Treatment of equine glaucoma by transscleral neodymium:yttrium aluminum garnet laser cyclophotocoagulation: a retrospective study of 23 eyes of 16 horses

Contact neodymium:yttrium aluminum garnet (Nd:YAG) laser transscleral cyclophotocoagulation (TSCP) was performed on 23 eyes of 16 horses for treatment of glaucoma. The mean highest preoperative IOP was 51 ± 17 mmHg. Follow-up evaluation was available for 19 eyes 1 day after surgery, 14 eyes from 1 to 2 weeks, 16 eyes from 4 to 6 weeks, 9 eyes from 12 to 16 weeks, and 10 eyes greater than 20 weeks after laser treatment. The mean intraocular pressure (IOP) the day following surgery was 34 ± 13 mmHg. The mean IOP for each follow-up period was: one to two weeks postoperative, 23 ± 9 mmHg; four to six weeks, 24 ± 7 mmHg; 12–16 weeks, 28 ± 10 mmHg; and  20 weeks, 22 ± 9 mmHg. IOP measurements were significantly different from pretreatment values for all follow-up intervals except for weeks 12–16 ( P < 0.05). Treatment success was defined as maintenance of IOP < 30 mmHg. Treatment success was achieved in 93%, 88%, 78%, and 70% of the treated eyes at the 1–2 weeks, 4–6 weeks, 12–16 weeks, and the  20 weeks re-evaluation, respectively. No significant difference was found between the number of eyes visual at presentation (52.2%) and visual at 20 weeks (60%). The most common laser complications were conjunctival hyperemia (21.7%) and corneal ulcers (13.0%). Results of this study indicate that Nd:YAG TSCP is an effective method of controlling IOP and preserving vision in horses with glaucoma. An effective Nd:YAG laser protocol for TSCP in the equine glaucomatous eye is a power setting of 11 W, duration of 0.4 s, applied 5 mm posterior to the limbus at 60 sites, resulting in a total energy dose of 264 J.     

Corneal esthesiometry in the healthy horse

Objective To determine corneal sensitivity in healthy adult horses in order to establish reference values. Animals studied One hundred eyes of 50 healthy adult horses. Procedure Corneal sensitivity was determined by evaluating the corneal touch threshold (CTT) in five different corneal regions using a Cochet‐Bonnet esthesiometer. Results Comparing CTT values (in mm filament length) of the five prescribed corneal regions revealed regional variations in corneal sensitivity, with the central region (21.15 ± 6.23 mm) being the most sensitive, followed by the nasal (20.75 ± 5.14 mm), temporal (20.70 ± 5.37 mm), ventral (20.15 ± 5.88 mm) and dorsal (15.85 ± 3.70 mm) region. However, differences between the central, nasal, temporal and ventral regions were not statistically significant, whereas the dorsal region was significantly (P < 0.0001) less sensitive compared to the other regions. Division of the horses into three age groups revealed an insignificant decrease in corneal sensitivity with age in the nasal, temporal, ventral and central region, and an insignificant increase with age in the dorsal region. Correlation of corneal sensitivity with age was statistically significant in the central, ventral and temporal region. No statistically significant difference in the CTT was found between left and right eyes and between males and females. Conclusions CTT values in 100 eyes of 50 healthy adult horses evaluated with a Cochet‐Bonnet esthesiometer generated reference values. Reference values are necessary to determine alterations of corneal sensation accompanying various eye diseases or systemic diseases.     

The long‐term effects of semiconductor diode laser transscleral cyclophotocoagulation on the normal equine eye and intraocular pressurea

Objective To describe the long‐term histologic and intraocular pressure (IOP) lowering effects of diode laser transscleral cyclophotocoagulation (TSCP) on the normal equine eye. Animals Eight normal adult horses. Procedures TSCP was performed in one randomly assigned eye. Sixty spots were treated at settings of 1500 ms and 1500 mW. Two horses were randomly selected for euthanasia at 2, 4, 12, or 24 weeks post‐TSCP. Both eyes were enucleated and histologically evaluated. Intraocular pressure was measured by applanation tonometry prior to TSCP, immediately post‐TSCP, twice daily for 7 days post‐TSCP and then monthly until study conclusion. A longitudinal model estimated the average IOP values for the treated and untreated eyes at 1 week, 1, 3, and 6 months post‐TSCP. Results All treated eyes at all time periods exhibited four characteristic histologic lesions: scleral collagen hyalinization, ciliary body pigment dispersion and clumping, focal disruption of the ciliary body epithelium, and focal ciliary process atrophy. After TSCP, there were no significant changes in IOP from baseline for the control eyes, while the IOP in treated eyes was significantly decreased from baseline (P < 0.05) at all time periods. The estimated decrease in IOP in the treated eyes compared to baseline IOP at 6 months was ‐3.76 mmHg for an average decrease in IOP of 20% from baseline. Conclusion  Diode laser TSCP produces histologic lesions in the equine ciliary body that result in a significant and sustained decrease in IOP. TSCP may be an effective management for equine glaucoma.     

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 ≥15 mm/min) and 20 eyes with low STT values (STT ≤14 mm/min) were examined. The mean STT value for eyes with normal STT values was 22.9 ± 3.9 mm/min (mean ± standard deviation), and the mean STT value for eyes with low STT value was 7.2 ± 4.8 mm/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.     

Scleral rupture in dogs, cats, and horses

OBJECTIVES: The aim of this retrospective study was to summarize the most frequent clinical signs, ultrasonographic, and histological findings accompanying scleral rupture as a result of blunt trauma in dogs, cats, and horses. ANIMALS STUDIED AND PROCEDURES: Thirty small animals and three horses diagnosed with scleral rupture resulting from blunt trauma. B-mode ultrasonography was performed on 20 animals. Histopathology was carried out on 18 enucleated globes. RESULTS: In small animals, 80% presented hyphema, 60% subconjunctival hemorrhage, and 53% eyelid and conjunctival swelling. In horses, 100% presented eyelid and conjunctival swelling, 67% hyphema, subconjunctival hemorrhage, and collapsed anterior chamber. Ultrasonographic findings were an area with ill-defined scleral margins (90%), echoic/hyperechoic contents in the anterior and posterior chamber (55%) and in the vitreous (80%). In small animals, scleral rupture location noted on gross examination was: at the posterior pole (4), close to the optic nerve (3), near the limbus (2), and in the dorsal aspect of the globe (1). In horses, the lesion was located at the limbus (3). In small animals, histopathology showed presence of hemorrhage in the anterior, posterior chamber, and vitreous (94%), retinal detachment (94%), choroidal edema and hemorrhages (88%), and choroidal detachment as a result of suprachoroidal hemorrhage (88%). The same lesions were found in the globes of two horses. In small animals, rupture location noted on histopathology was: at the posterior pole (8), close to the optic nerve (4), near the limbus (1), near the ciliary body (1). CONCLUSIONS: The most frequent clinical signs observed were hyphema, subconjunctival hemorrhage, and eyelid and conjunctival swelling. Ultrasonographic findings suggestive for scleral rupture were ill-defined scleral borders and/or echoic/hyperechoic material in the cavities of the globe. On histopathology, lesions severely altering the anatomy of the eye structures were: hemorrhage into the chambers of the globe, subretinal and suprachoroidal hemorrhage leading to retinal and choroidal detachment, respectively. In small animals, the most frequent locations for scleral rupture were the posterior pole and close to the optic nerve, whereas in horses it was the limbus.     

Treatment of serous retinal detachments associated with optic disk pits in dogs

Serous retinal detachment, associated with optic disk pit, was diagnosed in 28 eyes of 24 dogs. Xenon arc photocoagulation was used in treatment of the detachment. Of 24 dogs, 21 were Collies. In 23 eyes, retinal detachments affected temporal and/or inferior portions of the retina. In 5 eyes, detachments were predominantly superior and/or nasal. A single photocoagulation treatment resulted in reattachments in 25 eyes. Of the 3 remaining detachments, 2 eyes improved with additional photocoagulation, and 1 eye, which was not treated further, had a complete retinal detachment.     

Intracapsular lensectomy and sulcus intraocular lens fixation in dogs with primary lens luxation or subluxation

Objective  To evaluate the postoperative results of lensectomy and sulcus intraocular lens fixation (SIOLF) via an ab interno approach in dogs with progressive lens subluxation or early luxation.
Study design  Retrospective study.
Animals studied  Twenty eyes from 19 dogs presented to the Animal Eye Clinic for lens luxation or subluxation between 1999 and 2006.
Methods  Medical records were reviewed to evaluate preoperative lens position, vision status, intraocular pressure (IOP), and whether surgery was performed on an emergent or elective nature. Lensectomy and SIOLF were performed and postoperative status including vision, glaucoma, and retinal detachment was assessed.
Results  Average age was 8.6 years (range 4–14 years) and 55% (11/20) were terriers. Patients were followed a mean of 29.2 months (range 1–92 months) after surgery. Retinal detachment or secondary glaucoma was observed in 1 of 20 (5%) and 5 of 20 (20%) eyes, respectively, with 1 of 20 (5%) exhibiting both. Mean preoperative IOP was 16 mmHg and preoperative lens position was equally divided between luxated and subluxated lenses. Surgery was performed more frequently as an elective procedure (18/20; 90%) due to normalized IOP vs. an emergency procedure (2/20; 10%). Vision was retained in 70% (14/20) of eyes with a mean time to vision loss of 41 months in the remaining eyes due to glaucoma, retinal detachment, or retinal degeneration.
Conclusions  Complications of glaucoma and retinal detachment after SIOLF in this study were less when compared with previously reported incidence rates in the literature for lensectomy alone which may reflect improved patient selection.     

Semiconductor diode laser transscleral cyclophotocoagulation for the treatment of glaucoma in horses: a retrospective study of 42 eyes

Objective To evaluate the outcome of diode laser transscleral cyclophotocoagulation (TSCP) for the treatment of glaucoma in horses. Procedure Medical records at The Ohio State University were reviewed. All horses that underwent diode laser TSCP between the years of 1995 and 2007 were included. Preoperative, procedural and clinical follow‐up data were collected, and telephone follow‐up was performed. Results Forty‐two eyes of 36 horses were included. Twenty‐four hours prior to surgery mean intraocular pressure (IOP) was 37.17 ± 13.48 mmHg (42 eyes). Forty‐one of 42 eyes (98%) were sighted and 39 of 39 (100%) of eyes were receiving topical glaucoma medication. At 3–5 weeks postoperatively the average IOP was 19.36 ± 12.04 mmHg (22 eyes). IOP remained significantly lower than pretreatment values at all periods of clinical follow‐up (P < 0.05). There was no significant difference in vision outcome, or the requirement for topical glaucoma medication relative to pretreatment values at any follow‐up period. Hyphema in 5 of 42 eyes was the only complication noted. Of the 27 eyes seen for clinical follow‐up, 2 were enucleated because of refractory elevation of IOP. Mean telephone follow‐up was 49 months. Twenty‐one of 22 owners contacted (95%) reported that the treatment had been of value, 14 of 22 eyes (64%) were receiving topical glaucoma medication, and 13 of 22 eyes (59%) were considered sighted. Conclusions Diode laser TSCP aided in the control of IOP and maintenance of vision but did not eliminate the need for topical glaucoma medication during the period of clinical follow‐up.     

Lens morphometry determined by B-mode ultrasonography of the normal and cataractous canine lens

Purpose To determine axial lens thickness, anterior chamber depth and axial globe length in canine eyes with normal lenses and in eyes with immature, mature, congenital, posterior polar and diabetic cataract. Methods B‐mode ultrasonography was performed in 50 normal dogs and, as a prephacoemulsification screening procedure, in 100 dogs with cataract. Axial B‐mode ultrasonograms were used to determine lens thickness, anterior chamber depth and globe diameter. Statistical comparisons between groups were made by analysis of variance and multivariate analysis, with a significance level of P < 0.05. Results Axial globe lengths were not statistically significantly different between groups apart from the smaller globes in younger dogs with congenital cataract. Axial lens thickness in diabetics (8.4 ± 0.9 mm) was statistically significantly different from the lens thickness in normal eyes (6.7 ± 1.0 mm), eyes with immature cataract (6.4 ± 0.8 mm) and eyes with mature cataract (7.4 ± 0.9 mm) although these groups, while varying in thickness, were not statistically significantly different from each other. Anterior chamber depth was statistically significantly reduced in eyes with diabetic cataract (2.9 ± 0.1 mm) from that in normal eyes (3.8 ± 0.1 mm), eyes with immature cataract (3.5 ± 0.1 mm) and eyes with mature cataract (3.2 ± 0.6 mm) although these groups, while varying in chamber depth, were not statistically significantly different from each other. Conclusions Lenses with diabetic cataracts were significantly increased in axial thickness compared to lenses in other eyes, although lenses with mature cataracts showed a trend towards increased axial thickness and immature cataracts demonstrated a trend towards reduced thickness. While previous studies on cataract pathobiology have suggested a reduction in lens thickness in immature cataract through lens protein loss and an increase in thickness in mature cataracts through intumescence, this study is the first to document these changes in the canine lens.     

Effects of transcorneal iridal photocoagulation on the canine corneal endothelium using a diode laser

Objective To investigate the potential damage to the canine corneal endothelium following transcorneal iridal laser photocoagulation using a semiconductor diode laser. Animals studied Sixteen young mongrel dogs. Procedures Baseline corneal endothelial cell counts and corneal thickness were measured in the central and temporal quadrants using a noncontact specular microscope under general anesthesia. Transcorneal iridal photocoagulation was applied using a semiconductor diode laser in a continuous mode with the use of an operating microscope. Fifteen dogs were treated, and the sixteenth dog served as a control. Fifteen different treatment combinations were randomly assigned to the 30 eyes; the fellow eye was treated differently. Three treatment factors were investigated: (1) laser energy intensity, (2) target tissue to endothelial distance, and (3) laser application duration. After 3 weeks the dogs were euthanized, specular microscopy was repeated, and the cornea was examined by scanning electron microscopy. Results Dyscoria and focal iris darkening were noted in all eyes immediately following laser treatment. Focal corneal edema (n = 2) and an incipient anterior capsular cataract (n = 1) were also noted. Baseline mean corneal endothelial cell densities were 2530 cells/mm² centrally and 2607 cells/mm² temporally. Postlaser corneal endothelial cell densities were 2499 cells/mm² centrally and 2523 cells/mm² temporally. Mean prelaser corneal thickness measurements were 0.555 mm centrally and 0.549 mm temporally. Postlaser corneal thickness measurements were 0.580 mm centrally and 0.554 mm temporally. Statistical analyzes revealed no significant changes in endothelial cell densities (P > 0.05) or corneal thickness (P > 0.05) induced by any treatment combination. Aside from tissue handling and processing artifacts, scanning electron microscopy revealed no endothelial cell damage. Conclusions Our study demonstrated by specular and scanning electron microscopy that diode laser iridal photocoagulation had no significant effect on the canine corneal endothelium within the parameters described. However, one must take into consideration the young age of the dogs and the potential for corneal endothelial cell regeneration in young dogs, and the relatively short period of postoperative study.     

Toxic equine parkinsonism: an immunohistochemical study of 10 horses with nigropallidal encephalomalacia

Chronic ingestion of yellow star thistle (Centaurea solstitialis) or Russian knapweed (Acroptilon repens) causes nigropallidal encephalomalacia (NPE) in horses with an abrupt onset of neurologic signs characterized by dystonia of lips and tongue, inability to prehend food, depression, and locomotor deficits. The objectives of this study were to reexamine the pathologic alterations of NPE and to conduct an immunohistochemistry study using antibodies to tyrosine hydroxylase and α-synuclein, to determine whether NPE brains show histopathologic features resembling those in human Parkinson disease. Results confirm that the NPE lesions are located within the substantia nigra pars reticulata, sparing the cell bodies of the dopaminergic neurons in the substantia nigra pars compacta, and in the rostral portion of the globus pallidus, with partial disruption of dopaminergic (tyrosine hydroxylase-positive) fibers passing through the globus pallidus. No abnormal cytoplasmic inclusions like the Lewy bodies of human Parkinson disease were seen in these NPE brains. These findings indicate that equine NPE may serve as a large animal model of environmentally acquired toxic parkinsonism, with clinical phenotype directly attributable to lesions in globus pallidus and substantia nigra pars reticulata rather than to the destruction of dopaminergic neurons.     

Enhanced expression of cyclooxygenase-2 in glaucomatous dog eyes

Objective Cyclooxygenase‐2 (COX‐2)‐derived prostaglandins (PGs) are shown to play important pathophysiologic roles in various disease states. Recently, the effectiveness of topical PGs in reducing intraocular pressure (IOP) has stimulated further interest in the physiologic function of COX‐2 and PGs in normal and glaucomatous eyes. Therefore, we investigated the cell‐type distribution and expression of COX‐2 in normal and glaucomatous dog eyes. Procedures Using isoform‐specific antibodies, we immunohistochemically evaluated COX‐2 expression in formalin‐fixed and paraffin‐embedded normal (n = 5) and glaucomatous (n = 17) dog eyes. Results In the normal eyes, only minimal COX‐2 immunoreactivity was observed in the ciliary epithelium. In the glaucomatous eyes, COX‐2 expression was further observed in the cornea and corneoscleral limbus. In the cornea, moderate to strong COX‐2 expression was observed in all corneal layers (epithelium, stromal cells and endothelium), with the greatest expression present in the epithelial layer. In the corneoscleral limbus area, COX‐2 immunoreactivity was noted in the stromal cells of sclera, trabecular meshwork and endothelial cells of the angular aqueous plexus. Conclusions Increased expression of COX‐2 in dog glaucomatous eyes suggests that COX‐2‐derived PGs may have a potential role in the pathogenesis of canine glaucoma.     

DOSIMETRIC IMPACT OF DAILY SETUP VARIATIONS DURING TREATMENT OF CANINE NASAL TUMORS USING INTENSITY-MODULATED RADIATION THERAPY

Intensity-modulated radiation therapy (IMRT) can be employed to yield precise dose distributions that tightly conform to targets and reduce high doses to normal structures by generating steep dose gradients. Because of these sharp gradients, daily setup variations may have an adverse effect on clinical outcome such that an adjacent normal structure may be overdosed and/or the target may be underdosed. This study provides a detailed analysis of the impact of daily setup variations on optimized IMRT canine nasal tumor treatment plans when variations are not accounted for due to the lack of image guidance. Setup histories of ten patients with nasal tumors previously treated using helical tomotherapy were replanned retrospectively to study the impact of daily setup variations on IMRT dose distributions. Daily setup shifts were applied to IMRT plans on a fraction-by-fraction basis. Using mattress immobilization and laser alignment, mean setup error magnitude in any single dimension was at least 2.5 mm (0–10.0 mm). With inclusions of all three translational coordinates, mean composite offset vector was 5.9±3.3 mm. Due to variations, a loss of equivalent uniform dose for target volumes of up to 5.6% was noted which corresponded to a potential loss in tumor control probability of 39.5%. Overdosing of eyes and brain was noted by increases in mean normalized total dose and highest normalized dose given to 2% of the volume. Findings suggest that successful implementation of canine nasal IMRT requires daily image guidance to ensure accurate delivery of precise IMRT distributions when non-rigid immobilization techniques are utilized. Unrecognized geographical misses may result in tumor recurrence and/or radiation toxicities to the eyes and brain.     

Density of corneal endothelial cells and corneal thickness in eyes of euthanatized horses

OBJECTIVE: To determine density of corneal endothelial cells and corneal thickness in eyes of euthanatized horses. SAMPLE POPULATION: 52 normal eyes from 26 horses. PROCEDURE: Eyes were enucleated after horses were euthanatized. Eyes were examined to determine that they did not have visible ocular defects. Noncontact specular microscopy was used to determine density of corneal endothelial cells. Corneal thickness was measured, using ultrasonic pachymetry or specular microscopy. RESULTS: Mean density of corneal endothelial cells was 3,155 cells/mm2. Cell density decreased with age, but sex did not affect cell density. Values did not differ significantly between right and left eyes from the same horse. Cell density of the ventral quadrant was significantly less than cell density of the medial and temporal quadrants. Mean corneal thickness was 893 microm. Sex or age did not affect corneal thickness. Dorsal and ventral quadrants were significantly thicker than the medial and temporal quadrants and central portion of the cornea. We did not detect a correlation between corneal thickness and density of endothelial cells in normal eyes of horses. CONCLUSIONS AND CLINICAL RELEVANCE: Density of corneal endothelial cells decreases with age, but corneal thickness is not affected by age or sex in normal eyes of horses. The technique described here may be useful for determining density of endothelial cells in the cornea of enucleated eyes. This is clinically relevant for analyzing corneal donor tissue prior to harvest and use for corneal transplantation.     

Effect of topical tropicamide on tear production as measured by Schirmer's tear test in normal dogs and cats

Objective To evaluate the effect of a single dose of topical 1% tropicamide on tear production as measured by the Schirmer tear test (STT) in the normal dog and cat. Material and methods Twenty‐eight dogs and 32 cats received 50 µl : l of 1% tropicamide in one eye and the opposite eye served as the control. STTs were performed immediately before instillation of tropicamide and then at 1, 4, 8 and 24 h post drug instillation. STT results were compared between the control and treated eyes at the different times. Results Aqueous tear production in dogs, measured by STT, was not significantly reduced. The mean ± SEM STTs for the baseline time for control and tropicamide‐treated eyes were 19.9 ± 0.8 and 20.3 ± 0.8 mm wetting/min, respectively. For the control eyes, the subsequent mean ± SEM STT levels were 20.3 ± 0.9 (1 h), 21.1 ± 0.8 (4 h), 20.1 ± 0.9 (8 h), and 18.7 ± 0.7 (24 h). For the tropicamide‐treated eyes, the subsequent mean ± SEM STT levels were 19.4 ± 0.9 (1 h), 19.3 ± 0.9 (4 h), 20.0 ± 0.9 (8 h), and 18.4 ± 0.8 (24 h). Aqueous tear production of both eyes was significantly reduced in cats at 1 h but returned to baseline by 4 h post tropicamide instillation. The mean ± SEM STT levels for the baseline time in cats for control and tropicamide‐treated eyes were 14.9 ± 0.8 and 14.7 ± 0.8 mm wetting/min, respectively. Subsequent mean ± SEM STT levels for the control eyes were 6.4 ± 1.1 (1 h), 11.9 ± 1.0 (4 h), 13.9 ± 0.8 (8 h), and 16.4 ± 1.0 (24 h). For the tropicamide‐treated eyes, the subsequent mean ± SEM STT levels were 5.3 ± 0.8 (1 h), 10.2 ± 0.8 (4 h), 14.7 ± 1.0 (8 h), and 16.6 ± 1.0 (24 h). Conclusion Single dose 1% tropicamide does not significantly lower tear production rates, as measured by the STT, in normal dogs. However, in normal cats single doses of 1% tropicamide in one eye cause significant reductions in tear production of both eyes at 1 h that recovered to baseline levels by 4 h.     

Estimation of lacrimal level and testing methods on normal beagles

Five methods of testing tears including the Schirmer tear test (STT-1), phenol red thread tear test (PRT) and modified Schirmer tear test (STT-2) were conducted on 44 eyes of 22 normal Beagles, and the tear film break up time (BUT) and lacrimal pH were tested in 32 eyes of 16 normal Beagles. The coefficient of variation of PRT demonstrated a low value (C.V. 14%) compared to the value of STT-1 (C.V. 12%). The lacrimal pH showed a more constant value (C.V. 3%). Measurements of STT-2 (C.V. 48%) and BUT (C.V. 34%) varied significantly. The results show the clinical usefulness of the PRT. Mean values (mean ± SD) of tests were: PRT, 29.3 ± 3.45 mm/15 s; STT-1, 18.89 ± 2.62 mm/60 s; STT-2, 9.52 ± 4.55 mm/60 s; pH, 7.29 ± 0.22 and BUT, 21.53 ± 7.42 s.     

Optic nerve head neuroretinal rim blood flow differences in monkeys with laser-induced glaucoma

INTRODUCTION: The blood flow of the neuroretinal rim (NRR) of the optic nerve head (ONH) of the rhesus monkey with laser-induced glaucoma was examined. METHODS: Argon laser photocoagulation of the trabecular meshwork to induce elevated intraocular pressure (IOP) was performed in one eye of nine normal male rhesus monkeys. The nasal and temporal NRR of the monkey ONH were examined by the Heidelberg retina tomograph/flowmeter (HRT/HRF) under neuromuscular blockade. A mixed effect analysis of variance was used to determine significant differences between eyes and between locations in the eyes. RESULTS: The average IOP in the hypertensive glaucoma and normal eyes was 34.8 +/- 7.2 and 16.0 +/- 1.9 mmHg, respectively. The HRT determined average overall cup to disc (C/D) area ratio in the glaucoma and normal eyes, which was 0.49 +/- 0.28 and 0.22 +/- 0.16, respectively. The mean temporal NRR HRF flow in the hypertensive eyes was significantly greater than in the normotensive eyes (P < 0.0001), than in the nasal NRR of the hypertensive eyes (P < 0.0001) and than in the nasal NRR of the normotensive eyes (P < 0.01). The mean nasal NRR HRF flow in the hypertensive eyes was significantly less than in the nasal NRR of the normotensive eyes (P < 0.01). There was no statistical difference between the mean HRF flow of the temporal and nasal NRR of the normotensive eyes. The elevated IOP positively influenced the flow values in the hypertensive eye (r = 0.724). CONCLUSIONS: The capillary microcirculation of the temporal NRR of the rhesus monkey ONH with laser-induced glaucoma has significantly increased blood flow, and the nasal NRR significantly reduced blood flow compared to blood flow in the NRR of normal normotensive monkey eyes.     

Effect of topical 0.02% tacrolimus aqueous suspension on tear production in dogs with keratoconjunctivitis sicca

Objective To investigate the effect of 0.02% tacrolimus in aqueous suspension on tear production in dogs with keratoconjunctivitis sicca (KCS). Animals studied One hundred five dogs diagnosed with KCS [Schirmer tear test (STT) ≤ 10 mm/min and clinical signs of dry eye]. Eyes with marginally decreased STT (11 ≤ 15 mm/min) and clinical signs of dry eye were also evaluated. Procedure The investigation was conducted in two parts: an initial efficacy study and a subsequent double blinded controlled study. In the efficacy study, the effect of topical tacrolimus (formerly FK‐506) on tear production in dogs with primary KCS was evaluated. Dogs were divided into four categories: 1) 59 eyes (38 dogs) naïve to tear stimulation therapy with initial STT ≤ 10 mm/min; 2) 28 eyes (21 dogs) naïve to tear stimulation therapy with initial STT 11 ≤ 15 mm/min; 3) 30 eyes (15 dogs) maintained successfully on CsA therapy; 4) 47 eyes (24 dogs) unresponsive to CsA therapy. STT and clinical signs were evaluated prior to and after 6 to 8 weeks of twice daily tacrolimus administration. Tacrolimus was substituted for CsA therapy in categories 3 and 4. The controlled study compared the effect of topical tacrolimus in aqueous suspension to administration of the aqueous carrier alone on tear production in 20 dogs with primary KCS. Results In the efficacy study, STT increased by 5 mm/min in 84.7%, 25.0%, 26.7% and 51.1% of eyes in categories 1, 2, 3 and 4 respectively after tacrolimus administration. Eighty‐three percent of eyes with extremely low initial STT (≤ 2 mm/min), increased 5 mm/min after tacrolimus. In the controlled study, STT increased by 5 mm/min in 7/10 dogs (14/20 eyes) that received tacrolimus and in none of the 10 dogs that received aqueous carrier alone. Dogs receiving just the aqueous carrier were subsequently treated with tacrolimus, and STT increased 5 mm/min in 9 dogs (18/20 eyes) after administration. Conclusions Twice daily administration of 0.02% tacrolimus in aqueous suspension effectively increased tear production in dogs with KCS. Topical tacrolimus is a promising alternative to topical CsA for treatment of KCS and may be beneficial in patients with less than optimal response to topical CsA.     

Tear production in dogs with epiphora and corneal epitheliopathy

Measurement of tear volume by phenol red thread tear test (PRT), Schirmer's tear test (STT-1) and Schirmer's tear test with topical anesthesia (STT-2), and vital staining with a combination of fluorescein and rose Bengal of the cornea were performed in dogs with normal eyes and those with epiphora. The breeds included the Shih-Tzu ( n  = 26), and five other breeds ( n  = 50). The PRT, STT-1 and STT-2 results from the five breeds of normal dogs were 26.9 ± 3.0 mm, 17.4 ± 4.3 mm, and 8.8 ± 3.2 mm, respectively. The PRT, STT-1, and STT-2 results for the Shih-Tzu eyes were (mean ± standard deviation): 28.2 ± 4.3 mm, 19.5 ± 4.1 mm, and 9.2 ± 4.5 mm, respectively. In the five breeds, corneal epitheliopathy, as evidenced by the retention of topical fluorescein and rose Bengal, occurred in 97% of dogs with epiphora and in 55% of the dogs without epiphora. Also in the dogs with corneal epitheliopathy the STT-2-value was low (4.0 ± 2.8 mm) compared with those eyes without corneal epitheliopathy (8.8 ± 3.1 mm). In the Shih-Tzu breed the STT-2 results were not significantly different between those dogs with corneal epitheliopathy and those with normal corneas. In the non-Shih-Tzu breeds the decrease in basic tear secretion, as measured by the STT-2, is associated with the corneal epitheliopathy.     

Macromorphometric study on ciliary body location in canine eyes

This macroscopic study firstly examined the precise locational information of the canine ciliary body, i.e., the ciliary crown and the ciliary ring in the beagle. The safe and effective transscleral laser photocoagulation technique requires the accurate location of the ciliary body. In both sides of the eyeball in 10 beagle dogs, the width of the ciliary ring and the distance from the limbus to the ciliary ring were measured with calipers using a stereomicroscope at the 8 points. The widest portion of ciliary body was found at the dorsal to ventro-temporal area of the lateral canthus (lateral portion of the eyelid; ear side). In contrast, the narrowest portion was seen at the ventro-nasal to nasal area of the medial canthus (medial portion of the eyelid; nasal quadrants). Use of transscleral photocoagulation at the present narrowest area of ciliary body may carry a high risk of destruction of the optic portion of retina.