Clinical Signs and Diagnosis of the Canine Primary Glaucomas

Effect of a Collar and Harness on Intraocular Pressure and Respiration Rate of Brachycephalic and Dolichocephalic Dogs

BACKGROUND

Dogs are a popular pet in many countries, and for them to gain appropriate exercise, many owners opt to walk them on a leash. Despite health and welfare concerns, brachycephalic breeds remain common as pets, with limited research existing that investigates the best restraint type for these animals.

OBJECTIVES

This study aimed to test the effect of a collar and harness during stationary and exercise conditions on the intra-ocular pressure (IOP) and respiration rate (RR) of brachycephalic and dolichocephalic dogs.

METHODS

A total of 24 healthy dogs, both brachycephalic and dolichocephalic, were recruited for the study and underwent stationary and exercise conditions in two restraint types in a within-between-subjects design. IOP was measured by rebound tonometry, and RR was measured using clinical and visual methods by the same experimenter.

RESULTS

Just wearing a collar in a stationary condition increased IOP in brachycephalic dogs (p < 0.05) but not in dolichocephalic dogs (p > 0.05). Exercising in a collar increased IOP for both groups of dogs (p < 0.05), whereas exercising in a harness did not affect IOP for either group (p > 0.05). RR increased in exercise conditions for both restraint types in brachycephalic dogs (p < 0.05), with no difference between collar and harness (p > 0.05).

CONCLUSIONS

Data suggest that collars may elevate IOP during exercise for all dogs and also during stationary conditions for brachycephalic breeds. Owners need to be conscious of the most appropriate restraint for their dog to avoid deleterious effects on IOP and RR.

Comparative analysis of iridocorneal angle in cats and dogs using ultrasound biomicroscopy: implications for glaucoma prevalence

BACKGROUND

This study aims to investigate the anatomical differences in the anterior segment of the eyes between dogs and cats using ultrasound biomicroscopy (UBM) to understand the higher prevalence of primary angle-closure glaucoma (PACG) in dogs compared to cats. Retrospective analysis was performed on clinical data from 16 eyes of 16 dogs and 14 eyes of 14 cats with normal eye conditions. UBM was utilized to measure nine specific parameters, including Schwalbe's Line Distance (SLD), Iridocorneal Angle (ICA), Angle-Opening Distance (AOD), and three ciliary cleft parameters: width (CCW), length (CCL), and area (CCA). To account for differences in body size, ciliary cleft parameters were adjusted accordingly.

RESULTS

Significant anatomical differences in the anterior segment were found between the two species. Dogs had smaller values for SLD, ICA, AOD, and ciliary cleft parameters (CCW, CCL, CCA) compared to cats. Even after body-size adjustment, the rectified ciliary cleft parameters remained smaller in dogs.

CONCLUSION

The anatomical differences, particularly the smaller ciliary cleft and narrower drainage angles in dogs, may contribute to the higher prevalence of PACG in this species. Conversely, the larger ciliary cleft in cats may explain the lower occurrence of primary glaucoma in cats.

Vision outcomes in dogs with primary glaucoma surgically treated with lensectomy and endolaser cyclophotocoagulation after an Ahmed valve gonioimplantation failure

OBJECTIVE

The aim of this study was to retrospectively evaluate vision outcomes of dogs with primary angle closure glaucoma (PACG) that underwent Ahmed valve gonioimplantation (AVG) followed by lensectomy and endolaser cyclophotocoagulation (ECP) with or without bleb resection after AVG failure.

PROCEDURE

Medical records from 2008 to April 2022 were reviewed. All patients selected had an AVG performed first. Following valve failure, lensectomy-ECP was performed in addition to bleb resection as indicated. Additional ECP and AVG replacement surgeries were performed as deemed medically necessary. Main outcomes evaluated included vision preservation, average IOP reduction, and the number of glaucoma medications (both oral and topical) at 6, 12, 24, and 36 months.

RESULTS

Fourteen eyes from 13 patients were included in the study. Females were predominant (n = 9) compared with males (n = 4). Mean age at initial glaucoma diagnosis was 6.82 years. Following AVG and lensectomy-ECP, vision was preserved in 93%, 84%, 60%, and 48% of eyes at 1, 2, 3, and 4 years respectively. Following lensectomy-ECP, there was a significant reduction in mean IOP of 9.64 mmHg (p = .015) and 9.71 mmHg (p = .016) at 2 and 6 months, respectively. There was a reduction in mean IOP of 2.45, 7.25, and 12.25 mmHg at 12, 24, and 36 months, respectively, which was not statistically significant. There was a significant decrease in the number of glaucoma medications at all evaluated time points except 24 months.

CONCLUSIONS

Combined AVG and lensectomy-ECP is successful in maintaining vision long term as well as decreasing IOP, and the number of glaucoma medications administered.

An in-depth review on utilizing ultrasound biomicroscopy for assessing the iridocorneal angle and ciliary body in canines

In this review, we explore the transformative role of Ultrasound Biomicroscopy (UBM) in veterinary ophthalmology, focusing on its utility in evaluating the iridocorneal angle and ciliary body in dogs. We begin by outlining UBM's foundational principles, providing a holistic understanding of its operational mechanics. This is followed by an exploration of the techniques and considerations for optimal UBM imaging, including the use of topical anesthesia, probe positioning, and maintaining a controlled measurement environment. A major section is dedicated to the detailed anatomy of the anterior segment, emphasizing the iridocorneal angle and ciliary body in controlling aqueous humor dynamics within canine and feline eyes. By comparing anatomical structures in humans and animals, we highlight the need for distinct parameters in veterinary medicine. The review also analyzes the parameters obtainable via UBM, emphasizing its potential in monitoring drug-induced ocular changes, gaging post-cataract surgical outcomes, and observing inter-species variations. We conclude by encapsulating the current state of research, addressing existing challenges, and suggesting future research avenues. This synthesis underscores the pivotal role of UBM in advancing veterinary ophthalmic diagnostics and research.

Stem Cell-Based Therapies for Glaucoma Treatment: A Review Bridging the Gap in Veterinary Patients

Retinal diseases are characterized by progressive damage to retinal cells, leading to irreversible vision loss. Among these, glaucoma stands out as a multifactorial neurodegenerative disease involving elevated intraocular pressure, retinal ganglion cell apoptosis, and optic nerve damage, ultimately resulting in blindness in both humans and dogs. Stem cell-based therapies have emerged as a promising therapeutic option for such conditions due to their regenerative and neuroprotective potential. These therapies, particularly those based on mesenchymal stem cells, offer the potential to repair and protect retinal tissues through the bioactive molecules (growth factors, cytokines, chemokines) secreted, their secretome. However, research in this field, especially on the use of umbilical cord mesenchymal stem cells' secretome, remains sparse. Most clinical trials focus on human glaucomatous patients, leaving a significant gap in veterinary patients' application, especially in dogs, with additional research being needed to determine its usefulness in canine glaucoma treatment. Future studies should aim to evaluate these therapies across both human and veterinary contexts, broadening treatment possibilities for glaucoma.

Gender differences in canine anterior chamber dimensions: Potential implications for primary angle-closure glaucoma

OBJECTIVES

This study aimed to explore anatomical differences in the aqueous humor (AH) outflow pathway between male and female dogs using ultrasound biomicroscopy (UBM).

ANIMALS STUDIED

Clinical data were collected from 30 eyes of 30 dogs (15 males: 10 right eyes, 5 left eyes; and 15 females: 7 right eyes, 8 left eyes) treated at the Veterinary Medical Teaching Hospital of Chungbuk National University, South Korea, between August 2018 and February 2024.

PROCEDURE

The study conducted an in-depth UBM examination, specifically observing peripheral anterior chamber depth (ACD), geometric iridocorneal angle (ICA), and angle-opening distance (AOD) alongside measurements of ciliary cleft width (CCW), length (CCL), and area (CCA), and assessed the longitudinal fibers of ciliary muscle thickness (Lf-CMT) and the longitudinal and radial fibers of ciliary muscle thickness (LRf-CMT) for gender-based differences.

RESULTS

The study identified a significant sex difference in peripheral ACD, with females displaying shallower depths compared to males, potentially clarifying the higher incidence of glaucoma in female dogs. No significant gender differences were found in ICA, AOD, CC parameters, or ciliary muscle parameters measurements.

CONCLUSION

This research uncovered that peripheral ACD is significantly shallower in females than in males, potentially indicating a risk factor that could contribute to the development of primary angle-closure glaucoma.

Quantitative analysis of iridocorneal angle and ciliary cleft structures in canine eyes using ultrasound biomicroscopy

Introduction

This study aimed to examine the relationship between the relative opening of the ICA (RO-ICA) and the structure of the ciliary cleft (CC) using Ultrasound Biomicroscopy (UBM).

Materials and methods

Clinical data from 31 eyes of 17 dogs at the Veterinary Teaching Hospital of Chungbuk National University, Korea, were analyzed. RO-ICA was categorized as "Slightly Narrow", "Narrow", "Open", and "Wide Open", with eyes further grouped into "Narrow" (including Slightly Narrow and Narrow) and "Open" (including Open and Wide Open) for analysis. Statistical methods, including linear regression and average comparisons between groups, were employed to explore correlations between RO-ICA and parameters such as ICA, CC width (CCW), CC length (CCL), and CC area (CCA).

Results

The distribution showed "Narrow" (3 eyes, 9.7%), "Slightly Narrow" (13 eyes, 41.9%), and "Open" (14 eyes, 45.2%) as the predominant categories. In the Open group, CCL and CCA were significantly larger compared to the Narrow group. A positive correlation was observed between RO-ICA and CCL, and CCA across all groups. Notably, in the Narrow group, RO-ICA demonstrated a particularly significant positive correlation with all assessed parameters, including ICA, CCW, CCL, and CCA. However, no significant correlation was observed between RO-ICA and the assessed parameters in the Open group. In conclusion, while a smaller RO-ICA generally correlates with a smaller CC, a larger RO-ICA does not guarantee a larger CC.

Conclusion

Additional UBM examinations are recommended for comprehensive evaluations, particularly in cases where gonioscopy indicates an open iridocorneal angle.

Interexaminer agreement of gonioscopy examinations in dogs using the European College of Veterinary Ophthalmologists Hereditary Eye Diseases grading scheme

OBJECTIVE

Prospective observational study with preregistered study protocol to assess interexaminer agreement using the 2022 European College of Veterinary Ophthalmologists Hereditary Eye Disease (ECVO-HED) gonioscopy grading scheme.

ANIMALS STUDIED

Sixty client-owned dogs presented for gonioscopy as part of the required certification process prior to breeding.

PROCEDURE

Two ECVO diplomates with comparable clinical experience performed gonioscopy with a Koeppe gonioscopy lens and slit-lamp biomicroscope at 10x magnification on all eyes in a randomized fashion.

RESULTS

One hundred and eighteen of 120 eyes (60 dogs) were included. In 110/118 eyes (93%), both examiners provided the same breeding recommendation (yes/no). This translated into an agreement on the final breeding recommendation in 58/60 dogs (97%). Examiners disagreed on pectinate ligament abnormality (PLA) grading in 19/118 eyes and iridocorneal angle width (ICAW) grading in 9/118 eyes. PLA grading disagreement was mostly observed between neighboring grades. Disagreement between PLA and ICAW grading sometimes occurred within the same eye accounting for an observed disagreement in iridocorneal angle abnormality (ICAA) grading in 19/118 eyes in total. Cohen's kappa was Κ = 0.62 (95% TI 0.34-0.89), whereas maximum kappa was maxΚ = 0.82 (95% TI 0.59-1). Mixed model analysis suggested no significant examiner influence on breeding recommendations (OR 0.17; 95% CI 0.02-1.12, p = .09).

CONCLUSIONS

Although examiners disagreed on ICAA grading in 19/118 eyes, this resulted in a different breeding recommendation (yes/no) in eight eyes and in two dogs only. Therefore, the use of the 2022 ECVO-HED gonioscopy grading scheme seems to result in examiners providing the same breeding recommendations in most cases.

Ultrasound biomicroscopy analysis of ciliary muscle dynamics and its relation to intra-ocular pressure after phacoemulsification in dogs

Introduction

This study investigates the relationship between ciliary muscle dynamics, thickness, and the regulation of intraocular pressure (IOP), focusing on the progression of cataracts and changes post-phacoemulsification. It explores how these factors impact canine ocular health, particularly in the context of cataract development and subsequent surgical intervention.

Materials and methods

Data was collected using Ultrasound Biomicroscopy (UBM) from dogs at the Veterinary Medical Teaching Hospital of Chungbuk National University, Korea. The study involved 57 eyes from 35 dogs, categorized into five groups: 13 normal eyes, 14 with incipient cataracts, 12 with immature cataracts, 6 with mature cataracts, and 12 post-phacoemulsification. UBM measurements assessed various ciliary muscle parameters including ciliary body axial length (CBAXL), ciliary process-sclera angle (CPSA), longitudinal fibers of ciliary muscle thickness (Lf-CMT), and longitudinal and radial fibers of ciliary muscle thickness (LRf-CMT).

Results

Findings indicated a decrease in CBAXL and an increase in Lf-CMT as cataracts progressed in severity. Post-phacoemulsification, there was a notable increase in CBAXL and a decrease in CPSA, Lf-CMT, and LRf-CMT, compared to both cataractous and normal eyes. Regression analysis revealed a significant positive association between CBAXL and IOP, alongside a negative association between Lf-CMT and IOP. These findings suggest that variations in ciliary muscle dynamics and thickness, as influenced by cataract progression and phacoemulsification, have distinct impacts on intraocular pressure.

Discussion

The study proposes that phacoemulsification leads to ciliary muscle contraction, causing an inward and anterior movement of the ciliary muscle. This movement results in the narrowing of the ciliary cleft and constriction of the unconventional outflow pathway, potentially causing an increased risk of glaucoma post-surgery. Our research contributes to understanding the anatomical and physiological changes in the canine eye following cataract surgery and underscores the importance of monitoring IOP and ciliary muscle dynamics in these patients.

Prevalence of pre-iridal monocellular and fibrovascular membranes in canine globes affected with congenital glaucoma associated with anterior segment dysgenesis, primary glaucoma associated with goniodysgenesis, and secondary glaucoma

Objectives

The objectives of this study were to (i) evaluate the prevalence of pre-iridal monocellular and fibrovascular membranes in canine globes affected with congenital glaucoma associated with anterior segment dysgenesis (ASD), primary glaucoma associated with goniodysgenesis (GD), and secondary glaucoma, and (ii) examine the associations between monocellular and fibrovascular membranes by breed, gender, age and histopathologic ocular changes on light microscopic examination.

Methods

Records of dogs who had eyes enucleated due to blindness and uncontrolled glaucoma were reviewed. Glaucoma was categorized clinically and histologically into three groups: congenital/ASD, primary/GD, and secondary glaucoma. The presence or absence and type of pre-iridal membrane (monocellular or fibrovascular) and other intraocular histologic findings were reviewed and compared statistically for each group.

Results

In total, 108 canine globes (101 dogs) were included. Pre-iridal monocellular membranes were identified with light microscopy in 10 out of 19 congenital/ASD, 29 out of 40 primary, and 23 out of 49 secondary glaucoma globes. Fibrovascular membranes were observed in 3 out of 19 congenital/ASD, 9 out of 40 in primary, and 24 out of 49 secondary glaucoma globes. There were no associations between the type of membrane and breed, gender, or age. Peripheral anterior synechiae were more common in globes with fibrovascular membranes, and uveal atrophy was more common in globes with monocellular membranes.

Conclusion

Pre-iridal monocellular membranes are common in all types of canine glaucoma. They are identified with light microscopy most easily in cases of primary glaucoma, and they are masked by pre-iridal fibrovascular membranes in other forms of glaucoma.

Role of Inflammation in Canine Primary Glaucoma

Primary glaucoma is a painful, progressive, and blinding disease reported in many canine breeds, characterized by intraocular pressure (IOP) elevation in the absence of antecedent intraocular disease. Clinical observations of dogs with primary glaucoma suggest that many affected eyes develop concurrent intraocular inflammation in addition to elevated IOP. In this work, we summarize the current knowledge that relates inflammation to primary glaucoma in dogs, reviewing studies focused on genetics, physiology, histopathology, bioanalysis of ocular fluids, therapeutics, and clinical outcomes of glaucomatous patients. Through disruption of the blood-aqueous and blood-retinal barriers, pigment dispersion, and biochemical changes to the aqueous humor and tear film, the pathogenesis of canine primary glaucoma appears to involve inflammatory changes to various extents and with various consequences from the front to the back of the eye. Among others, inflammation further impacts IOP by reducing aqueous humor outflow at the level of the iridocorneal angle and accelerates vision loss by promoting neuronal degeneration. As such, the vicious cycle of ocular inflammation and IOP elevation might warrant the use of anti-inflammatory medications as a core component of the treatment regime for dogs with primary glaucoma, either therapeutically (i.e., actively glaucomatous eye) or prophylactically in the yet unaffected contralateral eye.

Evaluation of ciliary cleft changes after phacoemulsification using ultrasound biomicroscopy in dogs with cataracts

Introduction

Glaucoma is one of the most serious complications that causes irreversible blindness after phacoemulsification in dogs; however, a clear mechanism has not been elucidated. This study aimed to analyse the possible anatomical factors associated with glaucoma after phacoemulsification using parameters that reflect the anatomical characteristics of dogs.

Materials and methods

A total of 69 eyes of 48 dogs were included in this study. The patients were divided into three groups: normal eye (n = 18), cataract (n = 39), and post-phacoemulsification for at least 2 months after surgery (post-phaco, n = 12). For further analysis, the dogs were subdivided into two groups according to cataract stage: phacoemulsification non-candidate and candidate groups. Non-cataracts and incipient cataracts were categorized into the non-candidate group, whereas immature and mature cataracts were categorized into the candidate group. Measurements of the ciliary cleft parameters, including the area of the ciliary cleft (CCA), length of the ciliary cleft (CCL), width of the ciliary cleft (CCW), iridocorneal angle, and angle opening distance, were obtained using ultrasound biomicroscopy.

Results

CCA, CCL, and CCW were significantly higher in the candidate group than in the non-candidate group. CCA, CCL, and CCW were significantly reduced in the post-phaco group compared to those in the cataract group. Based on these results, we found that the ciliary cleft expanded in cataract-affected eyes and narrowed after phacoemulsification. This may indicate that the space between the trabecular meshworks became narrower, potentially leading to an increase in the resistance of the aqueous humor.

Conclusion

A narrowed ciliary cleft after phacoemulsification may be an anatomical factor associated with glaucoma.

Iris angiography in ADAMTS10 mutant dogs with open-angle glaucoma (ADAMTS10-OAG)

OBJECTIVE

To evaluate anterior segment angiographic findings in hypertensive ADAMTS10-open-angle glaucoma (ADAMTS10-OAG) eyes as compared to normotensive control eyes.

ANIMALS STUDIED

Nine ADAMTS10-OAG beagles and four wild-type control dogs.

PROCEDURES

Anterior segment angiography was performed under general anesthesia following intravenous injection of indocyanine green (ICG; 1 mg/kg) and sodium fluorescein (SF; 20 mg/kg) using a Heidelberg Spectralis® confocal scanning laser ophthalmoscope. Time to onset of iridal angiographic phases and the presence/severity of dye leakage into the iris stromal and/or aqueous humor were recorded. Group findings were compared, and multiple linear regression analysis was performed to identify potential factor associations with disease status.

RESULTS

Time to onset of all angiographic phases visualized using ICG was significantly prolonged while time to onset of SF leakage into the aqueous humor was significantly reduced in glaucomatous eyes compared to controls. Only glaucomatous eyes (n = 9) demonstrated evidence of SF stromal leakage. Mean intraocular pressure (IOP) and age were significantly higher, while mean cardiac pulse was significantly lower in glaucomatous eyes compared to controls. Blood pressure and ocular perfusion pressure were not significantly different between groups. Multiple linear regression analysis, controlling for age, IOP, and pulse demonstrated glaucoma, was not predictive of the time to onset of any angiographic phase, stromal, or aqueous humor leakage. However, pulse was a significant factor contributing to the severity of aqueous humor leakage.

CONCLUSIONS

A compromised vascular supply to the anterior segment exists in dogs with ADAMTS10-OAG. These observations warrant further exploration of what role altered perfusion and/or disruption to the blood-aqueous barrier may play.

Inter-device agreement between spectral domain optical coherence tomography, ultrasound biomicroscopy, and gonioscopy in evaluating the iridocorneal angle in normotensive dogs

BACKGROUND

There has not been a thoroughly reported study of the comparison between spectral domain-optical coherence tomography (SD-OCT) with both ultrasound biomicroscopy (UBM) and gonioscopy on the evaluation of the iridocorneal angle (ICA) in dogs.

OBJECTIVES

To investigate the diagnostic value of SD-OCT for the early detection of narrowing ICA by comparing and assessing inter-device agreement in anterior chamber angle (ACA) measurements obtained by SD-OCT and UBM, and ICA evaluations by gonioscopy.

METHODS

A total of 28 eyes from 28 client-owned dogs with normal intraocular pressure were included for examination. The ACA and angle opening distance (AOD) were measured from the SD-OCT and UBM images, and gonioscopy images were analyzed using the ICA grade and ZibWest angle index.

RESULTS

The mean ACA and AOD for SD-OCT were 28.31° ± 5.37° and 658.42 ± 219.90 µm, and for UBM, 28.34° ± 5.82° and 859.29 ± 221.80 µm, respectively. The mean difference in ACA between the average values of SD-OCT and UBM measurements was 0.03° with a 95% limit of agreement (LoA) span of 16.2°, indicating positive agreement; that in AOD was 200.85 µm with a 95% LoA span of 1,110.95 µm, indicating poor agreement. The Pearson correlation coefficient of the ACA of SD-OCT and ZibWest indices of gonioscopy was 0.624, indicating strong agreement; that of UBM and gonioscopy was 0.43, indicating moderate agreement.

CONCLUSIONS

SD-OCT is well tolerated by canine patients due to its non-contact method and might be an alternative option for early screening of ICA narrowing in clinical settings.

Ocular morphologic traits in the American Cocker Spaniel may confer primary angle closure glaucoma susceptibility

Acute primary angle closure glaucoma is a potentially blinding ophthalmic emergency requiring prompt treatment to lower the elevated intraocular pressure in humans and dogs. The PACG in most of canine breeds is epidemiologically similar to humans with older and female patients overrepresented with the condition. The American Cocker Spaniel (ACS) is among the most common breeds observed with PACG development in dogs. This study initially sought to identify genetic risk factors to explain the high prevalence of PACG in ACSs by using a case-control breed-matched genome-wide association study. However, the GWAS failed to identify candidate loci associated with PACG in this breed. This study then assessed intrinsic ocular morphologic traits that may relate to PACG susceptibility in this breed. Normal ACSs without glaucoma have a crowded anterior ocular segment and narrow iridocorneal angle and ciliary cleft, which is consistent with anatomical risk factors identified in humans. The ACSs showed unique features consisting of posterior bowing of iris and longer iridolenticular contact, which mirrors reverse pupillary block and pigment dispersion syndrome in humans. The ACS could hold potential to serve as an animal model of naturally occurring PACG in humans.

A genome-wide association study to investigate genetic loci associated with primary glaucoma in American Cocker Spaniels

OBJECTIVE

To identify genetic associations with primary glaucoma (PG) in American Cocker Spaniels using a genome-wide association study (GWAS).

ANIMALS

A nationwide ambidirectional case-control cohort study was performed in American Cocker Spaniels that had an ophthalmic examination performed by a veterinarian. Ninety-four dogs with PG (cases) and 111 dogs without glaucoma (controls) met phenotypic criteria and had a blood sample collected after receiving informed owner consent.

PROCEDURES

Genomic DNA was extracted from whole blood samples and genotyped (CanineHD BeadChip, Illumina Inc). A case-control GWAS using a linear mixed model was performed, and 3 significance thresholds were calculated (1) using a Bonferroni correction on all single nucleotide polymorphisms (SNPs) included in the GWAS, (2) using a Bonferroni correction on only the unlinked SNPs from a pruned data set, and (3) using 10,000 random phenotype permutations.

RESULTS

Following genotype data quality control, 89 cases and 93 controls were included in the GWAS. We identified an association on canine chromosome (CFA10); however, it did not reach statistical significance. Potential candidate genes within the surrounding linkage disequilibrium interval include coiled-coil domain containing 85A (CCDC85A) and extracellular growth factor containing fibulin extracellular matrix protein 1 (EFEMP1).

CLINICAL RELEVANCE

Primary glaucoma in the American Cocker Spaniel is a complex heterogeneous disease that may be influenced by a locus on CFA10. The candidate genes CCDC85A and EFEMP1 within the identified linkage disequilibrium interval have been shown to be involved in human open-angle glaucoma.

Long-term results (>1 year) in 19 dogs treated with MicroPulse transscleral diode cyclophotocoagulation for refractory glaucoma

OBJECTIVE

To report the long-term (>1 year) outcome of MicroPulse transscleral diode cyclophotocoagulation (MP-TSCP) in dogs.

ANIMALS STUDIED

Client owned dogs that underwent MP-TSCP at a veterinary referral center.

PROCEDURE

Retrospective study of 19 dogs treated with MP-TSCP. Dogs were evaluated at a median follow-up time of 30.5 months postoperatively. Reported outcomes were intraocular pressure (IOP), retention or loss of vision, number of medications, and additional procedures performed. Variables associated with time to treatment failure were evaluated.

RESULTS

Data from 19 dogs (24 eyes) was available. Median laser settings employed were 140 s and 2200 mW at 31.3% duty cycle. Long-term postoperative IOP was lower than preoperative IOP values (14 mmHg (IQR = 22 mmHg, range: 4-52 mmHg) versus 30 mmHg (IQR = 31 mmHg, range: 8-62 mmHg), respectively). Laser settings >2000 mW were associated with a significantly longer time to reported failure. MP-TSCP was the sole therapy performed in 16/24 eyes resulting in long-term IOP control in 13/24 eyes and retention of vision in 6 of the 14 sighted eyes. Repeat MP-TSCP was performed in 10/24 eyes. Eight of 24 eyes required additional procedures with long-term IOP control in 4/8 eyes.

CONCLUSIONS

MicroPulse transscleral diode cyclophotocoagulation can be an effective treatment for refractory glaucoma in select cases. Higher laser settings increased time to reported failure, whereas age, glaucoma type, and preoperative IOP did not affect survival. MP-TSCP as sole therapy or coupled with additional glaucoma procedures controlled the IOP in 70% of cases.

Outcomes of baervedlt implant surgery in 17 dogs (20 eyes) with primary closed-angle glaucoma (2013-2019)

OBJECTIVE

To report outcomes and follow-up of Baerveldt implant surgery in dogs with primary closed-angle glaucoma (PCAG).

MATERIALS AND METHODS

Record review of client-owned dogs with PCAG that underwent Baerveldt implant surgery during a 6-year period. Postoperative intraocular pressure (IOP), vision and daily number of anti-glaucoma drops at fixed time points (3, 12, and 24 months) were compared with preoperative values; complications were recorded. Success was defined as IOP <20 mm Hg and a positive menace response and navigation/tracking ability.

RESULTS

Twenty eyes (17 dogs) were included. Mean follow-up was 575 days (range 30-1767 days) from implant surgery to last examination. Three months postoperatively 15/20 (75%) eyes had IOP <20 mm Hg and 14/20 (70%) eyes had vision. Twelve months postoperatively 11/17 (65%) eyes had IOP <20 mm Hg and 12/19 (63%) eyes had vision. Twenty-four months postoperatively 8/14 (57%) eyes had IOP <20 mm Hg and 7/15 (47%) eyes had vision. Denominators differ between time points as eyes were included when duration after surgery reached the relevant postoperative time point or failure was documented earlier. Within 3 months postoperatively 16/20 (80%) eyes had ≥1 complication, including transient IOP >20 mm Hg (14/20; 70% eyes), fibrin (12/20; 60% eyes), and hypotony (4/20; 20% eyes). After 3 months, postoperatively 13/16 (81%) eyes had ≥1 complication, including cataracts (13/16; 81% eyes), bleb fibrosis (3/16; 19% eyes), and conjunctival wound breakdown (1/16; 6% eyes). One patient (1 eye) was euthanized for blindness and 5/20 (25%) eyes were enucleated.

CONCLUSIONS

The technique was effective in controlling IOP and maintaining vision in most dogs in this study.

Comparing the behaviour of dogs before and after enucleation due to glaucoma

PURPOSE

There is limited literature on owner's attitudes towards enucleation and behavioural changes after enucleation in dogs. The aim of this study is to investigate the owner's perception of canine enucleation as well as gain insight into the behavioural changes of dogs before and after enucleation due to glaucoma.

METHODS

This retrospective study involved a questionnaire sent to the owners whose dogs were diagnosed with glaucoma and underwent enucleation at the Queen Mother Hospital for Animals between June 2015 and January 2018. Owners were asked about their attitude towards enucleation, and to assess factors that affect their dogs' behaviours (appetite, general activity, playfulness and lethargy) at three time points: before enucleation, immediately after and 2 months after (TMA) enucleation.

RESULTS

Twenty-six of 45 questionnaires were completed and returned by the owners. TMA enucleation showed the most strongly positive responses indicating that owners perceived an improvement in the behaviours of their pets. 96% of participants were happy with their decision to go ahead with the surgery; and no participants regretted opting for enucleation.

CONCLUSION

The present study found expression of "normal" behaviour to increase after enucleation.

Prophylactic anti-glaucoma therapy in dogs with primary glaucoma: A practitioner survey of current medical protocols

AIM

To examine the use of prophylactic anti-glaucoma medications in the normotensive fellow eye in dogs with unilateral overt primary glaucoma by veterinary ophthalmology clinicians.

METHODS

A survey of veterinary ophthalmology clinicians was distributed over two international list serves servicing veterinary ophthalmologists, trainees, and individuals whose practice consisted primarily of ophthalmic patients. The survey was developed following analysis of historical and currently available medical options for control of intraocular pressure and for neuroprotection.

RESULTS

Responses from 199 veterinary ophthalmology clinicians were evaluated. While a large variety of topical anti-hypertensive drugs and protocols were used, the most commonly used medications were aqueous humor production suppressors such as dorzolamide 2.0% ophthalmic solution, timolol 0.5% ophthalmic solution, and a combination product containing both drugs. Latanoprost 0.005% ophthalmic solution was used infrequently for prophylaxis by comparison. The majority of respondents do not use concurrent anti-inflammatory medications (61.22%), although a sizeable minority used prednisolone acetate, dexamethasone, or ketorolac as prophylactic treatment. Systemically administered ocular anti-hypertensive agents were rarely used. Only 40% of respondents used neuroprotectant agents; the most commonly prescribed were the calcium channel blocker amlodipine and the nutraceutical Ocu-Glo™. Recommended intervals between re-examination by the clinician ranged from one month to one year, with most re-evaluations occurring every 3 to 6 months. The majority of respondents recommended more frequent assessments of IOP at intervals between once monthly and once every 3 months.

CONCLUSIONS

Data analysis of medical therapy for the normotensive fellow eye of dogs previously diagnosed with primary glaucoma suggests that there is a great need for well-designed, prospective, controlled, multi-center studies to determine which protocols have the greatest efficacy in delaying an overt attack in the previously normotensive eye in dogs with a genetic predisposition to glaucoma. Prospective studies utilizing a carbonic anhydrase inhibitor such as dorzolamide and a prostaglandin analogue such as latanoprost would be reasonable as these two drugs are widely used in the treatment of overt glaucoma and would allow for an exploration of the impact of different mechanisms of action of lowering IOP on the pathophysiology of primary glaucoma.

Protocol for assessment of the pupillary light reflex in dogs without chemical restraint: preliminary investigation

OBJECTIVE

To explore the use of a modified pupillometry technique in dogs without chemical restraint.

MATERIALS AND METHODS

Following dark adaptation, pupillary light reflexes were assessed in six dogs with sudden acquired retinal degeneration syndrome, in the unaffected eye of eight dogs with unilateral primary glaucoma ("predisposed"), and in 11 healthy dogs. Responses to red, blue and white lights were recorded and relative pupil sizes subsequently determined based on video recordings of each test.

RESULTS

Mean testing time was 2.3 minutes (range 1.8 to 3.1 minutes), excluding time for dark adaptation. Baseline pupil size in dogs with sudden acquired retinal degeneration syndrome was greater than in normal and predisposed eyes. Pupil constriction was reduced in predisposed compared to normal and sudden acquired retinal degeneration syndrome eyes when stimulated with high-intensity blue light. Compared to normal eyes, those with sudden acquired retinal degeneration syndrome had reduced pupil constriction when stimulated with low- and high-intensity red light, low-intensity blue light and white light.

CLINICAL SIGNIFICANCE

Quantitative measures of pupil function were obtained from healthy and diseased eyes without the need for chemical restraint. Further investigations are warranted to validate the technique and evaluate its use in the management of canine glaucoma.

Gonioscopic iridocorneal angle morphology and incidence of postoperative ocular hypertension and glaucoma in dogs following cataract surgery

PURPOSE

To investigate the relationship between gonioscopic iridocorneal angle (ICA) morphology and the incidence of postoperative ocular hypertension (POH) and postoperative glaucoma in dogs undergoing cataract surgery.

ANIMALS STUDIED

Retrospective analysis of 138 eyes of 78 canine patients who underwent phacoemulsification at North Carolina State University from December 1, 2015 through April 30, 2017.

METHODS

Medical records of all phacoemulsification patients with preoperative RetCam gonioscopic images were reviewed for preoperative, intraoperative, and postoperative variables. Gonioscopic angle indices were calculated using a novel (ZibWest) angle grading system, and these indices were analyzed for outcome-related significance.

RESULTS

Increased surgeon experience was associated with increased probability of POH and vision loss. Higher average ZibWest Angle indices (ie, more open angles with less pectinate ligament dysplasia/ abnormality) were associated with a significantly decreased probability of medically unresponsive glaucoma. Increased patient age was significantly associated with an increased probability of both postoperative glaucoma and vision loss. Female dogs were significantly more likely to experience postoperative glaucoma compared to male dogs. Increased surgery time was significantly associated with increased probability of vision loss.

CONCLUSIONS

The ZibWest angle index may predict increased risk for developing medically unresponsive glaucoma with cataract surgery. Female sex, and increased patient age, surgical time, and surgeon experience were associated with increased postoperative morbidity.

Suspected Spontaneous Aqueous Humor Misdirection Syndrome in a Boston Terrier

An eight-year-old female spayed Boston Terrier presented to the North Carolina Veterinary Hospital with glaucoma in the left eye (OS). Initial ophthalmic examination revealed moderate ocular hypertension, a diffusely and markedly shallow anterior chamber with anteriorly displaced iris and lens, vitreal prolapse, and a normal iridocorneal angle (ICA) morphology. The patient displayed a paradoxical response to topical latanoprost with an increase in intraocular pressure. These examination findings led to a putative diagnosis of spontaneous aqueous humor misdirection syndrome (AHMS). The patient was successfully managed with topical carbonic anhydrase inhibitors (CAIs) and apraclonidine for eight months until progressive ulcerative keratitis necessitated enucleation of the affected globe. Histopathology and high-field magnetic resonance imaging (MRI) of the enucleated globe did not identify an underlying cause for the glaucoma. This case suggests that AHMS should be considered in dogs presenting with a shallow anterior chamber, vitreal prolapse, increased intraocular pressure, and no other causes of glaucoma.

Primary angle-closure glaucoma with goniodysgenesis in a Beagle dog

Background

Open angle glaucoma is the only type of primary glaucoma reported in Beagles. This case report describes a primary angle-closure glaucoma in a Beagle and its diagnostic and prognostic relevance.

Case presentation

A 12-year-old, neutered male Beagle presented to the Michigan State University (MSU) Comparative Ophthalmology Service for evaluation of suspected visual impairment. Complete ophthalmic examination of the left eye (OS) revealed: blepharospasm, absent menace response, moderate episcleral congestion, mild diffuse corneal edema, mydriasis, asteroid hyalosis, decreased myelination and cupping of the optic nerve head, and mild retinal vascular attenuation. Examinations of the right eye (OD) were within normal limits. Intraocular Pressure (IOP) were 24 mmHg OD and 49 mmHg OS. Gonioscopy OD revealed a narrow iridocorneal angle with moderate pectinate ligament dysplasia characterized by broad-based pectinate ligament strands (fibrae latae) and solid sheets (laminae) throughout all 4 quadrants. DNA testing revealed that the dog did not carry the Gly661Arg ADAMTS10 mutation responsible for primary open angle glaucoma (POAG) in Beagles. The OS was medically managed with latanoprost 0.005% and dorzolamide HCl 2% /timolol malate 0.5% ophthalmic solutions for 7 months and then enucleated due to uncontrolled IOP. Histopathologic evaluation was consistent with goniodysgenesis with a broad, non-perforate, sheet-like band of uveal stroma bridging from the base of the iris to the terminal arborization of Descemet’s membrane. Approximately 14 months from the initial diagnosis of glaucoma OS, OD also developed glaucoma and was enucleated. Histopathologic findings were consistent with goniodysgenesis OD.

Conclusions

To our knowledge, this is the first reported case of PACG with goniodysgenesis in a Beagle supported by clinical, genetic, and histopathologic data. It highlights the importance of gonioscopy in Beagles with glaucoma. Further studies with a larger number of dogs are warranted to characterize clinical manifestations and inheritance of PACG in this breed.

Primary closed angle glaucoma in the Basset Hound: Genetic investigations using genome-wide association and RNA sequencing strategies

Purpose

To investigate the genetic basis of primary closed angle glaucoma (PCAG) in European Basset Hounds using genome-wide association and RNA sequencing strategies.

Methods

DNA samples from 119 European Basset Hounds were genotyped on the 170 K SNP CanineHD BeadChip array (Illumina) comprising 37 with normal iridocorneal angles (controls), 57 with pectinate ligament abnormality (PLA cases), and 25 with PCAG (PCAG cases). Genome-wide association studies (GWASs) of the PLA and PCAG cases were conducted. Whole transcriptome sequences of iridocorneal angle tissues from five Basset Hounds with PCAG were compared with those from four dogs with normal eyes to investigate differences in gene expression between the affected and unaffected eyes in GWAS-associated loci. A variant in NEB, previously reported to be associated with PCAG in American Basset Hounds, was genotyped in cohorts of European Basset Hounds and non-Basset Hounds.

Results

The GWASs revealed 1.4 and 0.2 Mb regions, on chromosomes 24 and 37, respectively, that are statistically associated with PCAG. The former locus has previously been associated with glaucoma in humans. Whole transcriptome analysis revealed differential gene expression of eight genes within these two loci. The NEB variant was not associated with PLA or PCAG in this set of European Basset Hounds.

Conclusions

We identified two novel loci for canine PCAG. Further investigation is required to elucidate candidate variants that underlie canine PCAG.

Definition, Classification, and Pathophysiology of Canine Glaucoma

Glaucoma is a common ocular condition in humans and dogs leading to optic nerve degeneration and irreversible blindness. Primary glaucoma is a group of spontaneous heterogeneous diseases. Multiple factors are involved in its pathogenesis and these factors vary across human ethnic groups and canine breeds, so the clinical phenotypes are numerous and their classification can be challenging and remain superficial. Aging and oxidative stress are major triggers for the manifestation of disease. Multiple, intertwined inflammatory and biochemical cascades eventually alter cellular and extracellular physiology in the optic nerve and trabecular meshwork and lead to vision loss.