Reference values for selected ophthalmic diagnostic tests of the capuchin monkey (Cebus apella)

Ocular examination findings and selected ophthalmic diagnostic tests in African green monkeys (Chlorocebus aethiops sabaeus)

OBJECTIVE

To document ocular lesions and establish ophthalmic diagnostic test reference values in a colony of African green monkeys (Chlorocebus aethiops sabaeus).

ANIMALS STUDIED

Fifty one geriatric (GAGM, 19-30 years old), 10 adult (AAGM, 5-9 years old) and 10 juvenile (JAGM, <2 years old) African green monkeys housed in a single Caribbean research colony.

PROCEDURES

Ocular biomicroscopy, indirect fundoscopy, Schirmer tear test (STT), rebound tonometry (TonoVet®) and corneal fluorescein staining were performed. Mixed ANCOVA tests were performed to compare STT and IOP between groups.

RESULTS

Common ocular lesions in GAGM included vitreal degeneration (27/51, 51/102 eyes) and cataracts (21/51, 32/102 eyes). Vitreal degeneration was also common in AAGM (8/10, 16/20 eyes) and infrequent in JAGM (3/10, 6/20 eyes). Cataracts were not present in any JAGM or AAGM. All eyes in all three groups had perilimbal corneal pigmentation and faint lace-like anterior corneal stromal opacification. Median (range) STT values were 16.0 (18) mm/min in GAGM. Mean (SD) STT values were 14.2 (4.6) mm/min in AAGM, and 8.9 (3.4) mm/min in JAGM. Median (range) IOP values were 16.5 (27) mmHg in GAGM. Mean (SD) IOP values were 18.0 (2.8) mmHg in AAGM, and 14.1 (2.2) mmHg in JAGM. JAGM had significantly lower STT and IOP values compared to AAGM (p = .0449, .0057, respectively) and GAGM (p = .0002, .0130, respectively).

CONCLUSIONS

Spontaneous ocular lesions were common in geriatric monkeys in this research colony. IOP and STT values were lower in juvenile African green monkeys relative to adult or geriatric animals.

SELECTED OPHTHALMIC TESTS AND OCULAR DIMENSIONS IN RELATION TO ACTIVITY PATTERN IN THREE NEOTROPICAL NONHUMAN PRIMATES: BLACK-TUFTED MARMOSET (CALLITHRIX PENICILLATA), GUIANAN SQUIRREL MONKEY (SAIMIRI SCIUREUS), AND AZARA'S NIGHT MONKEY (AOTUS AZARAE INFULATUS)

The goals of this study were to compare ocular morphology, determine the reference intervals of selected ophthalmic tests, ocular measurements, intraocular pressure, and tear production, and to establish possible relationships in the visual ecology of three different Neotropical nonhuman primates (NHP). Nineteen black-tufted marmosets (Callithrix penicillate), 24 Guianan squirrel monkeys (Saimiri sciureus), and 24 night monkeys (Aotus azarae infulatus) were included in the study. Schirmer tear test, ocular dimensions, ocular ultrasonography, intraocular pressure, central corneal thickness, and corneal touch threshold were determined. The ratio of the average corneal diameters and axial diameters (CD/AGL) were established. No significant difference was noted between males and females, nor left and right eyes, for all three species for all measurements (P > 0.05). CD/AGL ratio was significantly higher (P < 0.0001) in night monkeys (a nocturnal species) as compared to black-tufted marmoset and Guianan squirrel monkeys (two diurnal species). The reference intervals will aid veterinary ophthalmologists to more accurately diagnose pathological changes in the eyes of these species. In addition, ocular dimension comparison will allow other NHP species to be evaluated and examined in relationship to behavioral traits (nocturnal versus diurnal).

FACTORS AFFECTING TEAR PRODUCTION AND INTRAOCULAR PRESSURE IN ANESTHETIZED CHIMPANZEES (PAN TROGLODYTES)

Measurements of intraocular pressure (IOP) and tear production are key components of ophthalmic examination. Chimpanzees (Pan troglodytes) were anesthetized using either tiletamine-zolazepam (TZ; 2 mg/kg) combined with medetomidine (TZM; 0.02 mg/kg), or, TZ alone (6mg/kg). Tear production was lower (P = 0.03) with TZM (5.63 ± 6.22 mm/min; n = 16) than with TZ (11.13 ± 4.63 mm/min; n = 8). Mean IOP, measured using rebound tonometry in an upright body position (n = 8) was 18.74 ± 3.01 mm Hg, with no differences between right and left eyes. However, positioning chimpanzees in left lateral recumbency (n = 27) resulted in higher IOP in the dependent (left) eye (24.77 ± 4.49 mm Hg) compared to the nondependent (right) eye (22.27 ± 4.65 mm Hg) of the same animal (P < 0.0001). These data indicate medetomidine anesthesia markedly lowers tear production in chimpanzees, and that body position should be taken into consideration when performing rebound tonometry.

Characterization of the normal equine conjunctival bacterial community using culture-independent methods

BACKGROUND

The equine conjunctival microbiota has often been reported to be dominated by Gram-positive species such as Staphylococcus sp., Bacillus sp., and Corynebacterium sp. However, traditional culture-based methods can only recover a fraction of the bacterial species present in the sample.

OBJECTIVES

This pilot study aimed at exploring the diversity of the equine conjunctival microbiota using culture-independent methods.

STUDY DESIGN

Eight horses were included in this study, and only eyes with normal ophthalmic examination (n = 15 eyes) were sampled.

METHODS

Conjunctival biopsies (culture-independent) were collected, and DNA was extracted from the tissues. Bacterial communities in conjunctival biopsies were characterized by next-generation sequencing of the 16S rRNA genes. Individual reads were ascribed to operational taxonomic units (OTUs) using BLASTn and Greengenes databases. Species richness, evenness, and Good's coverage were determined for each conjunctiva-associated microbial community.

RESULTS

Culture-independent samples produced a total of 329 bacterial OTUs. The main OTUs identified in the study belonged to the Gram-negative species Ralstonia mannitolilytica (88.0%), Nicoletella semolina (3.3%), and Pseudomonas tolaasii (1.5%).

CONCLUSIONS

Contrary to previously published data based on culture-dependent methods, the horse eye microbial community was dominated by Gram-negative bacteria of the phylum Proteobacteria.

A competitive drive? Same-sex attentional preferences in capuchins

In primates, faces provide information about several characteristics of social significance, including age, physical health, and biological sex. However, despite a growing literature on face processing and visual attention in a number of primate species, preferences for same- or opposite-sex faces have not yet been examined. In the current study, we explore the role of conspecific sex on visual attention in two groups of capuchin monkeys. Subjects were shown a series of image pairs on a Tobii Pro TX300 eye tracker, each depicting an unfamiliar male and an unfamiliar female face. Given the behavioral evidence of mate choice in both sexes, we hypothesized that capuchins would preferentially attend to images of unfamiliar conspecifics of the opposite sex. Our alternative hypothesis was that capuchins would preferentially attend to same-sex individuals to assess potential competitors. Our results provide support for our alternative hypothesis. When comparing attention to each stimuli type across sexes, females spent significantly larger percentages of time than males looking at female photos, whereas males spent significantly larger percentages of time than females looking at male photos. Within each sex, females looked for significantly larger percentages of time to female versus male images. Males also looked for larger percentages of time to same-sex images, though not significantly. To our knowledge, these data are the first to demonstrate significant sex-biased attentional preferences in adult primates of any species, and suggest that, for capuchins, potential competitors garner more attention than potential mates. In addition, our findings have implications for studies of visual attention and face processing across the primate order, and suggest that researchers need to control for these demographic factors in their experimental designs.

Determination of baseline values for routine ophthalmic tests in bearded capuchin (Sapajus libidinosus)

BACKGROUND

Establish baseline values for ophthalmic diagnostic tests in Sapajus libidinosus.

METHODS

Ophthalmic diagnostic tests, namely Schirmer tear test 1 (STT-1), intraocular pressure (IOP), B-mode ultrasound, culture of the bacterial conjunctival microbiota, and conjunctival exfoliative cytology, were performed in 15 S. libidinosus.

RESULTS

Mean values found were as follows: 2.50 ± 2.94 mm/min for the STT-1; 13.3 ± 3.32 mm Hg for the IOP; 2.47 ± 0.41 mm for the depth of the anterior chamber; 2.86 ± 0.96 mm for the axial length of the lens; 10.97 ± 0.48 mm for the depth of the vitreous chamber; and 16.32 ± 1.24 mm for the axial length of the eyeball. The bacterial genus most frequently found was Staphylococcus spp. Conjunctival cytology showed intermediate epithelial, squamous superficial epithelial, and keratinized cells.

CONCLUSIONS

Determination of baseline values for eye measurements and ophthalmic tests will assist in the diagnosis of eye diseases in S. libidinosus monkeys.

Evaluation of lacrimal production, osmolarity, crystallization, proteomic profile, and biochemistry of capuchin monkeys' tear film

BACKGROUND

To evaluate the composition and characteristics of capuchin monkey (CM) tear film.

METHODS

Eleven CM (Sapajus sp.) was evaluated. Strip meniscometry test (SMT), osmolarity, and tear ferning test (TFT) (by Rolando and Masmali scales) were assessed. Tear protein profile (SDS-PAGE), and total protein, albumin, urea, glucose, and cholesterol levels in tear film and blood serum were screened.

RESULTS

Median ± semi-interquatil range for SMT and osmolarity values were 8.0 ± 1.625 and 303.0 ± 9.875, respectively. TFT for Rolando was 2.0 ± 0.5, and Masmali was 2.0 ± 0.0. Monkeys's tear obtained type II and III for Rolando, and 1 and 2 for Masmali. Tear components showed protein bands among 23-217 kDa, and presence of albumin, urea, glucose, and cholesterol.

CONCLUSIONS

The results of SMT, osmolarity, TFT, SDS-PAGE, and tear biochemistry may serve as a reference baseline for CM, and the data may serve as a basis for future experimental model evaluations.

Morphological study of the eye and adnexa in capuchin monkeys (Sapajus sp.)

The objective of this study was to describe the anatomic and histologic features of the Sapajus sp. eye, comparing similarities and differences of humans and other species of non-human primates for biomedical research purposes. Computed tomography (CT) of adnexa, eye and orbit live animal, as well as formolized pieces of the same structures of Sapajus sp. for anatomical and histological study were also performed. The anatomical description of the eye and adnexa was performed using the techniques of topographic dissection and exenteration. Histological fragments were fixated in buffered formalin 10%, processed by the routine paraffin inclusion technique, stained with hematoxylin-eosin and special stains. CT scan evaluation showed no differences between the live animal and the formolized head on identification of visual apparatus structures. Anatomic and histologic evaluation revealed rounded orbit, absence of the supraorbital foramen and frontal notch, little exposure of the sclera, with slight pigmentation of the exposed area and marked pigmentation at the sclerocorneal junction. Masson's Trichrome revealed the Meibomian glands, the corneal epithelium and Bowman's membrane; in the choroid, melanocytes and Bruch's membrane were observed; and in the retina, cones and rods as well as, optic nerve, the lamina cribrosa of the nerve fibers bundles. Toluidine blue highlighted the membranes: Bowman, Descemet and the endothelium; in the choroid: melanocytes; and in the retina: nuclear layers and retinal pigment epithelium. In view of the observed results Sapajus sp. is an important experimental model for research in the ophthalmology field, which has been shown due to the high similarity of its anatomical and histological structures with the human species.

The eye of the Barbary sheep or aoudad (Ammotragus lervia): reference values for selected ophthalmic diagnostic tests, morphologic and biometric observations

The purpose of this study was to describe the normal ocular anatomy and establish reference values for ophthalmic tests in the Barbary sheep or aoudad (Ammotragus lervia). Aoudad eyes are large and laterally positioned in the head with several specialized anatomic features attributed to evolutionary adaptations for grazing. Normal values for commonly used ophthalmic tests were established, Schirmer tear test (STT) - 27.22 ± 3.6 mm/min; Predominant ocular surface bacterial microbiota - Staphylococcus sp.; Corneal esthesiometry- 1.3 ± 0.4 cm; Intraocular pressure by rebound tonometry- 19.47 ± 3.9 mmHg; Corneal thickness- 630.07 ± 20.67 µm, B-mode ultrasonography of the globe-axial eye globe length 29.94 ± 0.96 mm, anterior chamber depth 5.03 ± 0.17 mm, lens thickness 9.4 ± 0.33 mm, vitreous chamber depth 14.1 ± 0.53 mm; Corneal diameter-horizontal corneal diameter 25.05 ± 2.18 mm, vertical corneal diameter 17.95 ± 1.68 mm; Horizontal palpebral fissure length- 34.8 ± 3.12 mm. Knowledge of these normal anatomic variations, biometric findings and normal parameters for ocular diagnostic tests may assist veterinary ophthalmologists in the diagnosis of ocular diseases in this and other similar species.

Allometry and Scaling of the Intraocular Pressure and Aqueous Humour Flow Rate in Vertebrate Eyes

In vertebrates, intraocular pressure (IOP) is required to maintain the eye into a shape allowing it to function as an optical instrument. It is sustained by the balance between the production of aqueous humour by the ciliary body and the resistance to its outflow from the eye. Dysregulation of the IOP is often pathological to vision. High IOP may lead to glaucoma, which is in man the second most prevalent cause of blindness. Here, we examine the importance of the IOP and rate of formation of aqueous humour in the development of vertebrate eyes by performing allometric and scaling analyses of the forces acting on the eye during head movement and the energy demands of the cornea, and testing the predictions of the models against a list of measurements in vertebrates collated through a systematic review. We show that the IOP has a weak dependence on body mass, and that in order to maintain the focal length of the eye, it needs to be an order of magnitude greater than the pressure drop across the eye resulting from gravity or head movement. This constitutes an evolutionary constraint that is common to all vertebrates. In animals with cornea-based optics, this constraint also represents a condition to maintain visual acuity. Estimated IOPs were found to increase with the evolution of terrestrial animals. The rate of formation of aqueous humour was found to be adjusted to the metabolic requirements of the cornea, scaling as Vac(0.67), where Vac is the volume of the anterior chamber. The present work highlights an interdependence between IOP and aqueous flow rate crucial to ocular function that must be considered to understand the evolution of the dioptric apparatus. It should also be taken into consideration in the prevention and treatment of glaucoma.

Non-continuous measurement of intraocular pressure in laboratory animals

Glaucoma is a leading cause of blindness, which is treatable but currently incurable. Numerous animal models therefore have both been and continue to be utilized in the study of numerous aspects of this condition. One important facet associated with the use of such models is the ability to accurately and reproducibly measure (by cannulation) or estimate (by tonometry) intraocular pressure (IOP). At this juncture there are several different approaches to IOP measurement in different experimental animal species, and the list continues to grow. We feel therefore that a review of this subject matter is timely and should prove useful to others who wish to perform similar measurements. The general principles underlying various types of tonometric and non-tonometric techniques for non-continuous determination of IOP are considered. There follows discussion of specific details as to how these techniques are applied to experimental animal species involved in the research of this disease. Specific comments regarding anesthesia, circadian rhythm, and animal handling are also included, especially in the case of rodents. Brief consideration is also given to possible future developments.

Evaluation of standardized endodontic paper point tear test in New Zealand white rabbits and comparison between corneal sensitivity followed tear tests

OBJECTIVE

To evaluate endodontic paper point tear test (PPTT) in rabbits and compare changes in corneal touch threshold (CTT) induced by Schirmer tear test (STT) and PPTT. Normal corneal sensitivity recovery time after both tear tests was also measured. Also, mean PPTT and STT values were obtained.

METHODS

Tear production of 20 eyes, from 10 rabbits, was evaluated using STT and the PPTT. Central corneal touch threshold was measured by a Cochet-Bonnet esthesiometer before any tear test was performed (zero time), immediately after the test (1 min), and consecutively at 6, 11, 16, and 26 min. Tests were conducted on three consecutive days: Day 1 - control condition, no tear tests performed only the CTT; Day 2 - CTT before and after PPTT; and Day 3 - CTT before and after STT. CTT values were compared using repeated measures ANOVA.

RESULTS

Corneal touch threshold was significantly increased for at least 16 min after STT, indicating STT causes corneal discomfort. No difference was found between CTT following PPTT and controls, indicating PPTT caused minimal corneal discomfort. The mean (±SD) value for STT was 5.2 ± 1.0 mm/min and for PPTT was 13.8 ± 1.5 mm/min.

DISCUSSION

The aqueous fraction of rabbit's tears can be successfully measured by PPTT. This report established reference values for PPTT in rabbits. Additionally, the absence of a significant difference in CTT after PPTT compared with controls shows that PPTT is well tolerated by rabbits. Considering the improved comfort (compared with STT), accuracy, and low cost, PPTT is a bona fide method of measuring aqueous tear production in rabbits.

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

Objetivou-se relatar características morfológicas do bulbo ocular e determinar valores de referência para testes oftálmicos selecionados em corujas-orelhudas (Asio clamator). Foram estudados 32 olhos de 16 corujas (Asio clamator), adultas e jovens, machos e fêmeas, de vida livre. Sendo compilados dados referentes a observações morfológicas do crânio, bulbo ocular e anexos, além de mensuração de testes oftálmicos, incluindo, Teste Lacrimal de Schirmer (TLS), cultura da microbiota normal da conjuntiva, estesiometria, pressão intraocular (PIO), espessura de córnea central (ECC), diâmetro horizontal da rima palpebral, diâmetro horizontal da córnea e oftalmoscopia indireta. Vinte e dois tipos de bactérias foram identificados em 12 corujas havendo predominância de microrganismos Gram-positivos. A média encontrada para o TLS foi de 5,03±3,28mm/min, para o diâmetro horizontal da rima palpebral em 16 corujas foi 21,24±1,17mm, e 15,7±2,74mm para o diâmetro horizontal da córnea. O valor médio para o teste de estesiometria foi de 0,80±0,59cm, a PIO média de 13,81±5,62mmHg e ECC média de 0,28±0,03cm. O estudo contribuiu para a caracterização da morfologia ocular e para o estabelecimento de valores de referências de testes diagnósticos oftálmicos em corujas-orelhudas, sendo necessário ainda o desenvolvimento de estudos complementares sobre histologia ocular desta espécie.

Conjunctival flora, Schirmer's tear test, intraocular pressure, and conjunctival cytology in neotropical primates from Salvador, Brazil

BACKGROUND

This study aimed to establish reference values for selected ophthalmic diagnostic tests in healthy neotropical primates from Salvador, Brazil.

METHODS

A total of 73 intact adults, including Callithrix jacchus (n = 31), Callithrix penicillata (n = 8), Cebus sp. (n = 22), and Cebus xanthosternos (n = 9) were used to evaluate the normal conjunctival bacterial flora. Cebus xanthosternos (n = 12) were used to evaluate tear production with Schirmer's tear test (STT), intraocular pressure (IOP), and conjunctival cytology.

RESULTS

For all animals evaluated, Gram-positive bacteria were predominant. Results of the diagnostic tests in Cebus xanthosternos were as follows: STT: 14.92 ± 5.46 mm/minutes, IOP: 19.62 ± 4.57 mmHg, and conjunctival cytology revealed intermediate squamous epithelial cells in great quantities.

CONCLUSIONS

These ophthalmic reference values will be particularly useful to diagnose discrete or unusual pathological changes in the neotropical primates eye.

Evaluation of intraocular pressure in conscious Hermann's tortoises (Testudo hermanni) by means of rebound tonometry

OBJECTIVE

To determine intraocular pressure (IOP) in healthy Hermann's tortoises (Testudo hermanni).

ANIMALS

26 outdoor-housed Hermann's tortoises (13 males and 13 females); body weight ranged from 255 to 2,310 g, and age ranged from 4 to > 50 years.

PROCEDURES

After a preliminary ophthalmic evaluation was performed, IOP was measured by means of a rebound tonometer in both eyes of each tortoise. Three measurements were obtained for each eye; successive measurements were obtained from alternate eyes. Each measurement was based on the mean of 6 values automatically provided by the rebound tonometer. Statistical analysis was used to evaluate correlations between variables and to identify sex- or size-related IOP variations, and changes in IOP over multiple measurements.

RESULTS

Mean ± SEM IOP of the 52 eyes was 15.74 ± 0.20 mm Hg (range, 9 to 22 mm Hg). Results for t tests did not reveal significant differences in IOP between the right and left eyes or between males and females. A significant moderate negative correlation (r = -0.41; r(2) = 0.169) between IOP and body weight was detected. Results of repeated-measures ANOVA revealed a significant increase in IOP over multiple measurements.

CONCLUSIONS AND CLINICAL RELEVANCE

Rebound tonometry was a practical and rapid means of determining IOP in small- to medium-sized tortoises that required minimal manual restraint of the animals. Establishing IOP values in healthy Hermann's tortoises will provide a reference frame for use during complete ophthalmic examinations, thus allowing clinicians to diagnose a broader spectrum of ocular pathological conditions in tortoises.

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 Schirmer's 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 Schirmer's 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.