M. E. Kallberg

Endothelin 1 levels in the aqueous humor of dogs with glaucoma.

PurposeEndothelin 1 is a small peptide that is involved in regulation of intraocular pressure and modulation of ocular circulation. To investigate the role of endothelin 1 in canine glaucoma, the authors measured aqueous humor levels of endothelin 1 in healthy dogs and in dogs with hypertensive glaucoma. MethodsAqueous humor samples were obtained with general anesthesia from the eyes of healthy dogs (n = 5) and dogs with hypertensive glaucoma (n = 10). Measurements were made by enzyme immunoassay for endothelin 1. ResultsThe endothelin 1 aqueous humor range was 1.12 − 3.63 pg/mL for healthy dogs and 1.97 − 14.97 pg/mL for glaucomatous dogs. The healthy and glaucomatous canine endothelin 1 aqueous levels (mean ± SD) were 2.33 ± 0.90 and 8.11 ± 5.03 pg/mL, respectively. A two-way analysis of variance indicated that this difference was significant (P = 0.0084). The effect of age on endothelin 1 levels was not significant (P = 0.6283). The large variability found within the glaucomatous group could be explained by the degree of damage of the retina (P = 0.0006). There was no significant correlation between intraocular pressure and endothelin 1 aqueous humor levels within the glaucomatous group (P = 0.29). ConclusionsThe aqueous humor of dogs with hypertensive glaucoma contains significantly higher levels of endothelin 1 than that of healthy dogs.

Corneal transplantation for inflammatory keratopathies in the horse: visual outcome in 206 cases (1993-2007).

OBJECTIVE To evaluate the visual outcome of three techniques of corneal transplantation surgery in treating severe inflammatory keratopathies in the horse. DESIGN Retrospective medical records study. ANIMALS STUDIED Medical records of 206 horses that received corneal transplantation surgery at the University of Florida Veterinary Medical Center from 1993 to 2007 were reviewed. PROCEDURE Data collected from the medical records included signalment, types of ocular lesions, type of transplant surgery performed, length of follow-up, complications, and visual outcomes. RESULTS Full thickness penetrating keratoplasty (PK) was performed in 86 horses for melting ulcers, iris prolapse/descemetoceles, and medically nonresponsive full thickness stromal abscesses (SA). Posterior lamellar keratoplasty (PLK) and deep lamellar endothelial keratoplasty (DLEK) are split thickness penetrating keratoplasties that were utilized for medically nonresponsive deep stromal abscesses (DSA) in 54 and 66 eyes, respectively. The most common postoperative surgical complication was graft rejection and varying degrees of graft opacification. Wound dehiscence and aqueous humor leakage was also a common postoperative problem. A positive visual outcome was achieved for PK, PLK, and DLEK in 77.9%, 98.1%, and 89.4%, respectively. CONCLUSIONS Corneal transplantation is a tectonically viable surgery in the horse with an overall success rate of 88.5% in maintaining vision when treating vascularized and infected corneal disease in the horse.

Angiopoietin-like 7 secretion is induced by glaucoma stimuli and its concentration is elevated in glaucomatous aqueous humor.

PURPOSE To investigate the possibility that Angiopoietin-like 7 (ANGPTL7) protein is involved in the pathogenesis of glaucoma. METHODS Primary human trabecular meshwork (TM) cells and corneoscleral explants were stimulated with either dexamethasone (DEX) or transforming growth factor beta (TGFbeta), and ANGPTL7 protein secreted into culture medium was determined by Western blot analysis. The effect of stable overexpression of ANGPTL7 in transfected immortalized TM cell lines on collagen expression was investigated by immunocytochemistry. Localization of ANGPTL7 protein in human eyes was determined by immunohistochemistry. The concentration of ANGPTL7 protein in aqueous humor (AH) from patients with glaucoma and control patients was compared by Western blot analysis. The beagle model of primary open-angle glaucoma (POAG) was used to correlate ANGPTL7 protein levels in canine AH with disease progression. RESULTS TGFbeta and DEX stimulated secretion of ANGPTL7 protein by TM cells and corneoscleral explants. Overexpression of ANGPTL7 by immortalized TM cell lines increased expression of type I collagen. Expression of ANGPTL7 protein was located in the corneal stroma, near the limbus, and throughout the sclera, with lower expression in the TM. In the lamina cribrosa, ANGPTL7 expression was associated with the cribriform plates. The concentration of ANGPTL7 protein was elevated in AH from patients with glaucoma and increased as disease progressed in POAG beagle dogs. CONCLUSIONS Induction of ANGPTL7 secretion by glaucoma stimuli and increased concentration of ANGPTL7 in glaucomatous AH suggest that ANGPTL7 is overexpressed in glaucoma. Since overexpression of ANGPTL7 increases collagen expression, a potential disease mechanism, ANGPTL7 could have a pathogenic role in glaucoma, and may serve as a potential therapeutic target.

Corneal thickness and endothelial cell density measured by non-contact specular microscopy and pachymetry in Rhesus macaques (Macaca mulatta) with laser-induced ocular hypertension

PURPOSE Sustained increase in intraocular pressure (IOP) in humans results in a loss of corneal endothelial cells and an increase of corneal thickness. The effects of chronically elevated IOP on the corneal endothelium of monkeys with laser-induced ocular hypertension, a commonly used animal model of human glaucoma have not been documented. This study examined the central corneal thickness (CCT), the corneal endothelial cell density (ECD), and the corneal endothelial cell size (ACS) in Rhesus monkeys with experimental ocular hypertension. Materials and methods. Ten male monkeys with argon laser-induced ocular hypertension in one eye for an average duration of 2.4+/-0.7 years, were sedated with ketamine hydrochloride, and the CCT, ECD, and ACS measured at the center of the cornea of both eyes with a Topcon SP-2000P non-contact specular microscope (Topcon America Corporation((R)), Paramus, NJ, USA). CCT was also measured using a DHG-500 Pachette ultrasonic pachymeter (DHG Technology Inc., Exton, PA, USA). Mean and standard deviation (S.D.) of CCT, ECD and ACS for each eye was calculated and statistically compared.Results. Mean CCT in the hypertensive and normal eyes measured by specular microscopy was 0.477+/-0.023mm and 0.468+/-0.020 mm, respectively. Mean ECD in the hypertensive and normal eyes was 2601.7+/-631.8 and 3990.2+/-402.9 cells mm(-2), respectively. The mean size of the endothelial cells was 252.4+/-23.9 micro m(2) in the normal eye and 408.7+/-115.0 microm m(2) in the hypertensive eye. No significant difference in the measurement of CCT was observed between the specular microscope and the pachymeter (p=0.46). No significant difference in the mean CCT was observed between the two eyes (p=0.4820), whereas the mean ECD was significantly lower in the hypertensive eye than in the normal eye (p<0.001). The ECD was inversely related to the length of IOP elevation (p<0.001). CONCLUSIONS No difference in the corneal thickness measurement was observed between the specular microscopy and the pachymetry techniques. Chronic ocular hypertension did not significantly affect the CCT, but caused a significant loss of endothelial cells in the center of the cornea of the laser treated eyes compared to the normotensive eyes. The duration of elevated IOP was the most important factor affecting the ECD.

Deep lamellar endothelial keratoplasty in 10 horses

OBJECTIVE To describe and evaluate a surgical technique utilized for the therapy of deep corneal stromal abscesses (DSA) in horses. The DSA is excised and replaced with a partial thickness corneal lamellar allograft. METHODS A retrospective clinical study describing the indications for the surgical technique utilized and the outcomes of this procedure in 10 eyes of 10 horses. RESULTS Each affected eye had a discrete DSA within the posterior stroma. An initial partial thickness semicircular corneal incision was made at the limbus, followed by anterior stromal lamellar dissection over the lesion. After excision of the DSA and replacement with a larger diameter split-thickness donor button, the anterior stroma was replaced into its original position and the initial corneal incision was repaired. All of the animals that underwent deep lamellar endothelial keratoplasty (DLEK) procedure healed appropriately and with subjectively less postoperative scarring and complications than previously described surgical approaches to DSA. CONCLUSIONS This procedure is an effective technique for surgical removal of DSA in horses and, in most cases, results in a visual and cosmetically acceptable globe. The advantages of this technique compared to other surgical approaches to DSA are the peripheral location of the incision, shortened anesthesia times, the resultant minimal scarring and shorter healing times associated with DLEK.

Long-term effect of retinal ganglion cell axotomy on the histomorphometry of other cells in the porcine retina.

PURPOSE To determine the effect of retinal ganglion cell axotomy on the thickness of inner plexiform, inner nuclear, and outer plexiform layers, as well as the densities of short- and middle-to-long-wavelength cones, in the porcine retina. METHODS Unilateral retinal ganglion cell axotomy was performed in seven domestic pigs by either surgical optic nerve section or peripapillary argon laser photocoagulation. Damage to the retinal vasculature was ruled out with fluorescein angiography. Histologic examination of the retinal tissue was performed nine months later. Cone densities were determined immunohistochemically with the anti-visual pigment antibodies COS-1 and OS-2. Image analysis of semithin retinal cross sections was used to measure the thickness of the retinal layers. The effect of axotomy was quantified by optic nerve axon counts and estimations of retinal ganglion cell counts. The data were compared between the eyes with axotomy and the contralateral normal eye using the nonparametric Wilcoxon rank sum test. RESULTS Treatment of the peripapillary retina with the argon laser resulted in a median decrease in axon counts and retinal ganglion cell density estimates of 31%. No optic nerve axons and cells resembling retinal ganglion cells were found in the eyes with transected optic nerves. There was no significant difference in either the thickness of any retinal layers or cone densities between axotomized and normal control eyes. CONCLUSION No signs of retrograde transsynaptic degeneration were observed in porcine retinas nine months after retinal ganglion cell axotomy.

Intranictitans tacking for replacement of prolapsed gland of the third eyelid in dogs

OBJECTIVE To evaluate a new procedure for fixation of prolapsed nictitans glands to the cartilage of the nictitans that will not interfere with the mobility of the nictitating membrane. METHODS A prospective clinical trial utilizing a nonabsorbable suture to anchor the prolapsed gland to the cartilage of the third eyelid was undertaken. Fifteen eyes of 10 dogs were included in the study. A 4-0 nylon suture was passed from the anterior surface of the third eyelid through the base of the cartilage to the posterior aspect and then tunneled circumferentially beneath the conjunctiva over and around the prolapsed gland. The suture was then passed through the cartilage again to the anterior face of the third eyelid. The gland was replaced into its normal position as the suture was slowly tightened and then tied on the anterior aspect of the nictitans. RESULTS Over a period of several weeks, the glands reduced in size and took on a normal appearance. All glands but one remained in place for the length of follow-up, which ranged from 2 weeks to 33 months. CONCLUSIONS This procedure results in acceptable cosmetic effects with the return of the gland to its normal position posterior to the nictitating membrane. The advantage of this technique over traditional tacking to the orbital rim is that the third eyelid retains its normal mobility and, thus, its protective functions. The procedure once mastered is very quick and can be performed in less time than many of the traditional replacement techniques.

Aqueous humor myocilin protein levels in normal, genetic carriers, and glaucoma Beagles

OBJECTIVE The gene (myocilin: MYOC) has been attributed to be involved in over 6% of inherited types of human glaucoma, the highest correlation for any gene to date. This study determines myocilin protein levels in the aqueous humor (AH) of normal laboratory quality, genetic carrier (offspring of normal laboratory quality and POAG Beagles), and primary open angle glaucoma (POAG) Beagles. MATERIALS AND METHODS Eighteen dogs were used and classified as either normal, carrier or having mild, moderate or advanced POAG. A 0.1 mL sample of AH was drawn from the anterior chamber of each dog in the study and frozen on dry ice. A modified Coomassie stain and Western blot, using a polyclonal rabbit antihuman myocilin antibody (Santa Cruz Biotechnologies, Santa Cruz, CA), was run on each sample to compare the myocilin levels. A purified human trabecular meshwork excreted myocilin protein sample was used as a control (Alcon Research Laboratories, Fort Worth, TX) and its band/densitometry measurement was defined as one unit of myocilin for comparisons. RESULTS Comparisons of AH myocilin levels differed among normal laboratory quality, genetic carrier, and POAG Beagles at different stages of the disease. In the normal laboratory, Beagles the AH myocilin measured 0.817 +/- 0.075 units (mean +/- SEM); in the carrier Beagles the AH myocilin was 3.117 +/- 0.290 units. As POAG progressed, myocilin protein levels also increased to 6.097 +/- 0.810, 8.844 +/- 1.079, and 17.228 +/- 1.198 units in the early, moderate, and advanced forms, respectively. Overall comparisons between normal, carrier and all POAG Beagles combined showed significant differences (P < 0.0010). Individual comparisons between normal and carrier eyes showed significant differences (P < 0.0193). Comparisons between normal and all POAG eyes also showed significant differences (P < 0.0426). CONCLUSION This study shows myocilin protein is present in normal Beagles, markedly increased in POAG Beagles, and mildly increased in genetic carrier Beagles. There is a strong correlation between amounts of AH myocilin protein and the presence and severity of POAG. The exact role of AH myocilin levels in the genesis of ocular hypertension remains unresolved, but myocilin may adversely affect AH outflow.

Myocilin protein levels in the aqueous humor of the glaucomas in selected canine breeds

OBJECTIVE To compare aqueous humor myocilin protein levels in dogs with the primary glaucomas to those with the secondary glaucomas, primary cataracts, and diabetic cataracts. MATERIALS AND METHODS Four groups were selected, based on diagnosis by the attending veterinary ophthalmologists and included: primary glaucoma (primary open-angle glaucoma (POAG) and primary closed angle glaucoma (PCAG); n = 155); secondary glaucoma (n = 94); primary (presumed inherited) cataract (n = 142), and diabetic cataract (n = 83). A total of 474 samples (187 males, 263 females, 24 unreported) with average ages of 117 months for the males and 101 months for the females were analyzed. Myocilin protein was measured using the Coomassie staining and Western blot methods relative to a myocilin control. RESULTS Differences were seen between nonglaucomatous (cataractous) and glaucomatous dogs with myocilin levels in glaucomatous eyes being many times higher than those in the cataractous dogs. Primary glaucomatous dogs were found to have an aqueous humor myocilin protein level of 17.30 +/- 1.03 units. Secondary glaucomas had the highest level of myocilin in the aqueous humor with 19.27 +/- 1.41 units. Diabetic cataractous dogs had the lowest levels of myocilin reported with 6.60 +/- 0.88 (mean +/- SEM) units. Normal (cataractous) dogs had a myocilin level in the aqueous humor of 8.05 +/- 0.86 units. CONCLUSION Aqueous humor protein levels were elevated, relative to the myocilin control, in both the primary and secondary glaucoma groups compared to the cataract and diabetic cataract groups. Like in the Beagle POAG, aqueous humor myocilin protein levels are increased. Further studies are indicated to investigate the exact role of the aqueous humor myocilin protein in the genesis in increased IOP in these primary glaucomatous breeds.

Use of a biosynthetic material to repair the surgical defect following excision of an epibulbar melanoma in a cat

A limbal melanoma was surgically excised from the OS of a 4-year-old castrated male Domestic Short-haired cat (DSH). The resultant scleral defect was repaired by placement of A-cell bio-scaffold material. The patient responded well in the postoperative period with no apparent discomfort, nor any observable complications. No signs of recurrence have been evident nearly 2.5 years following surgical removal. A-cell appears to be a safe and reasonable option to lend support to corneoscleral defects following removal of neoplastic lesions. It carries with it the advantages of availability, minimal host rejection, and reduced potential for iatrogenic spread of infections agents.