AJVR, Vol 67, No. 10, October 2006 1743 P revious authors have suggested that ocular mea- surements obtained with A-mode ultrasonography are more accurate than those obtained with B-mode ultrasonography. 1-5 However, B-mode ultrasonography is widely available in veterinary practice, provides detailed 2-dimensional images of intraocular struc- tures and useful information on vascular function in patients with ophthalmic diseases, and allows mea- surement of the mediolateral and dorsoventral dimensions of the lens. In addition, B-mode ultra- sonography is the standard imaging method for assessing pathologic abnormalities of soft tissues, including intraocular structures. 6-13 Thus, in certain instances, it may be more convenient or practical to obtain ocular measurements with B-mode than with A-mode ultrasonography. For biological measurements to be clinically use- ful, it is of great importance that they be both precise and reproducible. In particular, for any particular mea- surement, the measurement error must be considerably smaller than the true biological variation for that mea- surement. Studies 14-17 determining the intra- and inter- observer repeatability of ocular measurements obtained by means of A-mode ultrasonography in peo- ple have been published, but to our knowledge, only a single study 18 on intra- and interobserver repeatability of B-mode ultrasonographic measurements of various structures and distances in the anterior segment of the eye in dogs has been published. Before B-mode ultrasonography can be used clini- cally for measurement of intraocular structures and distances in dogs, more information is needed about the repeatability of measurements that are obtained. Therefore, the purpose of the study reported here was to assess intra- and interobserver repeatability of ocu- lar biometric measurements obtained by means of high-resolution B-mode ultrasonography in dogs. Materials and Methods The experimental protocol was approved by the Committee of Ethical Care of Animals of the Utrecht University. Six healthy Beagles (3 males and 3 females) with- out evidence of ocular abnormalities were included in the study. Dogs ranged from 5 to 11 years old and weighed between 10 and 16 kg. In all dogs, results of a physical and complete ocular examination performed prior to the study were unremarkable. The ocular examination included exam- ination of the ocular adnexa, media, and fundus by means of slit-lamp biomicroscopy a (15X) and indirect ophthal- moscopy b before and after induction of mydriasis with tropi- camide. Intraocular pressure was measured with a MacKay- Marg electronic applanation tonometer. c For the present study, B-mode ultrasonography was per- formed in all dogs on 2 occasions, with a minimum of 1 week between examinations, by 2 individuals (SAEBB and GV). Various intraocular structures and distances were measured on freeze-frame images to 1 decimal place with electronic calipers and the ultrasound system software. Each individual was masked as to the measurements obtained by the other individual and, when performing the second examination, to measurements obtained during the first examination. All ultrasonography examinations were performed with a high-definition digital ultrasound system d and a 25.6-mm- long 10.5-MHz broadband compact linear-array transducer (lateral resolution, 0.8 and 0.9 mm at depths of 1 and 2 cm, respectively; axial resolution, 0.6 mm at depths of 1 and 2 cm). All examinations were performed in the same environ- ment. The corneal contact method 12 was used after lidocaine and sterile ultrasound gel were applied to the cornea. During each examination, horizontal and vertical images of both eyes were obtained. Images were considered Received March 29, 2006. Accepted May 16, 2006. From the Divisions of Diagnostic Imaging (Boroffka, Voorhout), Ophthalmology (Verbruggen), and Internal Medicine (Teske), Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 10, 3508 TD Utrecht, The Netherlands. Address correspondence to Dr. Boroffka. Intraobserver and interobserver repeatability of ocular biometric measurements obtained by means of B-mode ultrasonography in dogs Susanne A. E. B. Boroffka, DVM; George Voorhout, DVM, PhD; Anne-Marie Verbruggen, DVM; Erik Teske, DVM, PhD Objective—To assess intra- and interobserver repeatability of ocular biometric measurements obtained by means of high-resolution B-mode ultra- sonography in dogs. Animals—6 Beagles without ocular abnormalities. Procedures—B-mode ultrasonography was per- formed bilaterally with a 10.5-MHz broadband com- pact linear array transducer. All measurements were made on 2 different occasions by 2 observers. The Bland-Altman method was used to assess agreement between measurements obtained by the 2 observers and between the 2 sets of measurements obtained by each observer. Results—Intra- and interobserver repeatability was highest for larger measurements, such as depth of the eye and depth of the anterior chamber. When repeatability was examined, bias was significantly dif- ferent from 0 for only a few measurements, but the percentage difference between observations was as high as 180% for some measurements. Conclusions and Clinical Relevance—Results sug- gest that most measurements of intraocular distances and structures obtained by means of high-resolution B-mode ultrasonography have acceptable intra- and interobserver repeatability. However, the percentage difference between observations can be high for small- er measurements. (Am J Vet Res 2006;67:1743–1749)