Jaesang Ahn

Effect of central corneal thickness on intraocular pressure with the rebound tonometer and the applanation tonometer in normal dogs.

OBJECTIVE To evaluate the effect of central corneal thickness (CCT) on the measurement of intraocular pressure (IOP) with the rebound (TonoVet(®)) and applanation (TonoPen XL(®)) tonometers in beagle dogs. ANIMAL STUDIED Both eyes of 60 clinically normal dogs were used. PROCEDURES The IOP was measured by the TonoVet(®), followed by the TonoPen XL(®) in half of the dogs, while the other half was measured in the reverse order. All CCT measurements were performed 10 min after the use of the second tonometer. RESULTS The mean IOP value measured by the TonoVet(®) (16.9 ± 3.7 mmHg) was significantly higher than the TonoPen XL(®) (11.6 ± 2.7 mmHg; P < 0.001). The IOP values obtained by both tonometers were correlated in the regression analysis (γ(2) = 0.4393, P < 0.001). Bland-Altman analysis showed that the lower and upper limits of agreement between the two devices were -0.1 and +10.8 mmHg, respectively. The mean CCT was 549.7 ± 51.0 μm. There was a correlation between the IOP values obtained by the two tonometers and CCT readings in the regression analysis (TonoVet(®) : P = 0.002, TonoPen XL(®) : P = 0.035). The regression equation demonstrated that for every 100 μm increase in CCT, there was an elevation of 1 and 2 mmHg in IOP measured by the TonoPen XL(®) and TonoVet(®), respectively. CONCLUSIONS The IOP obtained by the TonoVet(®) and TonoPen XL(®) would be affected by variations in the CCT. Therefore, the CCT should be considered when interpreting IOP values measured by tonometers in dogs.

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.

Effects of conditioned media from human amniotic epithelial cells on corneal alkali injuries in rabbits.

This study was performed to evaluate the effects of conditioned media (CM) from human amniotic epithelial cells (HAECs) on the corneal wound healing process. Eighteen rabbits (36 eyes) were used and randomly assigned to three groups according treatment: CM from HAECs (group 1), vehicle alone (group 2), and saline (group 3). Corneal alkali injuries were induced with 1 N sodium hydroxide. Each reagent used for treatment evaluation was injected into the dorsal bulbar subconjunctiva and the area of the corneal epithelial defect was measured every other day. Two animals from each group were euthanized at a time on days 3, 7, and 15, and the cornea was removed for histological examination. The sum of the epithelial defect areas measured on day 0 to day 6 as well as day 0 to day 14 in group 1 was significantly smaller than those of other groups. Histological examination revealed that the group 1 corneas had less inflammatory cell infiltration and showed more intact epithelial features compared to the other groups. These results suggest that CM from HAECs promote corneal wound healing in rabbits.

Acute Changes in Central Corneal Thickness According to Experimental Adjustment of Intraocular Pressure in Normal Canine Eyes

ABSTRACT Central corneal thickness (CCT) can be a promising source of glaucoma monitoring and diagnosis. This study evaluated changes in CCT according to experimental adjustment of intraocular pressure (IOP) in canine eyes. To adjust and measure IOP, each eye was cannulated with two 26-gauge needles under inhalant anesthesia. One needle was connected to a pressure transducer, and the other was connected to an adjustable bag of physiologic saline. IOP was stepwise increased from 10 mmHg to 70 mmHg in 10 mmHg increments (Group T). IOP was maintained at 15 mmHg (Group C15), 30 mmHg (Group C30), 45 mmHg (Group C45), 60 mmHg (Group C60) and 75 mmHg (Group C75) during the experiment. CCT was measured with an ultrasonic pachymeter every 10 min after cannulation. There was a significant difference in the effect of time on CCT (P<0.001) and difference in CCT (dCCT; P<0.001) between groups. The CCT of group C15 remained constant during the experiment. However, group T showed an initial decrease and then an increase after passing the lowest point. Group C30 showed decreasing values for 30 min, after which the values remained constant. The values in Group C45 showed no changes for 40 min and then increased. The values in group C60 showed no change for 20 min and then increased. Group C75 showed a steady increase. In conclusion, the CCT showed two core changes according to increased IOP. This study provides essential basic data to enable further investigation into the association of IOP and CCT 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.

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.

Determining the age of cats by pulp cavity/tooth width ratio using dental radiography.

The purpose of this study was to evaluate the effect of age on the ratio of pulp cavity/tooth width (P/T ratio) in healthy cats. The dental radiographs of 32 cats (16 males and 16 females) were generated with a digital dental X-ray unit with the animals under general anesthesia. Standardized measurement of the canine teeth was performed by drawing a line on the radiograph perpendicular to the cementoenamel junction (CEJ) of the tooth. There was an inversely proportional correlation between chronological age and the P/T ratio. Moreover, a strong Pearson squared correlation (γ2 = 0.92) was identified by the curved regression model. No significant differences in the P/T ratio based on gender or breed were found. These results suggest that determination of age by P/T ratio could be clinically useful for estimating the chronological age of cats.

Combined Intraocular Silicone Prosthesis and Conjunctival Flap for Glaucoma after Corneal Perforation in a Dog

A 7-month-old intact male Maltese dog was presented with a 1.5-month history of glaucoma in the right eye (OD). Ophthalmic examinations revealed a corneal perforation with iris entrapment, corneal edema and neovascularization, and buphthalmos OD. Intraocular pressures were 33 mmHg OD and 19 mmHg in left eye (OS). The right eye was diagnosed with chronic glaucoma and corneal perforation with iris entrapment. Now that the eye was blind, implantation of intraocular silicone prosthesis (ISP) and conjunctival flap were elected to salvage the globe. The corneal perforation healed with the conjunctival pedicle flap and the cornea accommodated the ISP properly. A satisfactory cosmetic result was achieved without complications in the 15 months following the procedure. Therefore, this case report indicates the combined an ISP and a conjunctival flap would be an alternative for the treatment of glaucoma associated with corneal perforation in dogs.