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Vision is an extremely important sense in bats and can influence foraging activities. The present study aimed to evaluate morphometric aspects of the eyeballs of Neotropical bats with different feeding habits. Based on the hypothesis that frugivorous and nectarivorous bats likely possess better visual resolution compared to insectivorous and sanguivorous species due to their foraging modes, we predicted that these bats would have larger eyeballs and internal eye structures comparable to those of insectivorous and blood-eating species. Histological analysis allowed for estimating the thickness of the cornea, choroid, sclera, and retina, as well as counting the number of photoreceptor cells in the external nuclear layer of the retina of two frugivorous species (Artibeus obscurus, A. planirostris), two nectarivorous species (Glossophaga soricina, Anoura geoffroyi), two blood-eating species (Diphylla ecaudata, Desmodus rotundus), and one insectivorous species (Nyctinomops laticaudatus). Macroscopic measurements were obtained in four of these species. There is a statistically significant relationship between the type of diet and the morphological differences of the eyeball, confirming our predictions regarding fruit bats, which presented the highest means of ocular parameters while the insectivorous N. laticaudatus and the nectarivorous G. soricina exhibited the lowest. These latter two species had a thinner cornea, indicating a possible lower refractive power and, consequently, lower visual acuity. The blood-eating species showed divergent results. Additionally, the insectivorous N. laticaudatus also had a smaller number of photoreceptor cell nuclei in the outer nuclear layer of the retina, possibly indicating less transduction of light signals by the retina. [ABSTRACT FROM AUTHOR]

The anatomy and features of the histological structure of the components of the eye of a one-humped camel were investigated. Ultrasound examinations of the eye, determination of the iridocorneal angle with a gynoscope were carried out on live animals in the clinic after the introduction of eye drops (xylocaine 2%, atropine sulfate 3%). The condition of the eye membranes was determined by histological methods. The studies were carried out on twenty eyeballs from ten clinically healthy adult camels, selected during slaughter in a meat processing enterprise. The anatomical and topographic features of the organ, its membranes and structures, absolute and relative mass, and linear measurements were determined. Thin histological sections of the eye wall were stained with hematoxylin and eosin, impregnated with silver nitrate, followed by examination under a microscope. In a one-humped camel, the eyelashes of both eyelids are very thick and long. The internal architectonics of the eyeball of a one-humped camel is similar to that of other animal species. The lens was found to be a transparent biconvex structure located inside the eyeball just behind the iris. The cornea of the eye occupies almost the entire visible part of the eye. The ciliary body is located behind the iris near the lens. The main functions of the ciliary body are the formation of intraocular fluid (aqueous humor), which fills the front of the eye. The ciliary body contains muscles that enable the eye to focus on objects located at different distances. A feature of the camel’s eye is the very open iridocorneal angle. The retina is built up by nerve tissue that lines the back of the eye. The retina perceives light, generates impulses that pass through the optic nerve and are sent to the brain. The histological structure of the membranes of the eye was studied after applying routine methods. It has been established that the eyes are built by various types of tissues, in particular, epithelial (epithelium of the conjunctiva), dense loose connective tissue (the corneal substance itself), loose connective tissue and pigment tissue (choroid) and nervous tissue with a layer of melanocytes and keratinocytes.

It has been demonstrated that hypoxia retards the growth of fish, reduces the survival of their larvae, deforms their vertebral column, but despite this teleost fish have the ability to completely regenerate many of their tissues, particularly the retina. As we do not have enough information about the effects of hypoxia on the eyeball, orbit and retina of Atlantic salmon (Salmo salar), we propose the following objectives: 1) Compare the morphological changes of the eyeball of fish subject to hypoxia and normoxia. 2) Determine changes in the orbit structure. 3) Describe the retina of salmon alevins. 4). Recognize hypoxic cells using the anti-Hif1α antibody in the retina of alevins as a sensor. 5) Determine the Shh morphogenic expression in alevins exposed to different times of hypoxia. Around 1,000 Salmo salar alevins were placed in a continuous water flow of 9 °C at 100 % SatO2 and alevins maintained at a hypoxia of 60 % SatO2. The latter were transferred to normoxia (at days two, four, and eight after hatching). A control group maintained at continuous normoxia and another at continuous hypoxia was also considered. All the alevins were euthanized at 950 UTAs (±2 months after hatching). Diaphonization (double-stain) according to the Hanken & Wassersug technique was undertaken to describe the morphology of the periocular cartilage and to measure the ocular diameter. The HIF-1α factor antibody 1:50, and the anti-Shh antibody dilution of 1:100 were used. The alevins after hatching had large eyeballs with the optic cup having an embryonic shape, even a choroidal fissure. The greatest thickness was observed in the nasal ventral zone which corresponds to a zone of pluripotent cells. The optic cup aspect with embryonic characteristics has only been reported in salmonids. The central retina of the alevins those were cultivated with a 60 % saturation of O2 for two, four or eight days had positive immunostaining when analyzed with the anti-HIF1α antibody hypoxia sensor. The inner ganglion and nuclear layers had immunopositive cells, with the highest in the alevins that were two days in hypoxia and the lowest when the hypoxia was chronic. Nevertheless, in the latter case the alevins had anatomical deformation of the eyeball and periocular cartilage. The anti-Shh antibody clearly shows a gradient that is expressed in the germinative zone and in the cells of the inner ganglion and nuclear layers. The eyeball and particularly the retina in salmon alevins are an example of neuronal plasticity and neurogenesis. [ABSTRACT FROM AUTHOR]

Previously, phytanoyl-CoA alpha-hydroxylase-associated protein 1 (PAHX-AP1) was isolated as a novel neuron-specific protein to interact with Refsum disease (RfD) gene PAHX. Its expression in the brain increased after eyelid opening, and the elevated level was maintained through adulthood. In this report, to verify the hypothesis that light could trigger this increase, we have examined the developmental distribution pattern of PAHX-AP1 in rat retina and visual cortex, and changes of its expression by binocular deprivation. Northern blot analyses demonstrated PAHX-AP1 expression reached its highest level in the visual cortex and eyeball at 4 weeks after birth, and these levels were maintained through adult life. Two weeks after visual deprivation, its expression in the eyeball and visual cortex decreased compared with the control. In situ hybridization analyses of the retina showed that PAHX-AP1 expression was limited to the ganglionic cell layer at 10 days after birth, but expressed in the inner nuclear cell layer and extended to the outer nuclear cell layer at 2 and 3 weeks after birth, respectively. Two weeks after visual deprivation, however, it decreased in the ganglionic and inner nuclear cell layer, and disappeared in the rod and cone cell layers. In the visual cortex, strong signals of PAHX-AP1 were detected in layers IV and VI, and II–VI at 10 days and 2 weeks after birth, respectively. Its expression decreased after 2 weeks of visual deprivation. These results indicate that visual stimulation is essential for the maintenance of PAHX-AP1 expressions in the retina, especially in the rod and cone cell layers, and visual cortex, and suggest that PAHX-AP1 may be involved in the developmental regulation of the photoreceptor’s function. [Copyright &y& Elsevier]

In routine, histological techniques of ocular tissue damage commonly occur. From this weakness is devised a form of fixation and cleavage. For comparison, we used two methods in eyeball fixation. In one, we used intraocular injection of formalin, in another was used only his immersion in the fixative solution. Regarding the method of cleavage became a longitudinal tangential to the cornea. Then another cut from the optic nerve to obtain a sample with all ocular structures. In all eyeballs was observed some degree of retinal detachment which is mentioned only as a consequence of insufficient fixation, but the cleavage is also capable of such damage. The dehydration phase of processing causes retinal shrinkage also being able to detach the retina. The two methods of fixation on the cleavage method generate good microscopic images. [ABSTRACT FROM AUTHOR]

The efficient extraction and fixation of a tissue allows in preserving the cytoarchitecture, chemical composition and tissue organization, which is key in physiological and histopathological studies. The main goal of this study was to establish a microsurgery technique to obtain ocular tissue and provide an optimized immersion fixation protocol based on the 10 % formalin-intraocular injection on Olive ridley sea turtle hatchlings (Lepidochelys olivacea). To evaluate this optimized technique, a histological comparison between traditional immersion and intraocular/immersion protocols was done. The eyeball were processed into five protocols: Frozen eyes (Group 1), frozen eyes immersed in 10 % formalin (Group 2), fresh eyes immersed in 10 % formalin (Group 3), fresh eyes intraocularly injected with 0.1 M phosphate buffer solution (PBS) and then immersed in 10 % formalin (Group 4), and fresh eyes fixed by 10 % formalin-intraocular followed by 10 % formalin-immersion (Group 5). In comparison with all groups evaluated, the intraocular/immersion fixation protocol lead the conservation of eyeball shape, cell integrity and maintenance of the organization of the retina layers of sea turtle hatchlings. If this method will be the key in studying sea turtle, we suppose that this procedure, with minimal adjustments, could be useful in animals with similar eye anatomy. [ABSTRACT FROM AUTHOR]