Ocular Biometry and its Relationship with Body Size and Head in French Bulldog Dogs

Abstract

Background: Ocular biometrics is an easy to perform, safe, non-invasive and low-cost exam that provides immediate results with excellent definition. Brachycephalic dogs have a high risk of developing eye problems, and the early appearance is frequent due to factors linked to anatomical conformation. The aim of the present study was to perform eye biometrics in French Bulldog dogs through ultrasound, correlating with body and head size.Materials, Methods & Results: Clinical examination, ophthalmic examination and ocular biometrics were performed using B-mode ultrasonography, using a 10 megahertz frequency transducer in 30 French Bulldog dogs, aged 1-6 years old, male and females from the Br Lord's Staff kennel and the Radiovet - Rio de Janeiro veterinary clinic. A drop of anesthetic eye drops containing 1% tetracaine hydrochloride and 0.1% phenylephrine hydrochloride was instilled and the direct contact technique was performed with the cornea with the help of sterile water-soluble lubricating acoustic gel between the transducer and the examined eye. These measurements were correlated with cephalic measurements (frontal-occipital distance, skull circumference, distance between the zygomatic arches and frontal-nasal distance) and with body measurements (length of the dog from the cranial end of the sternum to the ischial tuberosity and height of the withers from the cranial angle of the scapula to the ground). No chemical restraint was necessary. Dogs were positioned seated or in sternal decubitus, with slight physical restraint. All measurements were performed by the same examiner. There was no significant difference between the parameters of male and female eye biometrics and there was no difference between the measurements of the right and left eyes. The mean value of axial bulb length was 19.51 ± 0.58 mm, for the thickness of the lens, 6.71 ± 0.66 mm, for depth of the anterior chamber, 2.36 ± 0.89 mm and for the depth of the vitreous chamber, 10.44 ± 1.32 mm, showing the same pattern as other studies with brachycephalic dogs. The size of the dog or skull did not interfere with the measurements of eye biometrics.Discussion: The French Bulldog breed was selected for this study due to the scarcity of publications on ocular biometrics in brachycephalic breeds.The knowledge of ocular biometrics is extremely important for the understanding and early diagnosis of some anomalies related to the growth of ocular structures. It is an essential method of exploration and diagnosis of diseases of the eye bulb and orbit, being indicated to evaluate variations in size, shape and position of the eye bulb. The casuistry of these dogs with eye diseases in the ophthalmological clinical routine is large, since they have a high risk of developing eye problems. Ultrasonography is an easy to access and safe, non-invasive exam and the direct corneal contact technique allows clearer images. As there was no significant difference in measurements of intraocular structures between the right and left eyes, the normal eye can be a reliable parameter to establish the prosthetic eye bulb for the injured or enucleated eye. In the present study, there were 21 females and 9 males, which may have generated interference in these values since there was no sex ratio. The measurements of axial length, lenticular thickness, depth of the anterior chamber and the vitreous chamber had values similar to other studies with brachycephalic dogs.