Intraocular pressure in normal dairy cattle

3D immuno-confocal image reconstruction of fibroblast cytoskeleton and nucleus architecture

Computational models of cellular structures generally rely on simplifying approximations and assumptions that limit biological accuracy. This study presents a comprehensive image processing pipeline for creating unified three-dimensional (3D) reconstructions of the cell cytoskeletal networks and nuclei. Confocal image stacks of these cellular structures were reconstructed to 3D isosurfaces (Imaris), then tessellations were simplified to reduce the number of elements in initial meshes by applying quadric edge collapse decimation with preserved topology boundaries (MeshLab). Geometries were remeshed to ensure uniformity (Instant Meshes) and the resulting 3D meshes exported (ABAQUS) for downstream application. The protocol has been applied successfully to fibroblast cytoskeletal reorganisation in the scleral connective tissue of the eye, under mechanical load that mimics internal eye pressure. While the method herein is specifically employed to reconstruct immunofluorescent confocal imaging data, it is also more widely applicable to other biological imaging modalities where accurate 3D cell structures are required.

Ocular echobiometry and head measurements in Jersey cattle from different age groups

A longitudinal study was conducted to identify the morphological development of eyes and head of Jersey cattle at different ages. A total of 48 healthy Jersey cattle, 1 to 58 months of age, were included in the study. Ophthalmologic examinations were performed to identify healthy cattle to form the age groups: GI (1- to 11-month-old), GII (16- to 24-month-old) and GIII (25- to 58-month-old). The animals were physically restrained and examined by transcorneal ultrasound of both eyes; the axial length (AxL), corneal thickness (CO), lenticular thickness (L), depth of the anterior (AC) and vitreous (VC) chambers were evaluated. The cranial measurements obtained included the total, cranial, and nasal lengths and widths. Subsequently, the cephalic index (CI) was calculated. The AxL (GI: 2.83 cm; GII: 3.16 cm; GIII: 3.24 cm), AC (GI: 0.44 cm; GII: 0.53 cm; GIII: 0.53 cm), L (GI: 0.88 cm; GII: 1.01 cm; GIII: 1.04 cm) and VC (GI: 1.44 cm; GII: 1.55 cm; GIII: 1.59 cm) increased (p ≤ .001) according to age, but the CO (GI: 0.07 cm; GII: 0.08 cm; GIII: 0.08 cm) (p > .05) did not. The total length (GI: 30.83 cm; GII: 43.29 cm; GIII: 44.15 cm), cranial length (GI: 18.11 cm; GII: 23.82 cm; GIII: 22.69 cm), nasal length (GI: 12.72 cm; GII: 19.47 cm; GIII: 21.46 cm) and nasal width (GI: 26.22 cm; GII: 33.82 cm; GIII: 34.00 cm) increased (p < .001), and the CI (GI: 85.66 cm; GII: 78.15 cm; GIII: 77.02 cm) decreased (p < .001). The AxL correlated positively (p < .001) with the cranial length and width and negatively with the CI (p > .05). The ocular biometry of Jersey cattle correlates with their cranial measurements at different ages. With increasing age, the eyes and the head grow, establishing growth curves similar to those of other mammals.

Gross anatomy, histological, and histochemical analysis of the eyelids and orbital glands of the neonate pygmy hippopotamus (Suina: Choeropsis liberiensis or Hexaprotodon liberiensis, Morton 1849) with reference to its habitat

The pygmy hippopotamus is phylogenetically related to members of both the Suidae and Cetacea. However, differences in their habitats may have resulted in variation in the anatomy and physiology of the ocular adnexa between these species. Therefore, this study focuses on the identification of accessory organs of the eye, which are typical for the pygmy hippopotamus and are comparable to organs present in mammals related to it. Moreover, the secretions produced by the superficial gland of the third eyelid, the deep gland of the third eyelid and the lacrimal gland were examined, as they ensure eyeball protection. In the upper and lower eyelids, numerous serous glands where identified, which were typical for the pygmy hippopotamus and similar as in the Cetacea. This study enabled to identify additional folds in the eyelids of the pygmy hippopotamus. Lymphoid follicles and diffuse lymphocytes were not found in the lymphoid region in the upper or lower eyelids and the third eyelid, which was most likely caused by the age of the studied hippopotamuses. An accurate histochemical analysis revealed that the secretions of the pygmy hippopotamus are very similar to the Sus scrofa. The structural differences between the pygmy hippopotamus and representatives of Cetacea are most likely caused by the fact that most of Cetacea live in saltwater and are exposed to more frequent fluctuations in water temperature compared to the pygmy hippopotamus, which lives in fresh water and does not lead a migratory lifestyle like the Cetacea.

Dose-dependent effect of romifidine on intraocular pressure in clinically healthy buffalo (Bubalus bubalis)

In the present study, changes in intraocular pressure (IOP) associated with romifidine sedation in buffalo were evaluated. Eighteen healthy adult, non-pregnant, buffalo without ocular abnormalities were used in a prospective randomized trial. Buffalo were allocated into three groups (six each). Buffalo in the treated groups received an intramuscular injection (IM) of romifidine at 40 or 50 μg/kg. The control group was administrated an equivalent volume of sterile saline (0.9% NaCl; 0.4 ml/100 kg). Baseline IOP (T0) values were obtained using applanation tonometry. Immediately afterwards, romifidine was administered and IOP values of both eyes were measured at 5, 15, 30, 45, 60, 90, 120, and 180 min post-administration. The pre-administration values (T0) of IOP for both the left and right eyes ranged from 30-36 (mean, 33 ± 1.5) mmHg and 30–35 (mean, 33.7 ± 1.4), respectively. IOP values decreased significantly after administration of both doses of romifidine compared with the placebo (P < 0.01). Compared with the control, the IOP decreased significantly in animals treated with both doses from 5-90 min post-administration in both eyes (P < 0.05). In the right eye, the lowest IOP value in the romifidine treated groups was observed at T30 (21.6 ± 1.0 and 23.3 ± 1.4 mmHg), respectively. In the left eye, the lowest IOP was observed at T60 (22.5 ± 3.0 and 23.3 ± 2.8 mmHg), respectively. In conclusion, romifidine could be recommended as an alternative analgesic in buffalo, especially for ocular affections associated with increased IOP. A dose of 40 μg/kg could be used at a low cost.

Avaliação da produção lacrimal, pressão intraocular, retinografia e biometria ocular em bovinos das raças Nelore e Gir hígidos

RESUMO No presente estudo, foram avaliados parâmetros oftalmológicos de 38 bovinos das raças Nelore (n= 19; grupo GN) e Gir (n= 19; grupo GG), machos, com idade média de 15 meses. Os exames oftalmológicos realizados foram teste lacrimal de Schirmer 1 (TLS-1), tonometria de aplanação, retinografia e biometria por ultrassonografia em modo B. Os resultados do TLS-1, tonometria de aplanação e biometria ocular foram avaliados por meio da análise de variância (ANOVA), e as médias comparadas pelo teste de Tukey. Para o exame de retinografia, foi realizada a análise descritiva das estruturas anatômicas. O TLS-1 e a tonometria não diferiram (P≥0,05) nas comparações entre os olhos e entre os grupos raciais. A retinografia permitiu a visualização do disco óptico, dos vasos retinianos, do fundo tapetal e não tapetal, sem constatação de diferenças anatômicas entre as raças. Por meio da biometria ocular, foram observados valores maiores nos animais da raça Gir para as medidas do comprimento axial (CAx), da espessura da lente (EL) e da profundidade da câmara vítrea (CV), em ambos os eixos, horizontal (CAH) e vertical (CAV). Os exames oftalmológicos realizados podem ser executados a campo sem comprometer o bem-estar dos animais. Somente na ultrassonografia em modo B foram identificadas diferenças entre os bovinos das raças Nelore e Gir.

The effect of body position on intraocular pressure in calves

Tonometry is one of the basic diagnostic tests used for the diagnosis of glaucoma and uveitis in veterinary ophthalmology. The Icare^® Rebound Tonometer which is a new tonometric device has been shown to be useful in a wide range of species. Eyes (n = 48) of 24 Simmental and Montafon calves with a mean age of 7.5 weeks (2–16 weeks), male and female, were subjected to intraocular pressure (IOP) measurement using the Icare^® Rebound Tonometer with calves standing and in lateral recumbency. The mean IOP was measured as 9.02 ± 2.38 mmHg in the right eye and 9.08 ± 2.55 mmHg in the left eye. No age-related change was found in intraocular pressure of the calves between 2 and 16 weeks of age. No difference in IOP values was observed between Simmental and Montafon calves. Body position had no effect on IOP in calves. The Icare^® Rebound Tonometer was shown to be a suitable diagnostic device for IOP measurement in calves.

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.

Noninvasive Intraocular Pressure Measurement in Animals Models of Glaucoma

Intraocular pressure (IOP) elevation is a critical risk factor for development and progression of glaucoma. As such, measuring IOP in animal models of the disease is important for any research work trying to understand the pathophysiologic mechanisms of glaucoma. Noninvasive IOP measurement in animals uses methods that have been adapted from use on humans. Calibration of the instruments used for the specific animal and even strain used is critically important for allowing meaningful comparisons of results. We describe below the methods used for noninvasive IOP measurement in animals that are relevant to glaucoma research.

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.

Bilateral buphthalmia in a 4-month-old Texas longhorn steer

Congenital ocular disease occurs uncommonly in cattle, with multiple abnormalities reported only sporadically in the literature. This report describes a case of anterior segment dysgenesis resulting in glaucoma in a 4-month-old Texas Longhorn steer. On clinical exam, bilateral buphthalmia was present and intraocular pressures exceeded 47 mm Hg in both eyes. On histopathologic examination, the iridocorneal angle and filtration apparatus were distorted due to collapse of the ciliary cleft and anterior displacement of the anterior portion of the ciliary body. No evidence of inflammation or other causes of glaucoma were recognized.

Evaluation of the Perkins handheld applanation tonometer in horses and cattle

The objective of this study was to evaluate and validate the accuracy of the Perkins handheld applanation tonometer for measuring intraocular pressure (IOP) in horses and cattle. Both eyes of 10 adult horses and cattle were evaluated in a postmortem study. The eyes from 10 clinically normal adult horses and cattle were also examined after bilateral auriculopalpebral nerve block and topical anesthesia for an in vivo study. IOP was measured postmortem using direct manometry (measured with an aneroid manometer) and tonometry (measured with a Perkins handheld applanation tonometer). The correlation coefficients (r(2)) for the data from the postmortem manometry and Perkins tonometer study were 0.866 for horses and 0.864 for cattle. In the in vivo study, IOP in horses was 25.1 ± 2.9 mmHg (range 19.0~30.0 mmHg) as measured by manometry and 23.4 ± 3.2 mmHg (range 18.6~28.4 mmHg) according to tonometry. In cattle, IOP was found to be 19.7 ± 1.2 mmHg (range 18.0~22.0 mmHg) by manometry and 18.8 ± 1.7 mmHg (range 15.9~20.8 mmHg) by tonometry. There was a strong correlation between the IOP values obtained by direct ocular manometry and the tonometer in both horses and cattle. Our results demonstrate that the Perkins handheld tonometer could be an additional tool for accurately measuring IOP in equine and bovine eyes.

An inverse finite element method for determining the anisotropic properties of the cornea

An inverse finite element method was developed to determine the anisotropic properties of bovine cornea from an in vitro inflation experiment. The experiment used digital image correlation (DIC) to measure the three-dimensional surface geometry and displacement field of the cornea at multiple pressures. A finite element model of a bovine cornea was developed using the DIC measured surface geometry of the undeformed specimen. The model was applied to determine five parameters of an anisotropic hyperelastic model that minimized the error between the measured and computed surface displacement field and to investigate the sensitivity of the measured bovine inflation response to variations in the anisotropic properties of the cornea. The results of the parameter optimization revealed that the collagen structure of bovine cornea exhibited a high degree of anisotropy in the limbus region, which agreed with recent histological findings, and a transversely isotropic central region. The parameter study showed that the bovine corneal response to the inflation experiment was sensitive to the shear modulus of the matrix at pressures below the intraocular pressure, the properties of the collagen lamella at higher pressures, and the degree of anisotropy in the limbus region. It was not sensitive to a weak collagen anisotropy in the central region.

Full-field deformation of bovine cornea under constrained inflation conditions

The viscoelastic response of bovine corneas was characterized using in vitro inflation (bulge) experiments combined with spatially-resolved deformation mapping via digital image correlation. A complex fixture conforming to the limbal annulus was developed to hold the attached sclera rigid while allowing deformation only in the cornea. A statistical set of experiments was performed for a pressure range of 3.6-8 kPa (27-60 mmHg), representing nominal bovine intraocular pressure (IOP) to acute glaucoma conditions. A broader pressure range of 0-32 kPa (0-240 mmHg) was also examined to characterize the nonlinear finite deformation behavior of the tissue. Results showed that for pressures near and above IOP, the majority of the deformation was localized in the limbus and peripheral regions, which left the central cornea largely undeformed. This observation was consistent with the known preferred circumferential alignment of collagen fibrils outside of the central cornea. In general, the inflation experiments observed viscoelastic behavior in the form of rate-dependent hysteresis in the pressure-deformation response of the apex of the cornea, creep in the apex deformation at a constant inflation pressure, and relaxation in the pressure response at a constant inflation volume. The 3.6-8 kPa (27-60 mmHg) pressure range produced small viscoelastic deformations and a nearly linear pressure-deformation response, which suggests that for physiological pressure ranges, the cornea can be approximated as a linear viscoelastic or linear pseudo-elastic material.

Ophthalmic examination findings in adult pygmy goats (Capra hicus)

OBJECTIVE

To document normal ophthalmic findings and ocular abnormalities in captive adult pygmy goats.

ANIMALS STUDIED

Ten healthy adult pygmy goats (five male, five female; 5-11 years of age; 26-45 kg body mass) underwent complete ophthalmic examinations.

PROCEDURE

Direct illumination, diffuse and slit-beam biomicroscopy, indirect ophthalmoscopy, IOP measurements and Schirmer tear tests were performed. TonoVet rebound tonometry, followed by topical application of 0.5% ophthalmic proparacaine, and Tono-Pen XL applanation tonometry were performed in each eye to obtain estimates of IOP.

RESULTS

Ophthalmic abnormalities included corneal scars and pigmentation, incipient cataracts, lenticular sclerosis, and vitreal veiling. Mean STT values were 15.8 mm/min, with a range of 10-30 mm/min. Mean IOP values were 11.8 mmHg for TonoVet-D, with a range of 9-14 mmHg; 7.9 mmHg for TonoVet-P, with a range of 6-12 mmHg; and 10.8 mmHg for Tono-Pen XL, with a range of 8-14 mmHg.

CONCLUSIONS

Ophthalmic examination findings in adult pygmy goats, including normal means and ranges for STT and IOP measurements, using applanation and rebound tonometry, are provided.

Central corneal thickness in koi fish: effects of age, sex, body length, and corneal diameter

OBJECTIVE

To establish the central corneal thickness (CCT) of normal koi fish by ultrasonic pachymetry, and its relationship to age, sex, body length and corneal diameter.

METHODS

Age, sex and body length of 33 koi fish (17 male and 16 female fish) were recorded. Horizontal and vertical corneal diameters of each eye were obtained using Jameson calipers. Central corneal thickness of all eyes was measured by ultrasonic pachymetry. Intraocular pressure (IOP) by rebound tonometry was obtained for a subgroup of nine koi (18 eyes).

RESULTS

Mean central corneal thickness was 325.9 microm. Central corneal thickness of female koi was greater than CCT of male fish (P < 0.01). Central corneal thickness increased with increasing age overall and within both sexes (P < 0.01). Central corneal thickness increased with increasing body length (P < 0.001). For male and female fish, CCT increased with increasing horizontal and vertical corneal diameters (P < 0.01). Mean horizontal corneal diameter (HCD) was 8.05 mm, mean vertical corneal diameter (VCD) was 7.38 mm, and HCD was consistently greater than VCD. Mean IOP of a subgroup of these koi was 4.9 mmHg by rebound tonometry.

CONCLUSIONS

Koi CCT increases with increasing age, body length and corneal diameter.

Normal ocular features, conjunctival microflora and intraocular pressure in the Canadian beaver (Castor canadensis)

OBJECTIVE

The aim of the study was to assess the ocular features, normal conjunctival bacterial and fungal flora, and intraocular pressure (IOP) in the Canadian beaver (Castor canadensis).

SAMPLE POPULATION

Sixteen, apparently healthy beavers with no evidence of ocular disease, and live-trapped in regions throughout Prince Edward Island.

PROCEDURES

The beavers were sedated with intramuscular ketamine (12-15 mg/kg). Two culture specimens were obtained from the ventral conjunctival sac of both eyes of 10/16 beavers for aerobic and anaerobic bacterial and fungal identifications. The anterior ocular structures of all beavers were evaluated using a transilluminator and slit lamp biomicroscope. Palpebral fissure length (11/16 beavers), and horizontal and vertical corneal diameters (10/16 beavers) were measured. IOPs were measured in both eyes of 11/16 beavers using applanation tonometry. Both eyes of 3/16 beavers and one eye of 1/16 beavers were dilated using topical tropicamide prior to sedation to effect timely maximal dilation. Culture specimens and IOPs were not evaluated in these four animals. Indirect ophthalmoscopy was performed on 7/8 eyes of these four beavers.

RESULTS

Conjunctival specimens from all eyes cultured positively for one or more isolates of aerobic bacteria. The most common isolate was Micrococcus spp. (five beavers; 9/20 eyes). Other isolates included a Gram-positive coccobacilli-like organism (four beavers; 7/20 eyes), Aeromonas hydrophila (three beavers; 4/20 eyes), Staphylococcus spp. (three beavers; 4/20 eyes), Gram positive bacilli (one beaver; 2/20 eyes), Enterobacter spp. (two beavers; 2/20 eyes), Streptococcus spp. (two beavers; 2/20 eyes), aerobic diphtheroids (one beaver; 1/20 eyes), and Pseudomonas spp. (one beaver; 1/20 eyes). Clostridium sordellii (one beaver; 1/20 eyes) and Peptostreptococcus spp. (one beaver; 1/20 eyes) were the sole anaerobic bacteria isolated. All conjunctival specimens were negative for growth of fungi. Ophthalmic examinations revealed the normal beaver eye and ocular adnexa included dorsal and ventral puncta, a vestigial third eyelid, and a circular pupil. Average palpebral fissure length was 9.36 mm (SD = 1.00) for both eyes. Mean horizontal and vertical corneal diameters of both eyes were 9.05 mm (SD = 0.64) and 8.45 mm (SD = 0.69), respectively. Mean IOP for the right and left eyes were 17.11 mmHg (SD = 6.39) and 18.79 mmHg (SD = 5.63), respectively. Indirect ophthalmoscopic examinations revealed normal anangiotic retinas.

CONCLUSIONS

Gram-positive aerobes were most commonly cultured from the conjunctival sac of normal beavers, with Micrococcus spp. predominating. The overall mean IOP in ketamine-sedated beavers was 17.95 mmHg. The beaver, an amphibious rodent, has an anangiotic retina.

Evaluation of intraocular pressure in eyes of clinically normal llamas and alpacas

OBJECTIVE

To estimate intraocular pressure (IOP) in eyes of healthy camelids, using applanation tonometry.

ANIMALS

The eyes of 34 camelids (16 llamas [Lama glamal and 18 alpacas [L. pacos]) that did not have major abnormalities of the ocular surface or intraocular abnormalities.

PROCEDURE

Tonometry measurements were obtained from each eye 3 times during a 24-hour period. Each measurement was the mean of several corneal applanations obtained by use of an applanation tonometer. Data were analyzed, using an ANOVA for a repeated-measures design.

RESULTS

Mean (+/- SEM) IOP of llamas and alpacas was 13.10+/-0.35 and 14.85+/-0.45 mm Hg, respectively. Range of IOP was 7 to 18 mm Hg for llamas and 11 to 21 mm Hg for alpacas. Mean IOP of llamas was significantly less than the mean IOP of alpacas. Significant differences in IOP were not detected between the right and left eye of animals. Significant differences in IOP were not attributed to sex, age, or time of measurement within llamas or alpacas.

CONCLUSIONS AND CLINICAL RELEVANCE

Establishing the mean and range of IOP of clinically normal llamas and alpacas provides a frame of reference that is important for use in a complete ophthalmic examination of camelids, which can assist clinicians in the diagnosis of glaucoma and uveitis. Reasons for the difference in mean IOP between llamas and alpacas are unknown. Although the difference may be unimportant clinically, this finding reiterates the fact that caution must be used when extrapolating IOP among species.