Dose-dependency and Time-course of Electrophysiologic Short-term Effects of VIAGRA®: A Case Study

The dose-dependency and time-course of the short-term visual effects of sildenafil citrate (VIAGRA) were tested in two subjects. Blood pressure was measured and samples of blood taken at 30 min intervals before and after drug administration. In the first experiment, prolongations of the implicit times of the scotopic maximum a-wave, cone a- and b-wave, 33 Hz flicker, ON-response a- and b-wave and 3.3 Hz a- and b-wave electroretinogram (ERG) recordings and of the oscillatory potentials OP1, OP2, and OP3 were observed for both eyes of both subjects, following 100 or 200 mg dosings. Interestingly, no prolongation was found for OP4, to which the OFF-bipolar cell pathway significantly contributes. In the second experiment, in which visual function was repeatedly assessed following a 200 mg dose, similar prolongations were found in both eyes of one subject for the implicit times of the oscillatory potential OP2, the cone b-wave response and the 3.3 Hz a-wave. Moreover, the steady-state (A0) and immediate extinction (B0) blue target thresholds of transient tritanopia were raised relative to the pre-drug administration baseline effects. While the maximum lowering of both systolic and diastolic blood pressure approximately correlated with the peak plasma concentration of sildenafil (c. 30-60 min after administration), the peak magnitudes of most visual effects were found at c. 110 min, consistent with a second compartment kinetic.     

Effects of phosphodiesterase type 5 inhibitor sildenafil on retinal function in isolated superfused retina.

After the oral ingestion of sildenafil, visual abnormalities have been reported constantly. The mechanism of these adverse events has been presumed to be a result of the interaction of sildenafil with the retinal phosphodiesterase (PDE) type 6. To investigate the physiological basis of the effects of sildenafil on retinal function, bovine retinas were isolated and perfused with an oxygen pre-equilibrated standard solution. The electroretinogram (ERG) was recorded as a transretinal potential using silver/silver-chloride electrodes. After reaching stable ERG amplitudes, sildenafil was added to the nurient solution at different concentrations, and its effect on the a- and b-wave amplitude was studied separately. The 0.1 microM and higher concentrations of sildenafil reduced the b-wave amplitude, while a reduction of the a-wave amplitude was observed at an elevated threshold of 0.3 microM. The changes of the ERG amplitudes were fully reversible for the b-wave at a concentration of 0.1 microM and for the a-wave at 0.3 microM sildenafil. At higher concentrations, sildenafil was found to be only partially reversible within recovery time. In conclusion, besides an inhibitory influence on photoreceptors, sildenafil performs additional effects on the postsynaptic neuronal network. Higher concentrations of sildenafil were found to have a potential for retinal degeneration, suggesting that further trials should be designed to evaluate the long-term effects of sildenafil. The physiological consequences of an abuse or long-term, daily use of sildenafil are not clear.     

综合视觉电生理检测对白内障术后视功能恢复的评估

目的 评价术前综合视觉电生理检测在判断白内障手术视功能预后中的作用。方法 白内障患者３１５例（４０８眼）术前常规检测图形翻转视觉诱发电位（ＰＶＥＰ）、红蓝光视网膜电图（ＦＥＲＧ）和视网膜电图的振荡电位（ＯＰｓ）。正常对照组１６２例（２６６眼）。术后检查眼底,术后３ｍｏ查矫正视力。结果 术后矫正视力≥０．５（Ⅰ组）和〈０．５（Ⅱ组）者与对照组相比,术前ＰＶＥＰ的Ｐ１００波振幅均下降、潜伏期均延长,后     

The effects of the phosphodiesterase type V inhibitor sildenafil on human and bovine retinal function in vitro

Background After the ingestion of sildenafil (Viagra), visual adverse events have been reported, possibly caused by an inhibition of the phototransduction cascade by sildenafil via phosphodiesterase (PDE 6). Therefore, we investigated the effects of sildenafil on photoreceptors and postsynaptic neurons of human and bovine retinas using the isolated superfused vertebrate retina technique. Methods Human and bovine retina preparations were perfused with an oxygen preequilibrated standard solution. The electroretinogram (ERG) was recorded using Ag/AgCl electrodes. After recording stable ERG amplitudes, sildenafil was added to the solution for 45 min. Thereupon, the preparations were reperfused with standard solution for 240 min. Results Following the application of sildenafil (3 μMol/l), the b-wave amplitude of bovine and human preparations was reduced continuously and disappeared completely. After reperfusion with the standard solution for 4 h, the b-wave amplitude did not recover completely. Using the same sildenafil concentration (3 μMol/l), the a-wave amplitude of the human retina was not totally abolished, but reduced to 21% of the initial amplitude and remained reduced at washout. For all retinal preparations, the implicit time of the ERG amplitudes remained significantly extended at the end of the washout. Conclusions Strong similarities were detected in the drug-induced changes of the ERG when comparing human and bovine retinas. The results suggest that sildenafil impairs retinal function at not only the level of the photoreceptors, but it also affects the neuronal network of the inner retina at concentrations of approximately 30-fold higher than at therapeutic plasma concentrations. Dedicated to the late Prof. Dr. Werner Sickel, who passed away on 18th December 2004.     

Electroretinographic monitoring in birdshot chorioretinopathy

PURPOSE: To evaluate electroretinography (ERG) during long-term follow-up in birdshot chorioretinopathy (BCR). DESIGN: Retrospective, comparative interventional case series. METHODS: SETTING: University subspecialty clinic. PATIENT POPULATION: Twenty-three HLA-A29-positive patients with BCR and 40 normal control subjects. INTERVENTION PROCEDURE: Patients were monitored with ERG approximately annually. Treatment was according to best medical judgment. main outcome measures: Baseline ERG values, vision, and ERG values during observed and treated intervals. RESULTS: Median age of patients was 52 years, and 19 patients were untreated at baseline. Eighty-two ERGs were performed. Eighteen patients had more than one ERG; mean follow-up of these patients was 40.2 months +/- 31.2, median 23 months. At baseline, several ERG parameters were statistically reduced compared with control subjects when adjusted for age. The combined rod-cone and cone b/a wave ratios did not differ from control subjects (P = .45 and 0.14). Scotopic rod and combined rod-cone b-wave amplitudes were statistically correlated with baseline vision, as were implicit times for the combined rod-cone a-wave, cone a-wave, and cone flicker b-wave. Median visual acuity was 20/25 and did not change during follow-up. Most ERG parameters showed marked worsening during observed intervals. During treated intervals, the ERG declined at a rate consistent with aging. CONCLUSIONS: Many ERG parameters in patients with BCR greatly differ from control subjects, correlate with vision, and worsen during observation. Selected patients may show improvement in ERG with treatment. The cone b-wave flicker implicit time was most often associated with clinically important measures such as vision, duration of symptoms, and deviation from normalcy.     

Sildenafil-mediated reduction in retinal function in heterozygous mice lacking the gamma-subunit of phosphodiesterase

PURPOSE: Retinitis pigmentosa (RP) is a common inherited degenerative retinal disease that has many causes including mutations in the genes coding for cyclic guanosine monophosphate (cGMP) phosphodiesterase 6 (PDE6). Sildenafil (Viagra; Pfizer Pharmaceuticals, New York, NY), a widely used medication for erectile dysfunction, is a specific inhibitor of PDE, with the potential to affect PDE6 in the retina. The purpose of this study was to investigate the retinal effects of sildenafil on knockout mice heterozygous for a mutation causing absence of the gamma subunit of rod PDE6 (PDEG:(tm1)/+). METHODS: Wild-type mice and PDEG:(tm1)/+ mice were subjected to electroretinography (ERG) 1 hour after exposure to one of three treatments: 1) no drug, 2) an intraperitoneal injection of sildenafil at 2 times the equivalent maximal daily recommended dosage for humans, or 3) 10 times this dosage. Control ERGs were also obtained to evaluate the reversibility of changes in retinal function after sildenafil treatment. A minimum of 48 hours elapsed between electroretinogram (ERG) recordings for drug washout and animal recovery. RESULTS: ERGs of the PDEG:(tm1)/+ mice treated with sildenafil showed a reversible, dose-dependent decrease in a- and b-wave amplitudes. Wild-type mice treated with sildenafil did not show significant differences in either a- or b-wave amplitudes compared with untreated control animals. CONCLUSIONS: These findings suggest that sildenafil has a significant impact on retinal function in PDEG:(tm1)/+ mice and may have implications in human carriers of RP. In addition, extension of these results in other model systems could be useful in understanding the mechanisms of RP and other forms of retinal degeneration.     

Comparison between Dawson, Trick, and Litzkow electrode and contact lens electrodes used in clinical electroretinography

PURPOSE: To determine the reliability of the Dawson, Trick, and Litzkow (DTL) electrode in electroretinographic recordings (ERG) in subjects of all ages, we evaluated ERG responses obtained with the contact lens (CL) and DTL electrodes and estimated a DTL/CL ratio for each sample. METHODS: Seventy-nine volunteers aged 2-84 years (79 normal eyes) were recruited for the study. Electroretinographic recordings elicited by monocular single-flash stimuli delivered by an automatic ERG recording system were recorded using both CL and the DTL electrodes (CL-ERG and DTL-ERG, respectively). RESULTS: The relative amplitude of the DTL-ERG to the CL-ERG was 79.6-99.8% (mean = 93.4%) for the a-wave and 84.4-106.3% (mean = 92.3%) for the b-wave. The relative latency of the DTL-ERG to the CL-ERG was 86. 0-107.6% (mean = 98.2%) for the a-wave and 96.1-113.0% (mean = 97. 9%) for the b-wave. The a- and b-wave amplitudes differed significantly between DTL and CL electrodes only in the 40- to 49-year-old age groups (P <.05). Regression analysis indicated moderate to strong relationships between the electrodes for amplitude (a-wave, r = 0.690; b-wave, r = 0.824) and latency (a-wave, r = 0.667; b-wave, r = 0.725). CONCLUSION: The DTL electrode has as high stability as the conventional CL electrodes for ERG recordings in most age groups.     

A double-blind placebo-controlled evaluation of the acute effects of sildenafil citrate (Viagra) on visual function in subjects with early-stage age-related macular degeneration

PURPOSE: To assess the effects of a single 100-mg dose of sildenafil citrate on visual function in men with early-stage age-related macular degeneration. DESIGN: Randomized double-blind placebo-controlled clinical trial. METHODS: Nine men (mean age 71 years, range 59-85 years) with early-stage (minimal visual impairment and large drusen in the macula) age-related macular degeneration and 20/40 or better-corrected visual acuity in at least one eye were prospectively randomized to receive either placebo or sildenafil citrate (Viagra; Pfizer Inc, New York, New York) 100 mg as a single oral dose. After 7-14 days, they received the alternate treatment. Subjects underwent visual acuity, Amsler grid, color discrimination (D15), traffic light, Humphrey perimetry, and photo-stress testing in each eye before and at specific intervals within 8 hours after dosing. RESULTS: Compared with placebo, no pattern of errors were evident in any visual function test following sildenafil administration. No statistically or clinically relevant changes from baseline were observed in visual acuity, Humphrey perimetry (corrected pattern standard deviation), D15 color discrimination, or photo-stress tests. No clinically relevant changes were observed in the Amsler grid or traffic light tests. Sildenafil treatment was associated with transient mild or moderate headache, flushing, and rhinitis. There were no visual adverse events spontaneously reported to the investigator. CONCLUSION: A single 100-mg dose of sildenafil was well tolerated and produced no acute visual effects or exacerbation of preexisting visual impairment in nine men with early-stage age-related macular degeneration.     

On-response deficit in the electroretinogram of the cone system in X-linked retinoschisis

PURPOSE: The purpose of this study was to evaluate the hypothesis that the reduced b-wave to a-wave ratio of the brief-flash electroretinogram (ERG) of the cone system typically observed in X-linked retinoschisis (XLRS) represents a relatively greater deficit in the ON response (response to light onset) than the OFF response (response to light offset). A second purpose was to investigate the use of sawtooth flicker as a stimulus for eliciting ERG ON and OFF responses. METHODS: Light-adapted, full-field ERGs were recorded in six patients with XLRS and six age-similar control subjects in response to 8-Hz rapid-on and rapid-off sawtooth flicker to emphasize ON and OFF responses, respectively. ERG responses were analyzed in terms of the amplitudes and implicit times of the a-wave, b-wave, and d-wave components. RESULTS: There was no significant difference between the patients with XLRS and the control subjects for either the amplitude of the a-wave of the ON response or the amplitude of the d-wave of the OFF response. However, the amplitude of the b-wave of the ON response was reduced significantly in the patients with XLRS, resulting in a significantly reduced b-wave to d-wave ratio. The patients' implicit times were increased significantly for all waveform components. CONCLUSIONS: The reduced b-wave to d-wave ratio of the ERG of the cone system in these patients with XLRS is consistent with a relative dysfunction of the cone ON bipolar cell pathway in this disorder. The results show further that sawtooth flicker is a promising stimulus for eliciting well-defined ERG waveforms that can provide a quantitative assessment of the properties of ON and OFF responses in retinal disease.     

Vitrectomy for diabetic eye disease. The prognostic value of pre-operative electroretinography and visual evoked cortical potentials

An investigation was carried out into the prognostic value of standard flash electroretinography (ERG) and visual-evoked cortical potentials (VECP) recorded for 87 diabetic eyes prior to vitrectomy. 95% of the eyes with a recordable ERG b-wave achieved a post-operative visual acuity (VA) of 0.05 or better (positive predictive value), but only 35% of the eyes with a good post-operative VA had a recordable b-wave (sensitivity). The corresponding values for the ERG a-wave were 67 and 72%, and for the VECP 77 and 69%, respectively. A non-recordable b-wave in the ERG was associated with a poor visual outcome (VA less than 0.05) in 45% of cases (negative predictive value), and 97% of the eyes with a poor visual outcome had a nonrecordable b-wave (specificity). The corresponding values for the ERG a-wave were 42 and 37%, and for the VECP 53 and 63%, respectively. Consequently, the odds ratio for an unfavourable visual outcome (VA less than 0.05) was greater for a non-recordable b-wave (15.7) than for a nonrecordable VECP (3.8) or a non-recordable a-wave (1.5). Recordability of the b-wave gave the best prediction for attached macula. Extensive photocoagulation diminished all ERG and VECP amplitudes. Vitreous opacities had no significant effect on the ERG or VECP.     

A form of congenital stationary night blindness with apparent defect of rod phototransduction

We report findings obtained from an individual with an unusual form of congenital stationary night blindness (CSNB). Although the rhodopsin density difference of this subject was normal, there was no evidence of rod-mediated visual function. Dark-adapted thresholds were cone-mediated, and dark-adapted electroretinograms (ERGs) represented activity of the cone system exclusively. ERG a- and b-waves obtained under light-adapted conditions were normal. The absence of a rod a-wave but the presence of normal rhodopsin density, in combination with normal cone function, indicates that this form of CSNB likely involves a defect of phototransduction that is limited to the rods. In addition, light-adapted b-wave responses to high luminance flashes were larger than dark-adapted responses, whereas a-wave amplitudes were reduced by light adaptation. These ERG results address proposed mechanisms by which light adaptation might enhance cone system responses.     

The effects of levodopa and haloperidol on flash and pattern ERGs and VEPs in normal humans

We investigated the effects of single doses of the dopamine agonist levodopa and the dopamine antagonist haloperidol on pattern and flash electroretinograms (ERGs) and visual evoked potentials (VEPs) in normal subjects. A placebo and two treatment regimens were administered in a randomized double-masked design. No significant intertreatment differences in the pattern ERGs and VEPs were noted. Although not statistically significant, a clearly discernible tendency was found for increased flash ERG b-wave amplitudes after levodopa administration compared with placebo. In comparison with placebo and levodopa, haloperidol was associated with significantly prolonged flash ERG b-wave implicit times, including each oscillatory potential, which also showed increased duration, particularly in the O1–O3 interpeak implicit time. The failure of pattern ERGs and VEPs to show changes after haloperidol may have been related to the timing of the recordings, which took place during the presumed phase of rising blood levels and before the flash ERG and VEP recordings. Our findings further demonstrated the reliability of the flash ERG in revealing changes in dopaminergic status in the visual system and suggest that steady-state (flicker) ERGs, cone ERGs, and oscillatory potentials have particular use in this regard.Abbreviations C-ERG Cone dominated ERG - M-ERG mixed rod and cone ERG - R-ERG rod dominated ERG - S-ERG steady-state (flicker) ERG - OP oscillatory potential - P-ERG pattern-reversal ERG - F-VEP flash visual evoked potential - P-VEP pattern reversal visual evoked potential - RCT retinocortical time     

Effects of protein tyrosine kinase inhibitor genistein on retinal function in superfused vertebrate retina.

The aim of this study was to evaluate safe concentrations of genistein for a potential intraocular application using the isolated retina technique on bovine retina preparations. Bovine retinas were isolated and perfused with an oxygen pre-equilibrated standard solution. The electroretinogram (ERG) was recorded as a transretinal potential using silver/silver-chloride electrodes. After recording of stable ERG amplitudes, genistein was added to the solution in different concentrations. The percentage of b-wave reduction under the drug was calculated. We also studied the influence of genistein on the a-wave amplitude. After the addition of aspartate, the b-wave amplitude was reduced continuously until unmasked a-wave amplitudes were reached. Genistein was then added to the aspartate containing perfusate. The percentage of a-wave amplitude reduction under the drug was calculated. Concentrations of 3.3 microMol/l and higher were found to reduce the b-wave amplitude. The a-wave amplitude was not changed by the applied concentrations. The ERG only showed toxic effects from genistein beyond concentrations that were found to inhibit endothelial cell growth in vitro. In previous studies, beneficial effects on trabecular meshwork cells were present for genistein concentrations which are distinctly higher than the maximum nontoxic concentration reported here. It was shown that the photoreceptor layer is not affected at the examined concentration range. Therefore, we attribute the toxic effects to postsynaptic interaction of genistein. Intraocular application of genistein in a sufficient concentration seems possible.     

Functional changes in rod and cone pathways after photoreceptor loss in light-damaged rats

PURPOSE: To determine the functional changes in the rod and cone pathways after photoreceptor loss by continuous light exposure. METHODS: Fifty-four male Sprague-Dawley rats were exposed to diffuse fluorescent light of 2000 lux for 24 or 48 hr. Two weeks after the light exposure, full-field scotopic and photopic electroretinograms (ERGs) were elicited by different stimulus intensities with a maximum luminance of 0.84 log cd-s/m2. The amplitudes of the a- and b-waves of the scotopic ERGs and the b-wave of the photopic ERGs were measured. The animals were sacrificed after the ERG recordings, and the number of surviving rod and cone nuclei in the outer nuclear layer was counted. RESULTS: The logarithm (log) of the amplitudes of the maximum rod a-wave (rod Va(max)) and b-wave (rod Vb(max)) was reduced monotonically with a decrease in the rod nucleus counts (p < 0.0001). The regression line for the rod Va(max) decrease was significantly steeper than that for the rod Vb(max) (p < 0.005). The maximum b-wave amplitudes of the photopic ERGs (cone Vb(max)) were significantly correlated with the number of cone nuclei in a log-linear fashion. The slopes of the regression lines for the rod Vb(max) and cone Vb(max) were 0.0067 and 0.0140, respectively, which indicates that the amplitude of the cone b-wave was more severely affected than that of the rod b-waves by light-induced photoreceptor degeneration (p < 0.005). CONCLUSIONS: The amplitudes of the rod and cone ERGs were correlated with rod and cone nuclei counts in a log-linear fashion in light-damaged rats. The functional loss from the photoreceptor death had a greater effect on the cone pathway than on the rod pathway when the retinal function was assessed by the b-wave.     

Cone phototransduction and growth of the ERG b-wave during light adaptation

The purpose of this study was to determine whether cone redepolarization accounts for the amplitude increase of the b-wave of the human electroretinogram (ERG) during light adaptation. The time course of the b-wave amplitude increase was compared to the time course of the change in the activation phase of cone phototransduction, as derived from a delayed Gaussian model applied to the leading edge of the ERG a-wave. ERG recordings were obtained from five visually normal subjects, alternately in the presence of the adapting field (adapt-on condition) and 300ms after its temporary extinction (adapt-off condition). The proportional increase in amplitude was less for R(mp3) (maximum amplitude of P3, the massed cone photoreceptor response) than for the b-wave for both adaptation conditions, and the time course of the amplitude increase for R(mp3) was faster than that for the b-wave in the adapt-off condition. The results demonstrate that time-dependent changes in the activation phase of cone phototransduction have only a minimal role in governing the increase in the amplitude of the human cone-derived ERG b-wave during light adaptation. In addition, the systematic increase in b-wave amplitude and the decrease in b-wave implicit time in the adapt-off condition indicates that the ERG response measured shortly after adapting field offset does not necessarily represent the waveform of the dark-adapted cone ERG.     

Intraretinal processing following photoreceptor rescue by non-retinal cells

Royal College of Surgeon (RCS) rats undergo retinal degeneration due to the inability of retinal pigment epithelial (RPE) cells to phagocytose shed outer segments. We explored the effect of introducing Schwann cells to the subretinal space of RCS rats (before the onset of retinal degeneration), by relying on electroretinogram (ERG) recordings and correlative retinal morphology. Scotopic ERGs recorded from cell-injected eyes showed preserved amplitudes of mixed a-wave b-wave, rod b-waves, and cone b-waves over controls (sham-injected eyes); photopic b-wave amplitudes and critical flicker fusion were also improved. Normal retinal morphology was found in areas of retinas that had received cell injections. Since Schwann cells have no phagocytic properties, their therapeutic effect is best explained through a paracrine mechanism (secretion of factors that ensure photoreceptor survival).     

Viagra (sildenafil citrate) and ophthalmology

Viagra (sildenafil citrate) improves penile erections in men with erectile dysfunction (ED) by selectively inhibiting cGMP-specific phosphodiesterase type 5 (PDE5), which is present in all vascular tissue. It also exerts a minor inhibitory action against PDE6, which is present exclusively in rod and cone photoreceptors. At higher doses, sildenafil causes mild and transient visual symptoms in a minority of patients (mainly blue tinge to vision, increased brightness of lights). Therefore, the effects of sildenafil on the visual system have been investigated in a wide variety of clinical and preclinical studies. In preclinical studies, sildenafil shows transient reversible effects on electrical response to light. In long-term toxicology studies in which animals were exposed to high multiples of the maximum human therapeutic dose, detailed examinations have revealed no adverse effects on the structure or function of the eye. The effects of sildenafil have been systematically investigated in visual function studies in volunteers and in patients with eye disease; sildenafil does not affect visual acuity, visual fields, and contrast sensitivity. The only definite effect is transient, mild impairment of color discrimination occurring around the time of peak plasma levels. In long-term studies, no long-term effects of sildenafil on the visual system have been observed. Postmarketing, sildenafil has been prescribed to over 15 million men with ED. Isolated examples of a variety of visual adverse events have been reported. No consistent pattern has emerged to suggest any long-term effect of sildenafil on the retina or other structures of the eye. Based on this experience, intermittent, short-term, partial inhibition of PDE5 or PDE6 by sildenafil is unlikely to induce any long-term visual change.     

Detecting color vision in a malingerer

A patient describing himself as totally color blind was ordered by the judicial system to have his color vision investigated in order to establish his suitability for military service. Basic clinical (Farnsworth Panel D-15, Moreland and Rayleigh anomaloscope equations), electroretinographic (ERG) and psychophysical techniques (spectral sensitivities) were applied to determine the extent of his color discrimination performance and cone function. These standard procedures were complemented by a test for cone interaction (transient tritanopia) and by newly developed cone-isolating flicker large-field ERG recordings. The patient's data consistently indicate the function as well as the functional interaction of the middle-wavelength-sensitive (M-) and the short-wavelength-sensitive (S-) cones. But the function of the long-wavelength-sensitive (L-) cones was completely absent. Hence the patient was correctly demonstrated to be a protanope. This study establishes that standard classical procedures, in combination with newly developed and easy to apply psychophysical and ERG ones, which can be reliably used to assess true color discrimination performance, in difficult cases of malingering.     

Predominant loss of the photopic negative response in central retinal artery occlusion

PURPOSE: To determine how the photopic negative response (PhNR) is affected in central retinal artery occlusion (CRAO). DESIGN: Observational case series. METHODS: Seven patients with unilateral CRAO were included. Full-field scotopic and photopic electroretinograms (ERGs) including the PhNR were recorded. Each ERG amplitude in the affected eye was expressed as a percentage of amplitude of the corresponding wave in the unaffected eye. RESULTS: Mean of the PhNR amplitude was reduced to 12.3 +/- 11.7% of that of unaffected eyes whereas the cone b-wave amplitude was attenuated to only 73.4 +/- 30.4%. This reduction of the PhNR amplitude was more significant than that of other waves including the rod b-wave, maximum a-wave and b-wave, cone a-wave and b-wave, and 30 Hz flicker ERG (P <.005). CONCLUSIONS: The PhNR was severely affected in CRAO despite relative preservation of the cone b-wave, implicating massive loss of ganglion cells and their axons.     

Partial preservation of rod and cone ERG function following subretinal injection of ARPE-19 cells in RCS rats

We quantified rod- and cone-related electroretinogram (ERG) responses following subretinal injections of the human-derived retinal pigment epithelial (hRPE) cell line ARPE-19 at age P23 to prevent progressive photoreceptor loss in the Royal College of Surgeons (RCS) rat. Culture medium-injected eyes served as sham controls. At P60, in comparison with sham-injected eyes, all recordings from hRPE-injected eyes showed preserved scotopic a- and b-waves, oscillatory potentials, double-flash-derived rod b-waves and photopic cone b-waves, and flicker critical fusion frequencies and amplitudes. Although the actual preservation did not exceed 10% of a-wave and 20% of b-wave amplitude values in non-dystrophic RCS and deteriorated rapidly by P90, rod- and cone-related ERG parameters were still recordable up to P120 unlike the virtually unresponsive sham-injected eyes.