RESUMO
Ocular surface diseases are often diagnosed in brachycephalic dogs. The ophthalmic parameters of the Shih Tzu dogs are evaluated in this study since this breed is among the most commonly affected by these diseases. In this study, ophthalmic parameters of this breed were partly studied under physical restraint. Schirmer tear test, breakup time test, aesthesiometry, biomicroscopy, non-contact specular microscopy, laser flaremetry, applanation tonometry, ultrasonography and ophthalmoscopy were carried in 48 eyes of 24 male and female dogs, aged from two to four years, weighing between 5 and 10kg. All dogs were from a breeding kennel. Descriptive statistics were applied to the data. Mean and standard error for Schirmer tear test was 26.145±0.803mm min-1; breakup time test, 13.668±0.538s; and aesthesiometry, 2.395±0.071cm. The biomicroscopy evaluation showed that 70.83% of the eyes had medial entropion; 42% caruncular trichiasis; 33% distichiasis, 27% mild paracentral corneal opacity; and 13% corneal melanosis. Mean and standard error for endothelial cell density was 2221.591±20.161cells mm-2; endothelial cell hexagonality, 63.770±1.805%; endothelial cell area, 451.895±4.179mm2; central corneal thickness, 0.490±0.007 mm; laser flaremetry, 1.720±0.216PC ms-1; applanation tonometry, 16.118±0.460mmHg; axial length, 20.255±0.134mm; lens thickness, 6.624±0.031mm; anterior chamber, 4.064±0.109mm; and vitreous chamber, 9.565±0.054mm. Ophthalmoscopy findings were not different from previous reports for other breeds. The results showed that the ophthalmic Shih Tzu parameters did not differ from other breeds according to data in the literature, except for the breakup time and Cochet-Bonnet aesthesiometry.
Afecções da superfície ocular são frequentes em cães braquicefálicos. Dentre as raças comumente acometidas, tem-se a Shih Tzu, cujos parâmetros oftálmicos não são conhecidos em sua plenitude e o foram, em parte, avaliados nesta pesquisa. Sob contenção física, empregou-se o teste lacrimal de Schirmer, o de ruptura do filme lacrimal, a estesiometria, a biomicroscopia, a microscopia especular de não contato, a flaremetria a laser, a tonometria de aplanação, a ecografia e a oftalmoscopia. Foram estudados 48 olhos de 24 indivíduos machos ou fêmeas, com idades variando entre dois a quatro anos e peso entre cinco a 10kg. Aos dados, aplicou-se a estatística descritiva. Relativamente às médias e aos erros padrão, encontraram-se, quanto ao teste lacrimal de Schirmer, 26,145±0,803mm min-1 e, quanto à ruptura do filme lacrimal, 13,668±0,538s. À estesiometria, encontraram-se 2,395±0,071cm. À biomicroscopia, observaram-se 70,83% dos olhos com entrópio de canto medial, 42% apresentaram pelos em carúncula medial, 33% distiquíase, 27% opacidade paracentral e 13% melanose corneal. Médias e erros padrão, no que concerne à densidade de células endoteliais, foram de 2221,591±20,161céls mm-2. Quanto à hexagonalidade, foram de 63,770±1,805%; quanto à área, foram de 451,895±4,179mm2; em relação à espessura corneal, foram de 0,490±0,007mm. À flaremetria a "laser", encontraram-se 1,720±0,216PC ms-1. À tonometria, 16,118±0,460mmHg. As médias e os erros padrão, à ultrassonografia, foram de 20,255±0,134mm para diâmetro axial horizontal; de 6,624±0,031mm, para espessura da lente; de 4,064±0,109mm, para profundidade da câmara anterior; e de 9,565±0,054mm, para a câmara vítrea. O padrão de imagens à oftalmoscopia não divergiu do já reportado em cães de outras raças. De consoante com os resultados obtidos, há como admitir que parâmetros de referência para cães adultos da raça Shih Tzu, estudados na presente pesquisa, não divergiram sobremaneira dos conhecidos para outras raças de cães, à exceção do tempo de ruptura do filme lacrimal, cujos valores ficaram aquém da média para a espécie, e os da estesiometria de Cochet-Bonnet, que foram superiores.
RESUMO
Electroretinography (ERG) is a reliable diagnostic tool for the diagnosis of retinal disease. It measures electric potentials occurring in the retina in response to light stimulation. In this study, we examined the normal electroretinogram using the Handheld Multispecies ERG (HMsERG) in Shih Tzu dogs. ERG recordings were performed in twelve eyes of six healthy Shih Tzu dogs. Dogs were anesthetized with a combination of medetomidine and ketamine. Proparacaine eye drops were also applied as a topical anesthetic. Tropicamide eye drops were applied for mydriasis. After 20 min of dark adaptation, we recorded the amplitudes and implicit times of the b-waves of the rod, standard rod and cone (Std R&C), high-intensity rod and cone (Hi-int R&C), and cone systems, and responses of the cones and inner retina by flicker light stimulation (cone flicker). Results showed that mean the amplitudes of a-waves of Std R&C, Hi-int R&C, and the cone responses were 141.25 microV, 173.00 microV, and 12.92 microV, respectively. The b-waves of the rod responses ranged from 141.58 to 155.25 microV; the Std R&C was 314.75 microV, the Hi-int R&C was 329.42 microV, the cones were 37.75 microV, and the flicker responses were 64.08 microV. The b/a ratios for the Std R&C, Hi-int R&C, and the cone response were 2.29, 1.94, and 3.71, respectively. Mean implicit time of the a-wave of the Std R&C was 15.12 ms, of Hi-int R&C was 13.42 ms, and of the cone response was 7.22 ms. The b-wave of the rod responses ranged from 68.12 to 72.68 ms, of Std R&C were 37.28 ms, of Hi-int R&C were 41.90, of the cone responses were 38.12 ms, and of the cone flicker responses were 22.80 ms. We believe that these parameters can be used as reference "normal" ERGs ranges for Shih Tzu dogs using the HMsERG under medetomidine and ketamine anesthesia.