The Retinal Ganglion Cell Layer and Visual Acuity of the Camel

Harman, A.M.; Dann, Jody; Ahmat, Alicia; Macuda, Todd; Johnston, Kevin; Timney, Brian

doi:10.1159/000047258

Cited by 41 publications

(12 citation statements)

References 19 publications

(21 reference statements)

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“…This strategy was used to ensure that we counted only ganglion cells. Small ganglion cells are indistinguishable from displaced amacrine cells and backlabeling with a neuronal tracer is the only reliable way to identify cells with an axon entering the brain which was not possible in our study [Harman et al, , 2000[Harman et al, , 2001. A true count should include a proportion of small cells and our numbers are therefore likely to be somewhat lower than the total.…”

Section: Number Of Ganglion Cells Is Correlated With Sizementioning

confidence: 78%

“…This definition may result in omission of some smaller ganglion cells, which are fairly indistinguishable from amacrine cells. We measured ganglion cell density from a systematic 6.25% sampling of the entire surface of retinal wholemounts as routinely performed by us previously Harman et al, 2000Harman et al, , 2001. For each retina, approximately 600 evenly spaced sites were sampled in a grid fashion across the eye.…”

Section: Discussionmentioning

confidence: 99%

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A Strong Correlation Exists between the Distribution of Retinal Ganglion Cells and Nose Length in the Dog

2003

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The domestic dog, Canis lupus familiaris, is a subspecies of the gray wolf, Canis lupus, with almost identical mitochondrial DNA. The dog is the most diverse species on earth, with skull length varying between 7 and 28 cm whereas the wolf skull is around 30 cm long. However, eye size in dogs does not appear to vary as much. For example, small dogs such as the chihuahua appear to have very large eyes in proportion to the skull. Our aim was to examine eye size and retinal cell numbers and distribution to determine whether the dog eye exhibits as much variation as the skull. We found a correlation between eye radius and skull dimensions. However, the most surprising finding was that the distribution of ganglion cells in the eye varied tremendously from a horizontally aligned visual streak of fairly even density across the retina (as seen in the wolf) to a strong area centralis with virtually no streak (for example, as observed in a pug from the current series). This variation in ganglion cell density within a single species is quite unique. Intriguingly, the ratio of peak ganglion cell density in the area centralis to visual streak was highly negatively correlated with skull length (r = –0.795, n = 22) and positively correlated with cephalic index (r = 0.687, n = 22). The orientation of eyelid aperture was also correlated with cephalic index (r = 0.648, n = 22). Therefore, the genetic manipulation of selective breeding, which has produced an abnormal shortening of the skull and eyelids with less lateral apertures, has also produced a considerably more pronounced area centralis in the dog.

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Section: Number Of Ganglion Cells Is Correlated With Sizementioning

confidence: 78%

Section: Discussionmentioning

confidence: 99%

A Strong Correlation Exists between the Distribution of Retinal Ganglion Cells and Nose Length in the Dog

2003

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“…This area of the tectum receives input from the area of the retina with the highest density of retinal ganglion cells. The density of retinal ganglion cells is one of the factors that determine visual acuity (Land, 2002); in other species this has been shown to be important for object discrimination (Harman et al, 2001). If a visual stimulus were presented to an area of the lamprey retina with a low visual acuity, where it is not possible to discriminate between prey and predator, it would be an advantage to evade this stimulus and avoid potentially orienting toward a predator.…”

mentioning

confidence: 99%

Selective projection patterns from subtypes of retinal ganglion cells to tectum and pretectum: Distribution and relation to behavior

Jones

Grillner

Robertson

2009

J of Comparative Neurology

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An important issue to understand is how visual information can influence the motor system and affect behavior. Using the lamprey (Petromyzon marinus) as an experimental model we examined the morphological subtypes of retinal ganglion cells and their projection pattern to the tectum, which controls eye, head, and body movements, and to the pretectum, which mediates both visual escape responses and the dorsal light response. We identified six distinct morphological types of retinal ganglion cell. Four of these distribute their dendrites in the inner plexiform layer (image forming layer) and project in a retinotopic manner to all areas of the tectum. The posterior part of the retina has the highest density of ganglion cells and projects to the rostral part of the tectum, in which the visual field in front of the lamprey will be represented. From this area both orienting and evasive behaviors can be elicited. In contrast, pretectum receives input from two ganglion cells types that send their dendrites only to the outer plexiform layer or the outer limiting membrane and therefore may directly contact photoreceptors, and transmit information without additional delay to pretectum, which may be particularly important for visual escape responses. One of these two types, the bipolar ganglion cell, is only found in a small patch of retina just ventral of the optic nerve. Due to its distribution, morphology, and projections we suggest that this cell may control the dorsal light response.

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“…In contrast, freshwater river dolphins that live in particularly turbid environments, such as the Amazonian river dolphin and the tucuxi Sotalia fluviatilis, have much lower numbers (Table 1). In comparison, the eyes of other large-eyed terrestrial artiodactyls, such as the giraffe, Giraffa camelopardalis, the camel, Camelus dromedarius, and the water buffalo, Bos bubalis, all have 1 million or more RGCs [Kassab and Sugita, 2000;Harman et al, 2001;Coimbra et al, 2013].…”

Section: Rgc Number and Topographymentioning

confidence: 99%

“…Furthermore, anatomical SRP in cetaceans is generally low when compared with values for large-eyed terrestrial mammals (calculated using similar methods), such as rhinoceroses (6-7 cycles/degree) [Pettigrew and Manger, 2008;, the river hippopotamus (8 cycles/degree) , the camel (approx. 10 cycles/degree) [Harman et al, 2001], the African elephant (approx. 14 cycles/degree) [Pettigrew et al, 2010], the horse (approx.…”

Section: Spatial Resolving Powermentioning

confidence: 99%

Retinal Topography in Two Species of Baleen Whale (Cetacea: Mysticeti)

Lisney

Collin

2018

Brain Behav Evol

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Little is known about the visual systems of large baleen whales (Mysticeti: Cetacea). In this study, we investigate eye morphology and the topographic distribution of retinal ganglion cells (RGCs) in two species of mysticete, Bryde’s whale (Balaenoptera edeni) and the humpback whale (Megaptera novaeanglia). Both species have large eyes characterised by a thickened cornea, a heavily thickened sclera, a highly vascularised fibro-adipose bundle surrounding the optic nerve at the back of the eye, and a reflective blue-green tapetum fibrosum. Using stereology and retinal whole mounts, we estimate a total of 274,268 and 161,371 RGCs in the Bryde’s whale and humpback whale retinas, respectively. Both species have a similar retinal topography, consisting of nasal and temporal areas of high RGC density, suggesting that having higher visual acuity in the anterior and latero-caudal visual fields is particularly important in these animals. The temporal area is larger in both species and contains the peak RGC densities (160 cells mm^–2 in the humpback whale and 200 cells mm^–2 in Bryde’s whale). In the Bryde’s whale retina, the two high-density areas are connected by a weak centro-ventral visual streak, but such a specialisation is not evident in the humpback whale. Measurements of RGC soma area reveal that although the RGCs in both species vary substantially in size, RGC soma area is inversely proportional to RGC density, with cells in the nasal and temporal high-density areas being relatively more homogeneous in size compared to the RGCs in the central retina and the dorsal and ventral retinal periphery. Some of the RGCs were very large, with soma areas of over 2,000 µm². Using peak RGC density and eye axial diameter (Bryde’s whale: 63.5 mm; humpback whale: 48.5 mm), we estimated the peak anatomical spatial resolving power in water to be 4.8 cycles/degree and 3.3 cycles/degree in the Bryde’s whale and the humpback whale, respectively. Overall, our findings for these two species are very similar to those reported for other species of cetaceans. This indicates that, irrespective of the significant differences in body size and shape, behavioural ecology and feeding strategy between mysticetes and odontocetes (toothed whales), cetacean eyes are adapted to vision in dim light and adhere to a common “bauplan” that evolved prior to the divergence of the two cetacean parvorders (Odontoceti and Mysticeti) over 30 million years ago.

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The Retinal Ganglion Cell Layer and Visual Acuity of the Camel

Cited by 41 publications

References 19 publications

A Strong Correlation Exists between the Distribution of Retinal Ganglion Cells and Nose Length in the Dog

A Strong Correlation Exists between the Distribution of Retinal Ganglion Cells and Nose Length in the Dog

Selective projection patterns from subtypes of retinal ganglion cells to tectum and pretectum: Distribution and relation to behavior

Retinal Topography in Two Species of Baleen Whale (Cetacea: Mysticeti)

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