Retinal abnormalities in the Siamese cat

Stone, Jonathan; Rowe, Michael H.; Campion, Joyce E.

doi:10.1002/cne.901800408

Cited by 63 publications

(35 citation statements)

References 18 publications

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“…In our da ta, as in a previous report [Stone et al, 1978b], there was no evidence of an abnor mally low number of Y cells in Siamese cats. Thus, some other factor is likely to be responsible for the reduced encounter rates reported for Y cells in recordings from the Siamese optic tract [Chino et al, 1977[Chino et al, , 1978.…”

supporting

confidence: 73%

Characteristics of Nasal and Temporal Retina in Siamese and Normally Pigmented Cats; pp. 103–113

Murakami¹,

Sesma²,

Rowe³

1982

Brain Behav Evol

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Properties of ganglion cells in nasal and temporal retina of Siamese and normally-pigmented cats are described. In agreement with earlier reports on normal cats, the somas of both X and Y cells are larger in temporal than in nasal retina, although these differences are not entirely independent of ganglion cell density. Furthermore, the axons of X cells in temporal retina were distinctly faster and larger than those of X cells in nasal retina. Since, in normal cats, almost all nasal X cells project contralaterally and almost all temporal X cells project ipsilaterally, it is difficult to assess independently the effects of retinal location and laterality of projection on either soma size or axon size of nasal and temporal X cells. However, taking advantage of the abnormal pattern of decussation seen in Siamese cats, in which a substantial number of temporal X cells project contralaterally, it is possible to demonstrate that the difference in soma size is independent of laterality of projection and appears to be a function of retinal location, whereas the difference in axon size is a function of laterality of projection and is independent of retinal location. Thus, soma size and axon diameter are at least partially independent. We were unable to obtain clear support for the suggestion that Siamese cats suffer a selective loss of X-type retinal ganglion cells, and an alternative mechanism for the reduced prominence of the area centralis in Siamese cats is proposed. The distinction between developmental mechanisms influencing the prominence of the area centralis and those influencing laterality of projection, as well as the relationship between retinal specializations associated with acuity and specializations associated with binocularity are also considered. The trajectory of axons arising from temporal retina and travelling above or below the area centralis towards the optic disc is described. In normal cats, the general features of this trajectory are the same for ipsilaterally and contralaterally projecting axons, and for axons of all ganglion cell groups. This also appears to be the case in Siamese cats. However, axons from temporal retina show a greater tendency to pass directly over the area centralis in Siamese than in normal cats, and the boundary between the region of temporal retina from which axons pass superior to the area centralis and the region from which they pass inferior to the area centralis may be closer to the vertical meridian in Siamese than in normal cats. These differences in trajectory could lead to a rearrangement of ipsilaterally projecting axons within the optic nerve. In both Siamese and normal cats, a small number of ganglion cells, scattered throughout nasal retina, project ipsilaterally. On the basis of soma size and dendritic morphology, all cells observed in our material can be identified as either alpha or gamma cells. In Siamese cats, such cells are consistently more numerous than in normal cats. In Siamese cats, however, this group of ipsilaterally projecting cells contains a hig...

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supporting

confidence: 73%

Characteristics of Nasal and Temporal Retina in Siamese and Normally Pigmented Cats; pp. 103–113

Murakami¹,

Sesma²,

Rowe³

1982

Brain Behav Evol

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“…We speculated that optic nerve hypoplasia, representing a reduced number of ganglion cells, as seen in Siamese cats [27] and humans with albinism [23], might further contribute to vision loss. However, this study did not find that reduction in neural tissue at the optic disk was associated the reduction in best-corrected visual acuity.…”

Section: Subjects With Albinism Controls P-valuementioning

confidence: 99%

The optic nerve and peripapillary vasculature in albinism

Conley¹,

Mancera²,

Holleschau³

et al. 2016

New Front Ophthalmol

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Albinism, an inherited disorder resulting in reduced ocular melanin, is usually associated with reduced best-corrected visual acuity, nystagmus, foveal hypoplasia, and iris transillumination. However, a spectrum of findings has been reported, with foveal hypoplasia, nystagmus, and misrouting of the retinostriate fibers having been purported to cause reduced visual acuity. The purpose of this case-controlled study is to describe the optic nerve anatomy and peripapillary retinal vasculature in albinism and to determine if there are changes related to visual acuity. We evaluated digital fundus photographs using computer analysis software in 34 patients with albinism and 51 controls. Our data indicate that the optic disc diameter and optic nerve area are significantly smaller in patients with albinism than controls (p <0.001; p=0.0008, respectively). Significantly more patients with albinism also had a double ring sign, situs inversus, and a nasally-directed artery (p ≤ 0.0148). There were no significant differences between groups for optic nerve color, vessel branching pattern, cilioretinal artery, or number of vessels crossing the optic nerve margin. Correlation of best-corrected visual acuity to disc diameter and optic nerve area was poor (r=0.0542 r=0.1527, respectively). In this study, patients with albinism had mild optic nerve hypoplasia when compared to controls. Reduced best-corrected visual acuity is not explained by the optic nerve findings. Further studies are required to elucidate the causes of reduced best-corrected visual acuity in albinism.

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“…Though the optical quality of the ferret's eye remains unknown, other comparative parameters of ferret's and cat's visual system are well studied and can be considered to match relative disparity coding between these species. Studies of the densityand distribution of ganglion cells in ferrets (Henderson 1985) and cats (Stone 1965;Stone et al 1978;Hughes 1975;Williams et al 1993) and behavioral and electrophysiological studies investigating visual acuity (cat: Blake and Antoinetti 1976;Smith et al 1980;but Jacobsen et al 1976;ferret: Pontenagel and Schmidt 1980;Price and Morgan 1987;Hupfeld et al 2006) indicate that visual acuity in ferret is about 50% lower than that of the cat. Furthermore, the geometrical aspect of interocular distance is fundamental for the generation of stereopsis.…”

Section: Relative Disparity Sensitivity In Pigmented Ferretmentioning

confidence: 99%

Sensitivity to relative disparity in early visual cortex of pigmented and albino ferrets

2008

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To investigate binocular interactions as the neuronal substrate for disparity sensitivity in the ferret (Mustela putorius furo), we measured the eVects of relative horizontal disparities on responses of neurons in areas 17 and 18 of the visual cortex. Stimulation by moving bars and sinusoidal gratings showed that about half of our sample in pigmented ferrets was sensitive to relative horizontal disparity. This also included many neurons, which were classiWed as only monocularly activated when testing either eye alone. However, the tuning width was about two or three times coarser (median tuning width 4° of visual angle) than that in the cat. In albino ferrets, only 8% of the neurons in the early visual cortex displayed some sort of disparitydependent binocular interactions, but none could be clearly identiWed as relative disparity-coding neuron.

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Retinal abnormalities in the Siamese cat

Cited by 63 publications

References 18 publications

Characteristics of Nasal and Temporal Retina in Siamese and Normally Pigmented Cats; pp. 103–113

Characteristics of Nasal and Temporal Retina in Siamese and Normally Pigmented Cats; pp. 103–113

The optic nerve and peripapillary vasculature in albinism

Sensitivity to relative disparity in early visual cortex of pigmented and albino ferrets

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