Ultrasonographic Anatomy of the Asian Elephant (Elephas maximus) Eye

Abstract

Bilateral transpalpebral ultrasonography was performed on 53 captive Asian elephants (Elephas maximus) in order to describe the normal ultrasonographic appearance and measurements of the Asian elephant eye. Transpalpebral ultrasonography was performed using a portable ultrasound unit and a 4-7-MHz broadband curvilinear transducer on animals housed at seven institutions in the United Kingdom and in Sri Lanka. Both males and females were included in the study and ages ranged from 14 mo to 65 yr. Ultrasonic examinations were conducted on unsedated animals, without the use of topical or local anesthesia. The ultrasonographic appearance of the globe and intraocular structures of the Asian elephant eye is similar to that in other species. Biometry measurements recorded for adult (n=41) and juvenile (n=10) Asian elephants were: axial length, 3.44 +/- 0.21 cm and 3.18 +/- 0.19 cm (mean +/- SD); equatorial diameter, 3.88 +/- 0.32 cm and 3.60 +/- 0.24 cm; corneal thickness, 0.17 +/- 0.02 cm and 0.16 +/- 0.02 cm; anterior segment depth, 0.45 +/- 0.08 cm and 0.36 +/- 0.07 cm; lens diameter, 1.90 +/- 0.14 cm and 1.75 +/- 0.19 cm; lens depth, 1.01 +/- 0.12 cm and 0.94 +/- 0.10 cm, and posterior segment depth, 1.82 +/- 0.17 cm and 1.72 +/- 0.15 cm, respectively. Multiple linear regression analysis indicated a significant relationship between the explanatory variables (age, sex, and height) and the dependent variables (axial length, equatorial diameter, corneal thickness, anterior segment depth, lens diameter, and lens depth). The main finding of this statistical test was that the globe increases in size as the animal ages. Transpalpebral ultrasonography was found to be an effective and practical imaging modality in the evaluation of the Asian elephant eye, without the need for chemical restraint.

The Retina of Asian and African Elephants: Comparison of Newborn and Adult

“…In contrast to the eyes of adult elephants, in which the equatorial diameter exceeds the axial length [Murphy et al, 1992;Bapodra et al, 2010;Pettigrew et al, 2010], the eyes of newborn elephants were rather spherical. This was also observed in an infantile African elephant [Stone and Halasz, 1989] but not in juvenile Asian elephants [Bapodra et al, 2010] (Table 3).…”

“…In contrast to the eyes of adult elephants, in which the equatorial diameter exceeds the axial length [Murphy et al, 1992;Bapodra et al, 2010;Pettigrew et al, 2010], the eyes of newborn elephants were rather spherical. This was also observed in an infantile African elephant [Stone and Halasz, 1989] but not in juvenile Asian elephants [Bapodra et al, 2010] (Table 3). The data obtained for the eyes of the newborn and adult Asian elephants suggest that the axial length of the eye increases during postnatal development and that the retinal surface area increases while the percental retinal coverage of the inner ocular surface decreases after birth (Table 3).…”

“…While the size and optical parameters of the eyes of (Asian) elephants are well described [Murphy et al, 1992;Bapodra et al, 2010], there is little knowledge regarding the retina of elephants. It has been shown that the elephant retina contains three regions of high ganglion cell density [Stone and Halasz, 1989;Pettigrew et al, 2010] and that the S and M/L cone densities display different retinal topographies [Schiviz et al, 2008].…”

Biometria do bulbo ocular de bovinos da raça Nelore

“…Ainda que ambos os eixos tenham sido menores na raça Nelore do que nas demais descrições encontradas, o que indica uma córnea comparativamente menor, a proporção entre a altura e a largura da córnea de 1:1,3 proposta para a espécie foi confirmada 9 . A lente do gado Nelore também se mostrou menor em relação ao descrito nas demais raças, pois o eixo ântero-posterior (espessura) da lente mediu 15 5 , uma vez que o córtex da lente aumenta ao longo da vida como resultado de produção contínua de novas fibras 10,11 . Dessa forma, as dimensões menores encontradas no gado Nelore não significam necessariamente que a lente desta raça seja menor em comparação com a das demais, pois não está explícita a idade dos bovinos usados nos outros estudos.…”

“…Dessa forma, as dimensões menores encontradas no gado Nelore não significam necessariamente que a lente desta raça seja menor em comparação com a das demais, pois não está explícita a idade dos bovinos usados nos outros estudos. Entretanto, sabe-se que as dimensões oculares como um todo tendem a aumentar significativamente com o avançar da idade em outros ruminantes (búfalos, camelos, elefantes asiáticos, caprinos) e também em cães 5,[11][12][13] . Assim, foi possível presumir que, se o motivo da diferença no tamanho da lente fosse a faixa etária da amostragem utilizada neste estudo, outras medidas também deveriam ter aparecido consistentemente menores.…”