Normal Canine Eyes Research Articles

Validation of the Reichert® Tono-Vera® Vet rebound tonometer in normal exvivo canine eyes.

To determine the accuracy of the Reichert® Tono-Vera® Vet rebound tonometer for canine intraocular pressure (IOP) measurement. Five normal canine exvivo globes. The anterior chambers of five freshly enucleated normal canine eyes were cannulated and connected to a reservoir of Plasma-Lyte A and a manometer. Starting at a manometric IOP of 5 mmHg, the pressure was progressively increased to 80 mmHg by raising the reservoir. Triplicate IOP measurements were taken with the Tono-Vera® Vet from the central cornea using the dog setting and compared to the manometric pressure by linear regression analysis and Bland-Altman plots. There was a strong positive linear regression trend when comparing central corneal Tono-Vera® Vet IOPs to manometric pressures (r2 = .99) with solid agreement between the two methods. Compared to manometric IOPs, the Tono-Vera® Vet underestimated IOPs at higher pressures ≥70 mmHg. Measurement of IOPs from the central cornea with the Tono-Vera® Vet provided accurate results over a large range in normal canine globes compared to direct manometry. The mild to moderate underestimation of IOPs at high pressures was not considered clinically relevant.

Validation of the eyeTelemed IOPvet indentation tonometer for use in dogs.

To assess the accuracy of canine intraocular pressure (IOP) estimates from the eyeTelemed IOPvet indentation tonometer. Part 1 included 54 eyes from 28 Beagle dogs-23 ADAMTS10-mutants with open-angle glaucoma and 5 normals. Part 2 involved five normal canine exvivo globes. Part 1 (in vivo) compared IOPvet estimates in normal and glaucomatous dogs to Reichert Tono-Vera® Vet rebound tonometry. The three IOPvet estimates were green (normal; <20 mmHg, according to the manufacturer), yellow (elevated; 20-30 mmHg), and red (high; >30 mmHg). In Part 2 (ex vivo), the pressure inside freshly enucleated normal canine eyes was progressively increased from 5 to 80 mmHg and compared to IOPvet estimates. Descriptive statistics compared IOPvet estimates to rebound tonometry and direct manometry, with the threshold from normal to glaucoma set at 30 mmHg. In Part 1 (in vivo), normal pressures (≤30 mmHg) were mainly identified correctly as green or yellow-110 of 111 estimates, corresponding to a specificity of 99%. Only 16 of 125 affected estimates were correctly displayed in the >30-mmHg range; the remaining 109 showed ≤30 mmHg, corresponding to a sensitivity of 13%. In Part 2 (ex vivo), all normal pressures were correctly estimated with green, but 64 of 88 manometric IOPs >30 mmHg were falsely estimated as 20-30 mmHg. The IOPvet is inaccurate in estimating canine IOP with a low sensitivity at identifying dogs with IOP > 30 mmHg. Canine-specific instrument revision is required to correctly identify elevated (yellow = 20-30 mmHg) and high (red >30 mmHg) IOPs.

Comparative effects of latanoprost and latanoprostene bunod on intraocular pressure and pupil size in ophthalmologically normal Beagle dogs.

To compare effects of latanoprost, a topical prostaglandin analogue (PGA) commonly used to treat glaucoma and lens instability in dogs, and latanoprostene bunod, a novel PGA with a nitric oxide-donating moiety, on intraocular pressure (IOP) and pupil diameter (PD). Ten ophthalmologically normal Beagle dogs. Dogs were treated twice a day for 5days in a randomly selected eye with either latanoprost or latanoprostene bunod. After a 6-week washout period, dogs were treated with the opposite drug. IOP and PD were measured at treatment times, at midday on days 1 and 5, and for 6days post-treatment. Both drugs significantly decreased IOP and PD. At midday on day 5 of treatment, mean IOP in eyes treated with latanoprost was 4.5mmHg lower than the fellow eye and 3.0mmHg lower than the same eye at baseline, while mean IOP in eyes treated with latanoprostene bunod was 5.5mmHg lower than the fellow eye and 3.6mmHg lower than baseline. Mean PD was 0.94mm in eyes treated with latanoprost and 0.76mmHg in eyes treated with latanoprostene bunod. There was no significant difference between the two drugs for either parameter at that time point (p=.372 and .619, respectively, for IOP relative to control and to baseline; p=.076 for PD) or when analyzed longitudinally. Significant diurnal variation in PD was noted and may have implications for treatment of lens' instability. Latanoprost and latanoprostene bunod produce similar IOP reduction and miosis in normal canine eyes.

3T high-resolution magnetic resonance imaging, conventional ultrasonography and ultrasound biomicroscopy of the normal canine eye

BackgroundAdvances in MRI coil technology and increased availability of high-field MRI in veterinary medicine enable the acquisition of images of increasingly high spatial resolution while preserving signal-to-noise ratio.The purpose of the present study was to compare 3T high-resolution magnetic resonance imaging (HR-MRI) with ultrasound (US) and ultrasound biomicroscopy (UBM) in the normal canine eye, to assess its potential to depict normal ocular anatomy.ResultsHR-MRI was compared with US and UBM in 10 eyes from 10 healthy beagle dogs. Ocular structures (cornea, anterior chamber, iridocorneal angle, iris, lens, ciliary body, choroid, vitreous body, posterior wall of the eye, optic nerve and optic nerve sheath, extraocular muscles) were assessed subjectively and central corneal thickness (CCT), anterior chamber depth (ACD), aqueous depth (AQD), anteroposterior, mediolateral and dorsoventral lens diameter (APLD, MLLD, DVLD), anteroposterior diameter of the globe including and excluding the scleroretinal rim (APDSRR, APD), vitreous chamber depth (VCD) and optic nerve sheath diameter (ONSD) were measured in HR-MRI and in US. Optic nerve diameter (OND) was measured in HR-MRI. HR-MRI and UBM appearance of the anterior segment were subjectively compared. Detailed reference high-resolution MRI images of normal eyes of Beagle dogs are provided.ConclusionsHR-MRI allowed assessment of all structures identified with US and UBM. The MRI examinations were performed under general anesthesia with the addition of a neuromuscular blocking agent, while US and UBM examinations were performed in conscious animals. Visibility of the entire ocular wall, the lens, the structures caudal to the ciliary body and the optic nerve and its sheath was superior with HR-MRI. HR-MRI allowed the distinction of retina, choroid and sclera, and the delineation of structures not previously identified in canine eyes with MRI, including Tenon’s capsule and the sub-Tenon’s space.Plane selection was more accurate with HR-MRI compared to US. In general, the range of measurements was narrower for MRI than for US. CCT, AQD, APLD, MLLD, APD, APDSRR and ONSD differed significantly between HR-MRI and US, respectively (p = 0.005-0.027).Micro-MRI may be useful for the assessment of ocular pathologies in the future.

Magnetic resonance imaging of the normal canine eye using a T1‐weighted volumetric acquisition

MRI is becoming increasingly available within the veterinary profession, and eyes are frequently included as part of a cranial study. The advantages of volumetric imaging are numerous, when compared to traditional two-dimensional imaging, and could be utilised within the veterinary setting. This report describing the normal MRI appearance of the canine eye, aimed to establish a standard reference range on a T1w volumetric acquisition. This study retrospectively assessed 62 eyes from 31 dogs that had undergone MRI at the Small Animal Hospital, Langford Vets, University of Bristol between 2016 and 2018 using a standardised MRI protocol. Dogs were excluded if they had presented with any reported ocular or orbital abnormalities. Measurements were performed from the 3D T1w volumetric sequence by a single observer using a previously published technique. Mean axial globe length was 2.13 cm and equatorial width 2.16 cm. Mean anteroposterior depth of the anterior chamber was 0.40 cm and 0.97 cm for the vitreous chamber. The mean anteroposterior and equatorial distance of the lens was 0.75 cm and 1.15 cm, respectively. Mean optic nerve width was 0.15 cm, and the mean width of the entire optic nerve sheath was 0.43 cm. Statistically significant relationships were noted between age and axial globe length and both lens dimensions. Highly significant relationships were noted between all variables, except lens dimensions and body weight Conclusion: This study provides reference values to assist in the interpretation of ocular structures during MRI on a T1w volumetric acquisition.

Pilot study supporting the existence of novel lymphatic channels within the canine anterior uveal tract using Lyve-1 and CD31.

To demonstrate the existence of lymphatics in the canine anterior uvea using lymphatic-specific markers Lyve-1, Prox-1, and podoplanin, the endothelial cell marker CD31, and basement membrane matrix marker collagen IV. Prospective Study. Eight normal globes from animals euthanized for unrelated health problems. Sagittally cut serial sections of six normal canine eyes were immunofluorescence double-stained with Lyve-1 and CD31 and single-stained with colorimetric Prox-1 and collagen IV. Three serial sections from 2 additional eyes were cut in the coronal plane at the level of the ciliary body and immunofluorescence double-stained with Lyve-1 and CD31 to map lymphatic channel distribution. Lymphatics from normal canine lymph nodes were used for validation of podoplanin. Four of 6 of the sagitally sectioned eyes had Lyve-1-positive lymphatic-like structures that were distinct from CD31-positive blood vessels in the iris base and ciliary body. Both of the coronally sectioned globes had Lyve-1-positive lymphatic-like structures in the ciliary body. The location of these structures was evaluated and found to be diffusely present circumferentially around the ciliary body. These results support the existence of lymphatic channels in the anterior uveal tract of the canine eye. This could indicate the presence of a novel uveolymphatic outflow pathway, which may play a role in aqueous humor outflow. Future studies are needed to confirm the existence and elucidate the role of this proposed uveolymphatic outflow pathway and potentially develop novel treatment options for managing glaucoma.

Aqueous Angiography in Normal Canine Eyes.

PurposeTo conduct aqueous angiography (AA) using a clinically applicable technique in normal dogs and to compare findings to intravenous scleral angiography (SA).MethodsWe examined 10 canine cadaver eyes and 12 eyes from live normal dogs. A gravity-fed trocar system delivered 2% sodium fluorescein and 0.25% indocyanine green (ICG) intracamerally (IC) in cadaver eyes. In vivo AA was subsequently performed in one eye of each of the 12 dogs via IC bolus of ICG under sedation. The same 12 dogs received SA via intravenous ICG (mean ± SD) 10.7 ± 3.3 days later. Identical scleral sectors were imaged using a Spectralis confocal scanning laser ophthalmoscope.ResultsThe gravity-fed trocar system permitted visualization of the conventional aqueous humor outflow (CAHO) pathways in cadaver eyes, but not in vivo. Fluorescence was observed superonasally in four of the 10 cadaver eyes within 24.0 ± 3.6 seconds. A single IC bolus of ICG showed CAHO pathways in vivo, demonstrating sectoral outflow patterns in the superotemporal sclera in 10 of the 12 eyes within 35.0 ± 4.3 seconds; four of the 12 eyes exhibited pulsatile aqueous movement. SA exhibited fluorescence patterns comparable to AA with weak pulsatile aqueous humor outflow.ConclusionsAngiography (AA or SA) in dogs permits visualization of the CAHO pathway and its vascular components in vivo. AA may be a more useful modality to assess aqueous humor outflow.Translational RelevanceIntracameral AA has potential utility for evaluating CAHO in vivo in dogs, an important animal model species.

Tear film concentrations of topically applied 0.5% oxytetracycline ointment in normal canine eyes.

To determine the tear film levels of oxytetracycline in normal canine eyes after application of the ophthalmic ointment, Terramycin™ (0.5% oxytetracycline, polymyxin B sulfate), to guide appropriate treatment frequency. Ten research beagles. Ten research beagles with confirmed normal eyes were administered 0.02mL of Terramycin™ ophthalmic ointment onto the dorsal bulbar conjunctival surface of the right eye. Tear samples were collected via dye-less Schirmer tear strips at 2, 4, 6, 8, and 12hours post-administration. The sample for each timepoint was collected on a separate day, and concentrations of oxytetracycline were determined using high-performance liquid chromatography (HPLC). There was a semi-logarithmic decline in the median tear concentration of oxytetracycline. The median (2.5th and 97.5th percentiles) tear concentrations of oxytetracycline at 2, 4, 6, 8, and 12hours were 43.5μg/mL (11.1-302.2μg/mL), 28.7μg/mL (8.04-113.7μg/mL), 16.1μg/mL (4.96-37.7μg/mL), 9.2μg/mL (4.52-28.1μg/mL), and 6.11μg/mL (4.36-26.7μg/mL), respectively. Mean (±SD) drug recovery via HPLC was 88% (±7.5%). Ophthalmic Terramycin™ achieves a substantially higher tear level than the MIC for common bacterial corneal pathogens up to 12hours post-administration in normal eyes. Anti-collagenolytic tear levels were not achieved at the timepoints evaluated or with the manufacturer-prescribed dosing frequency. HPLC can be used to analyze tear concentrations of ophthalmic ointment formulations.

Tumour, but not Age-associated, Increase of Senescence Markers γH2AX and p21 in the Canine Eye

Senescent cells display an irreversible cell cycle arrest with resistance to apoptosis. They are known to accumulate with age in mice, monkeys and man, and are suspected to drive the development and progression of neoplasia. Eyes develop age-associated changes, most commonly in the retina, cornea and lens. The aim of this study was to test whether senescent cells increase with age in the canine eye in general and in the microenvironment of ocular tumours in particular. The senescence markers γH2AX and p21 were tested in young (n=10, age≤2 years) versus old (n=9, age range 9.5-12.4 years) canine eyes, as well as in the microenvironment of intraocular tumours, namely uveal melanocytomas (n=13) and ciliary body adenomas (n=9). To consider a potential association of senescence with biological behaviour, we compared the expression of both markers in tumour cells of benign uveal melanocytomas (n=13) versus malignant conjunctival melanomas (n=7). Canine eyes showed no age-dependent changes in senescent cells. However, a significant increase of the percentage of γH2AX- or p21-labelled cells was found in the retina, uvea and lens of tumour-bearing eyes. Tumour cells in conjunctival melanomas had a significantly increased percentage of p21-expressing cells compared with uveal melanocytomas. We conclude, that senescent cells do not accumulate with age in otherwise normal canine eyes and that a senescent microenvironment of intraocular tumours is unlikely to be age driven. In addition, as in man, the percentage of p21-positive cells was increased in melanomas, supporting the theory that malignant tumours may override the senescence-associated cell cycle arrest.

Contrast-enhanced ultrasonography for evaluation of blood perfusion in normal canine eyes.

This study was performed to evaluate ocular structures using contrast-enhanced ultrasonography (CEUS) in dogs to assess the feasibility of CEUS for investigating the blood perfusion of canine eyes. Eight purpose-bred beagles were used. Blood perfusion and vascularity of the right eye were evaluated using color Doppler, power Doppler, and CEUS with Sonazoid® . Vascular changes were quantitatively evaluated by measuring peak intensity, time to initial upslope, and time to peak from the ciliary body, iris, choroid, retina, and the retrobulbar region by CEUS. On CEUS images, all parts of the examined ocular structures were markedly enhanced and clearly identified from the adjacent region. After injection, the contrast agent initially flowed to the choroid and retina at 14.2seconds, then to the ciliary body and iris at 20seconds. The blood signal reached its peak intensity in the ciliary body at 27.2seconds (47.4±10.63), in the iris at 31.6seconds (74.00±41.85), and in the retrobulbar region at 23.4seconds (149±24.59). The optic nerve was clearly distinguished from the retrobulbar region over 5minutes after the initiation of CEUS. Significantly, more vascular signals were detected in the ciliary body and iris by CEUS than by color and power Doppler. Blood perfusion of the intraocular structures and the retrobulbar region can be quantitatively and qualitatively analyzed by CEUS. CEUS may be a useful, noninvasive, and sensitive tool for the evaluation of blood perfusion in ocular diseases.

Evaluation of three hand-held tonometers in normal canine eyes

Tonometry, an indirect measurement of intraocular pressure (IOP), is important for the diagnosis and management of glaucoma and uveitis. The aim of this study was to compare the performance of three hand-held tonometers in normal canine eyes. Eyes from cadavers of dogs without observable ocular disease were used to compare tonometric measurements with direct manometry over a range of 7.4–65mmHg. In vivo measurements using the three tonometers in both eyes of 12 healthy dogs were compared. All tonometers significantly underestimated manometric values both ex vivo and in vivo. One tonometer showed a small fixed bias over the range of IOP, whilst the other two tonometers had a negative proportional bias. The results of this study show that differences exist between handheld tonometers across the clinically relevant range of IOP, and that all underestimate manometric measurements.

Effects of topical flurbiprofen sodium, diclofenac sodium, ketorolac tromethamine and benzalkonium chloride on corneal sensitivity in normal dogs.

To evaluate corneal sensitivity by using the Cochet-Bonnet® esthesiometer in normal canine eyes at different time points following instillation of three different topical non-steroidal anti-inflammatory drugs (flurbiprofen sodium 0.03%, diclofenac sodium 0.1% and ketorolac tromethamine 0.5%) and benzalkonium chloride 0.01%. Six healthy mixed breed dogs from the same litter were used in two different stages. First, one drop of flurbiprofen sodium 0.03% and diclofenac sodium 0.1% in each eye; second, one drop of ketorolac tromethamine 0.5% and benzalkonium chloride 0.01% in each eye. Baseline esthesiometry was obtained before eye drop application and every 15 minutes thereafter until a total of 105 minutes of evaluation time. A one-week interval was allowed between the two treatment phases. Statistical analysis was used to compare means according to time of evaluation and drug used. Diclofenac sodium 0.1% decreased corneal sensitivity at 75 and 90 minutes (P > 0.015) with possible interference on neuronal nociceptive activity and analgesic effect while ketorolac tromethamine 0.5% did not show any variation for esthesiometry means along the evaluation. Flurbiprofen sodium 0.03% resulted in increased esthesiometry values 30 minutes after instillation (P > 0.013), increasing corneal sensitivity and possibly producing a greater irritant corneal effect over its analgesic properties. Benzalkonium chloride 0.01% significantly increased corneal sensitivity at 15 minutes of evaluation (P > 0.001), most likely resulting from its irritating effect. Esthesiometry did not allow a definite conclusion over the analgesic effect of the NSAIDs tested; however it was effective in detecting fluctuations in corneal sensitivity.

Ocular biometry by computed tomography in different dog breeds.

To (i) correlate B-mode ocular ultrasound (US) and computed tomography (CT) (prospective pilot study), (ii) establish a reliable method to measure the normal canine eye using CT, (iii) establish a reference guide for some dog breeds, (iv) compare eye size between different breeds and breed groups, and (v) investigate the correlation between eye dimensions and body weight, gender, and skull type (retrospective study). B-mode US and CT were performed on ten sheep cadaveric eyes. CT biometry involved 100 adult pure-bred dogs with nonocular and nonorbital disease, representing eleven breeds. Eye length, width, and height were each measured in two of three planes (horizontal, sagittal, and equatorial). B-mode US and CT measurements of sheep cadaveric eyes correlated well (0.70-0.71). The shape of the canine eye was found to be akin to an oblate spheroid (a flattened sphere). A reference guide was established for eleven breeds. Eyes of large breed dogs were significantly larger than those of medium and small breed dogs (P < 0.01), and eyes of medium breed dogs were significantly larger than those of small breed dogs (P < 0.01). Eye size correlated with body weight (0.74-0.82) but not gender or skull type. Computed tomography is a suitable method for biometry of the canine eye, and a reference guide was established for eleven breeds. Eye size correlated with breed size and body weight. Because correlation between B-mode US and CT was shown, the obtained values can be applied in the clinical setting, for example, for the diagnosis of microphthalmos and buphthalmos.

Effect of preservative-free tafluprost on intraocular pressure, pupil diameter, and anterior segment structures in normal canine eyes.

This study was designed to evaluate the changes in intraocular pressure (IOP), pupil diameter (PD), and anterior segment parameters using ultrasound biomicroscopy (UBM) after instillation of preservative-free (PF) tafluprost in normal dogs. Six beagle dogs were used. PF tafluprost was instilled in one randomly selected eye, and PF artificial tear was instilled in the other eye (control). IOP and PD were measured every 15 min for the first hour, every 2 h for the next 17 h, and at 24 h and 36 h postinstillation (PI). Anterior segment parameters including geometric iridocorneal angle (ICA), width of the entry of the ciliary cleft (CCW), length of the ciliary cleft, area of the ciliary cleft, and depth of the anterior chamber were measured with UBM before and after PF tafluprost instillation. Compared with the control group, IOP was significantly lower from 4 h PI to 24 h PI and PD was significantly smaller from 30 min PI to 18 h PI (P < 0.05). Among UBM parameters, ICA and CCW significantly decreased and increased after PF tafluprost instillation, respectively (P < 0.05). Other parameters showed no significant changes. Instillation of PF tafluprost lowered IOP and induced miosis in normal canine eyes. Alterations in ICA and CCW occurred simultaneously, which probably affected the outflow of aqueous humor. PF tafluprost could be considered an alternative prostaglandin analog in the treatment of canine glaucoma.

Fluorescein gonioangiography of the normal canine eye using a dSLR camera adaptor

The purpose of this study was to describe fluorescein gonioangiography (FGA) of the normal canine eye using a digital single lens reflex (dSLR) camera adaptor. Dogs were anesthetized using intravenous propofol. Imaging was performed using a Lovac Barkan goniolens, dSLR camera, dSLR camera adaptor, camera lens, and accessory flash. Twelve dogs with a mean age of 2.0 +/− 0.8 years were imaged. No characteristic angiographic phases were observed. Leakage from the peri-limbal capillary network was a common finding and occurred 7.7 +/− 2.2 s post injection in 9 (75%) dogs. In 3 (25%) dogs, filling of the circumferential ciliary artery was observed 10.3 +/− 2.8 s post injection. Dye leakage within the iris base and into the aqueous humor was demonstrated in 4 (33%) and 6 dogs (50%) respectively. No adverse events were noted. This study demonstrates FGA findings in normal canine eyes using a cost effective dSLR camera adaptor.

CT dimensions, volumes and densities of normal canine eyes

Although ultrasound and MRI are the imaging modalities of choice for the investigation of ocular diseases, the eyes are included in routine CT examinations of the head and should be...

Comparison of two handheld applanation tonometers and the association of central corneal thickness, age, and intraocular pressure in normal and diseased canine eyes

To compare the intraocular pressure (IOP) measurements from two applanation tonometers (Tono-Pen XL(®) and AccuPen(®) in normal and diseased canine eyes (including corneal disease, cataract, glaucoma, uveitis, and noninflammatory intraocular disease) and evaluate the associations among the central corneal thickness (CCT), IOP measurements, and age. Sixty-eight normal and 191 diseased eyes. A topical anesthetic agent was applied to each eye. One minute later, IOP was measured with the Tono-Pen XL(®) and then the AccuPen(®), and then CCT was measured with an ultrasonic pachymeter. Measurements for the right eye were always taken first. The Tono-Pen XL(®) successfully measured IOP in all eyes, whereas the AccuPen(®) registered measurements in only 98.4% of diseased eyes. The AccuPen(®) measurements were significantly lower than the Tono-Pen XL(®) measurements in both normal and diseased eyes. The CCT did not affect the Tono-Pen XL(®) or AccuPen(®) measurements in normal or diseased eyes. Spearman's correlation coefficient by rank analysis of CCT and IOP yielded correlation coefficients (r) of 0.144 and 0.101 for the Tono-Pen XL(®), and 0.108 and 0.175 for the AccuPen(®) in normal and diseased eyes, respectively. In normal canine eyes, age correlated inversely with the CCT (r = -0.128) and IOP as measured using the Tono-Pen XL(®) (r = -0.446) and AccuPen(®) (r = -0.427). The AccuPen(®) measurements were slightly but significantly lower than the Tono-Pen XL(®) measurements in both normal and diseased canine eyes. The CCT affected the results of neither tonometer regardless of disease, while both IOP and CCT tended to decrease with age in normal eyes.

Comparison of the effects of topical and systemic atropine sulfate on intraocular pressure and pupil diameter in the normal canine eye

To compare the effects of topical 1% atropine sulfate and systemic 0.1% atropine sulfate on the intraocular pressure (IOP) and horizontal pupil diameter (HPD) in the canine eye. Four groups, each containing 10 dogs of varying age, breed, and sex were treated as follows: (i) One 30 μL drop of topical 1% atropine sulfate was applied unilaterally in each dog, (ii) A control group, one drop of 0.9% saline was used, (iii) 0.06 mg/kg atropine sulfate was given by intramuscular injection, and (iv) Control with saline injected intramuscularly. In all groups, IOP and HPD were measured every 5 min over 60 min. Topical atropine significantly increased IOP in the treated eye with no change in the untreated eye. A maximum increase in IOP from 17.7 ± 3.1 to 20.3 ± 3.1 mmHg (14.7% increase) was obtained 23.0 ± 14.3 min post-treatment. Maximal HPD of 12.1 ± 1.7 mm in the treated eye occurred 46.5 ± 6.3 min after treatment, with no increase in the untreated eye. Systemic atropine caused an increase in IOP in both eyes, showing a maximum at 15.5 ± 10.6 min post-treatment with an IOP of 17.3 ± 4.6 mmHg in the right eye and 17.1 ± 5.2 mmHg in the left eye (21.8% increase in the right eye and 21.6% in the left eye). Maximal HPD was noted in both eyes 30.0 ± 11.6 min after treatment. Atropine sulfate causes a significant increase in IOP when given both topically and by intramuscular injection. It should be used with caution, or indeed avoided entirely, in dogs with glaucoma or in those with a predisposition to the condition.

Anterior segment angiography of the normal canine eye: A comparison between indocyanine green and sodium fluorescein

The objective of this study was to assess and compare indocyanine green (IG) and sodium fluorescein (SF) angiographic findings in the normal canine anterior segment using a digital single lens reflex (dSLR) camera adaptor. Images were obtained from 10 brown-eyed Beagles, free of ocular and systemic disease. All animals received butorphanol (0.2mg/kg IM), maropitant citrate (1.0mg/kg SC) and diphenhydramine (2.0mg/kg SC) 20min prior to propofol (4mg/kg IV bolus, 0.2mg/kg/min continuous rate infusion). Standard color imaging was performed prior to the administration of 0.25% IG (1mg/kg IV). Imaging was performed using a full spectrum dSLR camera, dSLR camera adaptor, camera lens (Canon 60mm f/2.8 Macro) and an accessory flash. Images were obtained at a rate of 1/s immediately following IG bolus for 30s, then at 1, 2, 3, 4 and 5min. Ten minutes later, 10% SF (20mg/kg IV) was administered. Imaging was repeated using the same adaptor system and imaging sequence protocol. Arterial, capillary and venous phases were identified during anterior segment IG angiography (ASIGA) and their time sequences were recorded.ASIGA offered improved visualization of the iris vasculature in heavily pigmented eyes compared to anterior segment SF angiography (ASSFA), since visualization of the vascular pattern during ASSFA was not possible due to pigment masking. Leakage of SF was noted in a total of six eyes. The use of IG and SF was not associated with any observed adverse events. The adaptor described here provides a cost-effective alternative to existing imaging systems.

Infrared ocular thermography in dogs with and without keratoconjunctivitis sicca

Infrared thermography was used to measure temperature differences of the corneal surface between nasal and temporal limbus regions and central cornea of normal dogs and dogs with keratoconjunctivitis sicca (KCS), in order to establish temperature values in normal canine eyes and in patients with decreased Schirmer tear tests (STT) values. Dogs investigated were all either patients seen at the Veterinary Teaching Hospital of Federal University of Paraná or normal dogs that belonged to the same institution. STT were performed in all eyes. A total of 40 control eyes (STT ≥15mm/min) and 20 eyes with low STT values (STT ≤14mm/min) were examined. The mean STT value for eyes with normal STT values was 22.9±3.9mm/min (mean±standard deviation), and the mean STT value for eyes with low STT value was 7.2±4.8mm/min. The mean corneal temperature was significantly lower in eyes with low STT values than in control eyes (P<0.0001). The following significant correlations were found: (i) Schirmer and breakup time (BUT) (P=0.0001, r=0.5); (ii) STT values and corneal surface temperature (P=0.001, r=0.256); (iii) STT values and age (P=0.0001, r=-0.448); (iv) age and corneal surface temperature (P=0.0001, r=-0.281); and (v) BUT and corneal surface temperature (P=0.0001, r=0.36). Thermography is a method that can differentiate between eyes with normal and abnormal STT values. In the future, thermography might be incorporated as part of the ophthalmic examination and perhaps become a popular ancillary test for the diagnoses of ocular surface disorders.