Clinical features of the retinopathy, globe enlarged (rge) chick phenotype

AbstractThe purpose of the study reported here was to characterize the clinical aspects of the autosomal recessive retinopathy, globe enlarged (rge) phenotype in chicks (Gallus gallus). Rge/rge, rge/+ and +/+ chicks were studied from hatch to 336 days of age by general clinical examination, post-mortem examination, vision testing with an optokinetic device, ophthalmoscopy, biomicroscopy, tonometry, central corneal pachymetry, a-mode ultrasonography, infrared photoretinoscopy and photokeratometry. Additionally, preliminary electroretinographic and histopathologic investigations were performed. There is a variable degree of vision loss in rge/rge chicks at 1 day of age with further chicks losing vision over the next few weeks until all chicks become functionally blind by 30 days of age (although some optokinetic responses remain in some of the rge/rge chicks). Over the first few weeks of life rge/rge chicks develop thicker corneas with a larger radius, hyperopia, shallower anterior chambers and enlarged globes both radially and axially, compared to controls. A preliminary ERG study showed that 1 day old rge/rge chicks have an elevated response threshold, a lower amplitude a-wave with a markedly shallow leading slope, a lack of both oscillatory responses and c-waves and, at brighter flashes, an increased b-wave amplitude. Light microscopy revealed no gross retinal abnormalities in young chicks to account for the blindness. A thinning of all retinal layers developed in parallel with globe enlargement. The rge defect is a unique progressive retinal dystrophy that results in a severe visual deficit, abnormal electroretinographic waveforms, and secondary globe enlargement

HISTÓRIA DA ELETRORRETINOGRAFIA

The eye and its diseases have been studied since the time of the ancient Egypt; therefore, ophthalmology is recognized as one of the first medical specialties to ever exist. Along the years many advances in this area occurred, as the invention of the ophthalmoscope during the 19th Century and other ancillary methods in the 20th Century. After the invention of the ophthalmoscope, the observation and study of the retina, the anatomic part of the eye that transforms light energy into electric energy (phototransduction) stimulating the brain to form an image. Electroretinography is an ophthalmic examination that captures this electrical response generated by cells of the retina when stimulated by light. This is an excellent tool for studying the function of the retina, yet it is still a modestly widespread practice in the Brazilian veterinary medicine scenario. This paper aims to review the history of this valuable method of diagnosis.O olho juntamente com suas doenças vem sendo estudado desde o Egito antigo, sendo a oftalmologia, portanto, considerada como uma das primeiras especialidades médicas a existir. Com a invenção do oftalmoscópio no século XIX bem como de outros métodos de exames diagnósticos no século XX, iniciou-se a observação e o estudo da retina, tecido nervoso que realiza fototransdução e faz a passagem do estímulo elétrico para o cérebro, formando a imagem. A eletrorretinografia é um capítulo peculiar na história da oftalmologia. Trata-se de um exame oftálmico funcional que capta a resposta elétrica produzida pelas células da retina quando estimuladas. Tornou-se uma excelente ferramenta para estudar a funcionalidade da retina de animais e seres humanos, porém seu uso ainda encontra-se pouco difundido na Medicina Veterinária brasileira. O trabalho presente tem o objetivo de revisar a história deste valioso método de diagnóstico

Isolation of chick retina cones and study of their diversity based on oil droplet colour and nucleus position

The chick retina has four morphological cone types that differ not only in shape, but also in the visual pigment in the outer segment, in the colour of the oil droplet in the inner segment and in synaptic connectivity. Neither the type of droplet nor the visual pigment has been definitively established for the four cone types. The main aim of the present work has been the isolation of entire live photoreceptors in order to study the oil droplet colour in each cone type and to quantify each type. We have improved an earlier retinal cell isolation method and obtained large numbers of entire cones. Principal cones (27% of the cones) possess a yellow or colourless droplet. Accessory cones (27% of the cones) all contain a small pale green droplet. Straight cones (44% of the cones) have a red, orange, yellow, or colourless droplet. Oblique cones (1.66% of the cones) all have a colourless droplet. We have found that straight cones with a red, orange, or yellow droplet differ in terms of the position of the nucleus and their percentage and conclude that they are distributed in three rows in the outer nuclear layer (ONL) of the central retina. Our study of 4,6-diamidino-2-phenylindole-stained retinal sections has revealed three rows of nuclei instead of the two currently thought to form the ONL. Together, our results show a larger cone diversity than previously known, suggest a larger functional diversity and provide an efficient method for isolating entire chick photoreceptors

Ecobiometria ocular de cães glaucomatosos

Foram estudados olhos glaucomatosos de cães referidos no serviço de diagnóstico por imagem. Os pacientes foram submetidos à ultrassonografia em modo B de alta resolução para realização de biometria ocular, por meio da qual foram realizadas as seguintes medidas: espessura central da córnea, profundidade da câmara anterior, espessura da lente e profundidade da câmara vítrea. Para tal, foi realizada contenção física e instilado colírio anestésico. Foram aferidas a PIO e a paquimetria da córnea e, em seguida, foi realizada a ultrassonografia em modo B nos dois olhos. Além da diferença óbvia de PIO, maior nos bulbos glaucomatosos, os resultados mostraram-se estatisticamente significativos em dois parâmetros: aumento da profundidade da câmara vítrea nos casos de glaucoma crônico (1,24±0,26cm; P=0,01) quando se comparou aos olhos controle e aumento da espessura da córnea também nos casos de glaucoma agudo (0,987±0,28cm; P=0,027), quando se comparou aos olhos controle e aos olhos com glaucoma crônico. Observou-se que a câmara vítrea é a estrutura intraocular que mais contribui no processo de expansão de volume do bulbo (buftalmia) durante o glaucoma

Antimicrobial susceptibility and minimal inhibitory concentration of Pseudomonas aeruginosa isolated from septic ocular surface disease in different animal species

The purpose of this study was to evaluate the antibiotic susceptibility profile of Pseudomonas aeruginosa isolated from different animal species with septic ocular surface disease. Sixteen strains of P. aeruginosa were isolated from different species of animals (dog, cat, horse, penguin and brown bear) with ocular surface diseases such as conjunctivitis, keratocojnuctivits sicca and ulcerative keratitis. These isolates were tested against 11 different antimicrobials agents using the Kirby-Bauer disk-diffusion method. Minimum inhibitory concentrations (MICs) were determined using E-tests for two antibiotics (tobramycin and ciprofloxacin) commonly used in veterinary ophthalmology practice. Imipenem was the most effective antibiotic, with 100% of the strains being susceptible, followed by amikacin (87.5%), gentamicin, norfloxacin, gatifloxacin and polymyxin (both with 81.5%of susceptibility). MIC90 of ciprofloxacin was 2 µg/ml and the values found ranged from 0.094 µg/ml to 32 µg/ml. For tobramycin, MIC90 was 32 µg/ml and ranged from 0.25 µg/ml to 256 µg/ml. The most effective in vitro antibiotic tested against P. aeruginosa in this study was imipenem, followed by amikacin. The 3 mg/ml eye drops commercially available ciprofloxacin presentations were in vitro effective against all strains tested in this study if applied up to 4 hours after instillation. Whereas for tobramycin the 3 mg/ml eye drops commercial presentations were not in vitro effective against some strains isolated in this study. Thus for ocular infections with P. aeruginosa when using tobramycin the ideal recommendation would be to either use eye drops with higher concentrations or decrease the frequency intervals from four to a minimum of every two hours