Pattern electroretinogram can be more than the sum of local luminance responses

It is generally accepted that the pattern electroretinogram for very large spatial elements is the result of local luminance stimulation. Responses due to the luminance differences between elements may be assumed to be relatively unimportant because in the case of large elements only few retinal units are stimulated by gradients. With decreasing pattern element size one wonders to what extent the electroretinogram continues to be based on the local luminance stimulation. We investigated this question using 8 Hz checkerboard reversal and compared the pattern recordings with the recordings resulting from the same stimulus field modulated homogeneously (focal electroretinogram). A 100% modulated checkerboard at retinal level may be considerably less modulated because of imperfect optics of the eye. So the pattern electroretinogram should be compared with homogeneous field stimulation of correspondingly lower modulation depth. On the basis of the optical transfer properties of the eye we compared by subtracting the proper focal electroretinogram from the pattern electroretinogram. The difference response was virtually zero for check sizes larger than 120. For checks from 60 down the difference response was of the same order of magnitude as the adjusted focal recording. This difference response for eyes with normal optics is largest around 30; its wave form was found to be rather invariant with check size.     

The diagnostic use of the second oscillatory potential in clinical electroretinography

Of all the electroretinogram (ERG) components (a-wave, b-wave, and oscillatory potentials) only one oscillatory potential, OP₂, was found to be significantly correlated with the absolute intensity of the flash stimulus (i.e., the intensity of the stimulus irrespective of the state of retinal adaptation). Our finding was further confirmed in single cell recordings of lateral geniculate unit activity in rabbits in which peak time of OP₂ was found to correlate better with the geniculate activity. For these reasons we have identified OP₂ as the intensity coding oscillatory potential of the ERG. In order to investigate if this new feature could have some clinical significance, we examined photopic ERGs recorded from patients affected with various retinopathies. In most instances the peak time of OP₂ paralleled that of the b-wave, that is, in the ERG with delayed b-wave the peak time of OP₂ was also delayed, while in ERGs with normal b-wave peak time the peak time of OP₂ was also normal. However, in some conditions (especially in cone-rod diseases) a delayed OP₂ was found in ERGs with normal b-wave peak times.     

Large rod-like photopic signals in a possible new form of congenital night blindness

A 10-year-old Persian girl has symptoms of congenital stationary night blindness and some drusen-like lesions in the region of the vascular arcades. Her electroretinogram shows no rod response to a weak stimulus, but a large (475 V) slow scotopic response to a strong stimulus that is unchanged by photopic conditions (15 F1 background illumination). However, the response to flicker had the typical (smaller) amplitude of a cone signal. This may represent a new form of night blindness in which rod sensitivity is reduced so that there is no vision under dim conditions but rod function still persists under photopic conditions.     

Clinical and genetic characteristics of Stargardt disease in a large Western China cohort: Report 1

Stargardt disease 1 (STGD1) is the most prevalent retinal dystrophy caused by pathogenic biallelic ABCA4 variants. Forty‐two unrelated patients mostly originating from Western China were recruited. Comprehensive ophthalmological examinations, including visual acuity measurements (subjective function), fundus autofluorescence (retinal imaging), and full‐field electroretinography (objective function), were performed. Next‐generation sequencing (target/whole exome) and direct sequencing were conducted. Genotype grouping was performed based on the presence of deleterious variants. The median age of onset/age was 10.0 (5–52)/29.5 (12–72) years, and the median visual acuity in the right/left eye was 1.30 (0.15–2.28)/1.30 (0.15–2.28) in the logarithm of the minimum angle of resolution unit. Ten patients (10/38, 27.0%) showed confined macular dysfunction, and 27 (27/37, 73.7%) had generalized retinal dysfunction. Fifty‐eight pathogenic/likely pathogenic ABCA4 variants, including 14 novel variants, were identified. Eight patients (8/35, 22.8%) harbored multiple deleterious variants, and 17 (17/35, 48.6%) had a single deleterious variant. Significant associations were revealed between subjective functional, retinal imaging, and objective functional groups, identifying a significant genotype–phenotype association. This study illustrates a large phenotypic/genotypic spectrum in a large well‐characterized STGD1 cohort. A distinct genetic background of the Chinese population from the Caucasian population was identified; meanwhile, a genotype–phenotype association was similarly represented.     

Pattern electroretinogram plus visual evoked potential: A decisive test in patients suspected of malingering

Along the processing chain in the visual pathway the pattern electroretinogram (PERG) is a better indicator of the peripheral function than the visual evoked potential (VEP). Therefore the PERG and the VEP will be impaired equally by disturbances before the ganglion cell layer (e.g., blurred image or retinal disease) and differently by further centrally located diseases (e.g., tumor compression of the optic nerve). Thus in patients complaining of reduced visual acuity who show disturbed VEP but a normal PERG, malingering can be definitely ruled out. Representative combinations of PERG and VEP findings are described.     

Maturational topography of the visual evoked potential in fetal lambs

The normal maturational course of the visual evoked potential (VEP) in human newborns and infants is well documented. Unfortunately, there is a paucity of data about VEP maturation in the normal preterm infant. Since this population is at risk to develop many abnormalities affecting the VEP (intraventricular hemorrhage, hydrocephalus, and retinopathy of prematurity), one must question whether such VEP data collected from this group is representative of normal maturation. To provide normative parametric developmental data we have been studying VEP development in fetal lambs. Six fetal lambs between 105 and 120 days gestational age were externalized and surgically instrumented with subcutaneous recording electrodes placed over the occipital and parietal regions. High-intensity light-emitting diodes (LEDs) externalized fiberoptic cables were secured adjacent to the orbit. from 108 to 141 days gestation, fetal VEPs were recorded in response to bright flash stimulation and the maturational topography was investigated.Over the occipital regions, the emergence of major positivities at P400 and P650 were observed beginning around 120 days gestation. Over the parietal area, the emergence of P200 and P500 components was observed by 128 days gestation. The latency-maturation functions revealed that the slope of the parietal function was steeper than the occipital counterpart, suggesting that the maturation of parietal neurons occurs at a faster rate than neuronal development in the occipital regions.     

高血压性视网膜病变的视觉电生理改变探讨

目的：探讨高血压性视网膜病变的闪光视网膜电网（FERG）,振荡电位（OPs)改变,方法：比较正常对照组15例30只眼和不同眼底分毋组的原发性高血压病患者,共49例98只眼的FERG,OPs的变化。结果：1．FERG：a波潜伏期：对照组与I级组相比差异无显著性,与Ⅱ,Ⅲ级组相比差异均有显著性;I级组与Ⅱ级组间差异无显著性,但I级与Ⅲ级,Ⅱ级与Ⅲ级组间差异均有显著性;a波振幅：对照组与I级组间差异无显著性,与其他各组间差异均有显著性;各级患者组间差异均有显著性;b波潜伏期,除I级与II级组间差异无显著性外,其余各组间差异均显著;b波振幅;除对照组与I级组间差异无显著性外,其余各组间差异均有显著性,2．OPs潜伏期：对照组各子波与I级组以及OP1,OP4及Ⅱ级组间差异无显著性,与其他各组间差异均有显著性,I级各子波与II级组间差异无显著性,与Ⅲ级组间差异显著,Ⅱ级与Ⅲ级组间差异显著。OPs振幅：对照组OP3与I级组间差异无显著性,其余比较差异均有显著性,除I级与Ⅱ级组间的OP4振幅差异无显著性外,各级患者组间的各子波振幅以及总振幅差异均有显著性。结论：FERG,OPs可作为高血压性视网膜病变及其严重程度的客观定量指标。     

一种测量视网膜锥体闪烁光ERG的改良方法：闪烁指数分析法

闪烁光ＥＲＧ是反映视网膜锥体活动的客观指标。但在诸如视网膜色素变性等一些视锥功能处于高度受累的疾病，反应波形呈现非窦状，使用以往在分析中采用的峰－峰值测量法，则不能有效地反应出波形所代表的真切含义。本文根据病理状态下闪烁光反应的波形特点，特此提出一项测量闪烁光ＥＲＧ振幅的改良方法，即闪烁指数（ｆｌｉｃｋｅｒｉｎｄｅｘｔ．ＦＩ）分析法，并通过数学方法推导出一项闪烁指数测量公式以代替方格卡尺测量法。应用本法已在实践中获得良好的验证，从而认为应用此项方法可以准确、客观、迅速地测量得锥体闪烁光的反应状态，特别是在对锥体功能呈病理状态的一些视网膜疾病的观测。通过计算机程序化处理，ＦＩ分析法可为临床视觉电生理研究提供一种有效的手段。     

Pattern electroretinogram and visual evoked potential amplitudes are influenced by different stimulus field sizes and scotomata

The pattern electroretinogram and the visual evoked potential were recorded simultaneously with various stimulus fields and artificial scotomata of increasing sizes. In contrast to an earlier study, a smaller check size (20) and two stimulus field sizes (20° × 20° and 10° × 10°) for the scotomata were used. With a concentric decreasing stimulus field, a reduction of both the pattern electroretinogram and visual evoked potential was found. Both showed a simultaneous reduction of amplitudes, but, compared with the amplitude in the full field, the reduction was more extensive for the pattern electroretinogram at each test field size. This implies a greater contribution to the pattern electroretinogram from more eccentric retinal parts. An artificial central scotoma of increasing size in the 20° × 20° field had less influence on the pattern electroretinogram than on the visual evoked potential. The percentage amplitude loss of the visual evoked potential was more pronounced. The visual evoked potential was eventually abolished by a scotoma size from 10° × 10° upward, while the pattern electroretinogram was still registrable. When scotomata of similar size were introduced in a smaller (10° × 10°) field, percentage pattern electroretinogram and visual evoked potential amplitude losses were less separated than in a larger (20° × 20°) test field.