Leandro Lima

The chinchilla eye: morphologic observations, echobiometric findings and reference values for selected ophthalmic diagnostic tests.

PURPOSE To carry out a descriptive investigation into the most relevant morphological features of the chinchilla eye and bony orbit, as well as to perform selected ophthalmic diagnostic tests with the aim of establishing normal anatomic and physiologic references for this species. METHOD A total of 57 healthy, chinchillas were used to test most of the parameters in this investigation. Besides morphologic observations of the globe and adnexa, selected ocular tests and parameters were investigated, including blink frequency, palpebral fissure length (PFL), Schirmer tear test (STT), esthesiometry, intraocular pressure (IOP), central corneal thickness (CCT), B-mode echobiometric measurements of the globe and culture of the normal conjunctival bacterial microbiota. Morphologic observations were made using six formalin-fixed globes and four macerated skulls. RESULTS AND DISCUSSION Normal parameters found for selected ocular diagnostic tests were: blink frequency: 2.6 ± 0.84 blinks per 10 min; STT: 1.07 ± 0.54 mm; esthesiometry: 1.24 ± 0.46 cm; IOP: 17.71 ± 4.17 mmHg; CCT: 0.34 ± 0.03 mm; PFL: 1.44 ± 0.11 cm; anterior chamber depth: 2.01 ± 0.2 mm; axial lens thickness: 5.49 ± 0.43 mm; vitreous chamber depth (internal): 3.69 ± 0.52 mm; axial globe length: 1.14 ± 0.07 cm. The most frequent bacteria isolated from the conjunctiva were Streptococcus sp. (27.45%), Staphylococcus aureus (23.52%) and coagulase-negative Staphylococcus (19.60%). No statistically significant differences between left or right eyes or genders were found for any of the results. Reference data and morphologic observations obtained in this investigation will help veterinary ophthalmologists to recognize unique morphological features and more accurately diagnose ocular diseases in the chinchilla, an animal already being used as a biological model for ophthalmic studies.

Measurement of tear production in black-tufted marmosets (Callithrix penicillata) using three different methods: modified Schirmer’s I, phenol red thread and standardized endodontic absorbent paper points

OBJECTIVE To report normal tear production of healthy adult black-tufted marmosets and propose a novel alternative for the measurement of the aqueous portion of tear production in animals with small eyes. ANIMAL STUDIED Black-tufted marmosets (Callithrix penicillata). PROCEDURES Tear production of 19 animals was evaluated by the following methods: modified Schirmers I, phenol red thread and the novel use of standardized endodontic absorbent paper points. These methods and results were compared. Additionally, blink frequency and palpebral fissure length were measured. RESULTS Modified Schirmers test I, mean = -0.46 ± 3.41 mm/min; Phenol red thread, mean = 13.27 ± 5.41 mm/15 s.; Standardized endodontic paper points, size 30, mean = 9.32 ± 3.09 mm/min; Mean palpebral fissure length = 7.83 ± 0.72 mm. Blink frequency, mean = 20.27 ± 5.92/5 min. CONCLUSIONS Normal parameters for blink frequency, palpebral fissure length and tear production measurement are presented. The palpebral fissure of black-tufted marmoset is very small and tear production is one of the lowest reported for all animal species. A novel and practical alternative for tear production measurement using standardized endodontic absorbent paper points is presented and is indicated for animals with small eyes.

Reference values for the production of the aqueous fraction of the tear film measured by the standardized endodontic absorbent paper point test in different exotic and laboratory animal species

The aqueous fraction of the tear film and the horizontal palpebral fissure length (HPFL) were measured in exotic and laboratory animals, specifically saffron finches (Sicalis flaveola), chestnut-bellied seed-finches (Sporophila angolensis), red-eared sliders (Trachemys scripta elegans), rats (Rattus norvegicus) and mice (Mus musculus). These species possess small eyes making it difficult to perform the typical Schirmer tear test. Measurement of the aqueous fraction of the tear was performed using the standardized endodontic absorbent paper point tear test (PPTT), accomplished with manual restraint by a single operator. The following results were obtained: saffron finches (n = 42)-HPFL (4.46 ± 0.09 mm) and PPTT (5.10 ± 0.26 mm); chestnut-bellied seed-finches (n = 38)-HPFL (4.77 ± 0.05 mm) and PPTT (4.11 ± 0.34 mm); red-eared sliders (n = 56)-HPFL (8.59 ± 0.08 mm) and PPTT (8.79 ± 0.38 mm); rats (n = 60)-HPFL (6.45 ± 0.09 mm) and PTT (6.18 ± 2.06 mm); and mice (n = 22)-HPFL (3.59 ± 0.27 mm) and PPTT (4.39 ± 1.45 mm).

Proven cardiac changes during death-feigning (tonic immobility) in rabbits ( Oryctolagus cuniculus )

Tonic immobility (TI) is a response to fear or threat by remaining motionless, principally when attacked by predators from which there is no possibility of escape. Thus, here we demonstrate a way of easily reproducing this phenomenon in a laboratory setting and characterize the cardiac electromechanical alterations during TI. We observed a significant decrease in heart rate (HR) and changes of rhythm in electrocardiogram during TI in rabbits. Echocardiogram showed a significant increase in the left ventricle chamber diameter during systole and a consequent decrease in fractional shortening and ejection fraction, in addition to the HR and rhythm changes. There was also a significant decrease in aortic and pulmonary artery blood flow. Diastolic functional changes included a significant decrease of the peak atrial contraction velocity (A peak) and consequent increase in the ratio of peak early diastolic velocity to A peak and increased isovolumetric relaxation time. We were able to prove that TI changes the cardiac function considerably. Although the “fight-or-flight” response is the most common response to fear, which is characterized by the action of sympathetic nervous system with tachycardia and increased physical activity, TI is an alternative anti-predator behavior causing cardiac changes opposite to the “fight-or-flight” phenomenon.

Supposed primary conjunctival lymphoma in a dog.

A 7-year-old, male mixed-breed dog was presented for evaluation of a well-delineated, pink, oval and slightly firm mass with a smooth regular surface that was expanding approximately 60% of the lower eyelid conjunctiva and the lateral canthus. The dog had a supposed primary B-cell lymphoma at the temporal canthus of the upper eyelid conjunctiva of the same eye that had been removed approximately 3 years earlier. No metastases were detected at either presentation. Histologically, the conjunctival lamina propria was effaced by a well-delineated, unencapsulated and expansile highly cellular neoplasm composed of sheets of round cells that were immunohistochemically positive for CD20 and CD79a negative for CD3. Based on the microscopic and immunohistochemical findings, a diagnosis of supposed primary B cell conjunctival lymphoma was made. Primary ocular and adnexal ocular lymphomas in dogs are rarely reported and their behavior is poorly characterized. Further tumor recurrence was not observed one year post operatively. This case was considered unusual because of its conjunctival involvement and the clinical course with recurrence after three years of a surgical therapeutic procedure.

Intraocular signet-ring cell melanoma in a hamster (Cricetulus griseus).

A two-and-a-half year-old male Chinese hamster (Cricetulus griseus) was referred for evaluation of an intraorbital mass involving the right eye. Based on ophthalmic examination and ultrasonography, a diagnosis of intraocular neoplasia was made. Enucleation of the affected eye was performed. The mass was histologically diagnosed as a primary malignant intraocular signet-ring cell melanoma. No signs of recurrence were detected, and the hamster remained clinically healthy until it died 6 months after surgery. This case report attempts to contribute to the limited body of knowledge available in the literature on primary intraocular neoplasms in hamsters.

Bacterial microbiota of the ocular surface of captive and free‐ranging microbats: Desmodus rotundus, Diameus youngi and Artibeus lituratus

OBJECTIVES To investigate normal aerobic bacterial microbiota of the eye surface in vvcaptive and free-ranging bats belonging to the suborder Microchiroptera. ANIMALS STUDIED A total of 36 bats belonging to three different species (Desmodus rotundus, Diameus youngi, and Artibeus lituratus) were used to perform this investigation. Thirteen Diameus youngi and six Desmodus rotundus were trapped in a cave, and 17 captive Artibeus lituratus were obtained from an experimental colony. Both free-ranging and captive bats were free of apparent ocular or systemic disease. PROCEDURES Corneal and conjunctival swabs were collected from both eyes to identify the resident bacterial microbiota. RESULTS Seventeen bats had positive bacterial cultures in one or both eyes. Considering all isolates, Gram-positive bacteria (82.6%) predominated over those that were Gram-negative bacteria (17.4%). Coagulase-negative staphylococci (30.4%) were the most isolated genus, followed by Bacillus spp. (26%) and Corynebacterium spp. (21%). Only four Gram-negative species were isolated: Shigella spp., Hafnia alvei, Morganella morganii, and Flavobacterium odoratum. CONCLUSIONS In this study, bacterial microbiota of the ocular surface of bats was described, and Staphylococcus spp. were the most frequently isolated type of microorganism from healthy bat eyes.

Effects of prostaglandin analogs on blood flow velocity and resistance in the ophthalmic artery of rabbits

PURPOSE The aim of this study was to investigate the effects of prostaglandin analogs on blood flow in the ophthalmic artery of clinically healthy rabbits. METHODS Fifty-five clinically healthy New Zealand white rabbits were divided into six groups, and the left eyes were treated for four weeks with the preservative benzalkonium chloride (BAK) only or a topical formulation of different prostaglandin analogs (bimatoprost BAK, tafluprost BAK-free, travoprost BAK, travoprost POLYQUAD, and latanoprost BAK). Color Doppler imaging was performed before and after the treatments. The mean values of the peak systolic velocity (PSV) and end diastolic velocity and the resistive index (RI) were calculated. Statistical analysis was performed to compare the differences pre- and post-treatment for each drug and post-treatment among the drugs. RESULTS The prostaglandin analogs did not affect PSV. Bimatoprost BAK, travoprost POLYQUAD, and latanoprost BAK did not change RI. Tafluprost BAK-free and travoprost BAK therapy resulted in similar reductions in RI. No significant differences pre- and post-treatment were found when BAK was administered alone. CONCLUSION The prostaglandin analogs tafluprost BAK-free and travoprost BAK improved blood flow in the ophthalmic artery in healthy New Zealand white rabbits, which suggests that these drugs enhance the prevention of the progression the progression of glaucoma.

Characterization of the oculocardiac reflex during compression of the globe in Beagle dogs and rabbits

OBJECTIVE This investigation characterizes the occurrence of oculocardiac reflex (OCR) in conscious rabbits and dogs by observing the effect of an ocular compression stimulus on heart rate (HR). ANIMALS STUDIED Thirty-four clinically healthy adult rabbits and 15 clinically healthy adult Beagle dogs were studied. PROCEDURES An electrocardiogram was used to record the heart rhythm and HR continuously. Digital pressure was exerted over the eyelid on right eye, left eye and both eyes together for 1 min, with one-minute intervals between each compression. Variations in HR were observed in each minute by counting complexes on the electrocardiographs. RESULTS There were no differences in HR between stages without ocular compressions both in dogs and in rabbits. HR reduction caused by ocular compression was statistically significant in rabbits only when both eyes were compressed in contrast with all stages without compression. In dogs, a statistically significant reduction in HR was seen during compression of just the right eye or the left eye compared with the baseline HR, and when both the right and left eyes were compressed together compared with baseline or after compression of the right eye. In dogs, compression of individual eyes produced a change similar to that seen during compression of both eyes. CONCLUSIONS This study shows that OCR can occur during experimental ocular compression in conscious rabbits and Beagle dogs and characterizes the reduction in HR. Knowledge of this physiological response is important for veterinary anesthetists and ophthalmologists during ophthalmic surgery or eye manipulations.

O olho da coruja-orelhuda: observações morfológicas, biométricas e valores de referência para testes de diagnóstico oftálmico

The investigation aimed to describe the most relevant morphological characteristics of the eyes of the striped owl (Asio clamator) and determine normal values for selected ophthalmic diagnostic tests. A total of 32 eyes of 16 young and adult free-ranging healthy striped owls of both sexes were investigated. Data of different morphological observations of the skull, eye globe and adnexa, clinical tests and parameters were collected, including Schirmer Tear Test (STT), normal conjunctival bacterial microbiota, esthesiometry, intraocular pressure (IOP), central corneal thickness (CCT), horizontal palpebral fissure length, horizontal, corneal diameter and fundoscopy. Twenty two types of bacteria were identified in twelve owls, the most frequent bacteriae were the Gram-positive. The mean value found for the STT was 5.03±3.28mm/min; horizontal palpebral fissure lengths was 21.24±1.17mm, and 15.7±2.74mm for horizontal corneal diameter. The mean value for the esthesiometry was 0.80±0.59cm, IOP was 13.81±5.62mmHg and CCT was 0.28±0.03cm. This study contributes to establish reference values for selected ophthalmic diagnostic tests in the striped owl, as well as for morphological characterization of the eyeball of Asio clamator; but it is still necessary to characterize furthermore its histologic features.