Do the retinal abnormalities in X-linked juvenile retinoschisis include impaired phototransduction?

X-linked juvenile retinoschisis (XLRS), a hereditary retinal disorder primarily affecting males, is characterized by the formation of cystic spaces between the outer plexiform layer and outer nuclear layer of the retina. Mutations in the RS1 gene, which encodes the extracellular binding protein retinoschisin, are responsible for XLRS pathogenesis. While the role of retinoschisin in maintaining retinal integrity is well established, there is growing evidence suggesting compromised photoreceptor function in XLRS. To investigate the molecular pathways affected by RS1 deficiency, particularly in phototransduction, we performed electroretinographic (ERG) and proteomic analyses on retinae from Rs1 knockout mice, a model of human XLRS. The Rs1 knockout mice had reduced ERG a-wave amplitudes. Correspondingly, differential expression analysis revealed downregulation of proteins crucial for phototransduction, with Ingenuity Pathway Analysis (IPA) highlighting "phototransduction" as the most significantly downregulated biological theme. Compensatory mechanisms were also observed in the IPA, including upregulation of synaptic remodeling, inflammation, cell adhesion, and G-protein signaling. These findings strongly implicate an underrecognized role of photoreceptor dysfunction in XLRS pathology. We speculate that entrapment of mutant retinoschisin protein within photoreceptor inner segments as well as disrupted reciprocal regulation between L-type voltage-gated calcium channels and retinoschisin contribute to the dysfunction in photoreceptors.

Electroretinographic Responses in Retinopathy of Prematurity Treated Using Intravitreal Bevacizumab or Laser.

PURPOSE: Intravitreal injection of bevacizumab (IVB) offers advantages over laser photoablation for treatment of type 1 retinopathy of prematurity (ROP). However, retinal function has not, to date, been quantitatively compared following these interventions. Therefore, electroretinography (ERG) was used compare retinal function among eyes treated using IVB or laser, and control eyes. In addition, among the IVB-treated eyes, ERG was used to compare function in individuals in whom subsequent laser was and was not required. DESIGN: Prospective clinical cohort study. METHODS: ERG was used to record dark- and light-adapted stimulus/response functions in 21 children treated using IVB (12 of whom required subsequent laser in at least 1 eye for persistent avascular retina [PAR]). Sensitivity and amplitude parameters were derived from the a-wave, b-wave, and oscillatory potentials (OPs), representing activity in photoreceptor, postreceptor, and inner retinal cells, respectively. These parameters were then referenced to those of 76 healthy, term-born controls and compared to those of 10 children treated using laser only. RESULTS: In children with treated ROP, every ERG parameter was significantly below the mean in controls. However, these significant ERG deficits did not differ between IVB- and laser-treated eyes. Among children treated using IVB, no ERG parameter was significantly associated with dose or need for subsequent laser. CONCLUSION: Retinal function was significantly impaired in treated ROP eyes. Function in IVB-treated eyes did not differ from that in laser-treated eyes. Functional differences also did not distinguish those IVB-treated eyes that would subsequently need laser for PAR.

The relation of the multifocal electroretinographic response to macular layer volume.

PURPOSE: To determine the association of the multifocal electroretinographic (mfERG) response amplitude with the volumes of the inner, postreceptor, and photoreceptor retinal layers in the region stimulated by each mfERG element. METHODS: Sixteen healthy, young adult control subjects were studied. Each of the 103 hexagonal elements of the standard, scaled mfERG were aligned, where possible, with patches of retina imaged using optical coherence tomography. Stimuli falling on the fovea and on the optic nerve head were excluded. Linear mixed-effects modeling was then used to derive estimated coefficients (voltage/volume) for the mfERG response throughout the full 80 ms standard epoch. The resulting predicted response amplitudes originating in each layer were then compared to pharmacologically "dissected" mfERGs obtained from other studies in monkey eyes. RESULTS: Across the duration of the response, the amplitude of the modeled contribution from (1) the inner retina was small-to-modest, (2) the postreceptor retina was larger and contained two prominent peaks, and (3) the photoreceptor response was the largest and most closely paralleled the overall (i.e., intact) response, including late-appearing oscillations. The significance of each layer's contribution was greatest when the absolute amplitude of that layer's response was largest. The contribution of the inner retina was maximally significant in the interval between the prominent troughs and peaks of the intact response. The contributions of the postreceptor and photoreceptor responses were maximally significant at the prominent troughs and peaks of the intact response. CONCLUSIONS: The results of the model were in good overall agreement with previous interpretations of the cellular contributions to the mfERG. There was also fair agreement with pharmacologically dissected monkey mfERG responses. Thus, the estimations of the contributions of the retinal layers to the mfERG so produced appeared plausible.

Dark-adapted threshold and electroretinogram for diagnosis of Usher syndrome.

PURPOSE: To determine the utility of ophthalmology evaluation, dark-adapted threshold, and full-field electroretinogram for early detection of Usher syndrome in young patients with bilateral sensorineural hearing loss. METHODS: We identified 39 patients with secure genetic diagnoses of Usher Syndrome. Visual acuity, spherical equivalent, fundus appearance, dark-adapted threshold, and full-field electroretinogram results were summarized and compared to those in a group of healthy controls with normal hearing. In those Usher patients with repeated measures, regression analysis was done to evaluate for change in visual acuity and dark-adapted threshold with age. Spherical equivalent and full-field electroretinogram responses from dark- and light-adapted eyes were evaluated as a function of age. RESULTS: The majority of initial visual acuity and spherical equivalent results were within normal limits for age. Visual acuity and dark-adapted threshold worsened significantly with age in Usher type 1 but not in Usher type 2. At initial test, full-field electroretinogram responses from dark- and light-adapted eyes were abnormal in 53% of patients. Remarkably, nearly half of our patients (17% of Usher type 1 and 30% of Usher type 2) would have been missed by tests of retinal function alone if evaluated before age 10. CONCLUSIONS: Although there is an association of abnormal dark-adapted threshold and full-field electroretinogram at young ages in Usher patients, it appears that a small but important proportion of patients would not be detected by tests of retinal function alone. Thus, genetic testing is needed to secure a diagnosis of Usher syndrome.

Carbonic anhydrase inhibition in X-linked retinoschisis: An eye on the photoreceptors.

The retinoschisin protein is encoded on the short arm of the X-chromosome by RS1, is expressed abundantly in photoreceptor inner segments and in bipolar cells, and is secreted as an octamer that maintains the structural integrity of the retina. Mutations in RS1 lead to X-linked retinoschisis (XLRS), a disease characterized by the formation of cystic spaces between boys' retinal layers that frequently present in ophthalmoscopy as a "spoke-wheel" pattern on their maculae and by progressively worsening visual acuity (VA). There is no proven therapy for XLRS, but there is mixed evidence that carbonic anhydrase inhibitors (CAIs) produce multiple beneficial effects, including improved VA and decreased volume of cystic spaces. Consequently, linear mixed-effects (LME) models were used to evaluate the effects of CAI therapy on VA and central retinal thickness (CRT, a proxy for cystic cavity volume) in a review of 19 patients' records. The mechanism of action of action of CAIs is unclear but, given that misplaced retinoschisin might accumulate in the photoreceptors, it is possible-perhaps even likely-that CAIs act to benefit the function of photoreceptors and the neighboring retinal pigment epithelium by acidification of the extracellular milieu; patients on CAIs have among the most robust photoreceptor responses. Therefore, a small subset of five subjects were recruited for imaging on a custom multimodal adaptive optics retinal imager for inspection of their parafoveal cone photoreceptors. Those cones that were visible, which numbered far fewer than in controls, were enlarged, consistent with the retinoschisin accumulation hypothesis. Results of the LME modeling found that there is an initial benefit to both VA and CRT in CAI therapy, but these wane, in both cases, after roughly two years. That said, even a short beneficial effect of CAIs on the volume of the cystic spaces may give CAI therapy an important role as pretreatment before (or immediately following) administration of gene therapy.

Photoconducting Devices with Response in the Visible-Near-Infrared Region Based on Neutral Ni Complexes of Aryl-1,2-dithiolene Ligands.

Metal bis(1,2-dithiolene) complexes belonging to the class [Ni(Ar-edt)2]x- [Ar-edt2- = arylethylene-1,2-dithiolate; Ar = phenyl, (1x-), 2-naphthyl (2x-); x = 0 and 1] were fully characterized by NMR, UV-visible-near-infrared (UV-vis-NIR), diffuse reflectance, and FT-IR spectroscopy, as well as cyclic voltammetry and single-crystal X-ray diffraction analysis. These complexes have emerged as new photoconducting materials that allowed for the development of a prototype of photodetectors with response in the vis-NIR region. The photodetecting devices showed in some cases quantum efficiencies orders of magnitude higher than those of previously reported 1,2-dithiolene systems.

Retinal Function in X-Linked Juvenile Retinoschisis.

Purpose: To assess retinal function in young patients with X-linked juvenile retinoschisis (XLRS), a disorder that is known to alter ERG postreceptor retinal components and also possibly photoreceptor components. Methods: ERG responses to full-field stimuli were recorded under scotopic and photopic conditions in 12 XLRS patients aged 1 to 15 (median 8) years. A- and b-wave amplitudes and implicit times were examined over a range of stimulus intensities. Rod and cone photoreceptor (SROD, RROD, SCONE, RCONE) and rod-driven postreceptor (log σ, VMAX) response parameters were calculated from the a- and b-waves. Data from XLRS patients were evaluated for significant change with age. Results: A- and b-wave amplitudes were smaller in XLRS patients compared with controls under both scotopic and photopic conditions. Saturated photoresponse amplitude (RROD), postreceptor b-wave (log σ), and saturated b-wave amplitude (VMAX) were significantly lower in XLRS patients than in controls; SROD did not differ between the two groups. SCONE and RCONE values were normal. In XLRS patients, neither a- and b-wave amplitudes nor calculated parameters (SROD, RROD, log σ, VMAX,SCONE, and RCONE) changed with age. Conclusions: In these young XLRS patients, RROD and a-wave amplitudes were significantly smaller than in controls. Thus, in addition to XLRS causing postreceptor dysfunction, an effect of XLRS on rod photoreceptors cannot be ignored.

Extracting the ON and OFF contributions to the full-field photopic flash electroretinogram using summed growth curves.

Under cone-mediated (photopic) conditions, an "instantaneous" flash of light, including both stimulus onset and offset, will simultaneously activate both "ON" and "OFF" bipolar cells, which either depolarize (ON) or hyperpolarize (OFF) in response and, respectively, produce positive-going and negative-going deflections in the electroretinogram (ERG). The stimulus-response (SR) relationship of the photopic ON response demonstrates logistic growth, like that manifested in the rod-mediated (scotopic) b-wave, which is driven by a single class of depolarizing bipolar cell. However, the photopic b-wave SR function is importantly shaped by OFF responses, leading to a "photopic hill." Furthermore, both on and off stimuli elicit activity in both ON and OFF bipolar cells. This has made it difficult to produce meaningful parameters for ready interpretation of the photopic b-wave SR relationship. Therefore, we evaluated whether the sum of sigmoidal SR functions, as descriptors of the depolarizing and hyperpolarizing components of the photopic flash ERG, could be used to elucidate and quantitate the mechanisms that produce the photopic hill. We used a novel fitting routine to optimize a sum of simple sigmoidal curves to SR data in five groups of subjects: Healthy adult, 10-week-old infant, congenital stationary night blindness (CSNB), X-linked juvenile retinoschisis (XJR), and preterm-born, both without and with a history of retinopathy of prematurity (ROP). Differences in ON and OFF amplitude, sensitivity, and implicit time among the groups were then compared using parameters extracted from these fits. We found that our modeling procedure enabled plausible derivations of ON and OFF pathway contributions to the ERG, and that the parameters produced appeared to have physiological relevance. In adult subjects, the ON and OFF amplitudes were similar in magnitude with respectively longer and shorter implicit times. Infant, CSNB, and XJR subjects showed significant ON pathway deficits. History of preterm-birth, without or with a diagnosis of ROP, did not much affect cone responses.

Juvenile Macular Degenerations.

In this article, we review the following 3 common juvenile macular degenerations: Stargardt disease, X-linked retinoschisis, and Best vitelliform macular dystrophy. These are inherited disorders that typically present during childhood, when vision is still developing. They are sufficiently common that they should be included in the differential diagnosis of visual loss in pediatric patients. Diagnosis is secured by a combination of clinical findings, optical coherence tomography imaging, and genetic testing. Early diagnosis promotes optimal management. Although there is currently no definitive cure for these conditions, therapeutic modalities under investigation include pharmacologic treatment, gene therapy, and stem cell transplantation.

A New Medical Device Rigeneracons Allows to Obtain Viable Micro-Grafts From Mechanical Disaggregation of Human Tissues.

Autologous graft is considered the gold standard of graft materials; however, this approach is still limited due to both small amount of tissue that can be collected and to reduced cell viability of cells that can be obtained. The aim of this preliminary study was to demonstrate the efficacy of an innovative medical device called Rigeneracons® (CE certified Class I) to provide autologous micro-grafts immediately available to be used in the clinical practice. Moreover, Rigeneracons® is an instrument able to create micro-grafts enriched of progenitors cells which maintain their regenerative and differentiation potential. We reported preliminary data about viability cell of samples derived from different kind of human tissues, such as periosteum, cardiac atrial appendage biopsy, and lateral rectus muscle of eyeball and disaggregated by Rigeneracons®. In all cases we observed that micro-grafts obtained by Rigeneracons® displayed high cell viability. Furthermore, by cell characterization of periosteum samples, we also evidenced an high positivity to mesenchymal cell markers, suggesting an optimal regenerative potential.

Functional Loss of the Inner Retina in Childhood Optic Gliomas Detected by Photopic Negative Response.

PURPOSE: To determine whether the Ganzfeld ERG photopic negative response (PhNR), an assay of inner retinal activity, is altered in childhood optic glioma (OPG). METHODS: Seventeen pediatric patients with a diagnosis of OPG, established on neuro-ophthalmologic and brain/orbit magnetic resonance imaging (MRI) criteria, were enrolled. The examination protocol included determination of visual acuity (VA), fundus examination, retinal nerve fiber layer (RNFL) measurement with spectral-domain optical coherence tomography (SD-OCT) and photopic ERG. Fifteen normal children served as control group. Ten of the 17 OPG patients were retested 1 to 3 months after the first examination. Photopic ERGs were recorded after 10 minutes of light adaptation in response to a Ganzfeld flash presented on a steady light-adapting background. Amplitude and peak-time of b-wave and PhNR were measured. RESULTS: Compared with normal values, PhNR amplitude was significantly reduced (P < 0.0001) in the OPG group. Peak-time of PhNR as well as b-wave amplitude and peak-time were similar in both patients and controls. Losses of PhNR were found in patients with involvement of either anterior or retro-chiasmatic optic pathways. Linear regression analysis showed significant positive correlation between RNFL thickness and PhNR amplitude (r2 = 0.34, P = 0.008). Mean percentage test-retest difference for PhNR amplitude and peak-time was 12% and 6%, respectively. CONCLUSIONS: These findings indicate that flash ERG PhNR can detect a loss of inner retinal function in childhood OPGs supporting the use of this technique, as an adjunct to standard psychophysical and electrophysiological tests, to monitor visual function in OPG.

Functional effect of Saffron supplementation and risk genotypes in early age-related macular degeneration: a preliminary report.

BACKGROUND: To determine whether the functional effects of oral supplementation with Saffron, a natural compound that proved to be neuroprotective in early age-related macular degeneration, are influenced by complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) risk genotypes. METHODS: Thirty-three early AMD patients, screened for CFH (rs1061170) and ARMS2 (rs10490924) polymorphisms and receiving Saffron oral supplementation (20 mg/day) over an average period of treatment of 11 months (range, 6-12), were longitudinally evaluated by clinical examination and focal electroretinogram (fERG)-derived macular (18°) flicker sensitivity estimate. fERG amplitude and macular sensitivity, the reciprocal value of the estimated fERG amplitude threshold, were the main outcome measures. RESULTS: After three months of supplementation, mean fERG amplitude and fERG sensitivity improved significantly when compared to baseline values (p < 0.01). These changes were stable throughout the follow-up period. No significant differences in clinical and fERG improvements were observed across different CFH or ARMS2 genotypes. CONCLUSIONS: The present results indicate that the functional effect of Saffron supplementation in individual AMD patients is not related to the major risk genotypes of disease.

Synthesis and characterization of novel gold(III) complexes of asymmetrically aryl-substituted 1,2-dithiolene ligands featuring potential-controlled spectroscopic properties.

The tetrabutylammonium (TBA(+)) salts of square-planar monoanionic gold complexes of the unsymmetrically substituted Ar,H-edt(2-) 1,2-dithiolene ligands (Ar,H-edt(2-)=arylethylene-1,2-dithiolato; Ar=phenyl (1(-)), 2-naphthyl (2(-)), and 1-pyrenyl (3(-))) were synthesized and characterized by spectroscopic and electrochemical methods and the corresponding neutral species (1, 2, and 3, respectively) were obtained in CH(2)Cl(2) solution at room temperature by diiodine oxidation. The single-crystal X-ray diffraction structural data collected for (TBA(+))(2(-)), supported by DFT theoretical calculations, are consistent with the ene-1,2-dithiolate form of the ligand and the Au(III) oxidation state. All complexes feature intense near-IR absorptions (at about 1.5 microm) in their neutral states and Vis-emitting properties in the 400-550 nm range, the energy of which is controlled by the charge of the complex in the case of the 3(-)/3 couple. The spectroscopic and electrochemical features of 1(x-) and 2(x-) (x=0, 1), both in their cis and trans conformations, were investigated by means of DFT and time-dependent (TD) DFT calculations.

Pattern electroretinogram optimized for glaucoma screening (PERGLA) and retinal nerve fiber thickness in suspected glaucoma and ocular hypertension.

The purpose of this study is to evaluate pattern electroretinogram optimized for glaucoma screening (PERGLA) and retinal nerve fiber layer (RNFL) at spectral optical coherence tomography (OCT) in eyes with suspected glaucoma (GS) and in eyes with ocular hypertension (OHT). This is a cross-sectional, observational study. Twenty-four patients with GS (BCVA 20/20, normal visual field, intraocular pressure, IOP, less than 21 mmHg, and glaucomatous optic neuropathy, GON) and 14 patients with OHT (BCVA 20/20, intraocular pressure 25 mmHg, absence of glaucomatous optic neuropathy and normal visual field) were considered in this study. GON was intended as vertical cup-disk ratio of 0.5 or more; asymmetry of greater than 0.2, disk notching, disk splinter hemorrhages. PERGLA amplitude and phase were measured, while thickness of the RNFL was obtained with spectral OCT. A control group of 50 age-matched healthy patients was added. In the GS group, 16 eyes (66.7%) showed normal average RNFL analysis and normal PERGLA, 3 eyes (12.5%) showed abnormal average RNFL analysis and abnormal PERGLA, 5 eyes (20.8%) presented with normal average RNFL analysis and abnormal PERGLA. In the OHT group, 11 eyes (78.6%) showed an average normal RNFL and normal PERGLA, while 3 eyes (21.4%) presented with an average normal RNFL and abnormal PERGLA. PERGLA is a non-invasive, fast, and fully automatic version of the pattern ERG. In eyes with OHT and in eyes with GS, PERGLA abnormalities in presence of a normal RNFL could suggest an early functional damage of viable retinal ganglion cells.