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Comparative Anatomy and Physiology of the Mammalian Eye
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
All of the common laboratory animals possess a nictitating membrane (nictitans, third eyelid). Humans possess a plica semilunaris which is a vestigial nictitating membrane. The nictitating membrane is located in the inferonasal aspect of the eye, except in birds where it is found in the superior nasal fornix. It moves passively superior and temporal across the eye as the eye is withdrawn into the orbit, displacing the bulk of the base of the third eyelid resulting in this sweeping action. Most animals possess some smooth muscle which is under autonomic innervation (sympathetic) and which may contribute to the movement of the membrane or at least its position.
Ocular surface as mucosal immune site
Published in Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald, Principles of Mucosal Immunology, 2020
Rachel R. Caspi, Anthony St. Leger
Interestingly, in contrast to humans, the mouse and rat conjunctiva has a virtual absence of diffuse lymphoid cells including plasma cells, although some follicular structures and cells resembling M cells are present in the nictitating membrane of the eye. The nictitating membrane is part of the conjunctiva, is typically transparent, and slides across the eye like a third eyelid in some species that include rodents and other mammals as well as birds and reptiles. The CALT of larger animals, including rabbits, dogs, and cats, resembles the organization in humans more closely. It is likely that the tear fluid compensates for this lack of diffuse CALT and contains sufficient IgA and other effector molecules for the ecological situation of the rodent. The conjunctiva (including that of laboratory rodents) also contains many mast cells, whose mediators are released after binding allergen-IgE complexes to receptors expressed on their membrane, which are responsible for the unpleasant consequences of hay fever and allergy affecting the ocular surface.
The Renin-Angiotensin System
Published in Austin E. Doyle, Frederick A. O. Mendelsohn, Trefor O. Morgan, Pharmacological and Therapeutic Aspects of Hypertension, 2020
The response of guinea-pig ileum to angiotensin II appears to be partly due to stimulation of parasympathetic ganglia since it is reduced by atropine, botulinum toxin, or morphine.346,347 A drect ganglionic stimulant action of angiotesin was demonstrated by injecting the peptide into the arterial supply of the cat superior cervical ganglion.348 Contraction of the ipsilateral nictitating membrane occurred, and this could be prevented by postganglionic nerve section. Similar effects were produced by bradykinin. Stimulation of other autonomic ganglia by angiotensin has been reported.349,350
Human-relevant approaches to assess eye corrosion/irritation potential of agrochemical formulations
Published in Cutaneous and Ocular Toxicology, 2021
Amy J. Clippinger, Hans A. Raabe, David G. Allen, Neepa Y. Choksi, Anna J. van der Zalm, Nicole C. Kleinstreuer, João Barroso, Anna B. Lowit
The rabbit eye test is widely used to meet regulatory testing requirements for agrochemical formulations, and has been a requirement for pesticide registration for decades [109]. However, the rabbit test involves subjective examination of ocular lesions, uses an exaggerated exposure duration, provides limited mechanistic information, has never been validated for its relevance to humans, uses live animals, and is associated with considerable variability (see Table 1 for details). Furthermore, interspecies differences in structure, anatomy, and physiology exist between rabbit and human eyes, for example, rabbits have a nictitating membrane, higher pH of the eye, a larger conjunctival cul-de-sac, and are not as efficient in tear production. Thus, the rabbit test is not appropriate for use as a standard for evaluating new methods.
A New Rabbit Model of Chronic Dry Eye Disease Induced by Complete Surgical Dacryoadenectomy
Published in Current Eye Research, 2019
Robert Honkanen, Wei Huang, Liqun Huang, Kevin Kaplowitz, Sarah Weissbart, Basil Rigas
After sedation with acepromazine 1mg/kg, a wire lid speculum is placed between the lids. The nictitating membrane (NM) is infiltrated with 2% lidocaine with 1:100,000 epinephrine and gently pulled away from the globe and cut off with scissors close to its base. Care is taken not to cut off the NM too closely to its base, to avoid Harder’s gland prolapsing into the subconjunctival space. Cautery is generally not necessary, and its occasional use is minimal. Polysporin ophthalmic ointment is applied to the eye once. Further ocular procedures, or measurements are not performed for at least one week until clinical exam shows that the ocular surface has healed completely. Harder’s gland, adjacent to large venous sinuses in the orbit, is not removed to avoid the risk for massive bleeding.
Scene through the eyes of an apex predator: a comparative analysis of the shark visual system
Published in Clinical and Experimental Optometry, 2018
The nictitating membrane, found exclusively in carcharhiniform sharks, evolved as an extension of the lower eyelid and is thought to be similar to that found in amphibians, birds and mammals. Comprised of dense connective tissue covered in denticles (placoid scales),1978 the nictitating membrane is a mobile component of the ocular adnexa, which is well developed in at least four families of sharks including the family Carcharhinidae1963 (Figure 1G). During feeding, sharks close the nictitating membrane and open the jaw at the same time,2000 showing a close relation between prey capture and eye protection. Inter‐specific differences in the hexagonal arrangement of dermal denticles over the membrane suggest dynamic and biomechanical adaptation of this highly mobile structure to rapidly and efficiently protect against abrasion, mainly during predation events.2017