The Decline of the Photopic Negative Response (PhNR) in the Rat after Optic Nerve Transection

Purpose: To investigate the contribution to the photopic negative response (PhNR) of the electroretinogram (ERG) by retinal ganglion cells (RGCs). The PhNR was assessed longitudinally following optic nerve transection (ONTx). Methods: Photopic ERGs were recorded from each eye of an anesthetized (ketamine/xylazine, 60 mg/kg and 5 mg/kg) Brown Norway rat using custom made electrodes (PT-IR Tef., A-M System Inc). ERGs were elicited using green Ganzfeld flashes (11.38 scd/m², 22.76 cds/m²) and a rod suppressing green-background (40 cd/m²). PhNRs were compared before and after optic nerves were transected. Cresyl violet stained retinal flatmounts were used to estimate cell loss in the ganglion cell layer 3 and 15 weeks after optic nerve transection. The pharmacological effect of 1.3 μM intravitreal TTX on the PhNR was also evaluated. Results: There was a significant loss (p <0.05) in the PhNR of 20, 36, 34, 35, 48, 48 and 56% for ONTx eye versus the contralateral eye, at post ONTx times of 24 h, 1, 2, 3, 4, 8 and 15 weeks. B-wave amplitudes of ONTx eyes were not significantly different from the control eyes. In ONTx eyes, mean cell loss in the retinal ganglion cell layer was 27 and 55% at the 3 week and 15 week time periods. In the eyes with ONTx, the decline of PhNR amplitudes was correlated positively with RGC loss (r = 0.98; p < 0.01). Thirty minutes after intravitreal TTX injection, the PhNR was significantly reduced (57%, p<0.01). Conclusions: There was a time-dependent decline in the PhNR after ONTx, as exemplified by a 35% reduction from 1–3 weeks, a 48% decline for 4–8 weeks and a 56% decline after 15 weeks. The correlation between the decline in the PhNR and retinal ganglion cell loss suggests that the PhNR depends on inner retina integrity and the PhNR may be important biological signal or detecting glaucomatous damage and the monitoring of RGC function changes in early glaucoma.     

Comparisons of cone electroretinograms after indocyanine green-, brilliant blue G-, or triamcinolone acetonide-assisted macular hole surgery

Purpose

To compare the function of retinal ganglion cells (RGCs) using the photopic negative response (PhNR) in patients who had undergone indocyaine green (ICG)-assisted, brilliant blue G (BBG)-assisted, or triamcinolone acetonide (TA)-assisted internal limiting membrane (ILM) peeling during macular hole (MH) surgery.

Methods

Forty-eight eyes of 48 patients with a macular hole were randomly divided into those undergoing ICG-assisted, BBG-assisted, or TA-assisted vitrectomy (n?=?16 for each group). Full-field cone ERGs were recorded before and 1, 3, 6, 9, and 12 months postoperatively. The amplitudes and implicit times of the a-waves and b-waves and the amplitudes of the oscillatory potentials (OPs) and PhNRs were measured. The mean deviations (MDs) of standard automated perimetry and the best-corrected visual acuity (BCVA) were measured. The circumferential retinal nerve fiber layer (RNFL) thickness was evaluated by SD-OCT.

Results

All macular holes were closed with a significant improvement of the BCVA and MD without differences among the groups. There was no significant difference between the preoperative and postoperative RNFL thickness. The implicit times of the a-waves and b-waves were significantly prolonged, and the ΣOPs amplitude was significantly decreased postoperatively in all groups. These ERG changes were not significantly different among the groups. The postoperative PhNR amplitudes were significantly lower in the ICG group than in the BBG or TA group.

Conclusions

The results indicate that the PhNR may detect subclinical impairments of RGCs caused by the possible toxic effect of ICG. This finding adds to the data that BBG and TA may be safer than ICG for use during MH surgery.     

The photopic negative response of the flash electroretinogram in retinal vein occlusion

The photopic negative response (PhNR) has recently been shown to be severely affected in central retinal artery occlusion (CRAO), despite relative preservation of the cone b-wave compared to that in the healthy unaffected fellow eye. The aim of this study was to test how the PhNR of the flash electroretinogram (ERG) is affected in human retinal vein occlusion. PhNR was elicited with red stimuli (1 cd s/m², 5 cd s/m², and 7 cd s/m² with 4 ms duration) and blue background (10 cd/m²). Standard Ganzfeld flash ERG was produced according to the ISCEV standard for the clinical electroretinogram (2004). Sixteen patients with central retinal vein occlusion (CRVO), 14 patients with branch retinal vein occlusion (BRVO), and 16 controls were analyzed. The amplitude of the PhNRs was significantly smaller in the CRVO and BRVO eyes than those in the unaffected fellow or control eyes (p = 0.000). There was a significantly greater reduction of PhNR amplitudes than that of other waves including the OPs, rod b-wave, combined a-wave and b-wave, cone a-wave and b-wave, and 30 Hz flicker ERG. Thus, PhNR amplitude in retinal vein occlusion is severely affected. There is a potential role for PhNR in assessing inner retinal damage and evaluating the effect of treatment.     

正常眼视网膜电图明视负向反应研究

目的研究不同性别、年龄正常眼的视网膜电图（electroretinogram，ERG）中明视负向反应（photopic negative response，PhNR）的潜伏期和振幅，并分析性别、年龄对PhNR的影响。方法选取正常健康者和单眼外伤者共54例（60眼），进行ERG检查，记录其视网膜电图PhNR的潜伏期和振幅，分别按年龄（〈20岁组，20-40岁组，〉140岁组）和性别统计其正常值范围并进行比较。结果PhNR潜伏期女性较男性略短，PhNR振幅女性较男性略低，但差异无显著性（P〉0.05）。随年龄增大，PhNR的潜伏期延长，各组间差异均有显著性（P〈0．01）；随年龄增大，PhNR的振幅下降，差异出现在40岁以上组与其他两组之间（P=0．02）。结论与其他ERG成分类似，PhNR的潜伏期和振幅亦受年龄和性别的影响，故在进行视网膜电图PhNR分析时应综合考虑性别、年龄等因素。     

On and off responses of the photopic fullfield ERG in normal subjects and glaucoma patients

Recent studies suggest a diagnostic value of the photopic negative response (PhNR) with a long-duration stimulus. The aim of this study was to record the on and off responses of the photopic fullfield electroretinogram (ERG) in normal subjects and glaucoma patients. We focused on different waves of the responses after onset and offset of the long-duration stimulus ERG. Photopic fullfield ERGs were recorded in response to a white bright LED flash on a white 20 cd/m² background. Stimulus luminances were 40, 60 and 80 cd/m². Responses were averaged using a flash duration of 240 ms and an offset period of 500 ms. We examined 19 healthy subjects, 27 patients with glaucomatous optic disc atrophy and 7 ocular hypertensive patients. The amplitudes and implicit times of the on and off responses of the human ERG depended on flash luminance. Comparing patients with glaucoma and healthy subjects for the 60 cd/m2 flash, there was a significant change in the PhNRs (at onset: P < 0.01, at offset: P < 0.001) of the d-wave and of the i-wave at offset (P < 0.01). No significant difference was found for peak times of the fullfield ERG and for a- and b-wave amplitudes. PhNR amplitudes were significantly correlated with mean thickness of retinal nerve fibre layer as measured with OCT. In comparison with the normal photopic long-flash ERG, glaucoma patients showed changes in the PhNR amplitude following stimulus onset and in waves following stimulus offset.     

Selective amplitude reduction of the PhNR after macular hole surgery: ganglion cell damage related to ICG-assisted ILM peeling and gas tamponade

PURPOSE: The photopic negative response (PhNR) is a negative component of the photopic electroretinogram (ERG) that is observed after the b-wave and is thought to originate mainly from the activity of ganglion cells and their axons. The purpose of this study was to determine whether there are subclinical functional changes in the inner retina after macular hole surgery, by recording the PhNR before and after surgery. METHODS: In addition to the routine ophthalmic examinations, photopic ERGs were recorded in 16 eyes with an idiopathic macular hole, before and 3 months after surgery. Photopic ERGs were elicited by white Ganzfeld flashes on a rod-suppressing blue background. The amplitude of the PhNR and the a- and b-waves of the photopic ERGs before and after surgery were compared. PhNRs were also recorded in 14 eyes with epiretinal membrane, before and after surgery. RESULTS: Macular holes were closed and visual acuities were improved without any serious complications in all eyes with a macular hole. The amplitude of the PhNR was significantly reduced after surgery (P < 0.05), whereas the amplitude of the photopic a- and b-waves were not significantly altered. For eyes with an epiretinal membrane, the mean amplitude of the PhNR was slightly decreased after the surgery, but the degree of reduction was only one half of that after macular hole surgery. CONCLUSIONS: These results suggest that there are some functional impairments in the inner retina after macular hole surgery, even though the patients did not show any reduction on subjective visual tests. The PhNR can be a useful clinical test to assess the inner retinal function objectively, before and after vitreoretinal surgery.     

Photopic negative response of eyes with normal-tension glaucoma

PURPOSE: The purpose of this study was to investigate the behavior of the photopic negative response(PhNR) of cone-induced electroretinogram (cone ERG) in patients with normal-tension glaucoma (NTG). METHODS: Cone ERGs were recorded from 30 eyes of 30 patients with NTG according to the recording conditions of the International Society for Clinical Electrophysiology of Vision protocol which is now widely used in clinics. The amplitudes and implicit times of the PhNRs were measured and compared with normal controls. I further attempted to find a correlation between the PhNR amplitude loss and the cupping/disc ratio representing a loss of the nerve fiber layer and severity of visual field defbct. RESULTS: The PhNR amplitudes recorded from patients with NTG were significantly reduced compared with those from normal subjects (p < 0.05). However, the PhNR amplitude loss did not correlate with the cupping/disc ratio or the severity of visual field defect. CONCLUSIONS: The Results suggested that the PhNR amplitude qualitatively reflected ganglion cell loss in patients with NTG even under recording conditions which are widely used in the clinical field.     

Comparison of electroretinographic responses between two different age groups of adult Dark Agouti rats

AIM: To describe and compare the differences in electroretinographic responses between two different age groups of adult Dark Agouti (DA) rats and to better understand the effect of age on retinal histology and function.METHODS: The electroretinographic responses of two different age groups of adult DA rats were compared. Animals were divided into younger adult DA rats 10-12wk (n=8) and older adult DA rats 17-19wk (n=8). Full field electroretinography (ERG) was recorded simultaneously from both eyes after dark adaption and light adaption and parameters including the positive scotopic threshold response (pSTR), negative scotopic threshold response (nSTR), scotopic a-wave, b-wave, photopic a-wave, b-wave and photopic negative response (PhNR) were compared between groups.RESULTS: The older adult rats displayed lower stimulation thresholds of the STRs (pSTR and nSTR) and higher amplitudes of pSTR, scotopic a-wave and b-wave, photopic b-wave and PhNR amplitudes, with shorter implicit times. Photopic a-wave amplitudes were however higher in the younger adult rats.CONCLUSION:In summary, for the rod system, photoreceptor, bipolar cell and RGC activity was enhanced in the older adult rats. For the cone system, RGC and bipolar cell activity was enhanced, while photoreceptor activity was depressed in the older adult rats. Such age-related selective modification of retinal cell function needs to be considered when conducting ophthalmic research in adult rats.     

Comparison of photopic negative responses elicited by red and white xenon flashes in monkeys

PURPOSE: The photopic negative response (PhNR) is a negative component of the photopic electroretinogram (ERG), and is believed to originate mainly from the retinal ganglion cells. The PhNR is commonly elicited by red light-emitting diodes. The purpose of this study was to compare the amplitude of the PhNR elicited in monkeys by red stimuli and white stimuli obtained from a xenon light source. METHODS: The PhNRs were elicited from six rhesus monkeys by photopically matched red and white xenon flashes (peak output, 600 nm) on a rod-saturating blue background. The amplitudes of the PhNR elicited by white flashes were compared with those elicited by the red flashes before and after the intravitreal injection of tetrodotoxin (TTX). RESULTS: The differences in PhNR amplitudes between the red and white stimuli, and the changes in the PhNR amplitudes after the injection of TTX, were not statistically significant. CONCLUSION: These results suggest that red and white xenon flashes are of approximately equal value for assessing inner retinal function using the PhNR under our recording conditions.     

The photopic negative response of the flash electroretinogram in primary open angle glaucoma

PURPOSE. To determine whether the photopic negative response (PhNR) of the electroretinogram (ERG) is reduced in patients with primary open angle glaucoma (POAG). METHODS. ERGs were recorded with DTL electrodes from 62 normal subjects (16 to 82 years), 18 POAG patients (47 to 83 years) and 7 POAG suspects (46 to 73 years) to brief flashes (<6 ms), and also in a few subjects to long (200 ms) red, full-field ganzfeld flashes delivered on a rod-saturating blue background. At the time of ERG measurements, the intraocular pressures of most of the patients were controlled medically. Visual field sensitivities were measured with the Humphrey C24-2 threshold test and optic nerve head cup-to-disc ratio (C/D) was determined by binocular indirect ophthalmoscopy. RESULTS. ERGs of normal subjects contained a slow negative potential following the a- and b-waves, the PhNR, that increased slightly in latency with age. The a- and b-wave amplitudes and implicit times of POAG patients were similar to age-matched controls. In contrast, their PhNRs were small or virtually absent. PhNR amplitudes were reduced even when visual sensitivity losses were small, and were correlated significantly (P < 0.05) with mean deviation (MD), corrected pattern SD (CPSD), and C/D across the population of POAG patients whose MD losses ranged from 1 to 13 dB, CPSDs from 0 to 11 dB and C/Ds from 0.6 to 0.9. PhNRs of most POAG suspects also were small. CONCLUSIONS. PhNR amplitudes in POAG patients are smaller than those of normal subjects. PhNR amplitudes are reduced when visual field sensitivity losses are mild and become even smaller as sensitivity losses increase. There is a potential role for the PhNR in early detection and possibly in monitoring the progression of glaucomatous damage.     

Comparison on Photopic Electroretinogram Negative Response between Young and Old Lewis Rats

 Purpose: To investigate and compare the latency and amplitude of the electroretinogram (ERG) photopic negative response (PhNR) between young and old Lewis rats. Methods: Thirteen Lewis rats were divided into two groups according to ages, young group (3-month old, n=5) and old group (24 month old, n=8). The ERGs of the left eyes were measured and the latency and amplitude of a-wave, b-wave and PhNRs were recorded and compared according to ages. The mean values between two groups were statistically analysed by t-test. Results: The latency of PhNRs was evidently prolonged in old group and showed significant difference (P<0.05). There was no statistically significant difference between two groups regarding the amplitude and latency, and no significant difference was noted in the amplitude of PhNRs. Conclusion: The prolonged latency of PhNR in aged rats possibly associate with the influence of aging upon retinal ganglion cell layer (RGCL).     

电生理测试作为早期青光眼诊断指标的横断面研究

明视负向反应(PhNR)和图形视网膜电图(PERG)的结果作为评估青光眼的诊断指标.10例对照组和15例早期青光眼患者接受了完整的眼科检查,包括视力测量,眼压(IOP)测量,眼底检查和视野检查.同时进行图形视网膜电图和全视野视网膜点图纪录.青光眼组的平均偏差和图形平均标准偏差显著较低(P＜0.001,P＜0.01).PERGN95,PhNR,b波以及PhNR/b波的幅值显著较低(P＜0.001).眼压升高降低了PERG与PhNR的振幅.     

原发性视神经萎缩患者视网膜电图明视负向反应振幅异常

目的研究视网膜电图(ERG)明视负向反应(PhNR)在原发性视神经萎缩进展中的变化特点以及与视网膜神经纤维层厚度(RNFLT)的关系。设计前瞻性、对照性研究。研究对象正常健康者18例(18眼)和原发性视神经萎缩稳定期患者15例(18眼)及7例(7眼)视神经挫伤导致视神经萎缩的患者。方法对正常健康者和原发性视神经萎缩者进行ERG和相干光断层扫描(OCT)检查,比较两组PhNR振幅,并将原发性视神经萎缩者的PhNR振幅与RNFLT进行相关分析;另对视神经挫伤导致视神经萎缩者随访半年,研究其PhNR振幅与RNFLT变化规律。主要指标PhNR振幅与RNFLT。结果稳定期原发性视神经萎缩组和对照组的ERG中暗视反应、最大反应、30Hz震荡电位的振幅及明视反应a波和b波振幅差异均无显著性意义,但原发性视神经萎缩组的PhNR振幅比对照组明显下降(P<0.01),而且PhNR的振幅与RNFLT显著相关(r=0.688,P<0.01)。视神经挫伤导致视神经萎缩的患者随访第1~3个月,PhNR振幅下降先于RNFLT的变薄。结论原发性视神经萎缩眼ERGPhNR振幅明显下降甚至消失,且PhNR振幅下降早于RNFLT变薄。     

Photopic negative response of the human ERG: losses associated with glaucomatous damage

PURPOSE: To evaluate in glaucomatous eyes the photopic electroretinogram (ERG) negative response (PhNR), a component that follows the b-wave peak and is thought to be correlated with inner retinal activity. METHODS: Eleven patients with open-angle glaucoma (OAG) and moderate field loss (Humphrey 30-2 [Humphrey Instruments, San Leandro, CA] mean deviation < or = -6 dB), eight with ocular hypertension (OHT), and eight age-matched normal subjects were tested. Optic discs of patients and control subjects were evaluated by confocal scanning laser ophthalmoscopy. ERGs were recorded to long-duration stimuli (250 msec) of photopic luminance (78 candelas [cd] /m2), presented in the macular region (12 degrees x 12 degrees field size) on a steady, adapting background. Amplitudes of the a-wave and b-wave and the PhNR were measured. Pattern reversal ERGs to 30-minute checkerboards were also recorded from patients and control subjects. RESULTS: Compared with control subjects, patients with OAG showed reduced PhNR (average reduction: 62%, P < 0.01), but normal a- and b-wave amplitudes. In patients with OHT, PhNR and a- and b-wave amplitudes did not differ from control values. In individual patients with OAG, PhNR amplitudes were correlated positively with pattern ERG amplitudes (r = 0.80; P < 0.01) and central (12 degrees) perimetric mean deviations (r = 0.68; P < 0.05) and negatively with cup-to-disc area ratios (r = -0.79; P < 0.01) and cup shape measures (r = -0.78; P < 0.01). CONCLUSIONS: Similar to that found in monkeys with experimentally induced glaucoma, the PhNR is selectively altered in human glaucoma. The correlation between PhNR losses and clinical parameter abnormalities suggests that this component depends on inner retina integrity and may be of clinical value for detecting glaucomatous damage.     

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.     

视网膜电图明视负向反应对外伤性视神经萎缩的诊断意义

目的研究外伤性视神经萎缩的视网膜电图（ERG）各成分及其明视负向反应（PhNR）的变化特点，并进行PhNR与视网膜神经纤维层厚度（RNFLT）、视野平均缺损值（MD），以及杯盘比（C／D）的相关性研究，探索在外伤性视神经萎缩中PhNR的变化规律。方法选取外伤性视神经萎缩的患者21例（25眼）和与其性别年龄相匹配的正常人25例（25眼）。分别对两组进行ERG、视野、眼底照相和光学相干断层扫描（OCT）检查，比较两组视网膜电图，并将外伤性视神经萎缩组的PhNR振幅分别与MD、C／D和RNFLT进行相关性分析。结果外伤性视神经萎缩组的PhNR振幅比对照组明显下降（P〈0．01），而外伤性视神经萎缩组和对照组的ERG中暗视反应、最大反应、30Hz震荡电位的振幅差异无统计学意义，视神经萎缩组明视反应a波和b波振幅差异也无统计学意义。PhNR的振幅与视神经损伤情况如RNFLT（r=0．665）、MD（r=0．564）、杯盘比（r=0．686）等相关，且相关关系有统计学意义（P〈0．01）。结论视网膜电图PhNR振幅在外伤性视神经萎缩眼明显地下降甚至消失，PhNR可作为外伤性视神经萎缩的诊断和神经节细胞及其轴突功能评价的良好指标。     

Clinical Application of Photopic Negative Response of the Flash Electroretinogram in Primary Open-angle Glaucoma

 PURPOSE: To evaluate the diagnostic performance of the photopic negative response (PhNR) for the detection of primary open-angle glaucoma (POAG). METHODS: Fifty-two normal subjects (52 eyes) and 173 POAG patients (173 eyes) were studied. The PhNR was elicited using a white stimuli on a white background. The mean deviation (MD) and pattern standard deviation (PSD) of the visual field were measured using standard automated perimetry (SAP). Spectral domain optical coherence tomography (SD-OCT) was used to measure the mean thickness of the retinal nerve fiber layer (RNFL). RESULTS: In the glaucoma group, as compared to the normal group, the amplitudes of a-waves, b-waves and PhNR were significantly smaller (P<0.001), and the PhNR implicit time was significantly longer (P=0.004). The MD, PSD and mean thickness of the RNFL were significantly correlated with the amplitude of the PhNR (P<0.001). The area under the receiver operating characteristic curve (AUCs) for the amplitudes of a-waves, b-waves and PhNR were 0.853, 0.830 and 0.918, respectively. When the specificity was ≥95%, the sensitivities were 60.4%, 54.2% and 85.4% respectively. CONCLUSION：The PhNR amplitude was reduced even when the loss in visual field sensitivity was mild, which suggests that PhNR might be a useful indicator of early glaucoma disease.       

Correlation between photopic negative response and retinal nerve fiber layer thickness and optic disc topography in glaucomatous eyes

PURPOSE: To investigate whether there is a significant correlation between the photopic negative response (PhNR) of the electroretinogram (ERG) and retinal nerve fiber layer thickness and optic disc topography in glaucomatous eyes. METHODS: Ninety-nine eyes of 53 patients with open-angle glaucoma (OAG) and 30 eyes of 28 normal volunteers were studied. Photopic ERGs were elicited by red stimuli (644 nm, 1600 cd/m(2)) on a blue background (470 nm, 40 cd/m(2)). The mean deviation (MD) of the visual field was obtained by static visual field analyses. The topography of the optic nerve head was determined by confocal scanning laser ophthalmoscopy. The retinal nerve fiber layer thickness (RNFLT) around the optic nerve head was measured with a scanning laser polarimeter. RESULTS: The amplitude of the PhNR and the PhNR/b-wave ratio decreased with an increase in visual field defects. The logarithmic values of the PhNR amplitude and PhNR/b-wave amplitude ratio were significantly correlated with the MD better than the linear values. The PhNR amplitude and PhNR/b-wave amplitude ratio were significantly correlated with the RNFLT and the rim area of the optic disc and with the cup/disc area ratio. These correlations were higher when expressed linearly than when stated logarithmically. The sensitivity and specificity were 77% and 90% for the PhNR amplitude and 70% and 87% for the PhNR/b-wave amplitude ratio when the optimal cutoff values were used. Although the a-wave amplitude correlated with the MD, the a-wave amplitudes of most of the patients fell within the normal range. The correlation between the b-wave amplitude and MD was not significant. CONCLUSIONS: The PhNR amplitudes correlate with the decrease in function and morphology of retinal neurons in eyes with OAG. The linear relationship between the PhNR and the structural parameters indicates that inner retinal function declines proportionately with neural loss in eyes with glaucoma.     

Comparison of broadband and monochromatic photopic negative response in eyes of patients with diabetes with no diabetic retinopathy and different stages of diabetic retinopathy

Purpose:To evaluate the change in broadband (W/W), red on blue (R/B), and blue on yellow (B/Y) photopic negative response (PhNR) in patients with diabetes mellitus with no diabetic retinopathy (no DR) and different stages of DR and compare it with age-matched controls. This study was performed to provide a single PhNR protocol that can be used for early diagnosis of DR.Methods:It was a cross-sectional case-control study done in a hospital setup. Patients with diabetes with no DR and different stages of DR with no other associated ocular pathologies were included. Age-matched controls with no retinal pathologies were also included for comparison. All subjects underwent detailed ophthalmic examination and W/W, R/B, and B/Y electroretinography. Fifty control eyes and 52 treatment naïve eyes of 52 patients with diabetes [no DR = 11, mild nonproliferative diabetic retinopathy (NPDR) =11, moderate NPDR = 10, severe NPDR = 9, and proliferative DR = 11] were included in the study.Results:On comparing the ERG responses in patients with diabetes and age-matched controls, a significant reduction (P < 0.05) was noted in the amplitudes of a-wave (39.78 ± 11.34 μV vs. 67.28 ± 12.88 μV), b-wave (116.25 ± 45.25 vs. 134.39 ± 28.78 μV), W/W PhNR (33.86 ± 17.33 vs. 67.18 ± 15.99 μV), R/B PhNR (28.77 ± 15.85 vs. 53.48 ± 14.15 μV), and B/Y PhNR (55.04 ± 32.63 vs. 104.79 ± 24.37 μV). Post hoc analysis revealed that all the eyes in the diabetic group, including those with no DR, had a significantly reduced PhNR amplitude (P < 0.05) when compared with controls. PhNR was found to reduce in amplitude with increasing severity of DR (P < 0.05), with more significance in B/Y. Receiver operating characteristic showed highest area under the curve in B/Y PhNR (94%, P < 0.001), with maximum sensitivity and specificity of 88% and 87%, respectively.Conclusion:Changes in the amplitude and implicit time of ERG can reflect the severity of DR. PhNR amplitudes, especially B/Y PhNR, appear to be significantly reduced even in eyes with no DR.     

Changes of Oscillatory Potentials and Photopic Negative Response in Patients with Early Diabetic Retinopathy

Purpose

To investigate the clinical significance of the oscillatory potentials (OPs) and photopic negative response (PhNR) of the electroretinogram (ERG) in patients with early diabetic retinopathy.

Methods

One hundred two diabetic patients with diabetic retinopathy at different stages were examined. Thirty-two age-matched normal controls were also studied. Full-field maximal and photopic cone ERGs were recorded. The amplitudes and implicit times of the OPs, cone b wave, and PhNR were compared at the different stages of diabetic retinopathy.

Results

The a and b wave amplitudes of the maximal scotopic ERGs remained unchanged despite advancing stages of retinopathy, but the OP amplitudes were significantly attenuated even at an early stage of diabetic retinopathy. The amplitudes of both the PhNR and cone b wave were reduced at an early stage of diabetic retinopathy. Analysis of the receiver operating characteristic curves demonstrated that the amplitudes and implicit times of the OPs were more sensitive and specific than those of the PhNR in detecting changes of retinal function in the early stages of diabetic retinopathy.

Conclusions

The amplitudes of the OPs and PhNR progressively decrease with the progression of diabetic retinopathy. The PhNR amplitudes were reduced along with the cone b wave, indicating that earlier change of the PhNR in diabetic patients reflects reduced input to the retinal ganglion cell from the distal retina. The amplitudes and implicit times of the OPs are better indicators than those of the PhNR in detecting functional decreases in patients with early diabetic retinopathy.?Jpn J Ophthalmol 2006;50:367–373 © Japanese Ophthalmological Society 2006