The distribution of postganglionic autonomic nerve fibers in the lacrimal gland and gland of the third eyelid of dogs was studied by use of histochemical techniques. Adrenergic nerve distribution was identified by use of the sucrose-potassium phosphate-glyoxylic acid technique. A loose network of adrenergic nerves was found throughout the interstitium around acini and blood vessels and in vessel walls. Acetylcholinesterase staining was used to identify cholinergic nerve fibers. A cholinergic distribution pattern around acini and blood vessels similar to the adrenergic pattern was found, although the cholinergic innervation appeared more dense than the adrenergic. In the gland of the third eyelid, mucus-secreting lobules and lipid-secreting lobules appeared to be equally innervated by parasympathetic fibers. These lobules could not be differentiated when the sucrose-potassium phosphate-glyoxylic acid technique was used. The techniques used in this study could not demonstrate whether direct contact was made by either cholinergic or adrenergic nerve fiber with secretory or myoepithelial cells. The presence of both nerve fiber types around acini suggests an interrelationship between the sympathetic and parasympathetic nervous system in lacrimal gland secretion in dogs.

OBJECTIVE To describe qualitative blinking patterns and determine quantitative kinematic variables of eyelid motion in ophthalmologically normal horses. ANIMALS 10 adult mares. PROCEDURES High-resolution videography was used to film blinking behavior. Videotapes were analyzed for mean blink rate, number of complete versus incomplete blinks, number of unilateral versus bilateral blinks, and subjective descriptions of blinking patterns. One complete blink for each horse was analyzed with image-analysis software to determine the area of corneal coverage as a function of time during the blink and to calculate eyelid velocity and acceleration during the blink. RESULTS Mean ± SD blink rate was 18.9 ± 5.5 blinks/min. Blinks were categorized as minimal incomplete (29.7 ± 15.6%), moderate incomplete (33.5 ± 5.9%), complete (30.8 ± 13.1%), and complete squeeze (6.0 ± 2.8%); 22.6 ± 9.0% of the blinks were unilateral, and 77.3 ± 9.1% were bilateral. Mean area of exposed cornea at blink initiation was 5.89 ± 1.02 cm2. Mean blink duration was 0.478 seconds. Eyelid closure was approximately twice as rapid as eyelid opening (0.162 and 0.316 seconds, respectively). Deduced maximum velocity of eyelid closure and opening was −16.5 and 7.40 cm/s, respectively. Deduced maximum acceleration of eyelid closure and opening was −406.0 and −49.7 cm/s2, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Kinematic variables of ophthalmologically normal horses were similar to values reported for humans. Horses had a greater percentage of complete squeeze blinks, which could increase tear film stability. Blinking kinematics can be assessed as potential causes of idiopathic keratopathies in horses.

Schirmer tear test (STT), intraocular pressure (IOP) measurement, slit-lamp biomicroscopy, and indirect ophthalmoscopy were performed on 8 dogs with (13)l-induced hypothyroidism and 4 euthyroid control dogs at weeks 0, 9, 13, 17, immediately prior to treatment with levothyroxine, after 5 weeks of levothyroxine administration (0.022 mg/kg of body weight, PO, q 12 h), and at euthanasia 7 weeks after discontinuation of replacement therapy. Although the control group had higher baseline STT values than the hypothyroid group after randomization of dogs into the 2 groups (P < 0.01), STT values remained unchanged from their respective baseline values at all time intervals for both groups. Hypothyroid and control dogs had significant (P < 0.05) reduction in IOP from baseline values at all subsequent time points, but differences were not observed when hypothroid dogs were compared with controls. Goblet cell indices determined from biopsy samples of the inferior-nasal conjunctival fornix obtained before induction of hypothyroidism (baseline), immediately prior to and at conclusion of levothyroxine therapy, and at euthanasia were not significantly different when values for hypothyroid dogs were compared with their own baseline values or with values for control dogs. Histologic examination of the globes and adnexa at euthanasia also failed to indicate consistent qualitative differences between hypothyroid and control dogs. Marked reduction in serum thyroid hormone concentrations had little effect on the eye and ocular adnexa over the course of the study.

Conjunctiva-associated lymphoid tissue (CALT) in the eyelids of chickens was studied by gross, histologic, and electron microscopic techniques. Structural features were characterized at 1 day of age and at posthatching week (PHW) 1, 2, 3, 4, 6, 8, 12, and 16. Beginning at PHW 1, prominent lymphoid nodules containing a heterogenous population of lymphocytes, lymphoblasts, and macrophages were first observed within conjunctival folds and fissures of the lower eyelid. Nodules contained germinal centers by PHW 2 and plasma cells by PHW 4. The epithelium associated with these nodules was flat, had short, irregular microvilli, contained intraepithelial lymphocytes, and lacked goblet cells. High endothelial venules were located at the base of lymphoid nodules and contained lymphocytes within and below the cuboidal endothelium. In the upper eyelid, CALT was morphologically similar to lymphoid tissue in the lower eyelid, but nodules were smaller and more random, lacked association with epithelial folds and fissures, and were clustered around the opening of the nasolacrimal duct. By PHW 12, CALT was characterized by basal germinal centers outlined by collagenous stroma, suprafollicular plasma cells, columnar epithelium with goblet cells, and fewer intraepithelial lymphocytes. On the basis of these features, CALT in chickens has morphologic characteristics similar to other components of the mucosal immune system and, therefore, may have a role in mucosal immunity.

The connective tissue structures commonly referred to as the periorbita, orbital septum, muscular fasciae, and vagina bulbi or collectively, as the orbital fasciae were dissected then illustrated and described. Two sheets (layers) of the periorbita (endorbita) were found in our dogs. The periorbita should be renamed endorbita because of its anatomic relations. The periorbita did not always fuse with the periosteum of frontal and sphenoid bones. Rather, the periorbita and the periosteum were often distinct and separate; only medioventrally did several fibrous bands unite the superficial sheet of the endorbita with the periosteum. Two layers of the endorbita fused with the periosteum of the margin of the bony orbit and with the orbital ligament. The muscular fasciae were divided into 3 layers. The superficial layer extended caudally from the orbital septum, was thick, and was pierced by arteries, veins, and nerves. The middle layer was attached to the sclerocorneal junction and, at the temporal canthus of the eye, was divided into superficial and deep sheets. The deep portion was attached to the lateral angle of the third eyelid, similar to a strong ligament. The deep layer of the muscular fasciae extended caudally from the sclerocorneal junction in intimate contact with recti and oblique muscles of the eyeball. The deep portion of the deep muscular fascia covered the deep surface of all recti muscles and separated them from the retractor bulbi muscle. Intermuscular septa were observed between middle and deep muscular fascia layers. The body of the third eyelid was located between superficial and middle muscular fascia layers and was fixed ventrally to the lateral angle of the eye by the deep sheet of the middle muscular fascia.

Objective-To evaluate lactoferrin and lysozyme content in various ocular glands of bison and cattle and in tears of bison. Sample Population-Tissues of ocular glands obtained from 15 bison and 15 cattle and tears collected from 38 bison. Procedure-Immunohistochemical analysis was used to detect lysozyme and lactoferrin in formalin-fixed, paraffin-embedded sections of the ocular glands. Protein gel electrophoresis was used to analyze ocular glands and pooled bison tears by use of a tris-glycine gel and SDS-PAGE. Western blotting was used to detect lactoferrin and lysozyme. Results-Immunohistochemical staining for lactoferrin was evident in the lacrimal gland and gland of the third eyelid in cattle and bison and the deep gland of the third eyelid (Harder's gland) in cattle. Equivocal staining for lactoferrin was seen for the Harder's gland in bison. An 80-kd band (lactoferrin) was detected via electrophoresis and western blots in the lacrimal gland and gland of the third eyelid in cattle and bison, Harder's glands of cattle, and bison tears. An inconsistent band was seen in Harder's glands of bison. Lysozyme was not detected in the lacrimal gland of cattle or bison with the use of immunohistochemical analysis or western blots. Western blots of bison tears did not reveal lysozyme. Conclusion and Clinical Relevance-Distribution of lactoferrin and a lack of lysozyme are similar in the lacrimal gland of cattle and bison. Differences in other tear components may be responsible for variability in the susceptibility to infectious corneal diseases that exists between bison and cattle.