Through the eyes of a sea lion

Sarah Miller

Richard Dubielzig, DVM, DACVP

Large Diameterflattened cornea

Shorter internal axial lengthmore accurately defines optical function

The GlobeCornea thicker peripherally

Due to stroma

The CorneaFlattened region over a stenopaic pupil

not seen histologically

The cornea

Bowman’s membraneTEM

Descemet’s thin

Endothelium thin

Anterior Uvea

Extensive constriction of pupil protects from large changes in illumination

Iridocorneal angle

Thick pectinate ligament with intermittent open channels

Intermittent corneoscleraltrabecular meshwork

Anterior Uvea

Dilator muscle

absent at the pupil

Robust near iris base where it abutts sphincter m.

Near pectinate ligament

Extends over widened base of ciliary processes

Sphincter muscleThickest near iris base

Near pectinate ligament

Accomodation??

Ciliary Body

Dilator muscle extending up the base of the ciliary processes

Circumferential smooth muscle subtending zonular ligaments

accomodation??

Lens attachment: direct attachment of ciliary processes

zonular fibers

http://lifestyle.iloveindia.com/lounge/images/facts-about-pinniped-2.jpg

The Lens

Spherical lens

Spherical lensHeterogeneous  (multifocal) Lower R.I. in peripheryCompensates for the inability of the cornea to refract 

underwater

Tapetum lucidum

• Tapetum lucidum covers 2/3 to entire fundus

Extremely thick both dorsal & ventral to optic nerve

Tapetum lucidum

Ganglion cells!!

Dog

Pinniped

Monochromatic

loss of S opsin

Ganglion cells!!Very large but sparce

Sclera• Thick

– Near limbus– Near optic nerve

• Thin– At equator

Similar to the vascular plexus seen in cetaceans?

Vascular Plexus

Similar to the vascular plexus seen in cetaceans?

Vascular Plexus

References

•• Miller S., Miller S., ColtizColtiz C., C., DubielzigDubielzig R. (2010)  R. (2010)  Anatomy of the California sea lion Anatomy of the California sea lion globeglobe. Veterinary Ophthalmology supplement 1: 63. Veterinary Ophthalmology supplement 1: 63‐‐71.71.

•• YaYa SupinSupin, Alexander, et al. , Alexander, et al. The Sensory Physiology of Aquatic Mammals.The Sensory Physiology of Aquatic Mammals.Boston, Boston, KluwerKluwer Academic Publishers, 2001. (pp 239Academic Publishers, 2001. (pp 239‐‐264)264)

•• Mass A. & Mass A. & YaYa SupinSupin A. (2007) A. (2007) Adaptive Features of Aquatic MammalsAdaptive Features of Aquatic Mammals’’Eye.Eye. The Anatomical Record 290:701The Anatomical Record 290:701‐‐715.715.

•• PeichlPeichl L. et al. (2001) L. et al. (2001) For Whales and Seals the Ocean is Not Blue: A For Whales and Seals the Ocean is Not Blue: A Visual Pigment Loss in Marine Mammals. Visual Pigment Loss in Marine Mammals. European Journal of European Journal of Neuroscience 13: 1520Neuroscience 13: 1520‐‐1528.1528.