Natural history of adenoviral conjunctivitis in a US-based population: Viral load, signs, and symptoms.

PURPOSE: To report the clinical signs, symptoms, and viral clearance in individuals in the United States with adenoviral conjunctivitis (Ad-Cs). METHODS: Individuals ≥ 18 years presenting within 4 days of symptoms of Ad-Cs who met eligibility criteria and tested positive with both point-of-care immunoassay antigen and quantitative polymerase chain reaction (qPCR) testing were enrolled. Patient-reported symptoms, clinician-graded signs, and qPCR viral titers were collected at baseline, days 1-2, 4 (days 3-5), 7 (days 6-10), 14 (days 11-17) and 21 (days 18-21). RESULTS: There was no detectable viral titers by the day 14 visit in 6/8 patients. By day 21, there was no detectable viral titers in the 7 participants who completed the visit; however, signs and symptoms persisted including: blurry vision (5/7), discomfort (2/7) or redness (1/7). Masked clinicians also noted conjunctival redness (4/7), follicular conjunctivitis (4/7) and bulbar edema (3/7). CONCLUSION: Many patient-reported symptoms and clinical signs persist after viral titers are no longer detectable by qPCR. Using clinical signs and symptoms to determine quarantine duration may result in patients being furloughed longer than the time that the patient is infectious.

The association between pupillary responses and axial length in children differs as a function of season.

The association between pupillary responses to repeated stimuli and adult refractive error has been previously demonstrated. This study evaluated whether this association exists in children and if it varies by season. Fifty children aged 8-17 years (average: 11.55 ± 2.75 years, 31 females) with refractive error between + 1.51 and - 5.69 diopters (non-cycloplegic) participated (n = 27 in summer, and n = 23 in winter). The RAPDx pupilometer measured pupil sizes while stimuli oscillated between colored light and dark at 0.1 Hz in three sequences: (1) alternating red and blue, (2) red-only, and (3) blue-only. The primary outcome was the difference in pupillary responses between the blue-only and red-only sequences. Pupillary constriction was greater in response to blue light than to red for those with shorter eyes in summer (ß = - 9.42, P = 0.034) but not in winter (ß = 3.42, P = 0.54). Greater constriction comprised faster pupillary escape following red light onset and slower redilation following stimulus offset of both colors (P = 0.017, 0.036, 0.035 respectively). The association between axial length and children's pupillary responses in summer, but not winter may be explained by greater light-associated release of retinal dopamine in summer. Shorter eyes' more robust responses are consistent with greater light exposure inhibiting axial elongation and reducing myopia risk.

Correlation of Adenoviral Titers with Severity of Adenoviral Conjunctivitis and Time to Viral Clearance for 21 Days.

SIGNIFICANCE: This investigation reports the correlation of conjunctival viral titers in adenoviral conjunctivitis with patient-reported symptoms and clinician-graded signs for 21 days of follow-up. PURPOSE: Adenoviral conjunctivitis is a highly contagious viral eye infection with significant morbidity and economic impact. This study investigates whether severity of signs and symptoms and time to viral clearance are correlated with conjunctival viral titers at baseline and during 21 days of follow-up. METHODS: The Reducing Adenoviral Patient Infected Days study was a pilot study of the efficacy of a single in-office administration of ophthalmic 5% povidone-iodine. This article outlines longitudinal analyses after the primary outcome report. Of 212 participants screened, 28 participants with quantitative polymerase chain reaction-confirmed adenoviral conjunctivitis were randomized and had follow-up visits on days 1, 2, 4, 7, 14, and 21. At each visit, clinician-graded signs, participant-reported symptoms, and a conjunctival swab for quantitative polymerase chain reaction analysis were obtained. The correlation of viral titers with symptoms and signs was calculated: (1) cross-sectionally at each visit and (2) longitudinally for 21 days using a repeated-measures mixed-effects model. RESULTS: Twenty-five of 28 participants had sufficient data for this report. Higher viral titers for 21 days were correlated with greater severity of symptoms (tearing, matting, and redness, r ≥ 0.70; P < .02) and greater severity of clinical signs (bulbar redness and serous discharge, r ≥ 0.60; P < .01). Eyes with highest baseline viral titers required longer time to viral clearance ( r = 0.59, P = .008). Signs and symptoms persisted in approximately half of the eyes even after viral clearance. CONCLUSIONS: Higher conjunctival viral titers across 21 days were strongly correlated with more severe signs and symptoms and longer time to viral clearance. Our results also indicate that symptoms and signs can persist after viral clearance.

Foveal Phase Retardation Correlates With Optically Measured Henle Fiber Layer Thickness.

This study quantified and compared phase retardation distribution in the central macula with the thickness of the Henle fiber layer (HFL). A scanning laser polarimeter (SLP) was used to acquire 20° × 40° macular-centered images, either with fixed corneal compensation or with variable corneal compensation, in two cohorts of clinically normal subjects (N = 36). Phase retardation maps from SLP imaging were used to generate a macular cross pattern (fixed compensation) or an annulus pattern (variable compensation) centered on the macula. Intensity profiles in the phase retardation maps were produced using annular regions of interest at eccentricities from 0.25° to 3°. Pixel intensity was averaged at each eccentricity, acting as a surrogate for macular phase retardation. Directional OCT images were acquired in the horizontal and vertical meridians in all subjects, allowing visualization of the HFL thickness. HFL thickness was manually segmented in each meridian and averaged. In both cohorts, phase retardation and HFL thickness were highly correlated in the central 3° assessed, providing further evidence that the source of the phase retardation signal in the central macula is dominated by the HFL and that the center of the macula on cross sectional imaging corresponds closely with the center of the macular cross on SLP imaging.

Diagnostic accuracy of clinical signs, symptoms and point-of-care testing for early adenoviral conjunctivitis.

CLINICAL RELEVANCE: This study identifies key signs and symptoms of acute conjunctivitis, that when combined with a point-of-care test, can improve clinician accuracy of diagnosing adenoviral conjunctivitis. BACKGROUND: Adenoviral conjunctivitis is a common ocular infection with the potential for high economic impact due to widespread outbreaks and subsequent furloughs from work and school. In this report, we describe clinical signs and participant-reported symptoms that most accurately identify polymerase chain reaction (PCR)-confirmed adenoviral conjunctivitis. METHODS: Adults with 'red eye' symptoms of four days or less were enrolled. Participants rated 10 ocular symptoms from 0 (not bothersome) to 10 (very bothersome), and indicated the presence or absence of systemic flu-like symptoms. Clinicians determined the presence or absence of swollen lymph nodes and rated the severity of eight ocular signs using a 5-point scale. An immunoassay targeting adenovirus antigen was utilised for the point-of-care test, and conjunctival swab samples were obtained for subsequent adenovirus detection by PCR analyses. Univariate and multivariate logistic regression models were used to identify symptoms and signs associated with PCR-confirmed adenoviral conjunctivitis. The diagnostic accuracy of these clinical findings, and the potential benefit of incorporating point-of-care test results, was assessed by calculating areas under the receiver operating characteristic curves (AUC). RESULTS: Clinician-rated bulbar conjunctival redness, participant-rated eyelid swelling and overall ocular discomfort had the best predictive value in the multivariate logistic regression model with an AUC of 0.83. The addition of the point-of-care test results to these three clinical sign/symptom scores improved diagnostic accuracy, increasing the AUC to 0.94. CONCLUSIONS: Conjunctival redness severity and participant-reported eyelid swelling and overall discomfort, along with adenoviral point-of-care test results, were highly predictive in identifying individuals with PCR-confirmed adenoviral conjunctivitis. Improved diagnostic accuracy by clinicians at the initial presenting visit could prevent unnecessary work furloughs and facilitate earlier treatment decisions.

Predictive Accuracy and Densitometric Analysis of Point-of-Care Immunoassay for Adenoviral Conjunctivitis.

Purpose: Accurate diagnosis of adenoviral conjunctivitis (Ad-Cs) is important for timely and appropriate patient management to reduce disease transmission. This study assessed the diagnostic accuracy of a commercially available point-of-care adenovirus immunoassay and determined whether its predictive accuracy is influenced by signal intensities of test result bands. Methods: Point-of-care immunoassay (AdenoPlus) testing and quantitative polymerase chain reaction (qPCR) testing was performed on conjunctival swab samples obtained from eyes of 186 eligible adult participants with presumed infectious conjunctivitis and symptoms of ≤4 days. Masked observers assessed signal intensities of the immunoassay test and control bands using densitometry. Results: Ad-Cs was confirmed by qPCR in 28 of the 56 eyes that tested positive on the AdenoPlus, a 50% positive predictive value (95% confidence interval [CI] = 36.9, 63.1). No adenovirus was detected by qPCR in 128 of 130 eyes that tested negative on AdenoPlus, a 98.5% negative predictive value (CI = 96.3, 100). Sensitivity and specificity were 93% (CI = 84.4, 100) and 82% (CI = 76.0, 88.1), respectively. Viral titers significantly correlated with ratio of test band signal intensities (R2 = 0.32, P = 0.002). Higher positive predictive value was associated with higher densitometry ratios (receiver operating characteristic [ROC] area = 0.71; 95% CI = 0.59, 0.83). Conclusions: Densitometric analyses suggest that the diagnostic accuracy of AdenoPlus is influenced by the signal intensity of the test result bands. Visual comparison of the test band intensities by clinicians could reduce the false positive rate of point-of-care immunoassays and aid in the diagnosis of viral infections. Translational Relevance: Ratiometric densitometry of point-of-care immunoassays could aid clinicians' decision making in diagnosing infectious diseases, including Ad-Cs.

Efficacy of a Single Administration of 5% Povidone-Iodine in the Treatment of Adenoviral Conjunctivitis.

PURPOSE: To evaluate the safety and efficacy of a single, in-office administration of 5% povidone-iodine (PVP-I) compared to artificial tears (AT) for adenoviral conjunctivitis (Ad-Cs). DESIGN: Double-masked pilot randomized trial. METHODS: Patients presenting with presumed adenoviral conjunctivitis were screened at 9 U.S. clinics. INCLUSION CRITERIA: ≥18 years of age, symptoms ≤4 days, and a positive AdenoPlus test. EXCLUSION CRITERIA: thyroid disease, iodine allergy, recent ocular surgery, and ocular findings inconsistent with early-stage Ad-Cs. Randomization was to a single administration of 5% PVP-I or AT in 1 eye and examinations on days 1-2, 4, 7, 14, and 21 with conjunctival swabs taken at each visit for quantitative polymerase chain reaction. Primary outcome was percent reduction from peak viral load. Secondary outcomes were improvement in clinical signs and symptoms. RESULTS: Of 56 patients randomized, 28 had detectable viral titers at baseline. Day 4 posttreatment, viral titers in the 5% PVP-I and AT groups were 2.5% ± 2.7% and 14.4% ± 10.5% of peak, respectively (P = .020). Severity of participant-reported tearing, lid swelling, and redness as well as clinician-graded mucoid discharge, bulbar redness, and bulbar edema were lower in the 5% PVP-I group than AT group on day 4 (P < .05). After day 4, viral titers and severity of signs and symptoms decreased markedly in both groups and no differences between groups were detected. CONCLUSIONS: Pilot data suggest a single, in-office administration of 5% PVP-I could reduce viral load and hasten improvement of clinical signs and symptoms in patients with Ad-Cs.

Success of Masking 5% Povidone-Iodine Treatment: The Reducing Adenoviral Patient Infected Days Study.

SIGNIFICANCE: The effectiveness of masking is rarely evaluated or reported in single- or double-masked clinical trials. Knowledge of treatment assignment by participants and clinicians can bias the assessment of treatment efficacy. PURPOSE: This study aimed to evaluate the effectiveness of masking in a double-masked trial of 5% povidone-iodine for the treatment of adenoviral conjunctivitis. METHODS: The Reducing Adenoviral Patient Infected Days study is a double-masked, randomized trial comparing a one-time, in-office administration of 5% povidone-iodine with artificial tears for the treatment of adenoviral conjunctivitis. Masking was assessed by asking participants and masked clinicians at designated time points if they believed the treatment administered was povidone-iodine or artificial tears, or if they were unsure. Adequacy of masking was quantified using a modified Bang Blinding Index. RESULTS: Immediately after treatment, 34% of participants who received povidone-iodine and 69% of those who received artificial tears guessed incorrectly or were unsure of their treatment (modified Bang Indices of 0.31 and -0.38, respectively). On day 4, 38% of the povidone-iodine participants and 52% of the artificial tear participants guessed incorrectly or were unsure of their treatment (modified Bang Indices of 0.24 and -0.05, respectively), indicating adequate and ideal masking. On days 1, 4, 7, 14, and 21, masked clinicians guessed incorrectly or were unsure of treatment in 53%, 50%, 40%, 39%, and 42% among povidone-iodine participants compared with 44%, 35%, 38%, 35%, and 39% among artificial tears participants, respectively. The modified Bang Indices for clinician masking in the povidone-iodine group ranged from -0.05 to 0.25 and from 0.13 to 0.29 in the artificial tears group. CONCLUSIONS: Masking of participants and clinicians was adequate. Successful masking increases confidence that subjective measurements are not biased. We recommend quantitative assessment and reporting the effectiveness of masking in ophthalmic clinical trials.

The Effect of Refractive Error on Melanopsin-Driven Pupillary Responses.

Purpose: Human and animal studies suggest that light-mediated dopamine release may underlie the protective effect of time outdoors on myopia development. Melanopsin-containing retinal ganglion cells may be involved in this process by integrating ambient light exposure and regulating retinal dopamine levels. The study evaluates this potential involvement by examining whether melanopsin-driven pupillary responses are associated with adult refractive error. Methods: Subjects were 45 young adults (73% female, 24.1 ± 1.8 years) with refractive errors ranging from -6.33 D to +1.70 D. The RAPDx (Konan Medical) pupillometer measured normalized pupillary responses to three forms of square-wave light pulses alternating with darkness at 0.1 Hz: alternating long wavelength (red, peak at 608 nm) and short wavelength (blue, peak at 448 nm), followed by red only and then blue only. Results: Non-myopic subjects displayed greater pupillary constriction in the blue-only condition and slower redilation following blue light offset than subjects with myopia (P = 0.011). Pupillary responses were not significantly different between myopic and non-myopic subjects in the red-only condition (P = 0.15). More hyperopic/less myopic refractive error as a continuous variable was linearly related to larger increases in pupillary constriction in response to blue-only stimuli (r = 0.48, P = 0.001). Conclusions: Repeated light exposures to blue test stimuli resulted in an adaptation in the pupillary response (more constriction and slower redilation), presumably due to increased melanopsin-mediated input in more hyperopic/less myopic adults. This adaptive property supports a possible role for these ganglion cells in the protective effects of time outdoors on myopia development.

The Influence of Binocular Vision Symptoms on Computerized Neurocognitive Testing of Adolescents With Concussion.

Binocular vision disorders are commonly found postconcussion and associated with high symptom burden. We investigated the relationship between binocular vision symptoms and neurocognitive test performance. Thirty-four adolescents with concussion and 18 without concussion were assessed for cognitive performance using the CogState Brief Battery. Binocular vision disorders were determined using clinical examination and vision symptoms with the Convergence Insufficiency Symptoms Survey (CISS). A cutoff CISS score of 13 had high predictive accuracy for identifying individuals with a binocular vision disorder. CogState scores for processing speed and attention were significantly lower in the concussion group compared with the control group. Within the concussion group, scores for attention, learning, and working memory were significantly lower in those with vision symptoms. The presence of vision symptoms did not significantly affect CogState scores within the control group. The presence of vision symptoms in individuals with concussion is associated with significantly reduced scores on individual components of the CogState.

Safety and tolerability of a one-time, in-office administration of 5% povidone-iodine in the treatment of adenoviral conjunctivitis: The Reducing Adenoviral Patient Infected Days (RAPID) study.

PURPOSE: To report safety and tolerability of a one-time administration of ophthalmic 5% povidone-iodine (5% PVP-I) in a double-masked randomized trial for the treatment of adenoviral conjunctivitis (Ad-Cs). METHODS: Of 212 participants screened, 56 eligible participants with red eye symptoms ≤4 days and a positive adenoviral rapid immunoassay were randomized to a one-time administration of ophthalmic 5% PVP-I or preservative free artificial tears (AT). Safety was assessed by corneal fluorescein staining (baseline, immediate post-administration and Day 1) and visual acuity (VA) (baseline and Day 1). Tolerability was assessed using participant-rated overall ocular discomfort (baseline, immediately post-administration and on Day 1. RESULTS: In the 5% PVP-I group, corneal staining increased immediately post-administration but returned to baseline levels by Day 1. There was no change in VA between baseline and Day 1 in either 5% PVP-I or AT groups (p = 0.87). In the 5% PVP-I group, there was no change in participant-rated overall discomfort immediately post-administration (p = 0.78) or on day 1 (p = 0.10) compared to baseline. In the AT group, participant-rated overall discomfort was lower immediately post-administration but returned to baseline levels by Day 1. One adverse event was reported in the 5% PVP-I group on Day 1-2 that was classified as not related to treatment. CONCLUSION: These results suggest ophthalmic 5% PVP-I used as a one-time treatment is safe and well tolerated by patients with Ad-Cs.

µ-Opioid Receptor Activation Directly Modulates Intrinsically Photosensitive Retinal Ganglion Cells.

Intrinsically photosensitive retinal ganglion cells (ipRGCs) encode light intensity and trigger reflexive responses to changes in environmental illumination. In addition to functioning as photoreceptors, ipRGCs are post-synaptic neurons in the inner retina, and there is increasing evidence that their output can be influenced by retinal neuromodulators. Here we show that opioids can modulate light-evoked ipRGC signaling, and we demonstrate that the M1, M2 and M3 types of ipRGCs are immunoreactive for µ-opioid receptors (MORs) in both mouse and rat. In the rat retina, application of the MOR-selective agonist DAMGO attenuated light-evoked firing ipRGCs in a dose-dependent manner (IC50 < 40 nM), and this effect was reversed or prevented by co-application of the MOR-selective antagonists CTOP or CTAP. Recordings from solitary ipRGCs, enzymatically dissociated from retinas obtained from melanopsin-driven fluorescent reporter mice, confirmed that DAMGO exerts its effect directly through MORs expressed by ipRGCs. Reduced ipRGC excitability occurred via modulation of voltage-gated potassium and calcium currents. These findings suggest a potential new role for endogenous opioids in the mammalian retina and identify a novel site of action-MORs on ipRGCs-through which opioids might exert effects on reflexive responses to environmental light.

Blue and Red Light-Evoked Pupil Responses in Photophobic Subjects with TBI.

PURPOSE: Photophobia is a common symptom in individuals suffering from traumatic brain injury (TBI). Recent evidence has implicated blue light-sensitive intrinsically photosensitive retinal ganglion cells (ipRGCs) in contributing to the neural circuitry mediating photophobia in migraine sufferers. The goal of this work is to test the hypothesis that ipRGC function is altered in TBI patients with photophobia by assessing pupillary responses to blue and red light. METHODS: Twenty-four case participants (mean age 43.3; 58% female), with mild TBI and self-reported photophobia, and 12 control participants (mean age 42.6; 58% female) were in this study. After 10 minutes of dark adaptation, blue (470 nm, 1 × 10 phots/s/cm) and red (625 nm, 7 × 10 phots/s/cm) flashing (0.1 Hz) light stimuli were delivered for 30 seconds to the dilated left eye while the right pupil was recorded. The amplitude of normalized pupil fluctuation (constriction and dilation) was quantified using Fourier fast transforms. RESULTS: In both case and control participants, the amplitude of pupil fluctuation was significantly less for the blue light stimuli as compared to the red light stimuli, consistent with a contribution of ipRGCs to these pupil responses. There was no significant difference in the mean pupil fluctuation amplitudes between the two participant groups, but case participants displayed greater variability in their pupil responses to the blue stimulus. CONCLUSIONS: Case and control participants showed robust ipRGC-mediated components in their pupil responses to blue light. The results did not support the hypothesis that ipRGCs are "hypersensitive" to light in TBI participants with photophobia. However, greater pupil response variability in the case subjects suggests that ipRGC function may be more heterogeneous in this group.

Muscarinic acetylcholine receptor-mediated stimulation of retinal ganglion cell photoreceptors.

Melanopsin-dependent phototransduction in intrinsically photosensitive retinal ganglion cells (ipRGCs) involves a Gq-coupled phospholipase C (PLC) signaling cascade. Acetylcholine, released in the mammalian retina by starburst amacrine cells, can also activate Gq-PLC pathways through certain muscarinic acetylcholine receptors (mAChRs). Using multielectrode array recordings of rat retinas, we demonstrate that robust spiking responses can be evoked in neonatal and adult ipRGCs after bath application of the muscarinic agonist carbachol. The stimulatory action of carbachol on ipRGCs was a direct effect, as confirmed through calcium imaging experiments on isolated ipRGCs in purified cultures. Using flickering (6 Hz) yellow light stimuli at irradiances below the threshold for melanopsin activation, spiking responses could be elicited in ipRGCs that were suppressed by mAChR antagonism. Therefore, this work identified a novel melanopsin-independent pathway for stimulating sustained spiking in ganglion cell photoreceptors. This mAChR-mediated pathway could enhance ipRGC spiking responses in conditions known to evoke retinal acetylcholine release, such as those involving flickering or moving visual stimuli. Furthermore, this work identifies a pharmacological approach for light-independent ipRGC stimulation that could be targeted by mAChR agonists.

Circadian rhythm of intraocular pressure in the adult rat.

Ocular hypertension is a risk factor for developing glaucoma, which consists of a group of optic neuropathies characterized by progressive degeneration of retinal ganglion cells and subsequent irreversible vision loss. Our understanding of how intraocular pressure damages the optic nerve is based on clinical measures of intraocular pressure that only gives a partial view of the dynamic pressure load inside the eye. Intraocular pressure varies over the course of the day and the oscillator regulating these daily changes has not yet been conclusively identified. The purpose of this study was to compare and contrast the circadian rhythms of intraocular pressure and body temperature in Brown Norway rats when these animals are housed in standard light-dark and continuous dim light (40-90 lux) conditions. The results from this study show that the temperature rhythm measured in continuous dim light drifted forward relative to external time, indicating that the rhythm was free running and being regulated by an internal biological clock. Also, the results show that there is a persistent, but dampened, circadian rhythm of intraocular pressure in continuous dim light and that the circadian rhythms of temperature and intraocular pressure are not synchronized by the same central oscillator. We conclude that once- or twice-daily clinical measures of intraocular pressure are insufficient to describe intraocular pressure dynamics. Similarly, our results indicate that, in experimental animal models of glaucoma, the common practice of housing animals in constant light does not necessarily eliminate the potential influence of intraocular pressure rhythms on the progression of nerve damage. Future studies should aim to determine whether an oscillator within the eye regulates the rhythm of intraocular pressure and to better characterize the impact of glaucoma on this rhythm.

Adenosine modulates light responses of rat retinal ganglion cell photoreceptors througha cAMP-mediated pathway.

Adenosine is an established neuromodulator in the mammalian retina, with A1 adenosine receptors being especially prevalent in the innermost ganglion cell layer. Activation of A1 receptors causes inhibition of adenylate cyclase, decreases in intracellular cyclic AMP (cAMP) levels and inhibition of protein kinase A (PKA). In this work, our aim was to characterize the effects of adenosine on the light responses of intrinsically photosensitive retinal ganglion cells (ipRGCs) and to determine whether these photoreceptors are subject to neuromodulation through intracellular cAMP-related signalling pathways. Using multielectrode array recordings from postnatal and adult rat retinas, we demonstrated that adenosine significantly shortened the duration of ipRGC photoresponses and reduced the number of light-evoked spikes fired by these neurons. The effects were A1 adenosine receptor-mediated, and the expression of this receptor on melanopsin-containing ipRGCs was confirmed by calcium imaging experiments on isolated cells in purified cultures. While inhibition of the cAMP/PKA pathway by adenosine shortened ipRGC light responses, stimulation of this pathway with compounds such as forskolin had the opposite effect and lengthened the duration of ipRGC spiking. Our findings reveal that the modification of ipRGC photoresponses through a cAMP/PKA pathway is a general feature of rat ganglion cell photoreceptors, and this pathway can be inhibited through activation of A1 receptors by adenosine. As adenosine levels in the retina rise at night, adenosinergic modulation of ipRGCs may serve as an internal regulatory mechanism to limit transmission of nocturnal photic signals by ipRGCs to the brain. Targeting retinal A1 adenosine receptors for ipRGC inhibition represents a potential therapeutic target for sleep disorders and migraine-associated photophobia.

Small-molecule antagonists of melanopsin-mediated phototransduction.

Melanopsin, expressed in a subset of retinal ganglion cells, mediates behavioral adaptation to ambient light and other non-image-forming photic responses. This has raised the possibility that pharmacological manipulation of melanopsin can modulate several central nervous system responses, including photophobia, sleep, circadian rhythms and neuroendocrine function. Here we describe the identification of a potent synthetic melanopsin antagonist with in vivo activity. New sulfonamide compounds inhibiting melanopsin (opsinamides) compete with retinal binding to melanopsin and inhibit its function without affecting rod- and cone-mediated responses. In vivo administration of opsinamides to mice specifically and reversibly modified melanopsin-dependent light responses, including the pupillary light reflex and light aversion. The discovery of opsinamides raises the prospect of therapeutic control of the melanopsin phototransduction system to regulate light-dependent behavior and remediate pathological conditions.

Endogenous polysialylated neural cell adhesion molecule enhances the survival of retinal ganglion cells.

PURPOSE: During development, all retinal cells express polysialylated neural cell adhesion molecule (PSA-NCAM). PSA is localized only on glia in the adult retina, but as Müller glial processes ensheathe most retinal neurons, PSA remains in the extracellular environment of adult neurons. The authors sought to investigate the influence of endogenous PSA on the survival of neonatal as well as adult normal and injured retinal ganglion cells (RGCs). METHODS: Endogenous retinal PSA was selectively degraded by application of endoneuraminidase. PSA presence and removal were confirmed by immunohistochemistry and levels were assessed by Western Blot analysis. Neonatal RGC survival after PSA removal was assessed in vitro in RGCs immunopanned from rat pups. Adult RGC survival was assessed in vivo in mice by investigating RGC densities after removal of PSA in normal retinas and after optic nerve transection. RESULTS: Virtually all neonatal RGCs express PSA-NCAM and survive well in vitro; however, removal of PSA resulted in a 42% loss of these cells 3 days after the treatment. Similarly, removal of PSA in the adult retina in vivo induced a loss of 25% of RGCs at 14 days, and significantly reduced RGC densities after optic nerve transection by an additional 27% (relative to injured retinas with a vehicle injection) at 7 days. CONCLUSIONS: Together, these findings demonstrate that endogenous PSA supports the survival of neonatal as well as injured and normal adult RGCs and provide the first functional evidence of a role for PSA in the adult retina.

Glutamatergic calcium dynamics and deregulation of rat retinal ganglion cells.

A rise in intracellular calcium levels ([Ca(2+)](i)) is a key trigger for the lethal effects of the excitatory neurotransmitter glutamate in various central neurons, but a consensus has not been reached on the pathways that mediate glutamate-dependent increases of [Ca(2+)](i) in retinal ganglion cells (RGCs). Using Ca(2+) imaging techniques we demonstrated that, in the absence of external Mg(2+), the Ca(2+) signal evoked by glutamate was predominantly mediated by NMDA-type glutamate receptors (NMDA-Rs) in immunopanned RGCs isolated from neonatal or adult rats. Voltage-gated Ca(2+) channels and AMPA/kainate-Rs contributed a smaller portion of the Ca(2+) response at saturating concentrations of glutamate. Consistent with NMDA-R involvement, extracellular Mg(2+) inhibited RGC glutamate responses, while glycine had a potentiating effect. With Mg(2+) present externally, the effect of AMPA/kainate-R antagonists was enhanced and both NMDA- and AMPA/kainate-R antagonists greatly reduced the glutamate-induced increases of RGC [Ca(2+)](i). This finding indicates that the primary contribution of AMPA/kainate-Rs to RGC glutamatergic Ca(2+) dynamics is through the depolarization-dependent relief of the Mg(2+) block of NMDA-R channels. The effect of glutamate receptor antagonists on glutamatergic Ca(2+) signals from RGCs in adult rat retinal wholemounts yielded results similar to those obtained using immunopanned RGCs. Additional experiments on isolated RGCs revealed that during a 1 h glutamate (10-1000 microm) exposure, 18-28% of RGCs exhibited delayed Ca(2+) deregulation (DCD) and the RGCs that underwent DCD were positive for the death marker annexin V. RGCs with larger glutamate-evoked Ca(2+) signals were more likely to undergo DCD, and NMDA-R blockade significantly reduced the occurrence of DCD. Identifying the mechanisms underlying RGC excitotoxicity aids in our understanding of the pathophysiology of retinal ischaemia, and this work establishes a major role for NMDA-R-mediated increases in [Ca(2+)](i) in glutamate-related RGC death.