Determination of morphological, biometric and biochemical susceptibilities in healthy Eurasier dogs with suspected inherited glaucoma.

In both humans and dogs, the primary risk factor for glaucoma is high intraocular pressure (IOP), which may be caused by iridocorneal angle (ICA) abnormalities. Oxidative stress has also been implicated in retinal ganglion cell damage associated with glaucoma. A suspected inherited form of glaucoma was recently identified in Eurasier dogs (EDs), a breed for which pedigrees are readily available. Because of difficulties in assessing ICA morphology in dogs with advanced glaucoma, we selected a cohort of apparently healthy dogsfor the investigation of ICA morphological status, IOP and plasma concentrations of oxidative stress biomarkers. We aimed to establish correlations between these factors, to identify predictive markers of glaucoma in this dog breed. A cohort of 28 subjects, volunteered for inclusion by their owners, was selected by veterinary surgeons. These dogs were assigned to four groups: young males, young females (1-3 years old), adult males and adult females (4-8 years old). Ocular examination included ophthalmoscopy, tonometry, gonioscopy, biometry and ultrasound biomicroscopy (UBM), and the evaluation of oxidative stress biomarkers consisting of measurements of plasma glutathione peroxidase (GP) activity and taurine and metabolic precursor (methionine and cysteine) concentrations in plasma. The prevalence of pectinate ligament abnormalities was significantly higher in adult EDs than in young dogs. Moreover, in adult females, high IOP was significantly correlated with a short axial globe length, and a particularly large distance between Schwalbe's line and the anterior lens capsule. GP activity levels were significantly lower in EDs than in a randomized control group of dogs, and plasma taurine concentrations were higher. Hence, ICA abnormalities were associated with weaker antioxidant defenses in EDs, potentially counteracted by higher plasma taurine concentrations. This study suggests that EDs may constitute an appropriate canine model for the development of glaucoma. This cohort will be used as a sentinel for longitudinal monitoring.

Use of a combined slit-lamp SD-OCT to obtain anterior and posterior segment images in selected animal species.

OBJECTIVE: To obtain images of anterior and posterior segments of the eye using a slit-lamp (SL)/spectral domain (SD) optical coherence tomography (OCT) integrated system designed for the human eye, in the cat, dog, minipig and monkey. ANIMALS STUDIED: One healthy adult monkey, one healthy adult minipig, one healthy adult dog, one healthy adult cat, and three cats and four dogs affected by corneal or retinal diseases. PROCEDURE: A SL SCAN-1 SD-OCT, which is a slit-lamp SL-D7 that contains an integrated OCT module and a fundus viewer, was used to generate OCT images (512-2048), while simultaneously taking 'en-face' slit-lamp images (efSL). OCT images were obtained under sedation or anesthesia. These images were compared to histological retinal sections obtained from a monkey, a minipig, a dog, and a cat. RESULTS: 'en-face' slit-lamp images and OCT images of the ocular tissues were obtained allowing for the identification of different corneal and retinal layers in all animal species. Measurements of the total retinal thickness (TRT) from the inner limiting membrane to the retinal pigment epithelium were performed in various regions throughout the retina. Reduction in TRT was consistent with clinical features of retinal degeneration identified in dogs and cats. CONCLUSION: This noninvasive procedure is useful for both experimental and clinical assessments of ocular tissue damage. Images of anterior and posterior segments are readily obtained under routine clinical conditions. Future studies are warranted to establish normal OCT data in our patients with this new instrument.