B-wave Implicit Time Research Articles

Methamphetamine exacerbates the toxic effect of kainic acid in the adult rat retina

The recreational use of the psychoactive drug, methamphetamine has increased markedly over the last three decades. It has long been known that this drug has detrimental effects upon the mammalian brain monoaminergic system, but the long- or short-term effects on the retina, a neurological extension of the central nervous system, have received little attention. The aim of this study was, therefore, to determine whether intraocular injection of methamphetamine (MA) is toxic to the healthy adult rat retina and to analyse its effects on the compromised retina after an injection of the ionotropic glutamate receptor agonist, kainate, which is known to cause retinal neuropathology. The equivalent of 1 mM (in the vitreous humour) MA and/or kainate (40 μM) were injected intravitreally. Flash electroretinograms (ERGs) were recorded before and 2 and 4 days after treatment. Five days after treatment, animals were killed and the retinas analysed either for the immunohistochemical localisation of various antigens or for electrophoresis/Western blotting. Some animals were kept for 19 days after treatment and the retinas analysed for tyrosine hydroxylase immunoreactivity. No differences could be found between vehicle- and MA-treated retinas with respect to the nature or localisation of either tyrosine hydroxylase immunoreactivity after 5 or 19 days or other antigens after 5 days. Moreover, the normal ERG and GFAP and calretinin protein antigens were unaffected by MA. Kainate treatment, however, caused a change in the ERGs after 2 and 4 days, an alteration in every antigen localised by immunohistochemistry and an increase in the retinal levels of calretinin and GFAP proteins. Significantly, the changes seen in the b-wave amplitude and implicit time of the ERG after 4 days and the increased level of GFAP protein after 5 days following kainate treatment were enhanced when MA was co-injected. Intravitreal injection of methamphetamine had no detectable detrimental effect on the normal adult rat retina but exacerbated the damaging effects of kainic acid. Such data suggest that a neurotoxic effect of MA may be more obviously illustrated when the tissue is already compromised as occurs in, for example, ischemia.

Visual electrophysiologic findings in patients from an extensive Brazilian family with Leber's hereditary optic neuropathy.

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease, associated with mitochondrial DNA (mtDNA) point mutations and characterized by bilateral, usually sequential, rapid loss of central vision. The purpose of this study was to investigate electrophysiologically a small cohort of members from an extensive Brazilian family affected by LHON. Pattern-reversal visual evoked potentials (PVEP), and full-field electroretinograms (ERG) were performed on the four index members, all carrying the 11778 homoplasmic mtDNA mutation. They were a 14-year-old recently affected male, his unaffected mother, and her two affected brothers. The three affected members all had bilateral profound visual loss with visual acuities that ranged from 20/250 to CF, cecocentral defects, and severe dyschromatopsia (by FM-100). The unaffected (carrier) female had normal visual acuities, visual fields and color discrimination. Severely prolonged P100 latencies and decreased N75-P100 peak amplitudes were found in pattern-reversal VEPs for three affected members. Normal PVEP responses were found in the carrier female. Rod and cone ERG responses were normal in two affected members, but both the carrier mother and her affected son showed reduced peak-to-peak amplitude for single-flash cone response and 30 Hz flicker, with normal b-wave implicit times. Thus, optic nerve function, evaluated by PVEP, was severely reduced in LHON affected members and normal in the carrier female. However, reduced ERG cone responses suggest that LHON can also affect retinal elements, even in the absence of fundus and other clinical changes that constitute the full and classical expression of LHON.

Abnormal dark-adapted ERG in cats heterozygous for a recessively inherited rod-cone degeneration.

To study retinal function in cats homozygous and heterozygous for a recessively inherited rod-cone degeneration. Dark-adapted electroretinograms (ERGs) were performed on early affected, heterozygous (ophthalmoscopically normal), and clinically normal, nonrelated cats. Responses to blue stimuli over a 3.9-log unit range were recorded. Lower b-wave amplitudes than normal were observed in heterozygotes and early affected cats. The amplitudes of the heterozygotes took an intermediate position between normal and early affected cats. Normalized amplitude/intensity data suggest a normal dynamic range in carriers. B-wave implicit times in carriers were comparable to those of normal cats. These results show that heterozygotes have an altered retinal function, although they are ophthalmoscopically normal. It is difficult to electrophysiologically differentiate heterozygotes from affected cats with the very early stage of retinal degeneration.

Determination of Nontoxic Concentrations of Piperacillin/Tazobactam for Intravitreal Application

Background: To investigate the highest nontoxic intravitreal dose of piperacillin/tazobactam in rabbits. Material and Methods: Forty New Zealand white albino rabbits were used in this study. The rabbits were divided into four equal groups (10 rabbits in each) and the right eyes were treated with 0.1 ml intravitreal injections of 1,000 µg piperacillin/tazobactam in group 1, 500 µg in group 2, 250 µg in group 3, and 100 µg in group 4. The left eyes served as controls and were injected with 0.1 ml of saline solution. Ganzfeld electroretinogram (ERG) was performed on all eyes before and after 4 weeks of intravitreal injections. Then, the rabbits were killed and the eyes were enucleated for histopathological evaluation of the retina. Retinal sections were evaluated by morphometric analyses on cell counts of ganglion cell layer and thickness of the various retinal layers. Results: Baseline ERGs were similar among the groups (p > 0.05). After 4 weeks of injection, there were a reduction of the b-wave amplitude and extension of the b-wave implicit time in photopic and scotopic ERGs in group 1 and group 2 when compared with controls (for each, p < 0.001). Intravitreal injection of 100 and 250 µg piperacillin/tazobactam did not cause any deterioration of the b-wave of ERGs throughout the follow-up period of 4 weeks (for each, p > 0.05). After morphometric analysis of retinal sections in all groups, there were no statistically significant differences in the mean number of surviving ganglion cells, thickness of the whole retina and the inner plexiform layer compared with controls (p > 0.05). Conclusion: 250 µg/0.1 ml piperacillin/tazobactam is the highest nontoxic dose to the normal retinas of adult albino rabbits as intravitreal injection. Piperacillin/tazobactam may be a new, potentially important drug in the treatment of endophthalmitis as it has a broad antimicrobial spectrum.

A naturally occurring rat model of X-linked cone dysfunction.

To describe the electrophysiological, histologic, and hereditary features of a naturally occurring rat model of cone function loss. Dark- and light-adapted electroretinograms (ERGs) were used to evaluate retinal function. The thickness and architecture of the retina were observed by light microscopy. The cone density was investigated by wholemount immunocytochemistry. The inheritance pattern was defined by mating with control female rats. In affected rats, light-adapted ERGs were nearly absent, whereas dark-adapted responses were of normal amplitude with delays in b-wave implicit time. Overall retinal structure was normal at the light microscopic level. There was no difference in cone density between control and affected rats. The cone function abnormality is inherited as an X-linked trait. A spontaneous rat mutant was identified that has markedly affected cone function, whereas rod-mediated function is largely spared. The presence of the normal number of cone outer segments indicates that the defect does not involve cone photoreceptor degeneration. This rat model provides a model of X-linked cone dysfunction, and may also be used to examine aspects of rod-mediated visual function in the rat. Further studies are needed to identify the gene that is involved.

Avaliação da função visual em pacientes com distrofia de cones

OBJETIVO: Avaliar a função visual pela eletrorretinografia de campo total e pela acuidade visual em pacientes com distrofia de cones. MÉTODOS: Um grupo de 23 pacientes (16 do sexo feminino e 7 do sexo masculino) com distrofia de cones foi avaliado no Laboratório de Eletrofisiologia Visual Clínica do Departamento de Oftalmologia da Universidade Federal de São Paulo. A avaliação constou de: sinais e sintomas, acuidade visual medida pela tabela ETDRS ou de Snellen e função retiniana pela eletrorretinografia de campo total. As amplitudes pico-a-pico (µV) e o tempo de culminação da onda-b (ms) foram comparadas com normas descritas na literatura. RESULTADOS: A acuidade visual no melhor olho variou de 0,07 a 3,00 logMAR (20/25-MM a 10 cm), com média de 0,85±0,64 logMAR (20/140). A média da amplitude pico-a-pico das respostas escotópicas de bastonetes foi de 144,29±80,05 µV com média do tempo de culminação da onda-b de 92,85±9,02 ms (normal para a idade). A média da amplitude pico-a-pico para respostas fotópicas de cones foi de 5,06±8,59 µV (reduzida para a idade) com média do tempo de culminação da onda-b de 43,4±14,5 ms (atrasado para a idade) nos pacientes com resposta detectável e para as respostas do flicker, a amplitude foi de 5,00±9,00 µV (reduzida para a idade) com média do tempo de culminação da onda-b de 32,90±12,87 ms (atrasado para a idade). CONCLUSÃO: A acuidade visual média encontrada neste grupo de pacientes com distrofia de cones foi de 0,85 logMAR (20/140). A fotofobia foi o sintoma mais freqüente juntamente com a baixa de visão e deficiência de visão de cores. Em 10/23 pacientes o diagnóstico foi feito pela eletrorretinografia, devido à ausência de alterações fundoscópicas.

Flash electroretinography in standing horses using the DTL microfiber electrode.

The goal of our study was the evaluation of a practical method for the recording of flash electroretinograms (ERGs) in sedated, standing horses with the DTL microfiber electrode. The horses were sedated intravenously with detomidine hydrochloride (0.015 mg/kg). The pupil was dilated and the auriculopalpebral nerve was blocked. The ERGs were recorded with the active electrode on the cornea (DTL), the reference electrode near the lateral canthus, and the ground electrode over the occipital bone. The light intensities of the white strobe light were 0.03 cd x s/m2 (scotopic) and 3 cd x s/m2 (scotopic and photopic). Photopic and scotopic single flash and flicker responses to Ganzfeld stimulation were recorded. During the 20-min dark adaptation period the retina was stimulated every 5 min with the 0.03 cd x s/m2 single flash. The median b-wave amplitudes and implicit times were 38 microV and 33 ms (photopic cone-dominated response), 43 microV and 63 ms (5-min dark adaptation), 72 microV and 89 ms (10 min), 147 microV and 103 ms (15 min), 188 microV and 109 ms (20 min, 0.03 cd x s/m2, rod response), and 186 microV and 77 ms (20 min, 3 cd x s/m2, maximal combined rod-cone response). A steady increase in amplitude and implicit time was noted during dark adaptation. No oscillatory potentials could be isolated. The use of detomidine hydrochloride sedation and the DTL microfiber electrode allowed the recording of good quality ERGs. This protocol should permit the detection of functional problems in the retina without the risk involved with general anesthesia.

Visual acuity and retinal function in infant monkeys fed long-chain PUFA.

Previous randomized clinical trials suggest that supplementation of the human infant diet with up to 0.35% DHA may benefit visual development. The aim of the current study was to assess the impact of including arachidonic acid (AA) and a higher level of DHA in the postnatal monkey diet on visual development. Infant rhesus monkeys were fed either a control diet (2.0% alpha-linolenic acid as the sole n-3 FA) or a supplemented diet (1.0% DHA and 1.0% AA) from birth. Visual evoked potential acuity was measured at 3 mon of age. Rod and cone function were assessed in terms of parameters describing phototransduction. Electroretinogram (ERG) amplitudes and implicit times were recorded over a wide intensity range (-2.2 to 4.0 log scot td-sec) and assessed in terms of intensity response functions. Plasma DHA and AA were significantly increased (P < 0.001) in the diet-supplemented monkeys compared with the control monkeys. There was an approximately equal effect of diet for the rod phototransduction parameters, sensitivity, and capacitance but in the opposite directions. Diet-supplemented monkeys had significantly shorter b-wave implicit times at low retinal illuminances (<-0.6 log scot td-sec). There were no significant effects of diet for visual acuity or the other 23 ERG parameters measured. The results suggest that supplementation of the infant monkey diet with 1.0% DHA and 1.0% AA neither harms nor provides substantial benefit to the development of visual acuity or retinal function in the first four postnatal months.

Retinal sensitivity loss in third-generation n-3 PUFA-deficient rats.

A previous study conducted in guinea pigs suggested that ingestion of diets high in EPA and DHA may result in suboptimal retinal function. The aim of the present study was to evaluate retinal function in pigmented (Long-Evans) rats, raised to a third generation on diets that were either deficient in n-3 PUFA or adequate (with the addition of DHA). Electroretinographic assessment employed full-field white flash stimulation. Photoreceptor responses were evaluated in terms of peak amplitudes and implicit times (a-wave, b-wave), intensity-response functions (Naka-Rushton), and the parameters of a model of transduction (P3). Retinal phospholipid FA composition was measured by capillary GLC. DHA levels were reduced by 55% in n-3-deficient animals compared with the n-3-adequate group, whereas the levels of docosapentaenoic acid n-6 were 44 times higher in n-3-deficient animals. The level of arachidonic acid was marginally higher (12.8%) in n-6-adequate animals. The n-3-deficient animals exhibited significantly reduced retinal sensitivity (sigma and S values were both affected by 0.29 log units) and increased b-wave implicit times compared with those fed the n-3-adequate diet. These data suggest that n-3 PUFA are required for development of retinal sensitivity, more so than other indices of retinal function assessed by current methods, such as maximal response amplitude. However, the benefit for retinal function of adding preformed DHA to diets already replete in n-3 PUFA remains unclear.

Eletrorretinograma: considerações a respeito dos limites de normalidade e comparação entre valores normais de dois diferentes laboratórios

Objetivo: Comparar os valores dos limites de normalidade da amplitude e tempo de culminação do eletrorretinograma (ERG) de 2 laboratórios diferentes. Métodos: Dados normativos do ERG disponibilizados pelo fabricante de aparelhos de eletrofisiologia com o programa UTAS (LKC Technologies), que incluíam 110 indivíduos normais de 22 a 79 anos de idade, foram comparados com valores normais de nosso laboratório publicados anteriormente, referentes a 42 indivíduos normais com idades variando de 6 a 72 anos, cujo exame foi realizado em um dos modelos LKC (EPIC 2000). O método de registro do ERG foi o de estimulação simples ("single flash") e seguiu as recomendações da ISCEV (International Society of Clinical Electrophysiology of Vision). Resultados: Todos os parâmetros do ERG, tanto de amplitude quanto de tempo de culminação, com exceção da amplitude dos potenciais oscilatórios (p = 0,0779) e do tempo de culminação da onda-b da resposta máxima combinada (p = 0,7771), foram significativamente (p < 0,0001) diferentes. Conclusão: Cada laboratório de eletrofisiologia deve ter seus próprios parâmetros de normalidade, os quais podem ser resultado do intervalo de confiança de 95% da média de sua amostra de normais, ou os percentis 2,5 e 97,5. No primeiro caso os limites serão bastante estreitos, aumentando a sensibilidade do teste, ocorrendo o inverso no segundo.

Ethanol Consumption Alters Electroretinograms and Depletes Neural Tissues of Docosahexaenoic Acid in Rhesus Monkeys: Nutritional Consequences of a Low n‐3 Fatty Acid Diet

Alcohol amblyopia is a rare neuropathy characterized by the development of blurred vision and a reduction in visual acuity. Further diagnostic details of this condition have shown abnormalities in the electroretinogram (ERG) that include an increase in implicit times in the a- and b-waves and a depression of b-wave amplitude. Periodically, the ERGs and the fatty acyl composition of nervous tissue were analyzed from alcohol-consuming rhesus monkeys (Macaca mulatta) (mean consumption 2.6 g kg/day over a 5-year period) and controls that were maintained on a nutritionally sufficient diet that had low, yet adequate, amounts of linoleic acid but very low alpha-linolenic acid. Animals consuming alcohol had increased a- and b-wave implicit times and decreased b-wave amplitudes in their electroretinograms compared with those of the dietary control group at 2.5 and 5 years. The fatty acyl composition of brain specimens obtained by surgical biopsy at baseline, 2.5 years, and 5 years demonstrated that docosahexaenoic acid (DHA) had decreased in both groups of animals compared with baseline values. In the brains of the alcohol-treated animals, DHA was even further decreased (2.5 years: -20%; 5 years: -33%) compared with the diet controls. In the retinas of the alcohol-consuming animals at 5 years, there was a similar decrease in DHA (-35%) compared with controls. Generally, the n-6 fatty acid, docosapentaenoic acid (DPAn-6) increased in these tissues, apparently compensating for the loss of DHA. A reciprocal change in the DHA/DPAn-6 ratio is known to be associated with abnormal electroretinograms in a number of species. Thus, a marginal intake of n-3 fatty acids in some alcohol abusers may, in part, be responsible for the biochemical changes that underlie the diminished retinal function associated with the visual abnormalities observed in alcohol-amblyopic patients.

The b-wave of the dark adapted flash electroretinogram in patients with advanced asymmetrical glaucoma and normal subjects

AIMSTo evaluate whether the b-wave of the dark adapted flash electroretinogram (ERG) is affected by glaucomatous damage.METHODSERGs were recorded in 35 patients aged 33–65 years with advanced asymmetrical glaucomas (interocular...

The value of electrophysiology results in patients with epilepsy and vigabatrin associated visual field loss.

To determine the value of electrophysiological findings in patients with temporal lobe epilepsy and to relate these findings to the amount of concentric contraction of the visual field and the use of vigabatrin. Electro-retinograms and electro-oculograms were done on 30 patients, operated for temporal lobe epilepsy. The patients were divided into three groups: (A) concentric contraction of the visual field associated with a history of vigabatrin medication (15 patients), (B) normal visual field with vigabatrin use (11 patients) and (C) normal visual field without vigabatrin medication (4 patients). Electrophysiological abnormalities were found in 50% of the patients in group A. The Arden ratio of the EOG was lowered in 57%. Abnormalities in the ERG were found: b-wave implicit time photopic F was prolonged (50%), b-wave amplitudes scotopic B (53%), C (73%) and G (50%) and photopic H (50%) were diminished. The amount of visual field loss and the total dose of vigabatrin used, showed only slight correlation with the ERG and EOG. The use of vigabatrin during the ERG and EOG recording in group A, gave a higher b-wave amplitude scotopic G in 64% of cases. The a-wave implicit times scotopic G (73%) and photopic G (59%) and H (73%) were shortened in group B. EOG was abnormal in 57% in group A. ERG abnormalities could only be found in 50% of group A, mainly in the inner retina. Since also the total dose of vigabatrin and the amount of visual field loss did not really show a correlation with the electrophysiological findings and results of literature are not unanimous, electrophysiology does not appear at present to be a good method to detect patients with, or at risk of, vigabatrin associated visual field loss. Regularly performed visual field examination remains the cornerstone in screening.

RETINAL CIRCADIAN RHYTHMS IN HUMANS*

Circadian rhythms in the retina may reflect intrinsic rhythms in the eye. Previous reports on circadian variability in electrophysiological human retinal measures have been scanty, and the results have been somewhat inconsistent. We studied the circadian variation of the electrooculography (EOG), electroretinography (ERG), and visual threshold (VTH) in subjects undergoing a 36h testing period. We used an ultrashort sleep-wake cycle to balance effects of sleep and light-dark across circadian cycles. Twelve healthy volunteers (10 males, 2 females; mean age 26.3 years, standard deviation [SD] 8.0 years, range 19–40 years) participated in the study. The retinal functions and oral temperature were measured every 90 min. The EOG was measured in the light, whereas the ERG and the VTH were measured in the dark. Sleep was inferred from activity detected by an Actillume monitor. The EOG peak-to-peak responses followed a circadian rhythm, with the peak occurring late in the morning (acrophase 12:22). The ERG b-wave implicit time peaked in the early morning (acrophase 06:46). No statistically significant circadian rhythms could be demonstrated in the ERG a-wave implicit time or peak-to-peak amplitude. The VTH rhythm peaked in the early morning (acrophases 07:59 for blue and 07:32 for red stimuli). All retinal rhythms showed less-consistent acrophases than the temperature and sleep rhythms. This study demonstrated several different circadian rhythms in retinal electrophysiological and psychophysical measures of healthy subjects. As the retinal rhythms had much poorer signal-to-noise ratios than the temperature rhythm, these measures cannot be recommended as circadian markers. (Chronobiology International, 18(6), 957–971, 2001)

Clinical and electroretinographic findings in fetal alcohol syndrome

Purpose: Fetal exposure to alcohol is a serious public health problem and is associated with anomalies of the eye ground, as well as neurodevelopmental delay, growth delay, and characteristic facial features. Our purpose is to report the incidence of abnormal electroretinogram (ERG) results in children with fetal alcohol syndrome and raise awareness of the diagnosis of fetal alcohol syndrome in ophthalmology. Methods: A retrospective review was performed on the records of 11 children with the diagnosis of fetal alcohol syndrome. The results of the ophthalmologic examination, magnetic resonance imaging, visual acuity test, and ERG are reported. Results: The magnetic resonance imaging results were abnormal in all subjects tested. The ophthalmology examination showed optic nerve hypoplasia in 91% of the subjects. Visual acuity was reduced in all but one subject. The ERG results were abnormal, showing reduced b-wave amplitude, increased a- and b-wave implicit time, reduced Rmax, and increased log (k). The scotopic ERG was more severely affected than the photopic ERG. Conclusions: Prenatal alcohol exposure can lead to changes in retinal function as evidenced by an abnormal ERG response. The ERG can therefore be a tool with which to identify suspected alcohol embryopathy. (J AAPOS 2000;4:200–4)

Visual phenotype in patients with Arg41Gln and Ala196+1bp mutations in the CRX gene

Our aim was to describe the visual function characteristics of affected members from two unrelated families with different dominant mutations in the CRX gene. Standard full-field ERGs and high-intensity a-wave series were obtained. In addition, in most subjects, dark-adapted (DA) thresholds, color vision function (arrangement tests), and static perimetry were assessed. A point mutation in codon 41 of the CRX gene (Arg41Gln) was identified in family members from the RFS087 family who were tested on several occasions since 1983. Depending on age, affected members showed varying degrees of acuity loss, normal or slightly elevated DA thresholds, reduced cone a- and b-wave amplitudes, normal or minimally delayed cone b-wave implicit times, and normal rod and cone phototransduction gain parameters. An insertion mutation (Ala196+1bp) was found in two members of another family (RFS014). Affected members showed reduced visual acuity, normal or slightly elevated DA thresholds, relatively preserved rod ERG and substantially reduced or undetectable cone ERG, and normal rod phototransduction gain parameters. The Arg41Gln was associated with a late-onset, slowly progressing mild form of cone-rod dystrophy with cone loss but preserved rod and cone sensitivity until later in life. The Ala196+1bp mutation was associated with an early-onset, severe form of cone-rod dystrophy similar to that described in the original CORD2 family (Evans et al., Arch Ophthalmol 1995;113:195-201).

Clinical and electroretinographic findings of female carriers and affected males in a progressive X-linked cone–rod dystrophy (COD-1) pedigree

Objective To study the clinical and electroretinographic findings of affected males and female carriers in a family with X-linked cone–rod dystrophy (COD-1). Design Observational case series. Participants Twenty-five members of a five-generation pedigree were examined. Methods A history of visual impairment including age at onset, loss of acuity, color vision abnormalities, photophobia, and nyctalopia was obtained. A complete ophthalmologic examination was performed, including kinetic perimetry with a Goldmann perimeter, FM 100-hue testing, and standardized Ganzfeld electroretinography following the ISCEV protocol. Main outcome measures Patients were classified as affected or unaffected on the basis of the clinical examination. All carrier females had affected sons. Results Nine affected males and seven female carriers were identified. Affected males noted decreased visual acuity and poor color vision within the first two decades of life. Early in the disease, macular retinal pigment epithelial (RPE) changes were found that progressed to an atrophic macular scar by the fifth decade. Evidence of progression from macular pigment mottling to an atrophic macular lesion over a 13-year period was identified in one patient. The photopic, single-flash, b-wave amplitude was low in all affected males and declined with age. The 30-Hz flicker b-wave implicit times were abnormally prolonged in all affected males. Female carriers were asymptomatic although three had slightly abnormal color vision and small paracentral field defects and subtle RPE defects were found in three carriers. Carriers demonstrated prolongation of the 30-Hz flicker b-wave implicit time and interocular asymmetry. Five of seven carriers and two affected males demonstrated reduced oscillatory potentials and an abnormal-appearing flattened photopic a-wave. Five men and two women demonstrated a characteristic tapetal-like retinal sheen. Conclusions Affected patients in this pedigree demonstrate early loss of visual acuity and poor cone function with late rod involvement. Female carriers may appear clinically normal or may be identified by subtle color vision defects, fundus abnormalities, prolongation of the 30-Hz flicker implicit time with interocular asymmetry, or an abnormal flattened photopic a-wave. Genetic linkage analysis of this family was recently reported and the disease-causing gene has been mapped to an approximately 1-Mb interval on chromosome Xp11.4.

The 30-Hz flicker cone ERG for monitoring the early course of central retinal vein occlusion.

Investigation of the full-field ERG (electoretinography) within 24 hours after the onset of symptoms in central retinal vein occlusion, and repeated examination within the following days and weeks. Seven patients with central retinal vein occlusion were examined with full-field ERG within less than 24 hours after the onset of their symptoms and every second to third day during the first 3 weeks. They were then followed for a period of time of six months. The amplitudes as well as the implicit times in the 30 Hz flicker ERG changed considerably within the first three weeks. In the three patients who developed rubeosis, the cone b-wave implicit times as well as the amplitudes were altered considerably. In the patients that did not develop rubeosis, the cone b-wave implicit times as well as the amplitudes in the 30 Hz flicker ERG were more stable. The full-field cone ERG reflects the retinal function and the ERG parameters change considerably during the first weeks after the onset of the central retinal vein occlusion. The 30 Hz flicker ERG gives important information concerning the early development of the disease. The optimal time to do a predictive ERG could be after three weeks.

Visual phenotype in patients with Arg41Gln and Ala196+1bp mutations in the CRX gene

Our aim was to describe the visual function characteristics of affected members from two unrelated families with different dominant mutations in the CRX gene. Standard full-field ERGs and high-intensity a-wave series were obtained. In addition, in most subjects, dark-adapted (DA) thresholds, color vision function (arrangement tests), and static perimetry were assessed. A point mutation in codon 41 of the CRX gene (Arg41Gln) was identified in family members from the RFS087 family who were tested on several occasions since 1983. Depending on age, affected members showed varying degrees of acuity loss, normal or slightly elevated DA thresholds, reduced cone a- and b-wave amplitudes, normal or minimally delayed cone b-wave implicit times, and normal rod and cone phototransduction gain parameters. An insertion mutation (Ala196+1bp) was found in two members of another family (RFS014). Affected members showed reduced visual acuity, normal or slightly elevated DA thresholds, relatively preserved rod ERG and substantially reduced or undetectable cone ERG, and normal rod phototransduction gain parameters. The Arg41Gln was associated with a late-onset, slowly progressing mild form of cone-rod dystrophy with cone loss but preserved rod and cone sensitivity until later in life. The Ala196+1bp mutation was associated with an early-onset, severe form of cone-rod dystrophy similar to that described in the original CORD2 family (Evans et al., Arch Ophthalmol 1995;113:195-201).

Circadian regulation of chick electroretinogram: effects of pinealectomy and exogenous melatonin.

Melatonin is an important component of the avian circadian system. This study investigates the effects of pinealectomy (Pin-X) and melatonin implantation (Mel) on electroretinogram (ERG) rhythms in chicks. Feeding rhythms were monitored to obtain a phase reference for ERG recordings. Pin-X and Mel had little or no effect on feeding rhythms. Sham-operated Pin-X and vehicle implantation had no effect on ERG rhythms in the light-dark (LD) cycle or constant darkness (DD). ERG a- and b-wave amplitudes were higher during the day than during the night. The a- and b-wave implicit times were shorter during the day than during the night. a-Wave sensitivity was higher during the night than during the day, whereas b-wave sensitivity was not rhythmic. Pin-X abolished the circadian rhythm of b-wave amplitude and implicit time in DD but had no effect on a-wave rhythmicity. Mel abolished the rhythm of b-wave amplitude and of a- and b-wave implicit time in DD. Neither treatment affected ERG in LD. These results suggest that the circadian system regulates rhythmic visual function in the retina at least partially through Mel. The role played by the pineal gland and Mel may be specific to some physiological modalities (e.g., vision) while not influencing others (e.g., feeding).