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

Normal Range for the Schirmer Tear Test and Intraocular Pressure in Healthy Latvian Darkhead Lambs and Ewes

A complete ophthalmological examination, including basic diagnostic tests such as the Schirmer tear test (STT) and intraocular pressure (IOP) measurement performed by tonometry in particular species and breeds, is essential for obtaining a clear diagnostic result and avoiding diagnostic misinterpretations. STT and IOP values have been poorly described for sheep. Therefore, this study aimed to determine the normal range for STT and tonometry values in clinically normal Latvian Darkhead lambs and ewes. Both eyes of 100 sheep (200 eyes)-50 lambs (1-3 months old) and 50 ewes (1-8 years old)-underwent complete ophthalmic examinations, including STT and IOP evaluation. The mean ± standard deviation of STT values for both eyes in lambs and ewes were 13.12 ± 3.91 mm/min and 13.68 ± 4.09 mm/min, respectively. The IOP in lambs and ewes was 14.04 ± 3.68 mmHg and 19.16 ± 3.24 mmHg, respectively. Furthermore, the suggested reference range for the STT was 12.00-14.23 mm/min in lambs and 12.52-14.84 mm/min in ewes, while the reference IOP range was determined to be 13.00-15.08 mmHg in lambs and 18.24-20.08 mmHg in ewes. No statistically significant differences in STT and IOP values were observed for both eyes. However, the IOP value for both eyes was statistically significantly higher in ewes compared to lambs (p < 0.01). This study provides reference values for the STT and IOP in healthy Latvian Darkhead lambs and ewes.

Ultrasound, Dacryocystorhinography and Morphological Examination of Normal Eye and Lacrimal Apparatus of the Donkey (Equus asinus)

The study investigated normal macromorphological and ultrasonographic features of the eye and lacrimal gland, as well as normal dacryocystorhinography of the donkey (Equus asinus) in Egypt. A total of 36 donkeys of different ages, weights, and sexes were included in the study: 21 live animals for ultrasonography and dacryocystorhinography, and 15 cadaver skulls for morphological anatomy of the lacrimal apparatus. The ultrasound biometric values of the eye were 33.7 ± 1.7 mm for axial globe length (AGL), 39.8 ± 2.1 mm for globe diameter (GD), 10.8 ± 0.7 mm for lens thickness (LT), 3.2 ± 0.7 mm for anterior chamber depth (ACD), and 19.3 ± 1.6 mm for vitreous chamber depth (VCD). The lacrimal gland was recognized as a hypoechogenic structure with an anechoic core, located at the dorsolateral aspect of the orbit, and ovoid in shape. The mean NLD length was 193.0 ± 9.8 mm by radiography and 206.0 ± 20.4 mm by gross assessment. One NL orifice (NLO) was noticed on each side, with a diameter of 3.0 ± 0.1 mm and located 12.1 ± 2.1 mm from the dorsal commissure of the nostril. These results may act as the baseline for proper management of conditions of the eye and lacrimal apparatus in the donkey in the future.

The relative importance of phylogeny and habitat in determining the presence and prominence of a granula iridica in hooved mammals

PURPOSE

To investigate the relationship between phylogeny and amount of shade in a species' habitat regarding the presence or absence of an iridal granula iridica (GI) in a large sample of Artiodactyl and Perissodactyl clades and using online resources.

METHODS

The Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) archives were searched for glass slide material from Artiodactyl (even-toed) and Perissodactyl (odd-toed) ungulates. The slides were examined, and the presence or absence of the GI was noted. The phylogenetic tree of the ungulate species was inferred using TimeTree (http://www.timetree.org), and the habitat data are derived from Animal Diversity Web (https://animaldiversity.org/). We assessed the probability of the presence of GI occurring given the amount of shade in a species' environment using phylogenetic logistic regression.

RESULTS

Forty-eight artiodactyl species were able to be evaluated and tabulated. Nine perissodactyl species were able to be evaluated. The phylogenetic logistic regression showed that the probability of GI presence was lower in artiodactyl species that inhabited shaded environments (β_shaded  = -1.774). Arctiodacyl species inhabiting a nonshaded environment were slightly more probable to have the GI present (β_nonshaded  = 0.023), with species inhabitating ambiguously shaded environments having a high probability of GI presence (β_ambiguous  = 2.214).

CONCLUSIONS

Our results suggest that the GI may be a common morphological feature to shade the pupil in nonshaded environments, and, in its absence, increase the amount of light reaching the retina to improve vision in shaded environments for hooved mammals. Further research on the functional optics of the GI and studies that include additional ungulate species would further elucidate phylogenetic and ecological factors influencing the occurrence of GI in hooved mammals.

Reference values of Schirmer tear test in sheep and the effect of season on the test results

The aim of this study was to determine the reference range of Schirmer tear test (STT) values in sheep using Greek indigenous and mixed breeds and to investigate the potential effect of breed and season on these values. Ninety (30 Chios, 30 Florina and 30 Lacaune mixed breed) ewes aged 2 years or more were used for the study. The aqueous portion of the tear film was measured using Schirmer tear test (STT) commercial strips bilaterally by the same investigator with the animal in standing position. The average STT value recorded was 18.45 ± 3.93 mm/min and the range 10.8-26.2 mm/min. STT was significantly affected by the season and the recorded values were significantly higher in summer compared to winter. The breed had no significant effect on tear secretion. The results of the present study provide a reference range of STT values in sheep and indicate that tear secretion is significantly affected by the season.

Deep Genome Resequencing Reveals Artificial and Natural Selection for Visual Deterioration, Plateau Adaptability and High Prolificacy in Chinese Domestic Sheep

Sheep were one of the earliest domesticated animals. Both artificial and natural selection during domestication has resulted in remarkable changes in behavioral, physiological, and morphological phenotypes; however, the genetic mechanisms underpinning these changes remain unclear, particularly for indigenous Chinese sheep. In the present study, we performed pooled whole-genome resequencing of 338 sheep from five breeds representative of indigenous Chinese breeds and compared them to the wild ancestors of domestic sheep (Asian mouflon, Ovis orientalis) for detection of genome-wide selective sweeps. Comparative genomic analysis between domestic sheep and Asian mouflon showed that selected regions were enriched for genes involved in bone morphogenesis, growth regulation, and embryonic and neural development in domestic sheep. Moreover, we identified several vision-associated genes with funtional mutations, such as PDE6B (c.G2994C/p.A982P and c.C2284A/p.L762M mutations), PANK2, and FOXC1/GMSD in all five Chinese native breeds. Breed-specific selected regions were determined including genes such as CYP17 for hypoxia adaptability in Tibetan sheep and DNAJB5 for heat tolerance in Duolang sheep. Our findings provide insights into the genetic mechanisms underlying important phenotypic changes that have occurred during sheep domestication and subsequent selection.

Measurement of tear production and intraocular pressure in conscious captive European fallow deer (DAMA dama)

Normal values for intraocular pressure (IOP) and tear production in conscious cervids have not been reported to date. Based on trends in zoological institutions to perform non-anaesthetized health exams, it is applicable to establish normal values in conscious animals, as anaesthesia and sedation can alter these parameters. The goal of this study was to estimate intraocular pressures using rebound tonometry and measure tear production values in a group of healthy, conscious, European fallow deer utilizing chute restraint. Evaluation of these values with regards to instrumentation and restraint variables will be assessed. Complete ophthalmic examinations, including estimation of IOP with rebound tonometry and measurement of tear production with Schirmer tear tests (STT) were performed on nine conscious European fallow deer (Dama dama) restrained in a chute. Correlations between IOP on the unspecified (P) and the equine (H) settings, as well as IOP and STT differences between left (OS) and right (OD) eyes were evaluated, in addition to assessment of correlations between right and left lateral recumbency on IOP and STT. Tear production measurements were 18.7 ± 5.1 mm min-1 with a 95% confidence interval (CI) range of 16.4-21.1 mm min-1 . Intraocular pressure measurements for the P setting were 16.1 ± 4.5 mmHg with a 95% CI range of 14.1-18.2 mmHg, and for the H setting were 21.5 ± 5.1 mmHg with a 95% CI range of 19.1-23.9 mmHg. No statistically significant difference (P > 0.05) was found between OS and OD in any test. Neither left nor right lateral recumbency was found to have a statistically significant effect on IOP or STT. This study represents the first assessment of ophthalmic parameters in conscious fallow deer with rebound tonometry and STT.

Tear production, intraocular pressure and conjunctival bacterial flora in selected captive wild ruminants

OBJECTIVE

Evaluation of tear production (Schirmer's tear test, STT) and measurement of intraocular pressure (IOP) were performed in a population of captive wild ungulates in a Slovenian ZOO during routine annual health check.

ANIMALS STUDIED

In total, 10 fallow deer (Dama dama), 25 mouflons (Ovis aries musimon), 20 alpine ibexes (Capra ibex), and three alpine chamois (Rupicapra rupicapra) were included in the study.

METHODS

Tear production was performed by Schirmer's tear test, IOP was measured with an applanation tonometer, and ophthalmological examination was conducted with slit-lamp biomicroscopy and indirect ophthalmoscopy. Conjunctival swabs were taken and submitted for aerobic bacteriology and for detection of Chlamydia spp. and Mycoplasma spp. tested by PCR.

RESULTS

Average tear production (in mm/min) was 17.8 ± 3.16 for fallow deer, 17.9 ± 3.87 for mouflons, and 11.7 ± 3.87 for ibexes. Mean intraocular pressure (IOP, in mm Hg) was 14.1 ± 2.48 for fallow deer, 14.9 ± 2.20 for mouflons, and 13.1 ± 2.43 for ibexes. For chamois, average tear production and IOP were 14.5 ± 3.0 and 10.2 ± 2.5, respectively; this is the first record of STT I and IOP in chamois. Bacteriological swabs were positive for bacteria in 100% of the fallow deer, 56% of mouflons, 35% of ibexes, and 100% of chamois. Gram-positive bacteria were predominant. Moraxella spp., Chlamydia spp., and Mycoplasma spp. were not detected.

CONCLUSION

The reported values were obtained in animals under manual restraint only to be applicative in similar conditions.