Master of Science in Biomedical Sciences / Department of Clinical Sciences / Jessica Meekins / Objectives- To determine the effect of oral robenacoxib on experimentally-induced anterior uveitis, and to evaluate the ability of robenacoxib to cross an intact blood-aqueous barrier. Animals- Twelve healthy adult domestic shorthair cats. Procedures- Cats in the treatment group (n=6) received oral robenacoxib (1.51 ± 0.36 mg/kg ) once daily beginning 1 day before experimental induction of uveitis by anterior chamber paracentesis (ACP) and continuing 1 day after paracentesis. Anterior chamber paracentesis was performed using a 30 g needle attached to a 1 mL syringe, and 100 µL of aqueous humor were aspirated over 3-5 seconds. Anterior chamber fluorophotometry was performed in both eyes of each cat immediately before ACP (time 0), and at 6, 24, and 48 hours after ACP. An independent t-test was used to compare percent fluorescein increase in treatment versus control cats at each time point. Values of p<0.05 were considered significant. Concentrations of robenacoxib in aqueous humor were measured using liquid chromatography and mass spectrometry. Results- There was no statistically significant difference between the ACP and control eye at time 0 (p=0.322). When comparing the percent fluorescein increase between treatment and control groups, there was no statistically significant difference at any time point (p>0.05). Robenacoxib was present in small but detectable levels in 5/6 cats in the treatment group. Conclusions and clinical relevance- Administration of oral robenacoxib did not significantly lessen experimentally-induced anterior uveitis in normal cats, as assessed by fluorophotometry. Low concentrations of aqueous humor robenacoxib were detectable in the majority of cats receiving the drug.

No description available.

Master of Science / Department of Clinical Sciences / Amy Rankin / Objective - To establish the aqueous humor flow rate in normal cats via fluorophotometry, utilizing a noninvasive method previously established in other species and to evaluate the effect of topical 2% dorzolamide on aqueous humor flow rate and intraocular pressure (IOP) in normal cats. Animals - 20 clinically normal domestic shorthair cats. Procedures – Topical administration of 10% sodium fluorescein was performed using a 3-drop protocol to establish its use in this species. Aqueous flow was measured using fluorophotometry in the right and left eyes. The subjects were then divided into 2 groups: the first received topical 2% dorzolamide (Trusopt®) and the second received topical artificial tear solution (control). The study was divided into two phases: a 3 day acclimation phase (no treatments given) and a 5 day treatment phase (treatments given three times daily). IOP measurements were taken at 7am, 10am, 1pm, 5pm, and 9pm throughout all phases of the study. Fluorophotometry was performed to measure the aqueous flow rate just prior to and at the end of the treatment phase (days 3 and 9 respectively). Results - The calculated aqueous humor flow rate for normal cats in the right, left, and both eyes was 5.94 ± 2.30 μl/min, 5.05 ± 2.06 μl/min, and 5.51 ± 2.21 μl/min, respectively. No significant differences were noted between the right and left eyes. In the dorzolamide group, the average flow rate during treatment (3.47 + 1.50 μl/min ) was significantly lower than prior to treatment (5.9 + 2.20 μl/min)(P < 0.001). The mean IOP during treatment (11 + 3 mmHg) was significantly lower than the mean IOP prior to treatment (15 + 3 mmHg)(P < 0.001). In the control group, there were no significant differences in aqueous humor flow or IOP values before or during treatment. Conclusions - The technique utilized for this study met the standard for accurate fluorophotometric calculation of aqueous humor flow. The average aqueous humor flow rate for normal cats calculated in this study was 5.51 ± 2.21 μl/min. Topical 2% dorzolamide significantly lowers aqueous humor flow (a 41% reduction) and IOP (a 26% reduction) in normal cats.

Treatment of vision impairing diseases involves drug transport through the vitreous humor. Diffusion cells were used to measure macro-scale (mutual) diffusivity (Dm) to understand how solute size affects diffusion through the vitreous humor of rabbit and porcine eyes. Solutes examined included timolol maleate, dexamethasone sodium phosphate (DMSP), sodium fluorescein, and FITC-dextrans (4, 40, and 150kDa). Diffusivity was inversely dependent on solute size. The Dm's of small solutes in the vitreous were 30 – 65% of that in PBS, while the Dm's of large solutes were 40 – 60% of that in PBS. Extrapolations to the human eye produced similar results using diffusivities based on either species. We used Diffusion Ordered NMR Spectroscopy to measure micro-scale (self) diffusivity (Ds) of DMSP through vitreous humor. The Ds and Dm were significantly different in PBS, but similar in vitreous. A method for obtaining in vivo imagery and data of vitreous fluorophore distribution is also presented.

Treatment of vision impairing diseases involves drug transport through the vitreous humor. Diffusion cells were used to measure macro-scale (mutual) diffusivity (Dm) to understand how solute size affects diffusion through the vitreous humor of rabbit and porcine eyes. Solutes examined included timolol maleate, dexamethasone sodium phosphate (DMSP), sodium fluorescein, and FITC-dextrans (4, 40, and 150kDa). Diffusivity was inversely dependent on solute size. The Dm's of small solutes in the vitreous were 30 – 65% of that in PBS, while the Dm's of large solutes were 40 – 60% of that in PBS. Extrapolations to the human eye produced similar results using diffusivities based on either species. We used Diffusion Ordered NMR Spectroscopy to measure micro-scale (self) diffusivity (Ds) of DMSP through vitreous humor. The Ds and Dm were significantly different in PBS, but similar in vitreous. A method for obtaining in vivo imagery and data of vitreous fluorophore distribution is also presented.

Master of Science / Department of Clinical Sciences / Amy J. Rankin / Objective – To measure blood aqueous-barrier breakdown following aqueocentesis using various needle sizes and to monitor the intraocular pressure (IOP) response. Animals – 24 healthy, adult dogs received treatment (24 treated eyes, 24 contralateral eyes); 3 dogs were untreated controls (6 control eyes). Procedures – Dogs receiving treatment were divided into 3 equal groups (25-, 27-, or 30- gauge needle aqueocentesis). In each dog the treated eye was determined randomly, the contralateral eye was untreated. Dogs that did not have aqueocentesis performed in either eye were used as controls. Aqueocentesis at the lateral limbus was performed under sedation and topical anesthesia. Anterior chamber fluorophotometry was performed before and after aqueocentesis on day 1. On days 2-5 sedation and fluorophotometry were repeated. Intraocular pressure was measured with a rebound tonometer at multiple time points. Results – Aqueocentesis resulted in blood-aqueous barrier breakdown in all treated eyes with barrier reestablishment present by day 5 detected by fluorophotometry. On day 2 the contralateral untreated eyes of all groups also showed statistically significant increased fluorescence (P < 0.05) following treatment of the opposite eye, but these values were not statistically significantly greater than untreated controls. In treated eyes there was no statistical difference in fluorescein concentration or IOP between 27- and 30-gauge needles. Use of the 25- gauge needle resulted in a statistically significant increase in anterior chamber fluorescence on days 3 and 5. It also caused a statistically significant increase in IOP 20 minutes following aqueocentesis as compared to the 27- and 30-gauge needles. Aside from this transient ocular hypertension, rapid resolution of ocular hypotony following aqueocentesis was observed in all treatment groups. Conclusions and Clinical Relevance – Aqueocentesis using a 25-gauge needle resulted in a greater degree of blood-aqueous barrier breakdown and a brief state of intraocular hypertension following paracentesis. Use of a 27- or 30-gauge needle is recommended for aqueous paracentesis. A consensual ocular reaction appeared to occur in dogs following unilateral traumatic blood-aqueous barrier breakdown and may be of clinical significance. Statistical significance was limited in this study due to high variability and large standard deviations.