Bleb characteristics assessed by ultrasound biomicroscopy correlate with intraocular pressure after Ahmed glaucoma valve surgery in dogs.

OBJECTIVE: To assess the characteristics of blebs formed after Ahmed glaucoma valve (AGV) surgery in dogs using ultrasound biomicroscopy (UBM) and to analyze their correlation with postoperative intraocular pressure (IOP). ANIMALS: 16 eyes (13 dogs) were diagnosed with primary angle-closure glaucoma and were followed up after AGV surgery from June 2021 to September 2023. METHODS: In this prospective study, UBM examinations were performed to assess bleb characteristics, including bleb wall thickness and reflectivity. IOP at the time of UBM imaging and the duration from AGV surgery to UBM imaging were recorded. Histological examination of an enucleated eye removed due to uncontrolled IOP leading to blindness was also conducted. RESULTS: A significant correlation was observed between IOP and relative reflectivity (Pearson r = 0.60; P = .01), and a negative correlation was observed between bleb wall thickness and relative reflectivity (Pearson r = -0.72; P = .002). No significant correlation was observed between the duration from AGV surgery to UBM imaging and either bleb wall thickness or relative reflectivity, respectively. Histological examination of the enucleated eye revealed collagen-rich fibrous encapsulation of the bleb wall, including myofibroblasts that exhibited positive α-smooth muscle actin immunostaining. CLINICAL RELEVANCE: In dogs that underwent AGV surgery, less dense, thick-walled blebs on UBM tended to maintain IOP within the normal range. However, denser, thinner-walled blebs showed IOP levels above the normal range despite the use of antiglaucoma medications. UBM is a useful tool for evaluating bleb characteristics and their influence on IOP regulation after AGV surgery in dogs.

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.

Atypical chorioretinal lesions in Siberian Husky dogs with primary angle-closure glaucoma: a case series.

BACKGROUND: A number of etiologies for different canine chorioretinal lesions have been proved or suggested but some fundic lesions remain unclear in terms of an etiologic diagnosis, treatment options and prognosis. The purpose of this case series is to describe atypical chorioretinal lesions observed in dogs with primary angle-closure glaucoma (PACG). CASE PRESENTATION: Two spayed-female Siberian Huskies (3- and 4-year-old) and one Siberian Husky/Australian Shepherd mixed breed dog (11-month-old) that had multifocal depigmented retinal lesions and PACG were included. PROCEDURES: Ophthalmic examination, gross, and histopathologic examination findings are described. One of the dogs underwent further clinical diagnostics. Advanced clinical diagnostics on the fellow, presumed to be non-glaucomatous eye of a dog revealed: pectinate ligament dysplasia by gonioscopy, retinal thinning in the depigmented area and wedge shaped retinal thinning with delayed choroidal vascular perfusion by optical coherence tomography, confocal scanning laser ophthalmoscopy, fluorescein and indocyanine green angiography. Quantifiable maze testing for the same eye revealed mild nyctalopia but the full-field electroretinogram showed no generalized decrease of retinal function. Genetic testing for mutations within the retinitis pigmentosa GTPase regulator gene causing X-linked progressive retinal atrophy in Siberian Huskies was negative. Histopathologic evaluations on enucleated eyes in two dogs confirmed goniodysgenesis, PACG with optic nerve head cupping, and diffuse inner retinal atrophy. In addition, segmental profound retinal atrophy, loss of retinal pigment epithelium, and adhesion of the retina to Bruch's membrane was observed and coincided with multifocal depigmented lesions noted on fundic examination. CONCLUSIONS: To our knowledge, this is the first case series with clinical and histopathologic data of chorioretinal lesions, most likely caused by severely impaired choroidal perfusion. Further studies are warranted to elucidate the etiology and pathophysiology, including its possible association with PACG.

Development and validation of methods to visualize conventional aqueous outflow pathways in canine primary angle closure glaucoma.

PURPOSE: Angle closure glaucoma (PACG) is highly prevalent in dogs and is often refractory to medical therapy. We hypothesized that pathology affecting the post-trabecular conventional aqueous outflow pathway contributes to persistent intraocular pressure (IOP) elevation in dogs with PACG. The goal of this study was to determine the potential for aqueous angiography (AA) and optical coherence tomography (OCT) to identify abnormalities in post-trabecular aqueous outflow pathways in canine PACG. METHODS: AA and anterior segment OCT (Spectralis HRA + OCT) were performed ex vivo in 19 enucleated canine eyes (10 normal eyes and 9 irreversibly blind eyes from canine patients enucleated for management of refractory PACG). Eyes were cannulated and maintained at physiologic IOP (10-20 mmHg) prior to intracameral infusion of fluorescent tracer. OCT scleral line scans were acquired in regions of high and low perilimbal AA signal. Eyes were then perfusion fixed and cryosections prepared from 10/10 normal and 7/9 PACG eyes and immunolabeled for a vascular endothelial marker. RESULTS: Normal canine eyes showed segmental, circumferential limbal AA signal, whereas PACG eyes showed minimal or no AA signal. AA signal correlated with scleral lumens on OCT in normal dogs, but lumens were generally absent or flattened in PACG eyes. Collapsed vascular profiles were identified in tissue sections from PACG eyes, including those in which no lumens were identified on AA and OCT. CONCLUSIONS: In canine eyes with PACG, distal aqueous outflow channels are not identifiable by AA, despite normalization of their IOP, and intra-scleral vascular profiles are collapsed on OCT and histopathology.

Evaluation of matrix metalloproteinases and tissue inhibitors of metalloproteinases in aqueous humor of dogs with versus without naturally occurring primary angle-closure glaucoma.

OBJECTIVE: To compare concentrations of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in aqueous humor from ophthalmologically normal dogs and dogs with naturally occurring primary angle-closure glaucoma (cPACG). SAMPLE: Aqueous humor samples from 12 eyes with cPACG and 18 ophthalmologically normal eyes of dogs. PROCEDURES: A multiplex fluorescence-based ELISA was used to measure concentrations of MMP-1, MMP-2, MMP-3, MMP-8, MMP-9, MMP-10, MMP-13, TIMP-1, TIMP-2, and TIMP-4. Results for eyes with versus without cPACG were compared. RESULTS: Significantly higher mean concentrations of MMP-1 (45% higher), MMP-2 (55% higher), MMP-3 (39% higher), MMP-8 (79% higher), MMP-9 (29% higher), MMP-10 (60% higher), TIMP-1 (63% higher), and TIMP-2 (136% higher) were detected in aqueous humor from eyes with cPACG, compared with ophthalmologically normal eyes. CLINICAL RELEVANCE: MMPs and TIMPs have pivotal roles in extracellular matrix turnover and homeostasis in the outflow pathways of the eye. Results of the present study documented higher concentrations of MMPs and TIMPs in aqueous humor samples from dog eyes with late-stage cPACG. Although, to our knowledge, TIMPs have not previously been evaluated in the context of cPACG, the markedly higher concentration of TIMPs in eyes with cPACG suggested that inhibition of proteolysis and extracellular matrix turnover might be a factor in the development of glaucoma in susceptible individuals. However, because the present study used samples from dogs with late-stage cPACG, further work is required to characterize the temporal relationship between MMP and TIMP concentration changes and onset or progression of disease.

Proteomic analysis of aqueous humor in canine primary angle-closure glaucoma in American Cocker Spaniel dogs.

OBJECTIVE: To analyze proteomic profiles of the aqueous humor (AH) of canines with primary angle-closure glaucoma (PACG) and identify associated protein alterations. ANIMALS STUDIED: Six American Cocker Spaniels with PACG and six American Cocker Spaniels without ocular diseases. METHODS: Aqueous humor samples were collected from six American Cocker Spaniels with PACG at Seoul National University, VMTH, and six healthy Cocker Spaniels without ocular disease at Irion Animal Hospital. For the PACG group, AH samples were obtained by anterior chamber paracentesis prior to glaucoma treatment. For the AH control group, AH samples were collected from patients anesthetized for other reasons. Total AH protein concentration was determined by the bicinchoninic acid (BCA) assay. AH protein samples were quantified by liquid chromatography-mass spectrometry (LC-MS/MS). Raw MS spectra were processed using MaxQuant software 30, and the Gene Ontology (GO) enrichment analysis was performed using ClueGO. RESULTS: The AH protein concentration in the PACG group (10.49 ± 17.98 µg/µl) was significantly higher than that of the control group (0.45 ± 0.11 µg/µl; p < .05). A total of 758 proteins were identified in the AH. Several proteins both significantly increased (n = 69) and decreased (n = 252) in the PACG group compared to those in the control group. GO enrichment analysis showed that the "response to wounding," "negative regulation of endopeptidase activity," and "cell growth" pathways were the most enriched terms in the PACG group compared to the control group. The top 5 proteins that were significantly increased in the AH of the PACG group were secreted phosphoprotein 1 (SPP1), peptidoglycan recognition proteins 2 (PGLYRP2), tyrosine 3-monooxygenase (YWHAE), maltase-glucoamylase (MGAM), and vimentin (VIM). CONCLUSIONS: Gene Ontology enrichment analysis using the proteomic data showed that proteins and pathways related to inflammation were significantly upregulated in the various stage of PACG. Proteomic analysis of the AH from the PACG may provide valuable insights into PACG pathogenesis.

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.

Diffusion tensor imaging of the visual pathway in dogs with primary angle-closure glaucoma.

OBJECTIVE: To describe measurements of in vivo structures of the visual pathway beyond the retina and optic nerve head associated with canine primary angle-closure glaucoma (PACG). METHODS: A prospective pilot study was conducted using magnetic resonance diffusion tensor imaging (DTI) to obtain quantitative measures of the optic nerve, chiasm, tract, and lateral geniculate nucleus (LGN) in dogs with and without PACG. 3-Tesla DTI was performed on six affected dogs and five breed, age- and sex-matched controls. DTI indices of the optic nerve, optic chiasm, optic tracts, and LGN were compared between normal, unilateral PACG, and bilateral PACG groups. Intra-class correlation coefficient (ICC) was calculated to assess intra-observer reliability. RESULTS: Quantitative measurements of the optic nerve, optic tract, optic chiasm, and LGN were obtained in all dogs. There was a trend for reduced fractional anisotropy (FA) associated with disease for all structures assessed. Compared to the same structure in normal dogs, FA, and radial diffusivity (RD) of the optic nerve was consistently higher in the unaffected eye in dogs with unilateral PACG. Intra-observer reliability was excellent for measurements of the optic nerve (ICC: 0.92), good for measurements of the optic tract (ICC: 0.89) and acceptable for measures of the optic chiasm (ICC: 0.71) and lateral geniculate nuclei (ICC: 0.76). CONCLUSION: Diffusivity and anisotropy measures provide a quantifiable means to evaluate the visual pathway in dogs. DTI has potential to provide in vivo measures of axonal and myelin injury and transsynaptic degeneration in canine PACG.

A variant in OLFML3 is associated with pectinate ligament abnormality and primary closed-angle glaucoma in Border Collies from the United Kingdom.

PURPOSE: Canine primary closed-angle glaucoma (PCAG) is a complex disease caused by multiple genetic factors. A c.590G>A variant in OLFML3 was recently reported to be a candidate for pectinate ligament abnormality (PLA) and PCAG in the Border Collie. We investigated the association of this variant with PLA and PCAG in Border Collies from the United Kingdom. METHODS: The OLFML3 variant was genotyped in 106 Border Collies comprising 90 with normal eyes (controls) and 16 with PLA (n = 11) and/or PCAG (n = 5) (cases). Genotyping was performed in an additional 103 Border Collies to estimate variant frequency within the population. To investigate the association of the variant with disease in other breeds, genotyping was performed in 337 non-Border Collies with PLA and/or PCAG. RESULTS: Of the 90 controls, 71 were homozygous for the wild-type allele, two were homozygous for the variant, and 17 were heterozygous. Of the 16 cases, three were homozygous for the wild-type allele, 11 were homozygous for the variant, and two were heterozygous. The association of the variant allele with disease was significant (P = 1.1 x 10-9 ). We estimated the frequency of this variant to be 4.4% within the United Kingdom Border Collie population, and it was not identified in clinically affected dogs of any other breed. CONCLUSIONS: This study confirms the association of the OLFML3 variant with PLA and PCAG in Border Collies from the United Kingdom. DNA testing for the variant and selective breeding can reasonably be expected to result in a reduction of PLA and PCAG prevalence in the breed.

Iridocorneal angle assessment of companion rabbits using gonioscopy, spectral-domain optical coherence tomography (Optovue iVue® ), high-resolution ultrasound, and Pentacam® HR imaging.

OBJECTIVE: Iridocorneal angle (ICA) narrowing is a known risk factor for primary glaucoma in multiple species, but has not been described in companion rabbits. This study aimed to develop an ICA grading scheme for companion rabbits to enable early glaucoma predisposition diagnosis. ANIMALS STUDIED: Twenty healthy rabbits of varying breeds and ages. PROCEDURES: Rabbits received complete ophthalmic examinations, including gonioscopy, and imaging of the ICA using spectral-domain optical coherence tomography (SD-OCT), Scheimpflug imaging (Pentacam® HR), and high-resolution ultrasound (HRUS). Angle opening distance (AOD) and angle recess area (ARA) of the ICA were measured and assessed for agreement using a Bland-Altman analysis. A five-stage gonioscopy grading scheme was created, and Spearman-rank test assessed for correlation between gonioscopy grades and ICA measurements. Differences among age and sex were analyzed with a nonparametric ANOVA and Wilcoxon rank-sum test, respectively. RESULTS: Analysis revealed AOD medians of 0.28mm for SD-OCT [95% CI: 0.24-0.31], 0.20mm for Pentacam® HR [95% CI: 0.18-0.21], and 0.25mm for HRUS [95% CI: 0.22-0.28]. The median ARA was 0.14mm2 for SD-OCT [95% CI: 0.117-0.163], 0.09mm2 for Pentacam® HR [95% CI: 0.082-0.100], and 0.06mm2 for HRUS [95% CI: 0.046-0.054]. The association between gonioscopy grade and SD-OCT ARA was significant (P < 0.05), and there was a significant difference (P < 0.001) between imaging modalities for both ARA and AOD. CONCLUSIONS: Gonioscopy grade correlated well with SD-OCT ARA. Therefore, SD-OCT is recommended as a noncontact method for evaluating companion rabbit ICA. Each imaging device should not be used interchangeably for ICA evaluation.

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.

Evaluation of potential risk factors for development of primary angle-closure glaucoma in Bouviers des Flandres.

OBJECTIVE To evaluate potential risk factors for development of primary angle-closure glaucoma (PACG) in Bouviers des Flandres. DESIGN Prospective, observational study. ANIMALS 98 Bouviers des Flandres. PROCEDURES All dogs underwent slit-lamp biomicroscopy, indirect ophthalmoscopy, gonioscopy, applanation tonometry, streak retinoscopy, and A-scan, B-scan, and high-resolution ultrasonography. Iridocorneal angles and degree of pectinate ligament dysplasia sheeting were graded, and an angle index was mathematically derived for each eye on the basis of these values. Ciliary clefts evaluated by high-resolution ultrasonography were classified as open, narrow, or closed. Owners were contacted by telephone 7 to 9 years after the initial examination to determine whether dogs had a subsequent diagnosis of PACG. Relationships between previously recorded variables and the development of PACG were evaluated by logistic regression methods. Available pedigrees were reviewed to assess genetic relationships among affected dogs. RESULTS 9 of 92 (9.8%) dogs with follow-up information available developed PACG. An angle index < 1 and presence of a narrow or closed ciliary cleft in 1 or both eyes were each significantly associated with development of PACG. Odds of developing PACG for dogs with an angle index < 1 (indicating marked reduction in outflow capacity through the iridocorneal angle), a narrow or closed ciliary cleft in > 1 eye, or both findings were 13, 20, and 28 times those for dogs that did not have these findings, respectively. All dogs that developed PACG shared 1 common male sire or grandsire. CONCLUSIONS AND CLINICAL RELEVANCE Several anatomic factors were significant risk factors for development of PACG in this population of dogs. Results also suggested a genetic component for the disease.

The effect of prophylactic topical carbonic anhydrase inhibitors in canine primary closed-angle glaucoma.

OBJECTIVES: To determine the effect of 1% brinzolamide, 2% dorzolamide hydrochloride or combination 2% dorzolamide hydrochloride/0 · 5% timolol to delay the elevation of the intraocular pressure in second eyes of dogs with primary closed-angle glaucoma. METHODS: Analysis of retrospectively collated data from 40 dogs with primary closed-angle glaucoma, where the non-affected eye was treated prophylactically with brinzolamide (n = 10), dorzolamide (n = 18) or combination dorzolamide/timolol therapy (n = 12). RESULTS: The 40 treated dogs (median age of 76 · 2 months) comprised 25 females/15 males, 19 entire/21 neutered. Twenty dogs developed glaucoma in the contralateral eye (median time of 9 · 2 months). No statistically significant difference was identified during treatment failure between the treatment groups (P = 0 · 66). The second eye remained normotensive in 20 dogs; four dogs until the conclusion of the study (median: 27 · 0 months), three dogs until death (median: 15 · 4 months), seven dogs until lost to follow-up (median: 11 · 6 months). Out of these 20 dogs, treatment was discontinued because of lack of owner compliance in two dogs and following a local drug reaction in four dogs (median: 8 · 9 months). CLINICAL SIGNIFICANCE: There was no evidence that the tested drugs delayed elevation of intraocular pressure in contralateral eyes of dogs with primary closed-angle glaucoma.

Variants in Nebulin (NEB) Are Linked to the Development of Familial Primary Angle Closure Glaucoma in Basset Hounds.

Several dog breeds are susceptible to developing primary angle closure glaucoma (PACG), which suggests a genetic basis for the disease. We have identified a four-generation Basset Hound pedigree with characteristic autosomal recessive PACG that closely recapitulates PACG in humans. Our aim is to utilize gene mapping and whole exome sequencing approaches to identify PACG-causing sequence variants in the Basset. Extensive clinical phenotyping of all pedigree members was conducted. SNP-chip genotyping was carried out in 9 affected and 15 unaffected pedigree members. Two-point and multipoint linkage analyses of genome-wide SNP data were performed using Superlink-Online SNP-1.1 and a locus was mapped to chromosome 19q with a maximum LOD score of 3.24. The locus contains 12 Ensemble predicted canine genes and is syntenic to a region on chromosome 2 in the human genome. Using exome-sequencing analysis, a possibly damaging, non-synonymous variant in the gene Nebulin (NEB) was found to segregate with PACG which alters a phylogenetically conserved Lysine residue. The association of this variants with PACG was confirmed in a secondary cohort of unrelated Basset Hounds (p = 3.4 × 10-4, OR = 15.3 for homozygosity). Nebulin, a protein that promotes the contractile function of sarcomeres, was found to be prominently expressed in the ciliary muscles of the anterior segment. Our findings may provide insight into the molecular mechanisms that underlie PACG. The phenotypic similarities of disease presentation in dogs and humans may enable the translation of findings made in this study to patients with PACG.

Tumor necrosis factor-alpha concentration in the aqueous humor of healthy and diseased dogs: a preliminary pilot study.

OBJECTIVES: To determine reference values of tumor necrosis factor-alpha (TNF-α) concentrations in the aqueous humor of control dogs. To show whether these values are significantly different from those obtained in dogs affected with intraocular pathology: acute anterior uveitis (AAU) or chronic primary angle closure glaucoma (PACG). METHODS: Forty-four dogs were included in the study and were divided into two groups: a control group and a group with intraocular disease. Twenty-seven dogs (9 males and 18 females) were examined and found to be normal after a complete ophthalmological examination (control group), 7 (6 females and 1 male) presented with PACG, and 10 (7 females and 3 males) presented with AAU secondary to corneal perforation. One aqueous humor sample (volume ≥ 0.2 mL) was collected from one eye of all dogs. The aqueous TNF-α concentration was determined with an Elisa kit. RESULTS: TNF-α levels were detectable in all dogs. TNF-α levels were significantly higher in the group with intraocular disease compared to the normal control group (P=0.001). In the group with intraocular disease, TNF-α levels were significantly higher in the aqueous humor of the AAU group compared with the PACG group (P=0.001). CONCLUSIONS: In the dog, it is possible to measure the concentration of TNF-α in the aqueous humor. The level of TNF-α was significantly higher in the case of AAU. TNF-α is an interesting biomarker for longitudinal follow-up studies of comparative ophthalmology.

Identification of genetic loci associated with primary angle-closure glaucoma in the basset hound.

PURPOSE: Primary angle-closure glaucoma (PACG) in dogs is usually caused by the gradual collapse of the iridocorneal angle and cleft, eventually leading to aqueous humor (AH) outflow obstruction. The condition occurs in several breeds of dogs and the prognosis for affected animals is typically poor. We have identified several basset hound (BH) pedigrees, as well as unrelated cases with characteristic PACG that in many aspects recapitulates PACG in human patients. The goal of this study was to utilize the BH PACG model to characterize the genetics of PACG, and potentially discover genetic factors contributing to PACG in humans and animals. METHODS: We conducted a genome-wide logistic regression test for association using 37 PACG cases and 41 unaffected controls. Population stratification and cryptic relatedness were assessed using a multidimensional scaling analysis. The expression of two candidate genes within the target tissues of the BH eye was assessed by immunohistochemistry. RESULTS: We report significant associations at two novel loci, specifically BICF2P31912 in COL1A2 on chromosome 14 with a per-allele odds ratio (OR, 95% confidence interval [CI]) of 3.35 (1.73-6.51), P(genome)=3.6×10⁻4; and BICF2P893476 residing in proximity to RAB22A on chromosome 24 with a per-allele OR (95% CI) of 3.93 (1.78-8.66), P(genome)=4.9×10⁻4. COL1A2 and RAB22A demonstrated widespread expression throughout the eye and were prominently noted in the ciliary body (CB), trabecular meshwork (TM), and iris. CONCLUSIONS: Our finding of two genetic associations supports the potential segregation of PACG risk-conferring variants in the BH. The genetic associations identified may contribute to mechanisms underlying the pathogenesis of PACG, which remain to be elucidated.

Efficacy of prophylactic antiglaucoma and anti-inflammatory medications in canine primary angle-closure glaucoma: a multicenter retrospective study (2004-2012).

PURPOSE: To evaluate long-term efficacy of antiglaucoma medications with or without combined topical anti-inflammatory treatment in preventing increased intraocular pressure and clinical signs of glaucoma in eyes considered at risk of the development of the disease. METHODS: Retrospective analysis identified 88 canine patients presenting with unilateral acute congestive primary angle-closure glaucoma (IOP > 25 mm Hg) and gonioscopic findings of pectinate ligament dysplasia and/or narrow or closed iridocorneal angle in the contralateral nonglaucomatous eye. Patients with histopathologic confirmation of pectinate ligament dysplasia or angle closure in the initial glaucomatous eye receiving prophylactic medical therapy in the contralateral eye were included. Time to medical failure for each antiglaucoma medication and efficacy of the combination therapy were evaluated. RESULTS: The most commonly affected pure-breds were the American Cocker Spaniel (20.4%) and Basset Hound (11.36%). The patients receiving demecarium bromide 0.125% had the longest estimated median time to medical failure at 330.0 days, followed by latanoprost 0.005%, dorzolamide hydrochloride 2.0%, and demecarium bromide 0.25% at 284.0 days, 272.5 days, and 143.0 days, respectively. The estimated median time to medical failure for patients receiving topical antiglaucoma and anti-inflammatory medication was 324.0 days versus 195.0 days in patients receiving antiglaucoma medication alone. Survival analysis showed no statistical significance. CONCLUSIONS: None of the four antiglaucoma medications evaluated statistically delayed medical failure when compared to each other. Although significance was not achieved, our data suggest that adjunctive use of topical anti-inflammatory medications may be beneficial in these cases.

Early histopathologic changes in the retina and optic nerve in canine primary angle-closure glaucoma.

OBJECTIVE: To characterize the morphology of canine globes enucleated 1-5 days after the onset of overt clinical disease recognized by the owner. PROCEDURES: Paraffin-embedded globes from 47 dogs with acute primary angle-closure glaucoma (PACG) and 10 control dogs free of ocular disease were sectioned in the vertical plane sampling the optic nerve. Hematoxylin and eosin (H&E)-stained sections were used to count ganglion cell numbers. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay was used to quantify cell death, and MHCII immunohistochemistry was used to evaluate for antigen-presenting phagocytes in a smaller subset of cases. RESULTS: MHCII-labeled phagocytes were present in the optic nerve and retina within the first 24 h of documented glaucoma suggesting an early up-regulation. Globes removed within 1 day of overt clinical disease had a mild neutrophilic infiltrate in the retina and optic nerve as well as marked ganglion cell necrosis. By 5 days after clinical signs appear, there is a rapid decline in the number of ganglion cells and cell death detected by TUNEL labeling in the outer and inner nuclear layers of the retina, but not the ganglion cell layer. The neuropil of the optic nerve progresses from edema and neutrophilia to malacia. CONCLUSIONS: These findings suggest that retinal and optic nerve degeneration in dogs with PACG progresses rapidly to irreversible tissue loss within days of recognizable clinical disease.

Gender differences in iridocorneal angle morphology: a potential explanation for the female predisposition to primary angle closure glaucoma in dogs.

OBJECTIVE: Female dogs have approximately twice the risk of males for developing primary angle closure glaucoma (PACG). The cause of this gender difference is unknown, but one theory proposes that the gender differences in iridocorneal angle morphology are involved in this risk differential. PROCEDURES: Fifty beagles (25 males, 25 females) were included into this study and had normal baseline ophthalmic examinations. Normal dogs were selected so as to avoid any potentially confounding influence of goniodysgenesis. Standardized 20-MHz high-resolution ultrasound images of the iridocorneal angle were acquired from one eye of each dog with the scan plane perpendicular to the limbus in the superior temporal quadrant. Images were imported into ImageJ, and the angle opening distance (AOD) and angle recess area (ARA) were measured by a masked observer, and the analysis of variance method was used to compare differences. RESULTS: The mean (±SD) AOD was significantly smaller for female dogs (0.847 ± 0.241 mm) vs. male dogs (1.058 ± 0.322 mm) P-value = 0.012. The mean (± SD) ARA tended to be smaller for female dogs (0.584 ± 0.278 mm) vs. male dogs (0.748 ± 0.385 mm), but this difference was not significant (P-value = 0.092). CONCLUSIONS: Female dogs have a significantly smaller AOD vs. males. This difference may render the female iridocorneal angle more susceptible to closure and may partially explain the 2:1 female/male predisposition to PACG. Further studies using goniodysgenic dogs are warranted.