Euiri Lee

A sub-Tenon's capsule injection of lidocaine induces extraocular muscle akinesia and mydriasis in dogs.

The effect of local anaesthetic on the extraocular muscles was investigated in dogs by injecting lidocaine into the space between Tenons capsule and the sclera. A cross-over design was used with both eyes from five Beagle dogs randomly injected, under general anaesthesia, with 1 mL of 2% lidocaine (1 mL-lidocaine group), 2 mL of 2% lidocaine (2 mL-lidocaine group) or 2 mL of normal saline (control group). Each eye was assigned to all treatments with a minimum 14 day interval between injections. Changes in eye position, pupil diameter, and intraocular pressure (IOP) were evaluated during the procedure. All eyes in the 2 mL-lidocaine group exhibited akinesia and mydriasis (pupil diameter >10mm) with an onset time of 6.5 ± 4.9 and 4.2 ± 4.3 min, respectively. In the 1 mL-lidocaine group, akinesia was induced in nine eyes and mydriasis occurred in seven eyes at 10.7 ± 5.8 and 5.4 ± 2.4 min after the injection, respectively. No changes in eye position or pupil diameter were observed in the control group. Akinesia was maintained for 44.3 ± 26.7 min in the 1 mL-lidocaine group and for 88.5 ± 17.2 min in the 2 mL-lidocaine group. Duration of mydriasis was 51.7 ± 28.9 min in the 1 mL-lidocaine group and 82.9 ± 15.6 min in the 2 mL-lidocaine group. Marked chemosis and sub-conjunctival haemorrhage occurred in 16/30 and 15/30 eyes, respectively. No significant change in IOP was observed between the mean pre- and post-injection values in all groups. These results suggest that a sub-Tenons injection of 2 mL of 2% lidocaine provided effective extraocular muscle akinesia and mydriasis in dogs.

Experimental determination of a subantimicrobial dosage of doxycycline hyclate for treatment of periodontitis in Beagles

OBJECTIVE To identify a subantimicrobial dose of doxycycline hyclate (SDD) and for the treatment of periodontitis in dogs. ANIMALS 20 healthy Beagles for measurement of serum doxycycline concentration and 15 Beagles with periodontitis for evaluation of the efficacy of the SDD. PROCEDURES 5 dogs each received doxycycline hyclate PO at a dose of 1, 2, 3, or 5 mg/kg. Blood samples were collected before and after administration, and serum concentrations of doxycycline were measured via high-performance liquid chromatography. Mean serum doxycycline concentrations were calculated, and SDDs were identified. In a separate trial, the identified SDDs (1 or 2 mg/kg) were administered PO once a day for 1 month to dogs with periodontitis (n = 5/group) and a control group (5) was fed vehicle only during the same period. Degree of gingival attachment and bleeding on probing (present or absent) were recorded. Gingival samples were collected before and after the 1-month period from the same anatomic sites. Degree of matrix metalloproteinase inhibition in gingival samples was determined via gelatin zymography and compared among treatment groups. RESULTS Mean serum doxycycline concentrations in healthy dogs that received 1 or 2 mg of doxycycline/kg were consistently significantly lower than the minimal inhibitory doxycycline concentration for treatment of periodontitis throughout the 24-hour posttreatment period. Zymographic intensities were lower in dogs given 1 and 2 mg/kg than in the control dogs, and the degree of gingival attachment and bleeding significantly improved in dogs given 2 mg/kg, compared with in the control dogs and dogs given 1 mg of doxycycline/kg. CONCLUSIONS AND CLINICAL RELEVANCE A doxycycline dosage of 2 mg/kg daily appeared to be an appropriate subantimicrobial regimen for dogs with periodontitis. Furthermore, this dosage may be suitable for long-term treatment of gelatinolytic inflammatory diseases such as periodontitis in this species.

Effects of peribulbar anesthesia (sub-Tenon injection of a local anesthetic) on akinesia of extraocular muscles, mydriasis, and intraoperative and postoperative analgesia in dogs undergoing phacoemulsification

OBJECTIVE To evaluate the effects of peribulbar anesthesia (sub-Tenon injection of lidocaine hydrochloride) on akinesia of extraocular muscles, mydriasis, and intraoperative and postoperative analgesia in dogs undergoing phacoemulsification. ANIMALS 14 Beagles with ophthalmically normal eyes. PROCEDURES A blinded randomized controlled trial was performed. Dogs were anesthetized and assigned to 2 treatments: concurrent sub-Tenon injection of 2% lidocaine hydrochloride solution (2 mL) and IV injection of saline (0.9% NaCl) solution (0.02 mL/kg; lidocaine group [n = 7]) or concurrent sub-Tenon injection of saline solution (2 mL) and IV injection of 0.2 mg of atracurium/kg (0.02 mL/kg; control group [7]). Pupils were dilated by topical application of a combined tropicamide and phenylephrine ophthalmic solution. Ten minutes after the injections, pupil diameter was measured and phacoemulsification was performed. End-tidal isoflurane concentration was used to evaluate intraoperative pain. Subjective pain scores were recorded during the postoperative period. RESULTS Akinesia was induced and maintained throughout the surgery in all eyes. Mean ± SD pupil diameter was significantly greater in the lidocaine group (13.7 ± 0.7 mm) than in the control group (12.2 ± 0.8 mm). Isoflurane requirements were significantly lower in the lidocaine group than the control group. However, postoperative pain scores were not significantly different between the groups. CONCLUSIONS AND CLINICAL RELEVANCE Sub-Tenon injection of lidocaine was an effective method for inducing akinesia of extraocular muscles, mydriasis, and intraoperative analgesia for phacoemulsification in dogs. Therefore, this could be another option for surgical field exposure and pain management during phacoemulsification in dogs.

Accuracy of intraocular pressure measurements in dogs using two different tonometers and plano therapeutic soft contact lenses

OBJECTIVE To compare and evaluate the accuracy of intraocular pressure (IOP) measured through a therapeutic contact lens, using applanation (TonoPen XL(®)) and rebound (TonoVet(®)) tonometers in enucleated dog eyes. ANIMALS STUDIED A total of 30 enucleated eyes from 15 beagle dogs. PROCEDURES To measure accurate IOP, the anterior chamber of each enucleated eye was cannulated with two 26-gauge needles and two polyethylene tubes were connected vertically to an adjustable reservoir bag of normal saline and a pressure transducer. IOP was measured by the TonoPen XL(®) followed by the TonoVet(®) without a contact lens. After a contact lens was applied to the cornea, IOP was re-measured in the same order. Three consecutive IOP measurements were performed using both tonometers. RESULTS Without the contact lens, the IOP values obtained by both tonometers correlated well according to the regression analysis (TonoVet(®): γ(2) = 0.98, TonoPen XL(®): γ(2) = 0.97, P < 0.001). The TonoPen XL(®) consistently underestimated values as transducer IOP increased; however, IOP values measured with the TonoPen XL(®) were in close agreement and were less variable than those determined with the TonoVet(®) when a contact lens was applied to the cornea. Bland-Altman analysis was used to determine the lower and upper limits of agreement (TonoVet(®): -29.7 and +21.1 mmHg, TonoPen XL(®): -3.9 and +3.6 mmHg) between the two devices. CONCLUSIONS This study suggests that the TonoPen XL(®) is a useful tonometer for dogs wearing therapeutic contact lenses, and importantly, contact lenses would not need to be removed prior to IOP measurement.

Evaluation of fluid leakage into the canine vitreous humor during phacoemulsification using contrast‐enhanced magnetic resonance imaging

OBJECTIVE To evaluate the effects of phacoemulsification with different fluidic parameters on the intraocular tissues using contrast-enhanced magnetic resonance imaging (CE-MRI). PROCEDURES Phacoemulsification with intraocular lens (IOL) implantation was performed on 10 pairs of enucleated canine eyes. Irrigation fluid containing diluted MRI contrast agent was used, with the bottle height/the vacuum pressure set at 50 cm/80 mmHg for one eye (Group L) and at 120 cm/150 mmHg for the opposite eye (Group H). CE-MRI was carried out immediately after phacoemulsification to evaluate the presence of anterior hyaloid membrane detachment (AHD) and the leakage volume-to-vitreous volume ratio (LV/VV%). The ultrasound time, the volume of irrigation solution used, and the total irrigation time were recorded. RESULTS AHD was seen in seven of the 10 eyes in Group L and in nine of the 10 eyes in Group H. Fluid leakage into the vitreous humor (LV/VV%) was significantly greater in Group H than in Group L (P < 0.01). The LV/VV% was also correlated with the total irrigation time in both groups (P < 0.05). The volume of irrigation solution used in Group H was significantly greater than that used in Group L (P < 0.001). There was no statistically significant difference in the ultrasound time between the two groups. CONCLUSIONS Low fluidic parameters led to decreased fluid passage through the zonules, reducing fluid passage into the vitreous. These may also lead to reduced surgical stress on the intraocular tissues by decreasing the amount of irrigation solution used during phacoemulsification in the dog.

Air assisted lamellar keratectomy for the corneal haze model

To standardize the corneal haze model in the resection depth and size for efficient corneal haze development, air assisted lamellar keratectomy was performed. The ex vivo porcine corneas were categorized into four groups depending on the trephined depth: 250 µm (G1), 375 µm (G2), 500 µm (G3) and 750 µm (G4). The stroma was equally ablated at the five measurement sites in all groups. Significant differences were observed between the trephined corneal depths for resection and ablated corneal thickness in G1 (p < 0.001). No significant differences were observed between the trephined corneal depth for resection and the ablated corneal thickness in G2, G3, and G4. The resection percentage was similar in all groups after microscopic imaging of corneal sections. Air assisted lamellar keratectomy (AK) and conventional keratectomy (CK) method were applied to six beagles, after which development of corneal haze was evaluated weekly until postoperative day 28. The occurrence of corneal haze in the AK group was significantly higher than that in the CK group beginning 14 days after surgery. Alpha-smooth muscle actin expression was significantly higher in the AK group (p < 0.001) than the CK group. Air assisted lamellar keratectomy was used to achieve the desired corneal thickness after resection and produce sufficient corneal haze.

Comparison of systemic atracurium, retrobulbar lidocaine, and sub‐Tenon's lidocaine injections in akinesia and mydriasis in dogs

OBJECTIVE To compare the effect of sub-Tenons lidocaine injections (ST) on akinesia and mydriasis to those of systemic atracurium (AT) and retrobulbar lidocaine injections in dogs. ANIMAL STUDIED Ten healthy beagle dogs without apparent ocular disease. PROCEDURES Three treatments were performed on 10 beagle dogs with a minimum 7-day washout period: intravenous injection of AT (0.2 mg/kg, AT group); retrobulbar (RB) injection of 2% lidocaine (2.0 mL, RB group) in one eye; and sub-Tenons injection of 2% lidocaine (2.0 mL, ST group) in the opposite eye. When the akinesia was not obtained within 10 min, an additional 1 mL of lidocaine was administered in the RB and the ST groups. RESULTS Onset of akinesia in the AT (1.5 ± 0.9 min) and the ST (3.8 ± 5.8 min) groups was significantly shorter than that in the RB group (9.0 ± 6.5 min). Duration of akinesia in the ST group (116.2 ± 32.8 min) was longer compared to the AT (60.6 ± 23.6 min) and the RB (89.0 ± 52.8 min) groups, even though there was only a significant difference between the AT and the ST groups. Mydriasis was achieved in five eyes in the RB group and nine eyes in the ST group. There was no significant difference in onset (3.6 ± 3.1 and 2.9 ± 2.3 min, respectively) or duration (91.4 ± 31.9 and 102.1 ± 35.8 min, respectively) of mydriasis between the groups. CONCLUSIONS Sub-Tenons lidocaine injections provide excellent akinesia and mydriasis compared to systemic AT and retrobulbar lidocaine injections. Therefore, sub-Tenons anesthesia could be an alternative to the systemic administration of neuromuscular blockers and retrobulbar anesthesia for ophthalmic surgery in dogs.

Ultrasound biomicroscopic study of the effects of topical latanoprost on the anterior segment and ciliary body thickness in dogs.

OBJECTIVE The goal of this study was to evaluate the effects of topical latanoprost on the anterior segment and ciliary body using ultrasound biomicroscopy (UBM) in dogs. ANIMALS STUDIED This study included six eyes of six clinically normal beagles. PROCEDURES UBM scans were performed on six sedated dogs before and 2 h after topical latanoprost instillation. From the next day on, latanoprost was topically applied twice daily for 7 days. After 1 week of instillation, the UBM scans were repeated. The ciliary body thickness (CBT) and the anterior segment parameters, including the iridocorneal angle (ICA), the width of the ciliary cleft (CC) entry, the length of the CC, and the width of the mid-CC, were measured. RESULTS The topical latanoprost decreased the ICA and CC entry width and increased the mid-CC width without any significant alterations in the CC length. There were time-dependent alterations in the CBT: a reduction in the CBT after 2 h of instillation and rebound thickening after 1 week of instillation. CONCLUSIONS The topical latanoprost widened the ciliary cleft despite the narrowing of the ICA and CC entry. Time-dependent alterations in the CBT were demonstrated by the UBM and might be a reflection of the mechanism of the uveoscleral outflow enhancement induced by the topical latanoprost.

Clinical and microbiological effects of a subantimicrobial dose of oral doxycycline on periodontitis in dogs

Doxycycline is regarded as an effective treatment for periodontal inflammation. In humans, it has been shown that the long-term administration of a subantimicrobial dose of doxycycline (SDD) does not induce antimicrobial effects on the subgingival microflora and furthermore does not affect antimicrobial susceptibility. The present study was designed to evaluate the influence of oral administration of SDD on normal periodontal microflora and antimicrobial susceptibility in dogs. Experimental periodontitis was induced in 12 experimental dogs using a silk and wire-twisted ligature for 60 days. After the periodontitis induction period, the ligature was removed, and dental cleaning (subgingival and supragingival ultrasonic scaling) was performed. The dogs were randomly assigned to one of two groups: an SDD group with six dogs receiving 2 mg/kg PO once daily and a control group with six dogs receiving a placebo. At weeks 0, 4 and 8, clinical periodontal parameters were evaluated. After the clinical assessments, subgingival plaque was sampled and then cultured in an anaerobic system for one week, and the total anaerobes, Porphyromonas spp., Bacteroides spp. and Pasteurella spp. counts were investigated. Using the agar dilution method, the minimum bactericidal concentration of doxycycline was evaluated and the resistance for doxycycline was monitored during this experimental phase. The clinical periodontal status of the SDD group was significantly improved compared to the control group (P <0.05). Bacterial counts were not significantly different between the two experimental groups (P > 0.05), and antibacterial resistance was not established in the SDD group during the experimental periods (P <0.05). These results suggest that the once daily oral regimen of 2 mg/kg of doxycycline could serve as a SDD in dogs.

Effect of onion extract on corneal haze suppression after air assisted lamellar keratectomy

This study evaluated the effect of onion extract on corneal haze suppression after applying the air assisted lamellar keratectomy. The air assisted lamellar keratectomy was performed on 24 canine eyes. They were treated with an artificial tear (group C), prednisolone acetate (group P), onion extract (group O) and TGF-β1 (group T) three times per day from 7 to 28 days after the surgery. Corneal haze occurred on the all eyes and was observed beginning 7 days after the surgery. The haze was significantly decreased in groups P and O from day 14 compared with the group C using the clinical (group P; P=0.021, group O; P=0.037) and objective evaluation method (group P; P=0.021, group O; P=0.039). In contrast, it was significantly increased in group T from day 14 compared with group C based on the clinical (P=0.002) and objective evaluation method (P<0.001). Subsequently, these eyes were enucleated after euthanasia, and immunohistochemistry with α-SMA antibodies was done. The total green intensity for α-SMA was significantly more expressed in group T and significantly less expressed in groups P and O than in group C. Onion extract could have potential as a therapeutic in preventing corneal haze development by suppressing the differentiation of fibroblasts into myofibroblasts.