Blue-on-Green Flash Induces Maximal Photopic Negative Response and Oscillatory Potential and Serves as a Diagnostic Marker for Glaucoma in Rat Retina

The purpose of this study was to investigate the application of various electroretinography (ERG) to the diagnosis of inner retinal dysfunction induced by mild intraocular pressure (IOP) elevation in a rat glaucoma model. For inner retinal function measurements, available photopic ERG protocols were applied under various light conditions including monochromatic combinations, which complement conventional scotopic ERG. Three episcleral veins in the right eyes of Sprague-Dawley rats were cauterized to induce an experimental model of glaucoma, leading to mild IOP elevation. ERG responses were measured before surgery and at 1, 2, 4, and 8 weeks after cauterization. We first confirmed that the amplitude reduction in the standard photopic b-wave was almost comparable to the amplitudes of scotopic a- and b-waves in glaucomatous eyes over time. We have implemented additional photopic ERG protocols under different stimulus conditions, which consisted of a longer duration and different monochromatic combinations. Such a change in the stimulations resulted in more pronounced differences in response between the two groups. Especially in normal animals, blue stimulation on a green background produced the largest b-wave and photopic negative response (PhNR) amplitudes and caused more pronounced oscillatory potential (OP) wavelets (individual components). In glaucomatous eyes, blue stimulation on a green background significantly reduced PhNR amplitudes and abolished the robust OP components. These results, by providing the usefulness of blue on green combination, suggest the applicable photopic ERG protocol that complements the conventional ERG methods of accessing the progression of glaucomatous damage in the rat retina.

Separation of rod- and cone-driven oscillatory potential from retinal cone degeneration rat and congenital stationary night blindness rat / 中华实验眼科杂志

BackgroundOscillatory potentials (OPs) has been used extensively in experimental research and clinical diagnosis,but it is well known that OPs are the summating potentials originated from retinal rod and cone.To separate the rod and cone OPs is helpful for us to diagnose some retinal diseases.ObjectiveThis study was to analyze the characteristics of cone-and rod-driven OPs. Methods The retinal cone degeneration ( RCD ) and congenital stationary night blindness(CSNB) rats were used in this study and SD rats served as control,and 6 rats for each kinds of animals.Scotopic and photopic OPs were recorded in each rat under the dark adaptation for 12 hours and light adaptation for 10 minutes at the stimulate light intensities of -35,-25,-15,-5,0,5 db respectively with RETIscan Visual Electrophysical System.The scotopic and photopic OPs were extracted from flash electroretinogram (FERG) with Maflab7.0 Butterworth filtering waves,and the frequency spectrum of the OPs was analyzed by fast Fourier transform.The characteristics of OPs from RCD rats and CSNB rats were assessed and compared.Results The a wave and b wave of ERG were showed under the dark adaptation condition in both SD and RCD rats,but the b wave was absent in CSNB rat.Under the light adaptation condition,b wave was seen in both SD and CSNB rats,but a wave and b wave of RCD rat were absent.Two peaks were exhibited in both SD and RCD rats under the darkadaptation condition and high intensity of stimulate light at the lower frequency( domain frequency) of 75-110 Hz,90-120 Hz and high frequency ( minor frequency) 90- 120 Hz,110- 135 Hz respectively.In various intensities of stimulate light,CSNB rats appeared a peak at 70-100 Hz.But in light-adaptation and various intensities of stimulate light,the frequency peaks were seen at 75-95 Hz and 70-85 Hz from both SD and CSNB rats respectively.However,under the light adaptation condition,only one peak was seen in SD and CSNB rats at the 75-95 Hz and 70-85 Hz respectively.Compared with SD rats,the mean implied time of b wave was delayed and the amplitude was lowed under the light adaptation (P＜0.05 ),however,no significant differences were found in the implied time and amplitude of b wave of scotopic ERG between SD rats and RCD rats( P＞0.05 ).The scotopic OPs showed the prolong implied time and depressed amplitudes in RCD rats and CSNB rats compared with SD rats( P＜0.05 ),and the photopic OPs presented the prolong implied time and lowed amplitude in CSNB rat in comparison with SD rats (P ＜ O.05 ).ConclusionsCone- and rod-driven OPs appear very different characteristics.The results of this study imply that rod pathway gives more contribution to OPs than cone pathway.Analysis of these results will be helpful for the exploration of the origin of OPs and the diagnosis of the related disease.

Comprehensive examination of visual electrophysiology of visual function assessment after cataract operation / 眼科新进展

Objective　To study the value of comprehensive examination of visual electrophysiology in prognosis of visual function after cataract operation.Methods　315 patients with cataract(408 eyes) underwent preoperative routine examination with pattern reversal visual evoked potential(PVEP), red and blue flicker electroretinogram(ERG) and oscillatory potential (OPs). Normal control group included 162 cases (266 eyes). All of the ocular fundi were examined postoperatively and corrected visual acuities were obtained 3 months after operation. Results　Postoperative corrected visions ≥0.5(Ⅰ) and ＜0.5(Ⅱ) in case group compared with that in control group, amplitudes of PVEP P100-wave decreased significantly and PVEP P100-wave latency times prolonged significantly in group Ⅰ and Ⅱ. There was much more prominent changes in P100-wave of group Ⅱ due to other factors influencing visual function. There wasn't significant difference of the amplitudes and the latency times of a-wave and b-wave of Red-Blue ERG in group Ⅰ and the control group preoperatively. The amplitudes of a-wave and b-wave of Red ERG decreased, the latency times of a-wave and b-wave of Red ERG prolonged, the amplitudes of a-wave and b-wave of Blue ERG decreased but latency times didn' t prolong in group Ⅱ. The value of OPs decreased in groupⅡ compared with that of the control group, which was related to the retinopathy due to blood circulation obstruction.Conclusion　Combined examination of visual electrophysiology can estimate visual function thoroughly. The prognosis will be good if various examinations are normal before operation, but will not be good if PVEP P100 latency time prolong, the amplitudes of a-wave and b-wave of Red ERG decrease and the latency time prolong, the amplitudes of a-wave and b-wave of Blue ERG decrease and the value of OPs decrease.

The Effect of Experimental Ocular Hypertension on the Electroretinogram in Laser Treated Rabbit Eyes

The argon laser is widely used to coagulate the diabetic retina in order to inhibit the progression of diabetic retinopathy. To compare the electrophysiological changes of the photocoagulated retina according to the level of intraocular pressure(IOP), the right eyes of 24 pigmented rabbits underwent retinal photocoagulation with an argon laser. Retinal function was assessed electroretinographically at 4 weeks after retinal photocoagulation before treatment and under elevated IOP(40 mmHg, 60 mmHg, 80 mmHg) for 4 hours. In the 40 mmHg group, the amplitude of the a-, b-, oscillatory potentials(OPs) of the photocoagulated eyes showed a more rapid drop than the control eyes, and there was no recovery stage seen in the control eyes. In the 60 mmHg group the amplitude of the a-wave, b-wave, and OPs of photocoagulated eyes showed a rapid drop and were abolished after 3.5 hours, but that of the control eyes showed biphasic changes; first, a rapid drop with the same velocity as the photocoagulated eyes during the first 2 hours, then a steady stage for the last 1.5 hours. In the 80 mmHg group, electroretinogram was totally abolished within 20 minutes after elevation of IOP in both eyes. The above results showed that the photocoagulated eyes treated 4 weeks ago were more vulnerable to elevated IOP than the control, healthy eyes.

Changes in ERG b-wave and Oscillatory Potential in Relation to the Dark Adaptation and Light Adaptation Time

Authors studied characteristics of ERG b-wave and oscillatory potential, which can be applied to ERG protocol for clinical purposes. Following conclusions were obtained from the ERG test performed on 20 normal men(40 eyes) during dark adaptation and light adaptation time, under the conditions where other factors were equal. 1. In the scotopic ERG test, 88%(364/414uv) of maximum b-wave amplitude in 30 minutes were obtained in first 1 minute of dark adaptation. By using this shortening scotopic protocol for the acquired retinal disease, sufficient result can be expected without the over 20 minutes dark adaptation. 2. In the photopic ERG test, if over 30 minutes dark adaptation time were given, it would take at least 15 minutes to reach the regular initial photopic value. Therefore, it is recommended that photopic ERG test be done before the scotopic ERG test. 3. In the oscillatory potential test, light adaptation time has little effect on summed photopic oscillatory potential amplitudes and implicit time. Summed scoto pic oscillatory potential amplitude reaches the highest 1 minute after the dark adaptation. Therefore, it is recommended that to obtain higher amplitude and more sensitive test result, oscillatory potential test be done 1 minute after the dark adaptation.