Seonmi Kang

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

OBJECTIVE 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. PROCEDURES 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. RESULTS 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. CONCLUSIONS 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.

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.

Fluid dynamics and intraocular pressure using venturi phacoemulsification machine in dogs ex vivo

OBJECTIVE To optimize fluid dynamics through measuring intraocular pressure (IOP) in a venturi phacoemulsification machine in dogs. PROCEDURES In step I, flow and IOP of the test chamber were measured using a pressure transducer with the bottle height (BH) set at 50, 70, 100, and 120 cm and the vacuum from 30 to 450 mmHg. A 19-gauge phaco and a 0.3-mm irrigation/aspiration (I/A) handpiece were used. In step II, flow and IOP were measured in an enucleated canine eye with a 3.0- and a 3.2-mm clear corneal incision (CCI), respectively. IOP was measured using the pressure transducer at a 30-mmHg vacuum to allow corneal deformation, to define the fluidic parameters for preventing surge. RESULTS Flow was directly proportional to the BH and vacuum, whereas IOP was directly proportional to the BH and inversely to the vacuum. Flow with an I/A handpiece was significantly less than with a phaco handpiece, explaining why IOP with an I/A handpiece was significantly higher than with a phaco handpiece. With the I/A handpiece, vacuum parameters less than 450 mmHg did not result in corneal deformation. IOP with a 3.2-mm CCI was significantly lower than with a 3.0-mm CCI, with the 3.2-mm flow being greater than the 3.0-mm flow. CONCLUSIONS BH during the I/A stage could be reduced to avoid unnecessary stress on the canine eye when using a venturi system. Although phacoemulsification with a 3.2-mm CCI could induce lower IOP, a 3.0-mm CCI might lessen the irrigation flow stress on the eye.

Recurrence after exenteration for canine orbital malignant schwannoma

A 14-year-old Maltese dog presented with progressive exophthalmos and external deviation of the right eye. Ultrasonography revealed the presence of a retrobulbar mass and fine-needle aspiration cytology was performed, which detected a malignant mass. There was no evidence of metastasis on thoracic and abdominal radiography. Computed tomography showed no invasion into the bony orbit and no metastasis to the lung or lymph nodes. Exenteration was performed to remove the mass completely. Malignant peripheral nerve sheath tumor was confirmed by histopathological examination.

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.

Real-time intraocular pressure measurement during phacoemulsification in dogs ex vivo

This study was performed to evaluate changes in intraocular pressure (IOP) during standard coaxial phacoemulsification using 4 different bottle heights (BHs) and 2 different incision sizes. Coaxial phacoemulsification was performed with a venturi-based machine in 8 enucleated canine eyes through 3.0 and 3.2 mm clear corneal incisions (CCIs). A pressure transducer inserted in the peripheral cornea monitored the IOP in real-time. The surgery was subdivided into 4 stages: sculpt-segment removal, irrigation/aspiration, capsular polishing and viscoelastic removal. The mean IOP and the difference between the maximum and minimum IOPs were calculated at each stage and compared. The ultrasound time and volume of irrigation fluid used were recorded. The mean IOP increased with an elevation in the BH. The mean IOP in the irrigation/aspiration stage was significantly higher than that in the sculpt-segment removal stage at the same BH. The difference between the maximum and minimum IOP at each stage was greater in the 3.2 mm than the 3.0 mm CCIs, although the mean IOP was lower with the 3.2 mm than the 3.0 mm CCIs. The ultrasound time and irrigation fluid volume were greater with the 3.2 mm than the 3.0 mm CCIs. Therefore, fluidic parameters during each stage could be reassessed and adjusted to reduce complications arising from an elevated IOP. Phacoemulsification with 3.0 mm CCIs at a lower BH might lead to less stress on the eye from IOP fluctuations, ultrasound energy and irrigation fluid.

Influence of an intentionally induced posterior lens capsule rupture on the real-time intraocular pressure during phacoemulsification in canine ex vivo eyes

OBJECTIVE To evaluate the changes in the intraocular pressure (IOP) following an intentionally induced posterior lens capsule rupture (PLCR) during phacoemulsification in enucleated canine eyes. Furthermore, to compare the IOPs between different stages of phacoemulsification for two different bottle heights (BH). PROCEDURES Coaxial phacoemulsification was performed using a venturi-based machine at a 60 or 90 cm BH. A pressure transducer, inserted into the anterior chamber through the peripheral cornea, monitored real-time IOP. For one half of the lens, the sculpt-segment removal (SS) was followed by irrigation/aspiration (IA). The PLCR was intentionally created, and the SS and IA were repeated on the residual lens fragments. RESULTS For the 60 cm BH, the mean IOP following the PLCR was significantly higher than before the PLCR during SS (28.30 ± 12.56 and 38.71 ± 9.43 mmHg before and after PLCR, respectively) and IA (42.76 ± 12.46 and 47.88 ± 7.10 mmHg before and after PLCR, respectively) stages (P < 0.001). For the 90 cm BH, the mean IOP following the PLCR was also significantly higher than before the PLCR during SS (33.39 ± 11.09 and 58.17 ± 6.89 mmHg before and after PLCR, respectively) and IA (62.39 ± 12.46 and 72.04 ± 8.59 mmHg before and after PLCR, respectively) stages (P < 0.001). CONCLUSIONS The occurrence of a PLCR led to an increase in IOP during both the SS and IA stages. The elevated IOP after the PLCR might be one of the most important factors for ocular tissue damage, as it reduces ocular perfusion. Additionally, the BH should be reduced following PLCR to prevent complications stemming from the raised IOP.

A case of unusual persistent pupillary membrane with total anterior capsular pigmentation

A 5-year-old castrated male poodle presented with blindness. Ophthalmic examinations including slit-lamp biomicroscopy, tonometry, ultrasonography, and electroretinography were performed. The anterior lens capsule of the right eye (OD) was totally pigmented, with persistent pupillary membranes (PPMs). Ultrasonography of the same eye showed severe lens atrophy and retinal detachment. Electroretinography revealed flat a- and b-waves in OD, but normal amplitudes in the left eye (OS). No ocular defects were detected in OS except mature cataract. In this case, it was determined that hypermature cataract with PPMs caused both lens-induced-uveitis and total anterior lens capsule pigmentation. This condition needs to be differentiated from absent pupil. Notably, PPMs with total anterior lens capsular pigmentation are extremely rare in dogs.

Effects of prostaglandin-mediated and cholinergic-mediated miosis on morphology of the ciliary cleft region in dogs

OBJECTIVE To compare morphology of the ciliary cleft (CC) region in dogs after topical administration of latanoprost, pilocarpine, or a combination of latanoprost and pilocarpine. ANIMALS 6 Beagles. PROCEDURES A prospective 4-phase crossover study with washout periods was performed. Latanoprost (phase L), pilocarpine (phase P), pilocarpine followed by latanoprost (phase PL), and latanoprost followed by pilocarpine (phase LP) were administered to the right eye. Artificial tears were administered to the left eye (control eye). For each phase, pupil diameter and intraocular pressure (IOP) were measured and ultrasonographic biomicroscopy was performed 2 hours after topical treatment. Angle opening distance (AOD), ciliary cleft width (CCW), ciliary cleft length (CCL), and ciliary cleft area (CCA) were evaluated. RESULTS All treated eyes had marked miosis without significant differences in pupil diameter among phases. Significant IOP reductions were detected for all phases, except phase P. The AOD and CCA were significantly increased in all phases for treated eyes, compared with results for control eyes. The CCW was significantly increased in phases P, PL, and LP; CCL was significantly increased in phases PL and LP. Comparison of treated eyes among phases revealed that CCW differed significantly between phases L and P and between phases L and PL. CONCLUSIONS AND CLINICAL RELEVANCE Prostaglandin-mediated and cholinergic-mediated miosis caused variations in CC configurations. When latanoprost and pilocarpine were used in combination, the first drug administered determined the cleft morphology, which was not fully reversed by the second drug. The CC morphology did not fully explain IOP reductions.

Ultrasound biomicroscopy and tonometry in ophthalmologically normal pigeon eyes

OBJECTIVE To evaluate the feasibility of ultrasound biomicroscopy (UBM) and tonometry in pigeons and to provide biometric reference ranges for normal pigeon eyes. ANIMALS STUDIED Ten pigeons (Columba livia var. domestica) with ophthalmologically normal eyes. PROCEDURES Ophthalmic examinations, including slit-lamp biomicroscopy and tonometry, were performed to confirm that the eyes were normal. UBM was then performed on the left eye. On each obtained image, the ciliary cleft (CC) length, CC width, and CC area, and iridocorneal angle (ICA) were measured. RESULTS Richly vascularized iris was observed in all pigeon eyes. Mean intraocular pressure was 11.7 ± 1.6 mmHg, without any statistical difference between the left and right eyes. The UBM scanning procedure was well tolerated in all pigeons. Mean values of CC length, CC width, CC area, and ICA were 1.55 ± 0.17 mm, 0.36 ± 0.05 mm, 0.39 ± 0.04 mm2 , and 15.17 ± 1.06°, respectively. CONCLUSIONS Ultrasound biomicroscopy could be a useful diagnostic tool to evaluate anterior ocular segment of pigeons.