Photopic ERG Research Articles

A Naturally Occurring Canine Model of Autosomal Recessive Congenital Stationary Night Blindness

Congenital stationary night blindness (CSNB) is a non-progressive, clinically and genetically heterogeneous disease of impaired night vision. We report a naturally-occurring, stationary, autosomal recessive phenotype in beagle dogs with normal daylight vision but absent night vision. Affected dogs had normal retinas on clinical examination, but showed no detectable rod responses. They had “negative-type” mixed rod and cone responses in full-field ERGs. Their photopic long-flash ERGs had normal OFF-responses associated with severely reduced ON-responses. The phenotype is similar to the Schubert-Bornschein form of complete CSNB in humans. Homozygosity mapping ruled out most known CSNB candidates as well as CACNA2D4 and GNB3. Three remaining genes were excluded based on sequencing the open reading frame and intron-exon boundaries (RHO, NYX), causal to a different form of CSNB (RHO) or X-chromosome (NYX, CACNA1F) location. Among the genes expressed in the photoreceptors and their synaptic terminals, and mGluR6 cascade and modulators, reduced expression of GNAT1, CACNA2D4 and NYX was observed by qRT-PCR in both carrier (n = 2) and affected (n = 2) retinas whereas CACNA1F was down-regulated only in the affecteds. Retinal morphology revealed normal cellular layers and structure, and electron microscopy showed normal rod spherules and synaptic ribbons. No difference from normal was observed by immunohistochemistry (IHC) for antibodies labeling rods, cones and their presynaptic terminals. None of the retinas showed any sign of stress. Selected proteins of mGluR6 cascade and its modulators were examined by IHC and showed that PKCα weakly labeled the rod bipolar somata in the affected, but intensely labeled axonal terminals that appeared thickened and irregular. Dendritic terminals of ON-bipolar cells showed increased Goα labeling. Both PKCα and Goα labeled the more prominent bipolar dendrites that extended into the OPL in affected but not normal retinas. Interestingly, RGS11 showed no labeling in the affected retina. Our results indicate involvement of a yet unknown gene in this canine model of complete CSNB.

Visual Cone Arrestin 4 Contributes to Visual Function and Cone Health.

Visual arrestins (ARR) play a critical role in shutoff of rod and cone phototransduction. When electrophysiological responses are measured for a single mouse cone photoreceptor, ARR1 expression can substitute for ARR4 in cone pigment desensitization; however, each arrestin may also contribute its own, unique role to modulate other cellular functions. A combination of ERG, optokinetic tracking, immunohistochemistry, and immunoblot analysis was used to investigate the retinal phenotypes of Arr4 null mice (Arr4-/-) compared with age-matched control, wild-type mice. When 2-month-old Arr4-/- mice were compared with wild-type mice, they had diminished visual acuity and contrast sensitivity, yet enhanced ERG flicker response and higher photopic ERG b-wave amplitudes. In contrast, in older Arr4-/- mice, all ERG amplitudes were significantly reduced in magnitude compared with age-matched controls. Furthermore, in older Arr4-/- mice, the total cone numbers decreased and cone opsin protein immunoreactive expression levels were significantly reduced, while overall photoreceptor outer nuclear layer thickness was unchanged. Our study demonstrates that Arr4-/- mice display distinct phenotypic differences when compared to controls, suggesting that ARR4 modulates essential functions in high acuity vision and downstream cellular signaling pathways that are not fulfilled or substituted by the coexpression of ARR1, despite its high expression levels in all mouse cones. Without normal ARR4 expression levels, cones slowly degenerate with increasing age, making this a new model to study age-related cone dystrophy.

The Effect of PKCα on the Light Response of Rod Bipolar Cells in the Mouse Retina.

Protein kinase C α (PKCα) is abundantly expressed in rod bipolar cells (RBCs) in the retina, yet the physiological function of PKCα in these cells is not well understood. To elucidate the role of PKCα in visual processing in the eye, we examined the effect of genetic deletion of PKCα on the ERG and on RBC light responses in the mouse. Immunofluorescent labeling was performed on wild-type (WT), TRPM1 knockout, and PKCα knockout (PKC-KO) retina. Scotopic and photopic ERGs were recorded from WT and PKC-KO mice. Light responses of RBCs were measured using whole-cell recordings in retinal slices from WT and PKC-KO mice. Protein kinase C alpha expression in RBCs is correlated with the activity state of the cell. Rod bipolar cells dendrites are a major site of PKCα phosphorylation. Electroretinogram recordings indicated that loss of PKCα affects the scotopic b-wave, including a larger peak amplitude, longer implicit time, and broader width of the b-wave. There were no differences in the ERG a- or c-wave between PKCα KO and WT mice, indicating no measurable effect of PKCα in photoreceptors or the RPE. The photopic ERG was unaffected consistent with the lack of detectable PKCα in cone bipolar cells. Whole-cell recordings from RBCs in PKC-KO retinal slices revealed that, compared with WT, RBC light responses in the PKC-KO retina are delayed and of longer duration. Protein kinase C alpha plays an important modulatory role in RBCs, regulating both the peak amplitude and temporal properties of the RBC light response in the rod visual pathway.

Pikachurin Protein Required for Increase of Cone Electroretinogram B-Wave during Light Adaptation.

In normal eyes, the amplitude of the b-wave of the photopic ERGs increases during light adaptation, but the mechanism causing this increase has not been fully determined. The purpose of this study was to evaluate the contribution of receptoral and post-receptoral components of the retina to this phenomenon. To accomplish this, we examined the ERGs during light adaptation in Pikachurin null-mutant (Pika -/-) mice, which have a misalignment of the bipolar cell dendritic tips to the photoreceptor ribbon synapses. After dark-adaptation, photopic ERGs were recorded from Pika -/- and wild type (WT) mice during the first 9 minutes of light adaptation. In some of the mice, post-receptoral components were blocked pharmacologically. The photopic b-waves of WT mice increased by 50% during the 9 min of light adaptation as previously reported. On the other hand, the b-waves of the Pika -/- mice decreased by 20% during the same time period. After blocking post-receptoral components, the b-waves were abolished from the WT mice, and the ERGs resembled those of the Pika -/- mice. The extracted post-receptoral component increased during light adaptation in the WT mice, but decreased for the first 3 minutes to a plateau in Pika -/- mice. We conclude that the normal synaptic connection between photoreceptor and retinal ON bipolar cells, which is controlled by pikachurin, is required for the ERGs to increase during light-adaptation. The contributions of post-receptoral components are essential for the photopic b-wave increase during the light adaptation.

Short Communication: Contribution of Voltage-Gated Sodium Channels to the Rabbit Cone Electroretinograms

ABSTRACTPurpose: Although the rabbit eye is of a similar size to the human eye, our limited understanding of the differences in retinal physiology to other species hinders its use in retinal research. The role of voltage-gated sodium channels (Nav) in the propagation of excitatory potentials along bipolar cells remains unclear, as conflicting data have been reported in the rabbit. The present study assesses the relative contributions of Nav to the scotopic and photopic flash ERGs as well as the wavelength-dependence of Nav blockade on the rabbit flicker ERG.Materials and Methods: Tetrodotoxin (TTX, 1 μM) was injected into the vitreous cavity of Chinchilla bastard rabbits. Scotopic ERGs were evoked by white flashes ranging from 10−5 to 10 cds m−2, photopic ERGs on a background of 25 cdm−2 using flash intensities of 0.032–25 cds m−2. Flicker ERGs (3–50 Hz) were elicited by blue, green and yellow stimuli at 2.34 cds m−2 on a white background of 30 cdm−2.Results: The a- and b-waves of the scotopic ERG were unaffected by intravitreal injection of the Nav blocker TTX. In contrast, the b-wave, but not the a-wave, of the photopic ERG was selectively blocked by TTX. The reduction by TTX of the flicker ERG was greater for blue than for green and yellow stimuli.Discussion: The data suggest that Nav selectively contribute to the generation of the photopic b-wave in the rabbit, indicating that they play an important role in the propagation of excitatory signals on bipolar cells in the cone, but not rod pathways. Importantly, the present study resolves conflicting previous reports into the role of Nav in the retinal function of the rabbit.

Influence of the β2-Subunit of L-Type Voltage-Gated Cav Channels on the Structural and Functional Development of Photoreceptor Ribbon Synapses.

The cacnb2 gene encodes the β2 subunit (Cavβ2) of voltage-gated Ca2+ channels in photoreceptors, and its targeted deletion in mice has previously been shown to cause altered retinal morphology and synaptic transmission. The purpose of this study was to provide a detailed morphologic study combined with experiments on the altered functions of photoreceptor ribbon synapses lacking Cavβ2. A cacnb2-deficient mouse strain was generated and deletion of the Cavβ2 in the retina documented by biochemical and immunhistochemical approaches. Ultrastructural changes of photoreceptor ribbon synapses were examined by electronmicroscopy and functional implications of the lack of Cavβ2 studied by depolarization-induced Ca2+ influx into isolated photoreceptor cells and electroretinography. Voltage-gated Ca2+ influx into rod photoreceptors lacking Cavβ2 was abolished and the typical rod ribbon-type active zones were absent in Cavβ2-deficient retinas. The active zone and the architecture of the presynaptic terminals were severely altered in rod synapses. Cone photoreceptor and the bipolar cell ribbon synapses were largely spared from ultrastructural changes although peanut agglutinin (PNA) labelling and photopic ERG analyses demonstrated that also cone pathways were disturbed in Cavβ2-deficient retinas. The presence of the Cavβ2 is essential for the structural integrity and function of the rod photoreceptor synapse. The Cavβ2 is less essential for the morphology of cone and bipolar cell ribbon synapses, although the impaired photopic electroretinogram suggests a functional alteration also of the cone-mediated signaling in Cavβ2-deficient retinas.

Electrophysiological testing as a method of cone-rod and cone dystrophy diagnoses and prediction of disease progression.

To determine the characteristics of patients with cone (CD) and cone-rod dystrophies (CRD) and to evaluate the changes in flash electroretinograms in both groups. The retrospective study involved 48 patients-34 with CRD and 14 with CD. The patients underwent full ophthalmological examination, including Goldmann perimetry and full-field flash electroretinogram (FERG) within the initial examination. These examinations were then repeated seven, or more, years later. The longest follow-up period was 10years, with the mean at 8.2years. During both examinations, we assessed the amplitudes of the b wave in the scotopic ERG test 0.01 (which reflects rod response), the maximal scotopic ERG test 3.0 (which reflects cone and rod response) and the photopic 3.0 ERG test (which reflects cone response). The results were then compared against normal values. The progression over time of ERG b wave amplitudes in the scotopic ERG 0.01, maximal scotopic ERG 3.0 and photopic ERG tests was assessed. There were significant differences in rod, maximal and cone responses, between CD and CRD patients. While rod responses were markedly decreased in CRD patients during their initial examination, the decrease in the rod function in both CD and CRD patients was similar in their follow-up examination (p=0.2398). Moreover, during initial examination, maximal responses were less common amongst CRD patients, over those with CD. Following the observation period, patients suffering from CRD exhibited a significant decrease in both maximal (p=0.0125) and cone (p=0.0046) responses. The clinical course of CRD and CD may vary; however, the latter appears to have a more favourable course than former. Although, at initial examination, the cone function was more diminished in CD patients, the final examinations reveal a more significant drop for CRD patients. Consequently, a differential diagnosis is essential for treating patients and forecasting their disease progression.

Early retinal function deficit without prominent morphological changes in the R6/2 mouse model of Huntington's disease.

Huntington’s disease (HD) is an inherited neurodegenerative disorder that primarily affects the medium-size GABAergic neurons of striatum. The R6/2 mouse line is one of the most widely used animal models of HD. Previously the hallmarks of HD-related pathology have been detected in photoreceptors and interneurons of R6/2 mouse retina. Here we aimed to explore the survival of retinal ganglion cells (RGCs) and functional integrity of distinct retinal cell populations in R6/2 mice. The pattern electroretinography (PERG) signal was lost at the age of 8 weeks in R6/2 mice in contrast to the situation in wild-type (WT) littermates. This defect may be attributable to a major reduction in photopic ERG responses in R6/2 mice which was more evident in b- than a-wave amplitudes. At the age of 4 weeks R6/2 mice had predominantly the soluble form of mutant huntingtin protein (mHtt) in the RGC layer cells, whereas the aggregated form of mHtt was found in the majority of those cells from the 12-week-old R6/2 mice and onwards. Retinal astrocytes did not contain mHtt deposits. The total numbers of RGC layer cells, retinal astrocytes as well as optic nerve axons did not differ between 18-week-old R6/2 mice and their WT controls. Our data indicate that mHtt deposition does not cause RGC degeneration or retinal astrocyte loss in R6/2 mice even at a late stage of HD-related pathology. However, due to functional deficits in the rod- and cone-pathways, the R6/2 mice suffer progressive deficits in visual capabilities starting as early as 4 weeks; at 8 weeks there is severe impairment. This should be taken into account in any behavioral testing conducted in R6/2 mice.

Chromatic pupillometry for assessment functional rod and cone patterns in Usher syndrome patients

AbstractPurpose The aim of the study was to characterize the functional rod and cone patterns using chromatic pupillometry in Usher syndrome patients.Methods Prospective case series study enrolled 45 Usher syndrome patients. All patients underwent in‐depth phenotypic examination. Functional rod and cone patterns were obtained using custom‐made chromatic pupillometer(AMTech, Dosenheim, Germany). Pupil diameter was recorded monocular in response to red (640 nm) and blue (462 nm) light stimuli for varied intensity levels (ranged from 1000 cd/m2 to 0.001cd/m2). Response amplitudes were analyzed and compared to the clinical phenotype.Results Pupil responses to rod‐ and cone‐weighted stimulation were significantly diminished in all Usher syndrome patients for all intensity levels (mean decrease 60% and 30%, respectively p<0.001). Lower rod‐weighted responses were related with decreased b‐wave amplitude in full field ERG (r=0.37,p<0.001). Decreased cone‐weighted responses were correlated with diminished photopic ERG b‐wave amplitude (r=0.43,p<0.001) and mfERG amplitudes (r=0.65,p<0.001). Higher cones‐weighted responses were associated with preserved cone mosaic in adaptive optics and presence of inner/outer segment in optical coherence tomography, although not always related with preserved visual field and visual acuity. Rod‐ and cone‐weighted responses were recordable even in a very advanced Usher syndrome cases associated with abolished ERG.Conclusion Chromatic pupillography is an objective tool to assess functional rod and cone patterns in Usher syndrome, which potentially could be used as an outcomes measure to assess safety and efficacy in therapy trials, in particularly in advanced cases.

Loss of outer retinal neurons and circuitry alterations in the DBA/2J mouse.

The DBA/2J mouse line develops essential iris atrophy, pigment dispersion, and glaucomatous age-related changes, including an increase of IOP, optic nerve atrophy, and retinal ganglion cell (RGC) death. The aim of this study was to evaluate possible morphological changes in the outer retina of the DBA/2J mouse concomitant with disease progression and aging, based on the reduction of both the a- and b-waves and photopic flicker ERGs in this mouse line. Vertically sectioned DBA/2J mice retinas were evaluated at 3, 8, and 16 months of age using photoreceptor, horizontal, and bipolar cell markers. Sixteen-month-old C57BL/6 mice retinas were used as controls. The DBA/2J mice had outer retinal degeneration at all ages, with the most severe degeneration in the oldest retinas. At 3 months of age, the number of photoreceptor cells and the thickness of the OPL were reduced. In addition, there was a loss of horizontal and ON-bipolar cell processes. At 8 months of age, RGC degeneration occurred in patches, and in the outer retina overlying these patches, cone morphology was impaired with a reduction in size as well as loss of outer segments and growth of horizontal and bipolar cell processes into the outer nuclear layer. At 16 months of age, connectivity between photoreceptors and horizontal and bipolar cell processes overlying these patches was lost. Retinal degeneration in DBA/2J mice includes photoreceptor death, loss of bipolar and horizontal cell processes, and loss of synaptic contacts in an aging-dependent manner.

ERG assessment of the functional activity of the retina in following the surgical closure of idiopathic macular holes

Twenty patients with stage 3 or 4 idiopathic macular holes were evaluated with standard cone ERG, photopic flicker ERG at 8,3-30-Hz, to study the function of cone photoreceptors, bipolar cells, and Muller cells after the surgical correction of their macular hole. The correlations between the ERG parameters and the microperimetry and optical coherent tomography data were evaluated. IMH has been associated with the general reduction in the function of the cone photoreceptors and bipolar cells and with the sharp increase in the activity of Muller cells and their functional relationships with some bipolar cells. The nature of the changes in photopic standard and flicker ERGs demonstrated the dependence of the central retinal function on the dynamics of cone bipolar cells’ recovery. In the early period after the surgery of IMH, a sharp reduction in the flicker ERG at 24 Hz was found, to be followed by a progressive increase, which indicated a pronounced reduction in the bipolar cell function with the formation of the IMH and its substantial decrease after the vitreoretinal surgery. A significant increase in the glial index for flicker ERG at 24 Hz may be associated with a compensatory overreaction of retinal Muller cells in the preoperative and in the recovery period after the closure of IMH.

Relationship between the Magnitude of Intraocular Pressure during an Episode of Acute Elevation and Retinal Damage Four Weeks later in Rats

PurposeTo determine relationship between the magnitude of intraocular pressure (IOP) during a fixed-duration episode of acute elevation and the loss of retinal function and structure 4 weeks later in rats.MethodsUnilateral elevation of IOP (105 minutes) was achieved manometrically in adult Brown Norway rats (9 groups; n = 4 to 8 each, 10–100 mm Hg and sham control). Full-field ERGs were recorded simultaneously from treated and control eyes 4 weeks after IOP elevation. Scotopic ERG stimuli were white flashes (−6.04 to 2.72 log cd.s.m−2). Photopic ERGs were recorded (1.22 to 2.72 log cd.s.m−2) after 15 min of light adaptation (150 cd/m2). Relative amplitude (treated/control, %) of ERG components versus IOP was described with a cummulative normal function. Retinal ganglion cell (RGC) layer density was determined post mortem by histology.ResultsAll ERG components failed to recover completely normal amplitudes by 4 weeks after the insult if IOP was 70 mmHg or greater during the episode. There was no ERG recovery at all if IOP was 100 mmHg. Outer retinal (photoreceptor) function demonstrated the least sensitivity to prior acute IOP elevation. ERG components reflecting inner retinal function were correlated with post mortem RGC layer density.ConclusionsRetinal function recovers after IOP normalization, such that it requires a level of acute IOP elevation approximately 10 mmHg higher to cause a pattern of permanent dysfunction similar to that observed during the acute event. There is a ‘threshold’ for permanent retinal functional loss in the rat at an IOP between 60 and 70 mmHg if sustained for 105 minutes or more.

Intravitreal Administration of HA-1077, a ROCK Inhibitor, Improves Retinal Function in a Mouse Model of Huntington Disease

Huntington disease (HD) is an inherited neurodegenerative disease that affects multiple brain regions. It is caused by an expanded polyglutamine tract in huntingtin (Htt). The development of therapies for HD and other neurodegenerative diseases has been hampered by multiple factors, including the lack of clear therapeutic targets, and the cost and complexity of testing lead compounds in vivo. The R6/2 HD mouse model is widely used for pre-clinical trials because of its progressive and robust neural dysfunction, which includes retinal degeneration. Profilin-1 is a Htt binding protein that inhibits Htt aggregation. Its binding to Htt is regulated by the rho-associated kinase (ROCK), which phosphorylates profilin at Ser-137. ROCK is thus a therapeutic target in HD. The ROCK inhibitor Y-27632 reduces Htt toxicity in fly and mouse models. Here we characterized the progressive retinopathy of R6/2 mice between 6–19 weeks of age to determine an optimal treatment window. We then tested a clinically approved ROCK inhibitor, HA-1077, administered intravitreally via liposome-mediated drug delivery. HA-1077 increased photopic and flicker ERG response amplitudes in R6/2 mice, but not in wild-type littermate controls. By targeting ROCK with a new inhibitor, and testing its effects in a novel in vivo model, these results validate the in vivo efficacy of a therapeutic candidate, and establish the feasibility of using the retina as a readout for CNS function in models of neurodegenerative disease.

Persistence of retinal function after intravitreal melphalan injection for retinoblastoma

The risk/benefit profile of intravitreal melphalan injection for treatment of active vitreous seeds in retinoblastoma remains uncertain. We report clinical and electroretinography results after 6months of one patient who has shown a favorable initial clinical response to intravitreal melphalan injections for treatment of refractory vitreous seeds. Clinical case report. The patient presented at age 17months with bilateral retinoblastoma [OD: International Classification (ICRB) group E, Reese-Ellsworth (R-E) class Vb; OS: ICRB D, R-E Vb] with no known prior family history. The right eye was enucleated primarily. The patient received systemic chemotherapy and extensive local treatment to the left eye. Ten months later, she presented with recurrent disease, including fine, diffuse vitreous seeds. Tumor control was established with intra-arterial chemotherapy and local treatment. Subsequent recurrence was treated with further intra-arterial chemotherapy, local treatment, and plaque radiotherapy with iodine-125. Persistent free-floating spherical vitreous seeds were treated with 4 cycles of intravitreal melphalan injection via the pars plana, with doses of 30, 30, 30, and 20μg. After 6months of follow-up, the left eye remained free of active tumor. Visual acuity was 20/40. Photopic ERGs amplitudes were unchanged compared with those recorded prior to the intravitreal injection treatments. Intravitreal melphalan injection for refractory spherical vitreous seeds of retinoblastoma with favorable tumor response is compatible with good central visual acuity and preservation of retinal function as indicated by photopic ERG recordings.

Functional activity of retinal neurons and Muller cells in idiopathic full‐thickness macular holes

AbstractPurpose To determine the changes of neurons and Muller cells functional activity in idiopathic macular holes (MH).Methods 7 patients (59‐70years) with a full‐thickness MH (3rd stage by Gass, 6‐8 months duration) were examined. Optical coherent tomography (Stratus3000 OCT, Carl Zeiss) used to detect the maximum size of the MH, total macular volume (TMV) and foveal thickness (FT). The central and general macular sensitivity (Sc within 3° from the fixation point, and Sg) were tested with microperimetry (macula 12°, MP1 Nidek). The cone ERG, photopic flicker ERGs (FERG) at 8.3, 10, 12, 30Hz were recorded (RETIport/scan21, Roland Consult), and glial indices were calculated as the ratio of amplitudes of the ERG b‐wave and every FERG.Results The best corrected visual acuity was 0.23±0.09, FT=345±12μ; TMV=7.3±0.1mm3; the maximum hole size 581±62μ. Sc =7.9±1.1dB; Sg=12.2±1.3dB. In MH, a moderate reduction of a‐ and b‐wave amplitudes was noted up to 67% and 88.3% of the norm. The b/a ratio was to 50% higher than in control, reflecting a violations in the outer/post‐receptor retina interface. The amplitude of 24Hz‐FERG (but not the 8.3‐12Hz FERG) showed a sharp reduction (up to 31.4%), indicating to a drastic violation of the bipolar cell activity. The less significant depression in the single‐flash ERG b‐wave may reflect the compensatory hyperactivity of Muller cells, which masks the true reduction of bipolar cells activity. Glial indices increased more than two times at 24Hz, testifying a violation of cone bipolar and Muller cells interaction.Conclusion MH is associated with the reduction in the function of photoreceptor and bipolar cells, sharp increase in Muller cell activity and interaction of cone bipolar and Muller cells.

The flicker ERG and retinal blood flow relationship in diabetic patients without retinopathy

AbstractPurpose To evaluate the association between functional and hemodynamic alterations of the retina in diabetes mellitus (DM) without retinopathy (NDR).Methods 15 patients (63±6.3 years) with DM type II (duration 6±3.5years) and NDR, and 40 age matched controls were examined. Color Doppler Imaging (CDI) was conducted to visualize blood flow in ophthalmic artery (OA), central retinal artery (CRA), medial and lateral posterior ciliary arteries brevis (PCAB). Photopic and scotopic flicker ERGs (p‐FERG and s‐FERG) were recorded at 8.3, 10, 12, 30 Hz flickering.Results In NDR, the increase of the blood flow peak systolic velocity (V syst) and end diastolic velocity (Vdiast) was noted in AO. The most significant changes in blood flow were observed in CRA and PCAB. A reliable correlations were shown between Vdiast, the resistance index RI in CRA and insulin levels (r=0.64), serum C‐peptide (r=0.60) and the index of insulin resistance IR (r=0.65); between Vdiast, RI in PCAB and insulin levels, the C‐peptide level and IR (r=0.59, 0.56, 0.59, respectively). The amplitude of light and dark adapted FERG at 8.3‐12 Hz declined in more than 60% eyes up to 69‐80%. The p‐FERGs at 24 and 30 Hz did not differ from the control; but we found a sharp increase in s‐FERG (155.5±15.3 ‐ 319.9±21.4% for 24 ‐ 30 Hz respectively). Significant correlation was shown between the 10Hz‐FERG amplitude (but not the 24Hz or 30Hz‐FERG) and Vdiast in CRA and PCAB (r=0.51; r=0.50).Conclusion There is a significant relationship between the retina hemodynamics and physiological effects of insulin, leading to metabolic disorders. Signs of blood flow deficiency in CRA and PCAB in NDR correlated with an early alteration in the photoreceptor function.

Coats’’ disease : classification and current treatment

AbstractPurpose Coats’ disease is characterized by idiopathic telangiectasia with lipid exudates and retinal ischemia. Advanced cases develop total retinal detachment (RD)(stage 3B) and neovascular glaucoma (stage 4), resulting in enucleation in 7% and 78% of cases respectively.Methods Nine consecutive cases of Coats’ disease stage 3B (n=5) and 4 (n=4) received 1 or more intravitreal injections of 0.5 ml ranibizumab. In 3 cases, subretinal fluid drainage by sclerotomy was performed. Mean age at diagnosis was 17.9 months (range 1‐38). At the end of treatment, ERG was recorded (n=4) and amblyopia treatment was attempted in 6 patients. Mean follow‐up was 42.9 months.Results Rubeosis disappeared during the first week with the retina reattaching within 4 months, rendering pathological vessels and ischemic retina accessible to conventional therapy. A single injection was sufficient in 6 cases, 2 injections were necessary in 1 patient and another needed 4. One patient developed 10 months after complete retinal reattachment a severe fibrous vitreo‐retinopathy evolving to subtotal tractional RD. Amblyopic treatment was performed in 4 patients and restored measurable visual acuity in two patients. Scotopic ERG was unrecordable with a severely reduced photopic b wave in 3 patients. The last patient had a reduced scotopic b wave (50%) and a normal photopic ERG with slightly increased implicit time.Conclusion There is an increasing interest in anti‐VEGF therapy in Coats' disease. To our knowledge, this is the largest series of stage 4 and 3B Coats' disease treated by ranibizumab, demonstrating that it is a well‐tolerated and safe therapy in young children with advanced disease. Ranibizumab facilitates the management by suppressing rubeosis in stage 4 and decreasing exudation.

Recording of the full‐field electroretinogram in minipigs

To test a simple electroretinographic protocol on a representative sample of minipigs. Minipig. Electroretinogram recordings were conducted on 162 healthy minipigs (81 males and 81 females) aged 4-6 months. After a 1.5-h light-adaptation period, the animals were anesthetized with general anesthesia. First, binocular full-field photopic electroretinogram recordings were conducted under photopic conditions. Subsequently, scotopic electroretinogram recordings were conducted during dark-adaptation periods every 4 min for a 20-min period. At the end of this period, the maximal combined rod-cone response was recorded by measuring the retinal response to a single high-intensity flash. We used sclerocorneal clip electrodes as active electrodes and needle electrodes as reference and ground electrodes. The a-wave and b-wave peak times and amplitudes have been measured and statistically analyzed. For each of the statistical comparisons, normality and homogeneity of variances were evaluated. No significant gender differences were observed, with the exception of a higher b-wave amplitude for the photopic ERG recordings observed in females when compared to males (48.14 ± 12.909 μV vs. 42.88 ± 10.666 μV; P = 0.005). The process of dark adaptation was evaluated, and the maximal combined rod-cone response was measured (a- and b-waves amplitude and peak time). We conducted photopic and scotopic electroretinogram recordings from a protocol based on light adaptation followed by dark adaptation using sclerocorneal clip electrodes, which allows quick assembly and examination.

Long‐term expression of glial cell line‐derived neurotrophic factor slows, but does not stop retinal degeneration in a model of retinitis pigmentosa

Retinitis pigmentosa is a group of diseases in which one of hundreds of mutations causes death of rod photoreceptor cells and then cones gradually die from oxidative damage. As different mutations cause rod cell death by different mechanisms, mutation-specific treatments are needed. Another approach is to use a neurotrophic factor to promote photoreceptor survival regardless of the mechanism of cell death, and previous studies have demonstrated encouraging short-term results with gene transfer of glial cell line-derived neurotrophic factor (GDNF). We generated rd10 mice with doxycycline-inducible expression of GDNF in photoreceptors (Tet/IRBP/GDNF-rd10 mice) or retinal pigmented epithelial cells (Tet/VMD2/GDNF-rd10 mice). In doxycycline-treated Tet/IRBP/GDNF-rd10 mice, there was a 9.3 × 10(4) -fold increase in Gdnf mRNA at P35 and although it decreased over time, it was still increased by 9.4 × 10(3) -fold at P70. Gdnf mRNA was increased 4.5 × 10(2) -fold in doxycycline-treated Tet/VMD2/GDMF-rd10 mice at P35 and was not significantly decreased at P70. GDNF protein levels were increased about 2.3-fold at P35 and 30% at P70 in Tet/IRBP/GDNF-rd10 mice, and in Tet/VMD2/GDNF-rd10 mice they were increased 30% at P35 and not significantly increased at P70. Despite the difference in expression, Tet/IRBP/GDNF-rd10 and Tet/VMD2/GDNF-rd10 mice had comparable significant increases in outer nuclear layer thickness and mean photopic and scotopic ERG b-wave amplitudes compared with rd10 mice at P35 which decreased, but was still significant at P70. Compared with rd10 mice, Tet/IRBP/GDNF-rd10 and Tet/VMD2/GDNF-rd10 mice had comparable significant improvements in cone density at P50 that decreased, but were still significant at P70. These data indicate that despite a large difference in expression of GDNF, Tet/IRBP/GDNF-rd10 and Tet/VMD2/GDNF-rd10 provide comparable slowing of photoreceptor degeneration, but cannot stop the degeneration.

Slowed recovery of human photopic ERG a-wave amplitude following intense bleaches: a slowing of cone pigment regeneration?

We have used the post-bleach recovery of the ERG a-wave to estimate the time-course of regeneration of cone pigment, following bleaching exposures far stronger than in a previous study. We recorded the photopic electroretinogram a-wave from two subjects, in response to dim red flashes delivered following 1-min exposures to intensities ranging from 1.1 × 10(4) to 1.3 × 10(5) photopic cd m(-2). The measured response amplitudes were "linearized" to derive estimates of pigment level. These estimated pigment levels were found to increase at an initially linear rate, consistent with a "rate-limited" model of photopigment regeneration. The extracted time-course was similar to that previously reported in densitometric studies of cone pigment regeneration after similarly intense exposures. On the other hand, the rate of regeneration was slower than measured in the same subjects following less intense bleaches. These results are consistent with the notion that cone pigment regeneration is slowed following very strong bleaching exposures, possibly as a result of depletion of a pool of retinoid.