Abstract

Surgical removal of the lens has become more frequent in pinnipeds over the years and generally occurs through an intra or extra-capsular approach upon full ripening of the lens.^1,2,3 However most post-surgery controls have been limited to direct, indirect, and whenever possible slit-lamp observation.⁴

Ultrasound can help in the identification of disorders that are sometimes difficult to identify, through lack of pupillary dilatation and/or anterior opacities, and is thus an ideal approach to better understand the healing or potential complication processes that occur post-surgically.⁵

Open eye ultrasound examination of the internal structures of the eye globe can easily be performed by immersion through voluntary behavior in pinnipeds.⁶ Thanks to the excellent acoustic coupling of the water, higher quality visualization is obtained compared to trans-palpebral access. Reference images of the internal eye structures were henceforth obtained.⁷

The vitreous is an anechoic structure. Under normal circumstance, the only echogenic structures visible between the iris/ciliary body and posterior wall of the eye are portions of the anterior and posterior lens capsule with the primary beam.⁸

With age or as consequence of intra ocular surgery, the vitreous liquefies, forming liquid pockets. These cause the surroundings vitreous to collapse centrally, providing space for the hyaloid to separate from its point of attachment at the back of the eye. This separation is called posterior vitreous detachment (PVD). Very little symptoms (apart when a retinal tear is present) are visible through direct visualization, but it is the most common cause of "floaters", which can be seen by ultrasound.⁹ Ocular trauma or inflammation may also result in the accumulation of glittering cholesterol crystals in the vitreous, called then synchysis scintillans.¹⁰ Visually comparable is asteroid hyalosis (soaps suspended in the vitreous), which is a common degenerative process in which fatty calcium globules collect within the vitreous humour. These are moving with eye movements and studies seem to indicate that they are primarily associated with ageing.¹⁰

Thirty-two pinnipeds from 5 different species (11 Zalophus californianus, 8 Otaria byronia, 7 Arctocephalus pusillus, 5 Phoca vitulina, 1 Halichoerus grypus) and from 5 different facilities were assessed by voluntary eye immersion ultrasound. A Logiq e VET and Logiq e BT12 (General Electrics) with L8-18i-RS and 12L-RS probes, were utilized in 4 parks; while a SonoSite edge with a L25x transversal probe was used in the 5th one.

Twelve animals had had cataract surgery by 3 different surgeons in the last 15 years. At the time of this abstract, 7 animals had already been reviewed and none had a clear vitreous. 6 had signs of vitreous degeneration (2 Zc, 1 Ap, 3 Pv) - compatible with the mentioned pathologies, though a clear confirmation of which one was not possible - while the last one (1 Hg) had severe vitreous gel destruction with the presence of organized fibrinous membranes. Review of the 5 remaining operated animals, together with more results from other parks are expected before the presentation at the conference. These findings may indicate that full vitrectomy may be a recommendation when performing cataract surgery in pinnipeds.

Acknowledgements

SCIL France, distributor of the GE ultrasound machines in France, sponsored the project by providing the Logiq e BT12 and the L8-18i-RS probe.

The authors wish to thank Mr. Jean-Luc Bourgain and his team of Nausicaa, France; Mr. Pablo Joury and his team of Amneville, France; Dr. Carla Flanagan, Dr. Nuno Urbani, Mr. Miguel Silveira and their team of Mundo Aquatico, Portugal; Dr. Torsten Moller, Dr. Luise Guevara, Ms. Laura Riem and their team of Kolmarden Djurpark, Sweden; Dr. Abraham Cardenas and Mr. Wayne Phillips of Dolphin Adventure, Mexico.

* Presenting author

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