[Intraoperative Visual Evoked Potential].

In neurosurgery, the intraoperative visual evoked potential(VEP)has recently been used for the management of anterior skull base and parasellar tumors related to the optic pathways to prevent postoperative visual complications. We used light emitting diode photo-stimulation thin pad and stimulator(Unique Medical, Japan). We also recorded the electroretinogram(ERG)simultaneously to exclude technical errors. VEP is defined as an amplitude between the maximum positive wave at 100 ms(P100)and the prior negative wave(N75). In intraoperative VEP monitoring, reproducibility of VEP should be ascertained, particularly in patients with preoperative advanced visual impairment and an intraoperative diminished amplitude. Furthermore, a 50% reduction in the amplitude is critical. In such cases, we should consider suspending or changing surgical manipulation. We have not clearly verified the relationship between the absolute intraoperative VEP value and postoperative visual function. Mild peripheral visual field defects cannot be detected in the present intraoperative VEP system. However, intraoperative VEP with ERG monitoring can serve as a real-time warning to guide surgeons to avoid postoperative visual impairment. We should comprehend the principles, characteristics, disadvantages, and limitations of intraoperative VEP monitoring for reliable and effective utilization.

Case of convulsive seizure developing during electroretinographic recordings: a case report.

BACKGROUND: To present our findings in a case of convulsive seizures and loss of consciousness that developed during recording electroretinograms (ERG). CASE PRESENTATION: A 34-year-old man had reduced vision in his left eye for about 15 years, and night blindness for about two years. His visual acuity was 20/15 in the right eye and 20/50 in the left eye. The fundus was normal but the sensitivity in the macular region of the left eye was decreased. Optical coherence tomography (OCT) showed partial loss of the interdigitation zone. Upon completion of the flicker ERG recording, a paralysis developed in both upper limbs, then convulsions of the lower limbs followed by a loss of consciousness. The convulsions disappeared after an intravenous injection of diazepam. After that incident, he reported that he had had previous conscious-loss seizures. CONCLUSIONS: Photosensitive epileptic seizures can occur with the light stimuli used for conventional ERG recordings. We recommended that clinicians request information on any prior seizure episodes of the patients and their family members before ERG recordings.

Obtención, interpretación y usos del electrorretinograma multifocal / Obtaining, interpreting and using the multifocal electroretinogram

Las pruebas electrofisiológicas oculares constituyen un variado grupo de herramientas diagnósticas de extremada relevancia, sobre todo por su objetividad. El electrorretinograma multifocal se encuentra entre los más novedosos y promisorios de este selecto grupo y, a la vez, entre las de mayor complejidad de obtención. Se realiza una revisión bibliográfica de los aspectos relacionados con la obtención, representación y aplicaciones clínicas del electrorretinograma multifocal(AU)

The ocular electrophysiological tests are a varied group of extremely relevant diagnostic tools that stand out because of their objectivity. The multifocal electroretinogram is among the most novel and promising in this selected group, but at the same time, it is one of the most complex to be obtained. A literature review of the aspects related to obtaining, representation and clinical applications of the multifocal electroretinogram was made and presented in this paper(AU)

Ultrassonografia em modo A e B na avaliação pré-operatória da lente e do segmento posterior de olhos de cães com catarata / A and B mode ultrasonography in preoperative evaluation of lens and posterior segment of dogs eyes with cataract

Ultrasonography of the lens and posterior segment is an indispensable step in the preoperative evaluation of dogs with cataracts, since ophthalmoscopy is not feasible when there is opacification of the lens. This study evaluated the echographic conditions of cataractous lens and fundus of the eye in dogs affected by cataracts. The study was conducted in 30 dogs (56 eyes), 10 males and 20 females, with different types of cataracts at different stages of development. Echography in A and B modes, simultaneously, was carried out for the examination of the lens and posterior segment. The examinations revealed anterior cortical, posterior cortical and nuclear cataract in 12 eyes (21.4 percent), anterior cortical, posterior cortical, nuclear and posterior capsular in 23 eyes (41 percent), anterior cortical, posterior cortical and posterior capsular cataract in one eye (1.7 percent), anterior cortical and nuclear cataract in one eye (1.7 percent), anterior cortical, nuclear and posterior capsular cataract in five eyes (8.9 percent), and anterior cortical cataract in seven eyes (12.5 percent). Abnormal ultrasonographic alterations were observed in the posterior segment in 26 eyes evaluated (46.4 percent). Vitreal degeneration was detected in 12 eyes (21.4 percent), images of vitreal exudate or hemorrhage in seven eyes (12.5 percent), persistence of hyaloid artery in four eyes (7.1 percent) and lens subluxation in three eyes (5.3 percent). The results obtained reiterate the importance of ultrasonography in canine patients presented for cataract surgery given that alterations of the posterior segment are difficult to identify in a clinical examination when the lens is opacified.

A ultrassonografia do segmento posterior do bulbo do olho é etapa indispensável na avaliação de cães com catarata que serão submetidos à facectomia, uma vez que a oftalmoscopia não é factível quando há opacificação da lente, notadamente nas cataratas maduras. Este estudo avaliou as condições ecográficas da lente cataratogênica e do fundo de olho de cães cursando com catarata. Foram avaliados 30 cães (56 olhos), sendo 10 machos e 20 fêmeas, cursando com catarata em diferentes estágios de desenvolvimento. Realizou-se a ecografia em modo A e B simultaneamente. Os exames revelaram catarata cortical anterior, posterior e nuclear em 12 olhos (21,4 por cento), catarata cortical anterior, posterior, nuclear e capsular posterior em 23 olhos (41 por cento), catarata cortical anterior, posterior e capsular posterior em um olho (1,7 por cento), catarata cortical anterior e nuclear em um olho (1,7 por cento), catarata cortical anterior, nuclear e capsular posterior em cinco olhos (8,9 por cento) e catarata cortical anterior em sete olhos (12,5 por cento). Alterações no segmento posterior foram observadas, à ultrassonografia, em 26 olhos avaliados (46,4 por cento). Degeneração vítrea foi detectada em 12 olhos (21,4 por cento), imagens compatíveis com exsudato ou hemorragia em sete olhos (12,5 por cento), persistência da artéria hialóide em quatro olhos (7,1 por cento) e subluxação da lente em três olhos (5,3 por cento). Os resultados obtidos reiteram a importância da ultrassonografia em cães candidatos à cirurgia de catarata, uma vez que o exame do segmento posterior do bulbo do olho é de difícil execução, devido à opacificação da lente.

Importância do eletrorretinograma de campo total (Full field ERG) em cães da raça Cocker Spaniel Inglês portadores de catarata / Full field electroretinogram in English Cocker Spaniels presenting cataracts

Com o aumento do número de intervenções cirúrgicas para a remoção da catarata em cães, observa-se a necessidade de exames específicos que devem ser realizados antes da indicação cirúrgica. A catarata é uma das principais causas de cegueira em cães. Nos estágios mais avançados, impossibilita o exame fundoscópico e inviabiliza a observação de alterações retinianas como a atrofia progressiva da retina (APR), degeneração retiniana hereditária de acometimento bilateral que, quando diagnosticada, contra-indica a cirurgia. Com o intuito de reestabelecer a visão, o eletrorretinograma de campo total (Full field ERG) torna-se indispensável na avaliação pré-cirúrgica da remoção da catarata. Como os cães da raça Cocker Spaniel Inglês são predispostos à catarata e a degenerações retinianas, objetivamos neste estudo avaliar as respostas dos ERGs realizados nestes animais. Foram avaliados 136 eletrorretinogramas de cães da raça Cocker Spaniel Inglês (62 machos e 74 fêmeas, com idades entre 3 e 15 anos) no período de Setembro de 2004 a Maio de 2009. Todos os animais apresentavam baixa de visão e catarata durante o exame. O diagnóstico de degeneração retiniana foi baseado nos valores de amplitude pico a pico e tempo de culminação da onda-b nas 3 respostas (resposta escotópica de bastonetes, máxima resposta e resposta fotópica de cones), idade do paciente e estágio de maturação da catarata. Nos cães sem degeneração retiniana, a média da amplitude e do tempo de culminação nas três respostas obtidas foram, respectivamente: 71,55mV/65,15ms; 149,17mV/33,03ms; 31,06mV/27,90ms. Nos cães com degeneração retiniana, 38 animais apresentaram ERG extinto. Dentre os restantes que apresentavam baixas respostas, a média da amplitude e do tempo de culminação nas três respostas obtidas foram, respectivamente: 12,88mV/65,04ms; 24,16mV/36,25ms; 8,36mV/31,38ms. Foi observado que em 122 animais (89,7 por cento) os exames eram compatíveis com diagnóstico de atrofia progressiva ...

Cataracts are one of the most frequent ocular disorders that affects dogs and leads to blindness. In the late stages, lens opacity unables fundoscopy and consequently the diagnosis of retinal degeneration such as progressive retinal atrophy (PRA), which contraindicates surgery. Aiming the return of vision, full field electroretinogram (full field ERG) becomes indispensable before surgery. As English Cocker Spaniels are predisposed to cataracts and retinal degeneration, the objective of this study is the evaluation of the full field ERG records performed in dogs. One hundred thirty-six full field ERGs were recorded from English Cocker Spaniels (62 males and 74 females, with ages ranging from 3 to 15 years old), between September, 2004 and May, 2009. Each examined dog presented cataracts and vision loss before the exam. Diagnosis of retinal degeneration was made based on ERG parameters which were measured from peak to peak amplitude and b-wave implicit time in the 3 different responses (rod response, maximal response and cone response). Amplitude measured in rod, maximal and cone response, as well as the implicit time recorded from dogs that did not present retinal degeneration were respectively: 71.55mV/65.15ms; 149.17mV/33.03ms; and 31.06mV/27.90ms. No response was recorded in 38 dogs. Low responses were recorded from the remaining dogs: 12.88mV/65.04ms, 24.16mV/36.25ms, and 8.36mV/31.38ms. Results showed that 122 animals (89.7 percent) presented progressive retinal atrophy. Therefore, we conclude that full field ERG must be performed in English Cocker Spaniels presenting cataracts before its removal due to high incidence of retinal degeneration in this breed.

Evaluation of different recording parameters to establish a standard for flash electroretinography in rodents.

Different electrodes and stimulus protocols commonly used for electroretinography in rodent eyes were compared for convenience of use, degree of damage to corneal epithelium, and for magnitude of amplitude, reproducibility, left versus right eye accuracy, and reliability of recorded parameters of the flash electroretinogram (ERG). Adult C57BL/6 pigmented mice and albino Wistar rats were used to determine scotopic ERGs in response to Ganzfeld or strobe-light stimulation and light-adapted (photopic) ERGs recorded from both eyes at the same time. Test-retest data were used for statistical analyses to compare a monopolar gold-wire contact lens electrode (CLE), a cotton-wick silver-silver chloride electrode (CSCE), a DTL fiber electrode (DTLE), and a circular stainless steel wire electrode (SSE). Corneas were evaluated for abrasion after ERG recordings using fluorescein staining and also for the time taken, ease of insertion, and re-insertions required for the different electrodes. Compared to CSCE, DTLE, and SSE, the ERG potentials recorded by CLE had significantly larger scotopic amplitudes and oscillatory potentials under strobe or Ganzfeld stimulation and for light-adapted ERG b-wave amplitudes in both mice and rats. In analyzing test-retest data of scotopic ERG a-wave and b-wave amplitudes, the intraclass correlation coefficient showed the best agreement for the CLE (range 0.61-0.94) compared to the SSE (0.13-0.77), DTLE (0.02-0.69), and CSCE (0.12-0.51). In mice and rats, logistic regression analyses revealed significant correlations for amplitudes of most scotopic ERG parameters between contralateral eyes obtained with CLE and for some ERG components recorded by SSE. When comparing ERG amplitudes for stimulation by strobe or Ganzfeld, the difference was least with the CLE compared to DTLE, CSCE, or SSE. The time taken to insert the four different electrodes was greatest for the CLE in both mice and rats. The extent of corneal abrasion resulting from electrode use in mice was largest for the SSE followed by the CLE. However, in rats there was almost no corneal damage after ERG recordings with the CLE. Because of the stability of eye contact, the CLE allows ERGs to be determined over a longer recording session. Recording of scotopic and photopic (light-adapted) ERGs in rodents with monopolar gold-wire contact lens electrodes provides greater amplitudes and higher reproducibility when compared to other commonly used corneal electrodes. These electrodes are significantly better overall than others that were evaluated and should be considered for a standard protocol to monitor retinal function in rodent eyes.

Bright-flash electroretinography for the evaluation of eyes with opaque vitreous.

Standard retinal function tests are of limited value in assessing retinal function in eyes with opaque vitreous. We developed a method for obtaining an electroretinogram (ERG) from eyes with significant vitreous opacity by utilizing a much brighter than normal stimulating light. Of 115 eyes with vitreous opacities and good ERG responses to this bright-flash photostimulator, 47% would have been nonrecordable with a conventional ERG light source. Bright-flash ERG was often helpful in evaluating eyes with vitreous opacities for vitrectomy and was sometimes the only source of information regarding potential retinal function.