A comparison of photopic and scotopic electroretinographic changes in early diabetic retinopathy.

Previous studies of early diabetic retinopathy have shown that oscillatory potential (OP) amplitudes are reduced in many diabetic patients. OP amplitude is believed to be a more sensitive indicator of the development of future retinopathy than b-wave amplitude of the scotopic electroretinogram (ERG). Because OPs measured to a bright white flash reflect both rod and cone system activity, it is important to compare OP amplitudes to photopic ERG measures as well as scotopic measures in early diabetic retinopathy. In this study, OPs and ERG responses were measured under photopic and scotopic conditions in a group of diabetic patients. Although OPs were reduced in amplitude in the diabetic group, several other parameters of the scotopic and photopic b-waves were impaired. The results indicate that b-wave activity may indicate retinal changes in early diabetic retinopathy in the same manner as the OPs.     

Oscillatory potentials and the b-Wave: Partial masking and interdependence in dark adaptation and diabetes in the rat

Background Diabetes inhibits dark adaptation and both processes alter the electroretinogram (ERG) in similar ways. This study aimed to investigate the relationship between oscillatory potentials (OPs) and the b-wave during dark adaptation and to determine if this relationship changes during the development of diabetes. Methods Twenty-one rats were assigned to adaptation, control and diabetic groups. Rats were dark adapted for periods between 20 minutes and 4 hours, and ERGs recorded. Diabetes was induced with streptozotocin, and ERGs measured after 3, 6, 9 and 12 weeks after injection. Results Increasing periods of dark adaptation led to a logarithmic increase in the amplitude of the b-wave and the OPs. This was accompanied by a decrease in the peak times of the OPs and b-wave. Total OP amplitude and b-wave amplitude were linearly related, allowing an empirical OP constant to be developed to describe the relationship between the two parameters. Diabetes led to a progressive decrease in the amplitude and increase in the peak time of all waves. The OP constant decreased in a linear fashion with increasing duration of diabetes. Conclusions It is argued that OP masking of the b-wave could explain previous inconsistencies in reported ERG changes in diabetes and that a slowing of dark adaptation does not account for these ERG changes. The report concludes that the OPs and b-wave amplitudes and latencies are intimately related in the normal retina and that this correlation is lost predictably during the development of diabetes.     

Effect of levodopa on the human luminance electroretinogram

Scotopic and photopic electroretinograms (ERGs) were recorded in 12 healthy volunteers before and 90 and 180 min after administration of levodopa. After 90 min the drug significantly increased the scotopic ERG b-wave amplitude and implicit time. The dark-adapted oscillatory potentials (OPs) were selectively affected, while no changes were observed in the photopic ERG. Levodopa had no effect on the ERG after 180 min drug applications. As a control, the experimental procedure was repeated without drug administration, and no changes were observed.     

ERGs in female carriers of incomplete Congenital Stationary Night Blindness (I-CSNB) A family report

ERG findings in five sisters are reported. By pedigree analysis, four of the five must be obligate carriers for I-CSNB since their sons were affected (impaired night vision, reduced visual acuity, variable ametropia, congenital nystagmus and ERG with both scotopic and photopic b-wave reduced amplitude). The fifth was childless at the time of examination and her ERG analysis was normal. Three of the four obligate carriers showed significant reduction in the sum of the OPs amplitude as previously reported as being an electrophysiological signs in female carriers: two without alteration in other ERG components and the third with association with a flicker ERG amplitude significantly increased. The fourth female carrier showed a normal sum of the OPs amplitude whereas the other b-wave ERG or flicker amplitudes were significantly decreased. These last two ERG results suggest a possible modifications of synaptic transmission at a post-receptoral site (outer plexiform layer or involvement of the bipolar pathways) in these two carriers.     

Inter-ocular and inter-session reliability of the electroretinogram photopic negative response (PhNR) in non-human primates

PURPOSE: To assess the inter-ocular and inter-session reliability for a range of parameters derived from the photopic electroretinogram (ERG) in a group of normal non-human primates. METHODS: Inter-ocular differences for photopic ERGs were assessed in a group of normal anesthetized adult rhesus monkeys (Macaca mulatta, n=29); inter-session reliability was assessed for 23 eyes of 23 animals tested 3 months later. Signals were acquired using Burian-Allen contact lens electrodes, whereby the contralateral cornea served as a reference. Photopic ERGs were elicited using red Ganzfeld flashes (-0.5-0.67 log photopic cd.sm(-2)) on a rod suppressing blue-background (30 scotopic cdm(-2)). Measurement reliability was established for a-wave, b-wave, photopic negative response (PhNR) and oscillatory potential (OP) amplitudes, as well as for their implicit times, by calculation of the 95% limits-of-agreement (LOA) and the coefficient-of-variation (COV) for each parameter. RESULTS: OP and a-wave amplitudes increased with intensity up to 0.67 log photopic cd.sm(-2), following a typical saturating function, whereas b-wave and PhNR amplitudes both declined above 0.42 log photopic cd.sm(-2). Inter-session variability was greater than inter-ocular variability. The inter-session COVs for PhNR amplitude (10-20%) were similar to the other photopic ERG components (a-wave: 12-17%, b-wave: 12-17%, OPs: 13-19%). Inter-session LOAs were also similar across components, but on average, were smallest for responses to moderate intensities (0.0-0.42 log photopic cd.sm(-2)). CONCLUSION: In non-human primates, the 95% LOA for inter-session measurements of the photopic ERG a-wave, b-wave, OPs and PhNR are all similar. Inner-retinal damage may best be measured using the PhNR amplitude for moderately bright stimulus intensities. B-wave and PhNR amplitudes for brighter flashes are smaller and more variable. The ratio of PhNR:b-wave amplitudes manifests smaller variability and may therefore be useful for detection of selective PhNR loss.     

The postnatal development of the oscillatory potentials of the electroretinogram. I. Basic characteristics

The postnatal development of the oscillatory potentials (OPs) of the rat electroretinogram (ERG) was studied. The appearance and/or completion of the development of the individual oscillatory peaks differed from that of the a- and b-waves as well as from each other. The OPs appeared postnatally one to two days later than the a- and b-waves, respectively. The first oscillatory peak, O1, was present before the second, O2, which appeared before the later wavelets, O3, O4 and O5. The pattern of maturation of the oscillatory peaks in relatively more scotopic conditions differed from that in relatively more photopic ones. The summed amplitudes of the OPs attained adult size earlier (about two weeks) during relatively more scotopic conditions. The peak time of each oscillation gradually decreased with age. These findings show that the origin of the OPs is different from that of the a- and b-waves of the ERG and strongly indicate different origins of the earlier OPs from the later ones. Thirdly, the scotopic mechanism underlying the OPs seems to mature faster than the photopic system involved in the generation of the OPs.     

Temporal aspects of the electroretinogram in cone-rod dystrophy

Twelve patients with cone-rod dystrophy were studied in terms of the temporal aspects of electroretinography (ERG).The peak time of scotopic b-wave was within normal limits in all patients, while the amplitude was reduced in nine patients. The normal peak time of the scotopic-b wave may help explain rod involvement with normal or only slightly elevated final rod thresholds of subjective dark adaptation.The peak time of photopic b-wave and 30-Hz flicker response was normal in four patients and significantly delayed or nonrecordable in eight patients. Such variations of peak time in photopic and 30-Hz flicker ERG may reflect the stage of the disease or may be caused by the different hereditary mode.     

Contribution of retinal ganglion cells to the mouse electroretinogram

Purpose

To quantify the direct contribution of retinal ganglion cells (RGCs) on individual components of the mouse electroretinogram (ERG).

Methods

Dark- and light-adapted ERGs from mice 8 to 12 weeks after optic nerve transection (ONTx, n = 14) were analyzed through stimulus response curves for a- and b-waves, oscillatory potentials (OPs), positive and negative scotopic threshold response (p/n STR), and the photopic negative response (PhNR) and compared with unoperated and sham-operated controls, as well as to eyes treated with 6-cyano-7-nitroquinoxaline-2,3-dion (CNQX).

Results

We confirmed in mice that CNQX intravitreal injection reduced the scotopic a-wave amplitude at high flash strength, confirming a post-receptoral contribution to the a-wave. We found that ONTx, which is more specific to RGCs, did not affect the a-wave amplitude and implicit time in either photopic or scotopic conditions while the b-wave was reduced. Both the pSTR and nSTR components were reduced in amplitude, with the balance between the two components resulting in a shortening of the nSTR peak implicit time. On the other hand, amplitude of the PhNR was increased while the OPs were minimally affected.

Conclusion

With an intact a-wave demonstrated following ONTx, we find that the most robust indicators of RGC function in the mouse full-field ERG were the STR components.     

Luminance dependence of neural components that underlies the primate photopic electroretinogram

PURPOSE: At lower stimulus intensities, the amplitude of the photopic flash ERG b-wave increases with increasing stimulus intensities, but then plateaus and decreases at higher stimulus intensities (the "photopic hill"). The purpose of this study was to determine the mechanism underlying this unusual phenomenon. METHODS: Five adult monkeys (Macaca mulatta and M. fascicularis) were studied. Stimuli were obtained from xenon strobe flashes, and the intensity was reduced by neutral-density filters in 0.4-log unit steps. N-methyl-D-aspartic acid and tetrodotoxin citrate (NMDA+TTX) were used to suppress inner retinal activities and L-2 amino-4-phosphonobutyric acid (APB) and cis-2,3 piperidine dicarboxylic acid (PDA) to block postreceptoral ON- and OFF-pathway activities. The postsynaptic ON- and OFF-components were isolated by subtracting the postdrug ERGs from the predrug ERGs. RESULTS: The intensity-response curve of the photopic b-wave obtained after the intravitreal injection of TTX+NMDA had the same shape as a photopic hill, suggesting that the contribution from the inner retinal neurons to the photopic hill is not significant. At low and intermediate intensities, the photopic b-wave was mainly shaped by the overlapping of two positive peaks from the ON- and OFF-components. However, the amplitude of the positive peak from the ON-component became smaller and broader at higher stimulus intensities. In addition, the timing of the positive peak of the OFF-component was gradually delayed with increasing intensities. After APB+PDA, the remaining cone photoreceptor component contributed only to the negative a-wave at all stimulus intensities. CONCLUSIONS: The photopic hill in the primate ERG results mainly from two factors: the reduction of the ON-component amplitude at higher intensities and the delay in the positive peak of the OFF-component at higher intensities.     

Evidence supportive of a functional discrimination between photopic oscillatory potentials as revealed with cone and rod mediated retinopathies

We report on a family where four of the eleven children presented with reduced visual acuities, a red-green deficit at the Farnsworth-Munsel FM 100-hue test, normal appearing fundi and unexpected electroretinographic findings. Light- (photopic) and dark- (scotopic) adapted electroretinograms (ERG) and oscillatory potentials (OPs) were obtained following an accepted standard protocol. The b-wave of their photopic ERG was significantly more attenuated than the a-wave due to the specific abolition of OP4, while the amplitudes of OP2 and OP3 were within the normal range, giving to the b-wave a truncated appearance reminiscent of that seen in congenital stationary night blindness (CSNB) with myopia. Interestingly in the latter condition, which is believed to result from an ON-retinal pathway anomaly, it is OP2 and OP3 which are specifically abolished while OP4 is of normal amplitude thus resulting in an OP response pattern which complements that seen with our patients. Also of interest is the fact that, in our patients, the amplitude of the dark-adapted OP2 was, on average, 240% larger than that measured in light-adaptation while, in normal, a non-significant 14% increase is noted; a finding which is in keeping with other studies reporting supernormal scotopic ERGs in some forms of cone dystrophies. Based on the photopic OP response pattern, our patients represent the electrophysiological complement of patients affected with CSNB. Interestingly their symptoms are also complementary, a finding which could support a functional discrimination between the photopic OPs. This revised version was published online in July 2006 with corrections to the Cover Date.     

影响视网膜脱离患者视网膜功能的因素

目的:评价视网膜脱离患者年龄、病程、视网膜脱离面积、黄斑脱离情况等因素对视网膜功能的影响。方法:将孔源性视网膜脱离(retinal detachment,RD)188例189眼的患者年龄、病程、视网膜脱离面积、黄斑脱离情况、视力与视网膜脱离眼的fERG和mfERG各指标进行相关分析。结果:影响RD眼fERG和mfERG的主要因素是脱离面积、黄斑脱离和视力。以|γ|>0.4,且P≤0.05判定为有相关性。脱离面积与明视和暗适应最大反应ERG a、b波幅值,30Hz闪烁光幅值,OPs波数和幅值负相关;与mfERG象限野P1波幅值密度、幅值负相关。相关系数最高者为fERG暗适应最大反应b波幅值(γ=-0.704)。黄斑脱离与明视和暗适应最大反应ERG b波幅值,30Hz闪烁光ERG幅值负相关;与mfERG环形野环1的P1波幅值密度、幅值负相关,与mfERG象限野P1波幅值密度负相关,相关系数最高者为mfERG环形野环1的P1波幅值(γ=-0.584)。视力与明视和暗适应最大反应a、b波幅值,30Hz闪烁光幅值,OPs子波数和幅值正相关;与mfERG环形野环1的P1波幅值密度、幅值正相关,相关系数最高者为30Hz闪烁光ERG幅值(γ=0.597)。RD眼的fERG异常率最高者为暗适应最大反应ERG b波幅值,异常率为71.3%,视网膜脱离象限野mfERG异常率最高者为P1波幅值,异常率为85.3%。结论:影响RD患者视网膜功能的重要因素是脱离面积和黄斑脱离情况。RD眼对视网膜功能异常反应的mfERG对视网膜功能异常反应的敏感性高于fERG。     

Nontoxic concentration of kanamycin and gentamicin for intravitreal use — evaluated by in vitro ERG

The effects of kanamycin (KM) and gentamicin (GM) on the in-vitro electroretinogram of the albino rabbit were studied. The b-wave and oscillatory potentials (OPs) were unchanged by 0.1 mM KM. The photopic b-wave and OPs were slightly suppressed by 0.4 mM. The b-wave and OPs were not deteriorated by 23 µg/ml (approximately 0.05 mM) GM. The photopic b-wave and OPs were slightly suppressed by 46 µg/ml (approximately 0.1 mM) GM. The minimum concentration affecting the ERG was tentatively defined as the mean of the minimum concentration needed to change the ERG and the maximum concentration which induced no discernible changes in the ERG. The minimum concentration of KM and GM affecting the ERG were 0.25mM (approximately 150 g/ml) and 35 g/ml (approximately 0.075 mM) respectively. The minimum concentration of KM affecting the ERG was higher than its minimum inhibitory concentration against Staphylococcus aureus and Streptococcus pneumoniae. The minimum concentration of GM affecting the ERG was higher than its mimimum inhibitory concentration against Staphylococcus aureus, Streptococcus pneumoniae and Pseudomonas aeruginosa.     

Analysis of the photopic electroretinogram recorded before and after dark adaptation

To evaluate the effect of a long period of dark adaptation on the light-adapted electroretinogram (ERG), photopic ERGs were recorded before (light-adapted) and immediately after (light-readapted) 15 minutes of dark adaptation. The amplitude of the b-wave in the light-readapted ERG was 48% +/- 4% of that in the light-adapted ERG, and the peak time of the b-wave in the light-readapted ERG was delayed by an average of 3.49 +/- 1.09 ms. Segmental analysis of the b-wave showed that the last segment of the ascending limb of the b-wave (from the second oscillatory potential [OP] to the peak) was attenuated the most (61% +/- 8%). In fact, the reduction in the amplitude of the last segment alone accounted for more than 60% +/- 13% of the overall reduction observed for the entire b-wave. This last segment appears to correspond to OP4 in the 100- to 1000-Hz recordings. The amplitude of OP4 in the light-readapted ERG was 56.5% +/- 10% of that in the light-adapted ERG, a similar reduction to that observed for the last segment of the 1- to 1000-Hz b-wave. The results strongly support the concept that the b-wave of the photopic ERG may actually represent a composite of potentials whose individual contributions are best visualized when the ERG is recorded with the 100- to 1000-Hz bandwidth.     

Longitudinal changes in photopic OPs occurring with vigabatrin treatment

PURPOSE: Vigabatrin (gamma-vinyl-GABA) is an antiepileptic drug successful in the management of infantile spasms. Photopic ERGs were tested in children followed longitudinally before and during vigabatrin treatment. METHODS: Subjects were 26 infants (age range 1.5-24 months, median 7.6 months) on vigabatrin treatment who had been tested on multiple visits (two to four visits; mean, three visits). Eighteen of these were assessed initially before starting vigabatrin therapy and eight were assessed within 1 week of initiation of the drug. ERGs were recorded at 6-month intervals. Standard ISCEV protocol with Burian-Allen bipolar contact-lens electrodes (standard flash 2.0 cd.s/m2) was used. Although ISCEV standards were followed, a higher flash intensity (set at 3.6 cd.s/m2) was chosen for single-flash cone assessment to provide a better definition of OPs. Photopic OPs were divided into categories of early OPs and late OP (OP4). Responses were compared with age corrected limits extrapolated from our lab control database. RESULTS: Results showed differential effects of vigabatrin on the summed early OP amplitudes versus the late OP (OP4) and cone b-wave amplitude. The early OPs showed significant decrease (p = 0.0005, repeated measures analysis of variance) after 6 months and remained decreased for the duration of treatment. There was no significant change seen in the late OP. The cone b-wave amplitude showed initial increase (p = 0.04) after 6 months, followed by a decrease after 18 months; a trend similar to that of the late OP. CONCLUSION: Early photopic OPs were disrupted more than the late OP, suggesting relative deficit in the ON (depolarizing) retinal pathways.     

Electroretinographic abnormalities in a rat glaucoma model with chronic elevated intraocular pressure

The purpose of this study was to determine the ability of electroretinographic (ERG) measurements to document progression of the retinopathy in a rat glaucoma model. Thirty four rats with a chronic intraocular pressure (IOP) elevation induced in one eye by cautery of three episcleral/extra-orbital veins were studied in four separate groups. ERGs were recorded sequentially in Group A rats (n = 12) at baseline, and after approximately 20, 40 and 60 days of high IOP, and in three additional groups of rats (n = 6 or 10 per group) after approximately 58, 30 and 175 days of high IOP, respectively. Scotopic ERG parameters recorded simultaneously from both eyes in Group A rats were: a- and b-wave amplitudes, implicit times, oscillatory potential amplitudes (OPs) determined at three different light-flash intensities, and the light-adapted (photopic) ERG b-wave amplitude. In the other groups of rats, only scotopic ERG a-wave, b-wave and OP amplitudes were measured.In Group A rats that were followed sequentially, all the ERG parameters recorded with attenuated stimuli showed significant time-dependent changes in glaucomatous eyes relative to their contralateral normal eyes, with OPs showing the earliest significant difference after only 3 weeks of high IOP. When different groups of unilateral glaucomatous rats were compared beyond 8 weeks of elevated IOP only the OPs showed a continued decrease with time and good discrimination between glaucoma and normal eyes. Over a 25 week period of high IOP the scotopic OPs measured with attenuated light stimuli declined at the rate of approximately 1.5% per week and provided the best ERG measure to monitor progression of retinal pathophysiology in the vein-occlusion rat glaucoma model.     

Regional variations in local contributions to the primate photopic flash ERG: revealed using the slow-sequence mfERG

PURPOSE: To determine the variations with eccentricity of the primate photopic ERG and to separate contributions by different retinal cells by using intravitreal pharmacologic agents. METHODS: Slow-sequence multifocal (mf)ERGs were obtained from 19 anesthetized adult rhesus monkeys and 5 normal human subjects. Recordings in monkeys were obtained before and after injections of tetrodotoxin citrate (TTX) to block sodium-dependent spiking; TTX+N-methyl-D-aspartic acid (NMDA)+picrotoxin (PTX) or gamma-aminobutyric acid (GABA) to block all inner retinal activity; L-2 amino-4-phosphonobutyric acid (APB) to block the On-pathway; and cis-2, 3 piperidine dicarboxylic acid (PDA) to block the Off-pathway and the otherwise unblocked inner retinal activity. The stimulus consisted of 103 equal-sized hexagons within 17 degrees of the fovea; every 200 ms (15 frames), each hexagon had a 50% chance of remaining at 20 cd/m(2) or increasing briefly to 4.7 cd-s/m(2). Oscillatory potentials (OPs; 90-300 Hz) were extracted. RESULTS: The slow-sequence mfERG summed over the stimulated area looked similar to a standard photopic, full-field ERG, with a- and b-waves and OPs. OPs in the foveal and temporal retina were larger than in the nasal retina. This nasotemporal asymmetry was removed by TTX, and the OPs were eliminated, either by blocking inner retina activity or by blocking the On-pathway. The summed mfERG waveform, including OPs, was shaped mainly by the more peripheral retinal regions. The foveal b-wave peak occurred about 5 to 6 ms later than in the periphery, with the depolarizing peak of the On-pathway/bipolar contribution occurring earlier than the depolarizing peak of the Off contribution at all eccentricities. The a-wave was composed of a small photoreceptor contribution and postreceptoral portion originating from hyperpolarizing neurons. CONCLUSIONS: The variations in the primate photopic ERG with eccentricity are due to spike-driven oscillatory activity that is more prominent in central and temporal retina than in nasal retina and to the slower timing of all responses in the central, compared with the peripheral, retina. The full-field, photopic ERG most closely resembles the mfERG responses to stimulation of peripheral regions.     

The effect of a slow flicker on the human photopic oscillatory potentials.

Flicker-induced modifications of the human photopic oscillatory potentials (OPs) were investigated with the use of flash stimuli of 0.89 and 8.9 cd m-2 sec in strength. When the dimmest stimulus is used, increasing the rate of presentation from 0.5 to 20 Hz augments the amplitude and peak time of OP2. For a brighter stimulus, the 10 Hz flicker significantly reduces the amplitude of OP2 and OP3, increases the peak time of OP2 and reduces that of OP4. The 20 Hz flicker increases the peak time and reduces the amplitude of OP2 and completely abolishes OP3, while it has no significant impact on the amplitude and timing of OP4. The data presented support the claim that each OP making the photopic response represent independent electrophysiological entities.     

Evidence for a brief period of enhanced oxygen susceptibility in the rat model of oxygen-induced retinopathy

PURPOSE: Findings in a previous study have shown that the retina of newborn rats exposed to hyperoxia during the first days of life sustain permanent functional (as determined with the rod ERG) and structural (as determined with histology) damage that appears to be determined by the level of retinal maturity reached at the time of oxygen exposure-the retinas of rat pups being more susceptible to hyperoxic shock during the second week of life than during the first week. Given that the cone ERG has been shown to mature later than the rod ERG, the purpose of the present study was to examine whether cone responses also demonstrates a similar maturational susceptibility to postnatal hyperoxia. Also examined was whether the oscillatory potentials (OPs) were affected by postnatal hyperoxia. METHODS: Newborn rats were exposed to hyperoxia during selected postnatal day intervals either initiated at birth (early-onset exposure) or at a later postnatal age (late-onset exposure). Photopic and scotopic (mixed cone-rod) electroretinograms were recorded at 30 days. RESULTS: Data analysis reveals that photopic and scotopic responses (b-wave and OPs) demonstrated a similar maturational susceptibility to postnatal hyperoxia, in which exposure regimens initiated during the second week of life were most detrimental to retinal function. The results also revealed a temporal window of enhanced oxygen susceptibility at approximately postnatal day 10. The duration of this window was longer when estimated with the scotopic responses, but the extent of the functional damage was more pronounced when estimated with the photopic signals. Finally, compared with the b-wave, the OPs, especially the short-latency OPs, were proportionally more affected. CONCLUSIONS: The results suggest that cone function is significantly more susceptible to postnatal hyperoxia than rod function, and the OPs appear to be the most susceptible ERG components, thus suggesting a differential susceptibility to oxygen toxicity of the different retinal components. However, despite a clear demonstration of its existence, the exact nature of the temporal window of enhanced oxygen susceptibility as well as a possible equivalence in other animal models of oxygen induced retinopathy, including the human form (retinopathy of prematurity), remains to be determined.     

Time-Dependent Course of Electroretinograms in the Spontaneous Diabetic Goto-Kakizaki Rat

Purpose

This study evaluates the relevance to human retinopathy of electroretinograms (ERGs) from the spontaneously diabetic Goto-Kakizaki (GK) rat.

Methods

Starting from 4 weeks of age, we obtained ERGs every 4 weeks from six GK rats and seven Wistar (control) rats, and from two GK and two Wistar rats at 14 days of age. The a-wave, b-wave, and oscillatory potentials (OPs) were recorded after stimulation with a single bright flash. We compared the amplitudes and implicit times and measured a-wave latencies to evaluate photoreceptor function.

Results

The amplitudes of the a-wave, b-wave, and OPs (O1 and O2) of the GK rats were reduced between 4 and 48 weeks of age. The time-dependent courses of change in a-wave, b-wave, and O2 amplitude did not differ between the two groups. The a-wave latencies in GK rats were significantly prolonged, but not the implicit times of OPs. At 14 days of age, the a-wave amplitudes were significantly smaller in GK than in Wistar rats.

Conclusion

Functional abnormalities of photoreceptors might be induced by inheritable degeneration at an early age in the GK rat. Although hyperglycemia would cause retinal hypoxia, it would not be severe enough to disturb the generation of OPs.?Jpn J Ophthalmol 2006;50:211–216 © Japanese Ophthalmological Society 2006