Primary glaucoma in Burmese cats

OBJECTIVE: To document the clinical signs and management of primary glaucoma in Burmese cats. DESIGN: A retrospective study of six affected Burmese cats, from 1996 to 2001. Procedure Six Burmese cats diagnosed with primary glaucoma were managed over periods varying from 3 months to 4.5 years. Clinical details were obtained from practice records. Gonioscopic examination of the drainage or iridocorneal angle in eyes of these affected cats was made. RESULTS: Six desexed female Burmese cats (ages 7.0 to 10.5 years) presented with complaints of either unilateral (n = 4) or bilateral (n = 2) red eye, dilated pupil or enlarged eye. In one of the affected cats, one eye had been enucleated prior to the commencement of the study, thus a total of 11 eyes were examined. Clinically, all affected eyes (n = 8) had injected episcleral blood vessels and elevated intraocular pressure. Gonioscopy revealed the presence of nine narrow and two closed iridocorneal angles. Medical therapy included topical 2% dorzolamide (n = 8), 0.5% timolol maleate (n = 1), 0.005% latanoprost (n = 1) and 0.5-1.0% prednisolone acetate (n = 8). Surgery was performed in six eyes using either diode laser (n = 5) and/or cryothermy (n = 2) and one eye was eviscerated, with implantation of a prosthesis. With therapy, five affected eyes maintained vision and normal intraocular pressure, one eye remained blind with normal intraocular pressure, one eye remained blind with elevated intraocular pressure and one eye was eviscerated. CONCLUSIONS: The Burmese cat may be predisposed to primary narrow-angle glaucoma. Early diagnosis and continuous antiglaucoma therapy can help control intraocular pressure and maintain vision.     

Advances in topical glaucoma therapy

Significant advances have recently been achieved in the development of topical glaucoma medications. The primary advantage of a topical preparation is the reduced incidence of adverse systemic effects attributable to a given drug compared to its systemically administered counterpart. However, the strong protective barrier of the eye forces topical ophthalmic preparations to be highly concentrated and in some cases, they have the potential to produce unwanted systemic effects, particularly in smaller animals. Oral carbonic anhydrase inhibitors are commonly associated with adverse effects in both humans and animals. Two recently developed topical carbonic anhydrase inhibitors, dorzolamide and brinzolamide, have shown promise in reducing intraocular pressure in animals and systemic side effects are apparently limited with their use. The topical alpha2-agonist apraclonidine, on the other hand, effectively reduces intraocular pressure in cats and dogs, but in its currently available form is likely to induce unwanted systemic effects. Latanoprost is a topical prostaglandin F2alpha analog that has proven effective in reducing intraocular pressure in dogs and horses, but while systemic side effects have not yet been reported, this topical preparation may exacerbate pre-existing or concurrent ocular inflammatory disease.     

Effects of twice daily application of 2% dorzolamide on intraocular pressure in normal cats

The effect of the topical carbonic anhydrase inhibitor, dorzolamide, on intraocular pressure in cats was studied. The intraocular pressure of both eyes of eight healthy cats was measured using applanation tonometery (Tono-Pen) during two phases: control and treatment. Both eyes were treated with 2% dorzolamide twice a day during the treatment phase. Application of dorzolamide resulted in a significant decrease of intraocular pressure over the treatment phase. By the fourth and fifth day of treatment, the mean intraocular pressure (+/- standard deviation) was 9.7 (+/- 1.5) mmHg, whereas the mean (+/- standard deviation) for the last 2 days of the control period was 12.2 (+/- 2.0) mmHg. Based on this study, dorzolamide is a potentially effective treatment for glaucoma in cats, significantly lowering intraocular pressure.     

28例犬、猫角膜疾病的诊疗

临床选取确诊为角膜疾病但眼压正常的犬、猫共28例,运用雾化熏蒸给药法,结合中医疗法的优势,根据病症分型,辨证施治。结果治疗犬、猫角膜疾病总有效率达85%,此结合疗法可为眼压异常的犬、猫角膜疾病治疗提供一定治疗模式。     

Melanocytic neoplasia in the cat

Clinical features and histopathological details from 13 cases of melanocytic neoplasia in the cat are presented. The series includes cases of intraocular melanoma (n=5), limbal melanoma (n=2), dermal melanoma (n=5) and one case of metastatic melanoma for which a primary site was not identified. In the case of the intraocular tumours, there was apparent correlation between the degree of cellular pleomorphism, the mitotic rate and the extent of local infiltration. Such an association was not identified for the melanomas arising from the limbus or skin.     

Intraocular and Cardiopulmonary Effects of Low-dose Mannitol in the Dog

Fatal complications have been reported during anesthesia in dogs that received a standard (1–2 g/kg IV) dose of mannitol during intraocular surgery. A lower dose (0.25 g/kg IV), which had been shown to reduce intracranial pressure in humans, was evaluated during halothane anesthesia in dogs. There were no significant changes in intraocular pressure (IOP) or cardiovascular variables. This lower dose (0.25 g/kg IV) did not reduce IOP and would not be of benefit in dogs undergoing intraocular surgery.     

Intraocular pressure and tear production in five herbivorous wildlife species

The intraocular pressure and rate of tear production were measured in 18 addax antelopes (Addax nasomaculatus), four impalas (Aepyceros melampus), 11 wide-lipped rhinoceroses (Ceratotherium simum), 10 white-tailed wildebeests (Connochaetes gnou) and seven scimitar-horned oryxes (Oryx dammah). The animals were anaesthetised with an intramuscular injection of etorphine hydrochloride and acepromazine maleate, and the Schirmer tear test I was used to evaluate tear production, and applanation tonometry was used to evaluate the intraocular pressure. The mean (sd) rate of tear production ranged from 17.6 (3.1) mm/minute in the rhinoceros to 28.8 (8.3) mm/minute in the addax. The intraocular pressure ranged from 8.0 (1.2) mmHg in the impala to 32.1 (10.4) mmHg in the rhinoceros. The rate of tear production in the addax and the intraocular pressure in the rhinoceros appear to be the highest values of these variables to have been reported in any species.     

Effect of topical atropine on intraocular pressure and pupil diameter in the normal horse eye

The objective was to determine whether topically administered 1% atropine would alter intraocular pressure. The animals studied were four healthy adult horses. Intraocular pressure and pupil diameter were measured prior to and during a 2-day period of treatment with 1% atropine sulfate. No significant changes in intraocular pressure occurred as a result of the treatment with atropine. Pupil diameter increased significantly after atropine was applied. Available information on the outflow of aqueous humor from the horse eye suggests that atropine might reduce intraocular pressure in the horse by increasing uveoscleral outflow. This could prove beneficial in the treatment of equine glaucoma. We could not confirm a significant pressure-lowering effect of atropine. It is possible, however, that a longer treatment period may be required or that atropine may have a more profound effect on glaucomatous globes.     

Change in intraocular pressure during maturation in Labrador Retriever dogs

Objective To measure intraocular pressure (IOP) in a group of dogs as puppies and young adults to determine if there is any change during maturation. Animals studied Thirty‐two healthy Labrador Retriever dogs. Procedures Intraocular pressure was measured using a Tonopen XL initially at approximately 6 weeks of age (T1), then again approximately 1 year later (T2). Exact ages were known based on whelp date. Results The dogs had marginally higher IOP OU at T2 (mean = 14.9 mmHg) compared to T1 (mean = 13.4 mmHg). However, the difference was not statistically significant. No differences were seen based on sex and litter. Intraocular pressure OD was statistically greater than OS at T1 but not at T2. Conclusions Normal values for intraocular pressure are the same in puppies and adults. The results of this study do not support the previously suggested theory that younger dogs have sustained increased IOP as a requirement to drive growth of the globe. However, it does not rule out the possibility that a dynamic relationship between intraocular pressure and expansion of the globe may exist.     

Combined cycloablation and gonioimplantation for treatment of glaucoma in dogs: 18 cases (1992-1998)

OBJECTIVE: To evaluate a combined cycloablative and gonioimplantation technique for treatment of glaucoma in dogs. DESIGN: Retrospective study. ANIMALS: 18 adult dogs with glaucoma. PROCEDURE: Medical records of dogs that received a valved gonioimplant and a cyclodestructive procedure (cyclocryoablation or diode laser cyclophotocoagulation) during a 6-year period were reviewed. Retention of vision and intraocular pressure control were assessed, as well as number and nature of complications. RESULTS: 19 eyes of 18 dogs received a valved gonioimplant and either cyclocryoablation (n = 12) or diode laser cyclophotocoagulation (7). At > or = 1 year after surgery, 11 of 19 eyes had vision and 14 of 19 eyes had intraocular pressure < 25 mm Hg. Two dogs (2 eyes) were lost to follow-up 3 and 6 months after surgery. Despite the alternative route for aqueous humor flow created by the gonioimplant, 7 eyes had increased intraocular pressure (27 to 61 mm Hg) < 24 hours after surgery. Other complications included excessive intraocular fibrin, focal retinal detachment, corneal ulcer, retinal hemorrhage, cataract, and implant migration. CONCLUSIONS AND CLINICAL RELEVANCE: Combined cycloablation and gonioimplantation appears to be a promising technique for retention of vision and control of intraocular pressure in dogs with glaucoma.     

Implantation of a foldable intraocular lens in dogs

A 1-piece, tripod-shaped, acrylic intraocular lens was implanted in the posterior chamber after phacoemulsification to remove cataracts in 20 eyes of 16 dogs. Biomicroscopy and intraocular pressure measurements were performed at 1, 8, 30, and 90 days after surgery; retinoscopy was performed at day 30. Complications were not encountered during implantation of the lens. All dogs had mild ocular inflammation characterized predominantly by aqueous flare and mild corneal edema at day 1, which resolved completely by day 8; 3 eyes had mild hyphema at day 1, which resolved by day 8. Three eyes developed fibrin in the anterior chamber, which resolved by day 30. Two eyes developed distorted pupils caused by adherence of vitreous humor or fibrin to the incision site. Postoperative intraocular pressure ranged from 7 to 21 mm Hg. Implantation resulted in 9 emmotropic eyes, 5 myopic eyes, and 6 hyperopic eyes. Maintenance of central lens position was excellent in 19 eyes; in 1 eyes, a disclocated superior haptic at day 2 was easily repositioned.     

Antemortem diagnosis of congenital glaucoma in a white‐bellied caique (Pionites leucogaster)

A 34‐day‐old, male, white‐bellied caique (Pionites leucogaster) was presented for a complaint of bilateral buphthalmos. Clinical examination was unremarkable apart from the ophthalmic findings. The ophthalmologic examination was negative for direct, consensual, and dazzle reflexes in both eyes. The intraocular pressure exceeded 40 mm Hg OU. Fluorescein stain demonstrated corneal surface lesions suggestive of exposure keratopathy subsequent to bilateral buphthalmos. Diagnostic imaging tests were conducted to perform ocular biometric measurements and investigate the intraocular structures, including the iridocorneal angle and lens, by means of high‐resolution ultrasonography (HRUS). The presence of congenital glaucoma in this young parrot was strongly suspected after clinical and ophthalmological examination and the results of diagnostic imaging. Pharmacological treatment to reduce intraocular pressure was initiated using dorzolamide hydrochloride 2% and timolol maleate 0.5%. A month later, the parrot's eyes did not show any visual improvement, but the intraocular pressure had returned to normal. The parrot was unable to feed itself and died during a feeding procedure. Postmortem examination revealed ab ingestis pneumonia. Both eyes were submitted for histopathology, with severe anterior segment dysplasia and goniodysgenesis found OU. Histological findings added to the clinical presentation, the ophthalmologic examination and the imaging findings, confirmed the presence of congenital glaucoma.     

Effects of prostaglandin F2 alpha and leukotriene D4 on pupil size, intraocular pressure, and blood-aqueous barrier in dogs.

In each of 5 groups of dogs, 0.05 ml of 1 of the following solutions was injected into the anterior chamber of both eyes: phosphate-buffered saline solution, 0.001 microgram of prostaglandin F2 alpha (PGF2 alpha), 0.01 microgram of PGF2 alpha, 0.1 microgram of leukotriene D4 (LTD4), and 1 microgram of LTD4. A 10% solution of sodium fluorescein was injected IV (14 mg/kg of body weight) at the same time, and pupil size, intraocular pressure, and anterior chamber fluorescence were measured for 1 hour after injections. In a dose-dependent manner, PGF2 alpha was a potent miotic. A significant effect on intraocular pressure was not detected when the groups given PGF2 alpha were compared with the control group. When compared with LTD4, PGF2 alpha significantly (P less than 0.05) increased the breakdown of the blood-aqueous barrier, as evidenced by increased fluorescein leakage into the anterior chamber. Leukotriene D4 caused a decrease in pupil size only at 5 minutes, compared with that of the control group. Intraocular pressure was greater (but not significantly) in the group given 1 microgram of LTD4.     

Solid intraocular xanthogranuloma in three Miniature Schnauzer dogs

OBJECTIVE: Macrophages that contain abundant intracytoplasmic lipid are called 'foam cells'. In four canine globes submitted to the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW), foam cells formed a solid intraocular mass. The purpose of this study was to describe the histopathologic findings in these cases. PROCEDURE: The electronic COPLOW database (1993-2006) was searched for the diagnosis of 'foam cell tumor'. Clinical history, gross pathology and histopathology (5-micron sections, hematoxylin and eosin and Alcian blue periodic acid Schiff) were reviewed in all cases. Cases were included if the globe was grossly filled by a solid mass and if all intraocular structures were effaced by lipid-laden foam cell macrophages admixed with birefringent, Alcian blue-positive crystals oriented in stellate patterns. RESULTS: All three patients (four globes) satisfying the selection criteria were Miniature Schnauzers. In all cases the clinical history included diabetes mellitus, hyperlipidemia and chronic bilateral uveitis that was interpreted to be lens-induced. All globes were enucleated because of glaucoma. CONCLUSIONS: The term solid intraocular xanthogranuloma was used to describe these cases because the intraocular contents were effaced by a solid mass of foam cells and birefringent crystals. The cases in this report suggest that diabetic Miniature Schnauzers with hyperlipidemia are at risk for lipid and macrophage-rich uveitis, which may in some cases form a solid inflammatory intraocular mass, precipitate glaucoma, and lead to enucleation.     

Anesthesia in ophthalmic surgery

Ophthalmic surgical patients can be routinely anesthetized without complications if the surgeon has a thorough understanding of the effects of anesthetic agents on ocular physiology. The regulation of intraocular pressure is important for successful ophthalmic surgery and can be greatly affected by the anesthetic procedure. Agents utilized to intentionally decrease intraocular pressure are often employed for intraocular procedures. These agents have profound systemic effects that must be anticipated. Adverse drug interactions between sympathomimetic mydriatics and halogenated inhalation anesthetics also must be considered.     

Arterially perfused eye model of uveitis

OBJECTIVE: To develop an in vitro model of uveitis based on an ex situ perfused eye to evaluate the anti-inflammatory activity of new pharmacological products. PROCEDURE: Eyes were removed from more than 60 dogs and 9 horses immediately after euthanasia and perfused with nutrient medium through the lateral long ciliary artery. Perfused eyes produced aqueous humour, and perfusion pressure was adjusted to obtain an intraocular pressure in the physiological range. When the eyes were treated with histamine, a complement C5a analogue peptide and hydrogen peroxide, typical signs of uveitis were produced. These included miosis, vascular leakage, reduced intraocular pressure, reduced flow of perfusate and, in some eyes, conjunctival oedema. RESULTS: Canine eyes showed a decrease in intraocular pressure and a decrease in perfusate flow rate when challenged with 100 mumol/L hydrogen peroxide. Flunixin meglumine (5 mumol/L), ketoprofen (5 mumol/L), indomethacin (5 mumol/L) as well as a new drug pirfenidone (10 mumol/L) prevented changes in intraocular pressure induced by hydrogen peroxide, but did not significantly moderate the mediator-induced changes in perfusate flow. CONCLUSIONS: This model is suitable for evaluating potential anti-inflammatory activity of drugs without having to induce uveitis in an experimental animal. The technique is suitable for species that range in size from cats to horses.     

Comparison of applanation tonometers in dogs and horses.

Two Mackay-Marg tonometers and 2 Tono-Pen tonometers were evaluated in eyes in which intraocular pressure (IOP) had been altered and measured by use of a manometer. Eyes of anesthetized dogs and enucleated horse eyes were used. Compared with the manometer, none of the tonometers accurately measured IOP over the range between 0 and 100 mm of Hg. However at manometer measurements from 0 to 30 mm of Hg, several of the tonometers accurately measured IOP. In addition, significant differences were observed when the measurement accuracy of one tonometer was compared with that of another, especially at high IOP. Coefficient of determination (r2) values for a linear model ranged from 0.979 to 0.991 in dogs, and from 0.982 to 0.996 in horse eyes.     

Corneal sensitivity and aqueous tear production in dogs undergoing evisceration with intraocular prosthesis placement

OBJECTIVE: To determine whether there is an association between evisceration with intraocular prosthesis placement via a dorsal scleral approach and decreased corneal sensitivity or aqueous tear production in dogs. DESIGN: Prospective study. PROCEDURE: Twenty-one dogs scheduled to undergo unilateral evisceration with intraocular prosthesis, and with a normal normotensive contralateral eye, based on slit-lamp biomicroscopy, indirect ophthalmoscopy and applanation tonometry, were included in the study. Central corneal sensitivity was measured with a Cochet-Bonnet esthesiometer prior to (week 0) and 2, 7, 14 and 28 weeks following surgery. Other pre- and postoperative data collected were Schirmer's tear test (STT I), Schirmer's tear test with topical anesthesia (STT II), corneal fluorescein retention, and intraocular pressure (IOP; postoperative control eye only). Axial globe length was determined for both eyes. Scleral incision length in the surgery eye was also recorded. RESULTS: Corneal sensitivity was significantly lower in eyes undergoing evisceration with intraocular prosthesis than in control eyes both preoperatively and postoperatively at all time points. There was no significant difference between preoperative and postoperative corneal sensitivity within the two groups. There was no significant difference in STT I or STT II-values between control eyes and surgery eyes preoperatively. There was a significant difference between preoperative and 2-week postoperative STT I in the surgery eye. There was a significant difference between the preoperative and 28-week postoperative STT II in the surgery eye. The 28-week postoperative STT I-values differed significantly between control and surgery eyes. Corneal sensitivity tended to decrease with increased degree of buphthalmos or with increased scleral incision length, although neither relationship was statistically significant. CONCLUSIONS: Eyes that have sustained chronically elevated intraocular pressure had decreased axial corneal sensitivity compared to normal eyes, which persisted even after intraocular pressure was reduced. The presence of buphthalmos appeared to be a factor in globes developing decreased corneal sensitivity. Evisceration via a dorsal scleral incision did not result in a significant further reduction in axial corneal sensitivity. A mild reduction in aqueous tear production occurred over time in globes following evisceration with intraocular prosthesis.     

Combined transscleral diode laser cyclophotocoagulation and Ahmed gonioimplantation in dogs with primary glaucoma: 51 cases (1996-2004)

OBJECTIVE: To evaluate the combined diode laser cycloablation procedure and adjunctive Ahmed gonioimplant use in dogs with primary glaucoma. DESIGN: Retrospective study. ANIMALS: 48 dogs, 51 eyes with primary glaucoma. PROCEDURE: Medical records from two large private clinical ophthalmology services were reviewed. Signalment, duration of glaucoma, gonioscopic evaluation, laser power and duration settings, immediate postoperative and final intraocular pressure and visual results, short and long-term visual outcome, and surgical complications were recorded. RESULTS: The age range of affected dogs was 3.0-14.0 years, with a mean age of 7.5 +/- 2.6 years. Eleven pure breeds were represented, with the most common being the American Cocker Spaniel. The sex distribution was 22 neutered males, 1 intact male, 23 spayed females, and 2 intact female dogs. The right eye was affected in 33 cases, and the left eye in 18 cases. The average total joules, which was administered with the diode laser, was 109.6 +/- 23.6 J. Immediate surgical complications included fibrin formation in the anterior chamber (15), corneal ulcers (4), hyphema (7), and focal retinal detachment (1). Long-term complications included cataract formation (8 total, 2 of which were significant, vision-threatening), elevated intraocular pressure (IOP) (6), unstable gonioimplant (1), and glaucoma recurrence (14). Additional surgeries performed on the eyes over the course of study included: intrascleral prosthesis (4), enucleation (1), resection of fibrotic scar tissue (5), and repeat laser cycloablation (8). The dogs were examined for a mean follow-up time of 17.6 months (range: 2-83 months postoperatively). Twenty-nine cases were followed greater than one year. Vision was maintained in 42/51 eyes (82%) in the immediate short-term of this study. In all cases included in the study, good control of IOP was achieved in 39/51 (76%) of eyes, and IOP was poor or uncontrolled in 12/51 (24%) of eyes. Twenty out of 41 eyes (49%) maintained fair to excellent vision six months after surgery. Twelve months postoperative observations demonstrated that 12/29 (41%) of the eyes were still visual. CONCLUSIONS: In primary glaucoma, the combined procedure of laser diode cyclophotocoagulation and Ahmed valve implant was associated with return or maintenance of vision in 42/51 eyes (82%) in the immediate short-term of this study, and a long-term IOP control in 39/51 (76%) of the cases, with 12/29 eyes (41%) visual after 12 months.