6.8 (4.7) minutes spent documenting (57%). Total time expenditure per patient did not significantly change after EHR implementation (+0.17 minutes, 95% confidence interval [CI] for difference in means: -2.78, 2.45; p = 0.90). Documentation time did not change significantly after EHR implementation in absolute terms (+1.42 minutes, 95% CI: -3.13, 0.29; p = 0.10), but was significantly greater as a proportion of total time (48% on paper to 57% on EHR; +9%, 95% CI: 2.17, 15.83; p = 0.011). CONCLUSION: Total time spent per patient and absolute time spent on documentation was not significantly different whether ophthalmology trainees used paper charts or the recently implemented EHR. Percentage of total time spent on documentation increased significantly with early EHR use. Evaluating EHR impact on ophthalmology trainees may improve understanding of how trainees learn to use the EHR and may shed light on strategies to address trainee burnout.

Evaluating Self-Refraction and Ready-Made Spectacles for Treatment of Uncorrected Refractive Error.

PURPOSE: Uncorrected refractive error is the leading cause of visual impairment worldwide and has significant quality of life and economic implications. Treatment with subjective refraction and custom-made spectacles requires expensive equipment and highly trained personnel. We examine several alternatives. METHODS: Patients were taught to self-refract using two devices: AdSpecs and the I-test Vision Screener. Ready-made spectacles were fit to the self-refraction and visual acuity (VA) was measured. Donated-spectacles were fit to subjective refraction and VA was measured. Self-refraction and donated spectacles spherical equivalent (SE) and VA were compared to subjective refraction SE and VA. RESULTS: About 57 patients (102 eyes) were enrolled in the study. Patients accurately determined refractive power with self-refraction by both AdSpecs and the I-test (compared to subjective refraction SE, r2 = 0.97 and r2 = 0.94, respectively). SE of donated spectacles fit well with self-refraction SE (r2 = 0.91). There was no significant difference between best-corrected VA by subjective refraction and VA treated by ready-made spectacles fit to self-refraction by either device (analysis of variance (ANOVA), p non-significant). Patients fit with donated spectacles had significantly worse VA than best-corrected VA by subjective refraction (ANOVA, p < 0.01), although 80% improved to >20/40. CONCLUSION: Patients accurately self-refract using both devices and ready-made spectacles fit to self-refraction have excellent visual outcomes. Donated spectacles have worse visual outcomes but might be useful in a subset of patients. Ready-made spectacles fit to self-refraction may provide a treatment alternative to uncorrected refractive error.

Will Perimetry Be Performed to Monitor Glaucoma in 2025?

Visual field testing has played an essential role in the diagnosis and management of glaucoma for more than a century. Methods to examine the visual field have been refined from early kinetic perimetry to current standard automated perimetry (SAP). Clinicians now use SAP for the diagnosis and management of glaucoma throughout the world. Various testing paradigms and analytic methods have been developed to simplify the diagnosis of glaucoma and the interpretation of progression. Moreover, strategies have been implemented to improve patient experience with visual field testing and to increase reliability. Objective functional tests, such as electroretinography, provide an alternative to subjective visual field testing but are not yet ready for widespread adoption. Standard automated perimetry is being adapted and improved constantly. New devices may allow patients to complete visual field tests at home, which could relieve patients and clinicians from in-office testing and allow for more frequent examinations. Glaucoma detection and progression analysis also are incorporating progressively more information and will be improved as deep learning strategies are applied. Finally, perimetric and structural testing likely will become more closely intertwined as testing platforms and progression analysis incorporate both of these measures. Visual field testing will continue to have an important role in the diagnosis and management of glaucoma.

Structural correlation between the nerve fiber layer and retinal ganglion cell loss in mice with targeted disruption of the Brn3b gene.

PURPOSE: Mice with a targeted disruption of Brn3b (knockout Brn3b(-/-)) undergo the loss of a majority of retinal ganglion cells (RGCs) before birth. Spectral domain optical coherence tomography (SD-OCT) allows for the noninvasive examination of Brn3b(-/-) cellular loss in vivo. METHODS: The central retinas of Brn3b(-/-) and phenotypically wild-type (Brn3b(+/+) and Brn3b(±)) mice were imaged by SD-OCT. The combined nerve fiber layer (NFL) and inner plexiform layer (IPL) were manually segmented and thickness maps were generated. The results were confirmed by histologic and immunofluorescence cell counts of the RGC layer (RGCL) of the same retinas. RESULTS: The combined NFL and IPL of the Brn3b(-/-) retinas were significantly thinner, and the histologic cell counts significantly lower, than those of the phenotypically wild-type retinas (paired t-test; P < 0.01 and P < 0.01, respectively). The combined NFL and IPL thickness and the histologic cell count correlated highly (R(2) = 0.9612). Immunofluorescence staining revealed significant RGC-specific loss in Brn3b(-/-) retinas (paired t-test; P < 0.01). The distribution of combined central NFL and IPL loss was not localized or sectorial. CONCLUSIONS: The strong correlation between the combined layer thickness and histologic cell counts validates manual OCT segmentation as a method of monitoring cell loss in the RGCL. A retinal thickness map assessed if combined NFL and IPL thickness loss in Brn3b(-/-) eyes was topographically specific. Generalized RGC and combined NFL and IPL loss was observed in the Brn3b(-/-) retinas, in contrast to topographically specific RGC loss observed in glaucomatous DBA2/J eyes.

Vesicular glutamate transporter 3 in age-dependent optic neuropathy.

PURPOSE: To determine retinal vesicular glutamate transporter 3 (VGLUT3) expression alterations in a mouse model of progressive optic neuropathy (glaucoma). METHODS: Tissue specimens were obtained from age-matched DBA/2J and control C57BL/6J mice for western blot analysis. Enucleated globes from DBA/2J, C57BL/6J, and BALB/cJ mice were fixed in formalin, paraffin-embedded, and sectioned for VGLUT3 protein localization. RESULTS: western blot analysis of the control retinas revealed the expression of a ~55 kDa immunoreactive VGLUT3 protein that is to be expected in tissues such as retina, brain, liver, heart, and kidney tissue, but not in intestinal or lung tissue. Furthermore, a strong ~130 kDa immunoreactive VGLUT3 isoform that is restricted to the central nervous system (the brain and retinas) was also identified in the controls, but was not detected in the DBA/2J retinas. Immunofluorescence microscopy showed a lack of VGLUT3 expression in the synapses between amacrine and retinal ganglion cells in DBA/2J retinas, in contrast to its strong expression in the C57BL/6J and BALB/cJ controls. CONCLUSIONS: Our results implicate the dysregulated expression of a central nervous system-specific VGLUT3 isoform as a predisposing factor in the development of optic neuropathy in DBA/2J mice, a spontaneous mouse model of glaucoma. In striking parallel to the visual system defects of glaucomatous DBA/2J mice, the inner ear of VGLUT3 knockout mice displays a progressive loss of inner hair cell to spiral-ganglion neuron synapses. A significant reduction in the number of spiral-ganglion neurons leads to age-associated deafness. Thus, we propose that the absence of this biochemically uncharacterized 130 kDa VGLUT3 isoform in the DBA/2J retina is a predisposing factor in synaptic instability, and a contributing factor in the age-dependent and progressive loss of ganglion cells projecting to the brain.

PapR peptide maturation: role of the NprB protease in Bacillus cereus 569 PlcR/PapR global gene regulation.

The global transcriptional regulator PlcR controls gene expression in Bacillus cereus and Bacillus thuringiensis. Activity of PlcR is regulated by PapR, the product of an ORF located immediately downstream of plcR. To be active in B. cereus, PapR must be secreted and then processed to the mature peptide by an unknown protease. This peptide is transported by an oligopeptide permease into the cell, where it activates PlcR. In this study, we show that the neutral protease B (NprB) secreted by B. cereus 569 is required for extracellular PapR maturation. Purified recombinant NprB processed the synthetic PapR propeptide to produce a set of peptides derived from the C-terminal domain of PapR. Supplementation of growth media with synthetic PapR-derived C-terminal 5-, 7-, 8- and 27-amino acid (aa) peptides caused activation of intracellular PlcR in a PapR-deficient strain of B. cereus 569 while only the 5- and 7-aa peptides activated PlcR in a nprB mutant. The maximum activity was found for the 7-mer peptide. However, even the 7-mer peptide could not activate PlcR with a C-terminal truncation of as few as 6 aa. This indicates that interactions of the C-terminal regions of both PlcR and PapR are important in transcriptional activation of the B. cereus 569 PlcR regulon.