B-Mode Ultrasound biometry of the eye globe related with fronto-occipital and bizigomatic diameters in Canis familiaris

Beserra, Poliana S., Sales, Gustavo A., Santana, Expedito J.M., Miranda, Stefânia A., Brito, Adriel B., Nickolak, Elizabete, & Domingues, Sheyla F.S.. (2009). "Relação entre a biometria ultra-sonográfica em modo B do bulbo ocular e os diâmetros fronto occiptal e bizigomático em Canis familiaris". Pesquisa Veterinária Brasileira, 29(4), 286-290. https://dx.doi.org/10.1590/S0100-736X2009000400002



In the experiment 31 healthy mongrel dogs, 8 months to 7 years of age, 10 males and 21 females, weighing 1.5-28 kg. Initially, fronto-occipetal (FOD) and bizigomatic (BZD) diameters were measured using a caliper. The ophthalmologic transpalpebral B-mode ultrasonography (US) was performed to measure the ocular bulbi structures, as follows: The cornea thickness (D1), distance between cornea and anterior lens capsule (D2), distance between cornea and posterior lens capsule , Lens thickness (D6), distance between posterior lens capsule and retina (D7), distance between anterior lens capsule and retina (D8), and distance between cornea and retina ). Except for D4, there were effect of FOD and BZD on the measures of the internal structures of BO. The Linear Regression Analysis between the measures of the internal oculars structures and DFO and DBZ were significant for D1, D2, D3, D4, D5, D6, D7, D8 and D9.


Index terms: B-mode ultrasonography, biometry eye, bizigomatic diameter, fronto-occipital diameter, dogs.




Two-dimensional (2D) mode B ultrasonography is an important imaging technique for ophthalmology because of its ability to detect the contour and shape of the structures of the ocular bulb, even when opacity occurs (Osuobeni & Hamidzada 1999, González et al., 2001). The ocular biometry in B mode provides measurements of the axial length of the eyeball (BO), for assessing conditions such as glaucoma, microphthalmia, macrophthalmos, staphyloma, phthisis bulbi and coloboma (Hernández-War & López-Murcia 2007).


The study of the axial length of the BO, through ultrasonographic biometry, can aid in the calculation to obtain the size of the prosthetic BO, when it is necessary to enucleate it, as well as in the calculation of the degree (diopter) of the intraocular lens (IOL) in patients undergoing cataract surgery, where the replacement of the lens is performed by a prosthesis (IOL) (González 2001). This artificial lens (IOL) can achieve a near or equal dioptric power of an emétrope crystalline. Another advantage of B-mode echobiometry is that it allows the measurement of the axial length of the internal structures of the BO, such as: distance between the cornea and the anterior lens capsule, lens density, vitreous body (distance between posterior lens capsule To the retina) and the distance between the cornea and the retina (Cotrill et al., 1989, González 2001).


The shape and size of the canine skull vary according to the breed, the animal's age or the individual's conformation (Dyce et al., 1997). The skull variations in Canis familiaris are expressed by the relationship between the fronto-occipital diameter (FOD) and bizigomático (DBZ) (Dyce et al. , 1997), and those classified as: dolichocephalic (DFO> DBZ), brachycephalic (DFO <DBZ ) And mesocéphalos (DFO DBZ) (Getty 1986). In a study comparing ecobiometry in A and bidimensional B modes with pachymetry in the evaluation of normal eyes in cadavers of dolichocephalic and mesocéphalic dogs, two-dimensional B-mode ultrasound was shown to be as efficient as pachymetry to determine the length Axial direction of the BO. Their mean value in dolichocephalic dogs was significantly longer than in mesocéphal animals (Cotrill et al., 1989). These results demonstrate that the conformation of the skull can influence the axial length of the BO and its internal structures, which makes it difficult to define parameters of ocular ecobiometric normality in dogs, since the species presents a great variation of the shape of skulls.


Considering that the effect of conformation of the skull under the axial length and internal structures of the BO has not yet been completely elucidated in the canine species, the objective of the present study was to evaluate the relation and the effect between the fronto-occipital (DFO) and the bizigomatic diameters ( DBZ) and the biometric measurements of the structures of the ocular bulb of dogs, in order to establish reliable parameters of normality.




The experiment was carried out at the Laboratory of Biology and Medicine of Wild and Domestic Animals of the Amazon (BIOMEDAM), Federal University of Pará (UFPA), located in the city of Castanhal (Pará). Thirty-one healthy, undefined dogs were evaluated, being 10 males and 21 females, aged 1-7 years old and weighing 1.5-28 kg. Initially the DFO and skull DBZ were measured with the aid of a caliper (Zaas, São Paulo, SP, Brazil) ( Fig.1A and 1B ).



For the ultrasound examination, the animals were mechanically restrained. In the experiment, the technique adopted to perform the ultrasound examination of the ocular bulb was the transpalpebral, in the seated position or in sternal recumbency.


The images were obtained using Philips HDI 4000 ultrasound (Philips Medical Systems, Bothel, WA, USA) in mode B, with a 5-8 MHz multifrequency microconvex transducer. Prior to examination, it was applied between the transducer and the eyelids , Hypoallergic ultrasound gel (Aquasonic, Parker Laboratories, INC, Fairfield, New Jersey). After the examination the eyelids were carefully cleaned for the removal of the gel with cotton swabs (Moisture Gum Compressor, Cremer, Blumenau, SC, Brazil) moistened with physiological solution (NaCl 0.9%, Indufal, Mossoró, RN, Brazil) . The obtained measurements were as follows: D1- corneal thickness; D2 - distance between the central point of the cornea image and that of the anterior lens capsule (anterior chamber); D3 - distance between the central point of the cornea image and that of the posterior lens capsule; D4- thickness of the lens, which corresponds to the distance between the image of the anterior capsule and the posterior lens capsule; D5 - diameter of the lens, distance between the images of the lens crystals; D6- lens area; D7- vitreous chamber, distance between the image of the posterior lens capsule and the retina; D8 - distance between the anterior lens capsule and the retina; D9- distance between the image of the cornea and the retina ( Fig.2a and 2b ). The data were represented in mean ± standard error. The means of the right and left BO internal structures and between males and females were compared by the Student t test. To evaluate the DFO and DBZ effect on the diameter of the structures of the ocular bulb, ANOVA was used, dividing the animals into three different groups of DFO and DBZ in the measurements: 5.0-7.5cm, 8.0-10.0cm, 11.0-13.0cm and 5.0-6.5cm, 7.0-10cm, 11.0-12.0cm, respectively. Statistical differences between means were determined by the Fisher PLSD test. Regression analyzes were made between linear measurements of BO structures with the DFO and DBZ, respectively. All tests were applied at 1% probability. Statistical analysis was performed using statistical software Stat View (SAS Institute, Inc., Cary, NC, USA).





The total of 62 normal BOs was evaluated, referring to the 31 animals used in this experiment. The 5-8 MHz multifrequency microconvex transducer made it possible to perform the transpalpebral examination without recoil cushion. There were no statistical differences between the biometric measurements of the ocular bulb structures when comparing the right and left eyes between males and females.


Effect and relationship of DFO on measurements of ocular bulb structures


In Table 1 are shown the analysis of variance between groups of different sizes DFO and the parameters of the internal structures of the BO. There was a significant effect (P <0.01) of DFO on the measures of ocular structures D1, D2, D3, D5, D6, D7, D8, D9. D4 did not vary according to DFO size. The averages of the ocular bulb structures D1, D2, D3 and D9 were different among the three size groups of the DFO. Mean D5, D6, D7 and D8 were statistically different animals with DFO between 5-10cm and 11-13cm (P <0.01). In Table 3 are shown the regression analyzes between the biometrics of the ocular structures and DFO, all of which were significant for the intercept (P <0.05) and regression coefficients (P <0.01).



Effect and relationship of DBZ on measurements of ocular bulb structures


In Table 2 are shown the analysis of variance between groups DBZ different sizes and parameters of the internal structures of the BO. There was a significant effect (P <0.01) DBZ on the measures of the structures of the eyeball: D1, D2, D3, D5, D6, D7, D8, D9. D4 did not vary according to the DBZ. The averages D1, D2, D3, D7 and D9 were different between the three groups DBZ (P <0.01). In D5 was no statistical difference when compared with the animals DBZ between 5-6,5cm and 7,0-12,0cm (P <0.01), while D6 and D8 were statistically different between groups of animals with DBZ between 5 -10cm and 11-12cm (P <0.01). In Table 4 are shown the regression analyzes between the biometrics of the structures of the eyeball and the DBZ, all of which were significant for the intercept (P <0.05) and regression coefficient (P <0.01).





The use of the 5-8 MHz multifrequency microconvex transducer, with no recoil pad, provided reliable measurements of the structures of the ocular bulb, using the transpalpebral technique, ie closed eyelids. The advantages of the microconvex transducers in relation to linear transducers were: the easy execution of maneuvers in search of a good sonographic image and the smaller contact with the skin, provided by the transducer curve, obtaining images through a small acoustic window (King 2004 ). The transpalpebral technique provided a minor inconvenience to the patient, not requiring the use of a topical anesthetic, also avoiding the appearance of irritations and mechanical lesions due to the handling of the transducer on the cornea. The eyelid cleaning at the end of the ultrasound examination with physiological solution was performed according to Nyland & Mattoon (2005), avoiding that the gel reached the cornea and the conjunctiva and remained for a prolonged time causing possible lesions Irritative


In the present work, the measurements of the skull shape, such as DFO and DBZ, were used as parameters to compare the mean values of ocular bulb structures between animals with different conformations of the skull. Weight has been used as a parameter to compare the means D1, D2, D3 and D4 in dogs of different sizes (Sampaio et al., 2002). However, the weight may vary according to the physical state of the individual and is therefore not reliable for estimating normality of ocular ecobiometry, since the diameters of ocular bulb structures are not modified by the physical state of the animal .


According to the statistical analyzes, there was no difference between the structures of the right and left ocular bulbs, so the normal eye can be a reliable parameter to establish the schematic BO for the injured or enucleated eye. However, in cases of trauma, enucleation or congenital malformation in both eyes, DFO and DBZ measurements may aid in the calculation of prosthetic or schematic ocular bulbs, whereas it has been shown that measures D1, D2, D3, D5, D6 , D7, D8 and D9 are influenced by increases in DFO and DBZ. Concerning D4, the effect of DFO and DBZ was not significant. This result can be explained by the crystalline accommodation mechanism, which has the ability to change its contour according to the focal point at the time of the examination (Gonçalves et al., 2000), thus altering the biometric results of the same. In humans, it is easy to accurately calculate the thickness of the lens, since the patient is instructed to perform maneuvers of eye movement in varied directions, such as the lateral and caudal cranium, and not to perform flashing movements, thus accommodating the lens In GO, these types of maneuvers become useful in the biometric calculations of D4, D5, D6, D7 and D8 (Figueirêdo & Teixeira 2007). However, the linear relationship between D4 and DBZ and DFO were significant, with DBZ showed the most reliable model (R 2 = 0.80), which may be related to the fact that the two structures are in the same plane Of section in relation to the skull. Regression analyzes are important for estimating the schematic eye and comparing it with the actual eye of the dog and may be useful in clinical practice to assess diseases that alter the axial length of both the GO and its internal structures.




According to the data obtained in this study, it was demonstrated that D1, D2, D3, D5, D6, D7, D8, D9 are related by canine skull type.


Due to the changes in the crystalline accommodation during the exam, it was not possible to establish the effect of the conformation of the skull under D4.


The analysis of the conformation of the skull in relation to the ecobiometry of the internal structures of the BO are reliable parameters, allowing to evaluate pathologies that alter the biometry of the BO, as well as it can help in the study of canine schematic eye and in the choice of the best formula for the calculation of the lens Intraocular.




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Received on July 21, 2008.

Accepted for publication on December 3, 2008.

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