Abstract
BackgroundNineteen clinically normal snakes: six ball pythons (Python regius), six Burmese pythons (Python bivittatus), one Children’s python (Antaresia childreni), four Amazon tree boas (Corallus hortulanus), and two Malagasy ground boas (Acrantophis madagascariensis) were subjected to ultrasound imaging with 21 MHz (ball python) and 50 MHz (ball python, Burmese python, Children’s python, Amazon tree boa, Malagasy ground boa) transducers in order to measure the different structures of the anterior segment in clinically normal snake eyes with the aim to review baseline values for clinically important ophthalmic structures. The ultrasonographic measurements included horizontal spectacle diameter, spectacle thickness, depth of sub-spectacular space and corneal thickness. For comparative purposes, a formalin-fixed head of a Burmese python was subjected to micro computed tomography.ResultsIn all snakes, the spectacle was thinner than the cornea. There was significant difference in spectacle diameter, and spectacle and corneal thickness between the Amazon tree boa and the Burmese and ball pythons. There was no difference in the depth of the sub-spectacular space. The results obtained in the Burmese python with the 50 MHz transducer were similar to the results obtained with micro computed tomography. Images acquired with the 21 MHz transducer included artifacts which may be misinterpreted as ocular structures.ConclusionsOur measurements of the structures in the anterior segment of the eye can serve as orientative values for snakes examined for ocular diseases. In addition, we demonstrated that using a high frequency transducer minimizes the risk of misinterpreting artifacts as ocular structures.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-014-0313-5) contains supplementary material, which is available to authorized users.
Highlights
Nineteen clinically normal snakes: six ball pythons (Python regius), six Burmese pythons (Python bivittatus), one Children’s python (Antaresia childreni), four Amazon tree boas (Corallus hortulanus), and two Malagasy ground boas (Acrantophis madagascariensis) were subjected to ultrasound imaging with 21 MHz and 50 MHz transducers in order to measure the different structures of the anterior segment in clinically normal snake eyes with the aim to review baseline values for clinically important ophthalmic structures
The spectacle consists of three layers (Figure 1); an outer epithelium with basal cells and overlying keratin; a central stroma consisting of organized collagen fibrils; and an inner epithelium with flat cells with
Ultrasound examination revealed the anatomical structures within the anterior portion of the snake eye, with a superior image quality provided by a 50 MHz transducer compared to a 21 MHz transducer (Figure 2)
Summary
Nineteen clinically normal snakes: six ball pythons (Python regius), six Burmese pythons (Python bivittatus), one Children’s python (Antaresia childreni), four Amazon tree boas (Corallus hortulanus), and two Malagasy ground boas (Acrantophis madagascariensis) were subjected to ultrasound imaging with 21 MHz (ball python) and 50 MHz (ball python, Burmese python, Children’s python, Amazon tree boa, Malagasy ground boa) transducers in order to measure the different structures of the anterior segment in clinically normal snake eyes with the aim to review baseline values for clinically important ophthalmic structures. The snake eye differs considerably from that of mammals, with the most striking difference being the absence of moveable eyelids. Between the spectacle and the cornea a narrow subspectacular space is found [4]. This space receives fluid from a large post-ocular Harderian gland and drains through a lacrimal system into the roof of the mouth [3]. This drainage system may be the port of entry for ocular pathogens coming from the respiratory tract or the mouth
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