Accommodation in the Eyes of Mammals

Barrett, James

doi:10.1136/bjo.22.3.148

Cited by 7 publications

(8 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Duke-Elder (1958) proposed that the ciliary muscle of rodents is rudimentary and probably functionless. This agrees with Barrett's (1938) suggestion that the development of the ciliary muscle corresponds to the degree of accommodative ability. If this is true, then it is unlikely that an effective accommodative mechanism is present in the eye of the beaver.…”

Section: Beaversupporting

confidence: 92%

See 1 more Smart Citation

Intraocular muscles of the Canadian river otter and Canadian beaver and their optical function

Ballard¹,

Sivak²,

Howland³

1989

Can. J. Zool.

View full text Add to dashboard Cite

1989. Intraocular muscles of the Canadian river otter and Canadian beaver and their optical function. Can. J. Zool. 67: 469-474. The gross morphology and microscopic anatomy of the ciliary and iris musculature of the Canadian river otter (Lutra canadensis) and Canadian beaver (Castor canadensis) were studied to help evaluate whether either species has an exaggerated accommodative mechanism for use underwater. The intraocular muscles of the otter are of a size and organization indicative of an extreme lens-deforming accommodative ability involving both the ciliary body and iris. By contrast, the intraocular muscles of the beaver eye indicate that accommodation is not significant in this animal. Thus, the intraocular musculature of the class Mammalia is not homogeneous, even within the amphibious mammals. Refractive and corneal measurements on two living river otters confirm that this animal is capable of an accommodative range that can neutralize the loss of corneal refractive power when the eye is in water.

show abstract

Section: Beaversupporting

confidence: 92%

“…It is brought about by a large striate iris musculature and a ciliary muscle that is in direct contact with the lens. In general, the structure and development of the intraocular muscles are known to vary throughout the birds and reptiles and are believed to correspond to the degree of accommodative ability of the animal (Barrett 1938).…”

Section: Introductionmentioning

confidence: 99%

Intraocular muscles of the Canadian river otter and Canadian beaver and their optical function

Ballard¹,

Sivak²,

Howland³

1989

Can. J. Zool.

View full text Add to dashboard Cite

show abstract

“…Additionally, the accommodation reflex, which alters lens shape in order to focus on objects at variable distances, was lost in monotremes and, variably, in many other mammals. This was also cited by Walls [1942] as an indication of a nocturnal ancestry; the fine focus provided by the accommodation reflex is inherently less useful at night when most vision is blurry anyway [Barrett, 1938;Walls, 1942;Rowe, 2000].…”

Section: Introductionmentioning

confidence: 99%

The Nocturnal Bottleneck and the Evolution of Mammalian Vision

Heesy

Hall²

2010

Brain Behav Evol

126

132

View full text Add to dashboard Cite

Evidence from the early paleontological record of mammalian evolution has often been interpreted as supporting the idea that mammals were nocturnal for most of their early history. Multiple features of extant mammal sensory systems, such as evolutionary modifications to the light-regulated circadian system, photoreceptor complement, and retinal morphology, support this nocturnal hypothesis for mammalian evolution. Here, we synthesize data on eye shape and orbit orientation in mammals as these data compare to other amniotes. Most mammals differ from other amniotes in retaining an eye design optimized for high visual sensitivity, with the requisite reduction in acuity, which is typically restricted to scotopically (i.e. low light) adapted amniotes. Mammals also possess the more convergent (similarly facing) orbits and, on average, the largest binocular visual fields among amniotes. Based on our analyses, we propose that extant mammals retain a scotopic eye design as well as expanded binocular zones as a result of their nocturnal origin. Only anthropoid primates notably differ from general mammalian patterns, and possibly have evolved an eye shape more typical of the ancestral amniote condition.

show abstract

“…The extent of ciliary muscle development is thought to correspond to the degree of accommodation exhibited by a species (Barret 1938;Woolf 1956). For example, humans have a substantial accommodative ability (15 diopters in the young eye) and possess a well-developed ciliary muscle (Duke-Elder smooth muscle bundles ( Fig.…”

Section: Introductionmentioning

confidence: 99%

A comparative study of the anatomy of the iris and ciliary body in aquatic mammals

West¹,

Sivak²,

Murphy³

et al. 1991

Can. J. Zool.

View full text Add to dashboard Cite

1991. A comparative study of the anatomy of the iris and ciliary body in aquatic mammals. Can. J. Zool. 69: 2594-2607. The ciliary muscle exhibits considerable variation in its development among the vertebrates. The muscle is considered to be well developed in humans, primates, ungulates, and aquatic carnivores, and the extent of development is thought to correspond to the amplitude of accommodation. The recent finding of a well-developed ciliary muscle in the hooded seal (Cystophora cristata) has initiated interest in an accommodative mechanism for vision in air and in water. This study is a comparative investigation of the ciliary muscle in a number of aquatic mammals. The methods include gross inspection of the ciliary region and histological examination of the ciliary body and iris by means of light microscopy. The results indicate that in completely aquatic mammals the ciliary muscle is rudimentary, and in fact, appears to be lacking in one species (beluga whale). The ciliary muscle appears to be better developed in the amphibious pinnipeds (California sea lion, elephant seal, and walrus). The presence of circular muscle bundles suggests that the muscle is more developed in the elephant seal and California sea lion than in the walrus. The degree of ciliary muscle development and the need for accommodation can be related to the nctural history of each species.

show abstract

Accommodation in the Eyes of Mammals

Cited by 7 publications

References 2 publications

Intraocular muscles of the Canadian river otter and Canadian beaver and their optical function

Intraocular muscles of the Canadian river otter and Canadian beaver and their optical function

The Nocturnal Bottleneck and the Evolution of Mammalian Vision

A comparative study of the anatomy of the iris and ciliary body in aquatic mammals

Contact Info

Product

Resources

About