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.

Lack of effect of a topical regenerative agent on re-epithelialization rate of canine spontaneous chronic corneal epithelial defects: A randomized, double-masked, placebo-controlled study.

Spontaneous chronic corneal epithelial defects (SCCEDs) are characteristic ulcers in dogs that are refractory to healing. The aim of the study was to evaluate the use of a topical regenerative agent to promote healing of SCCEDs. Nineteen dogs (20 eyes) were randomized to receive either regenerative agent (10 eyes) or placebo (10 eyes) every 48h following corneal debridement, which was repeated 1 week later if the SCCED had not yet healed. The mean±standard deviation time to re-epithelialization was 17.3±12.8 days for the group treated with a topical regenerative agent and 19.3±11.7 days for the group treated with a placebo; the cumulative healing rates were not statistically different (P>0.650). A positive association was found between the initial size of the ulcer and the time to re-epithelialization (r=0.555, P=0.011). Although well tolerated by dogs, there was no therapeutic advantage in using a topical regenerative agent for re-epithelialization of SCCEDs.

Temporal and spatial frequencies interact in the contrast transfer function of the pattern electroretinogram.

The contrast transfer function (CTF) of the pattern electroretinogram (PERG) depends on temporal frequency. For transient stimulation it is fully linear; at faster stimulation rates it becomes strongly non-linear with an accelerated shape. In this study we investigated a range of stimulus parameters with the aim of studying the influence of temporal and spatial frequencies, as well as contrast levels, on the CTF; effects were quantified via an "index of linearity" IL. Both reversal rate and check size influenced linearity (p<.001), examples: At a constant check size of 0.8 degrees, 7.7 rps: IL=1.0; 0.8 degrees/24 rps: IL=0.5; at a constant reversal rate of 19 rps, IL was 0.5 for 0.8 degrees, but rose to 0.8 both for 0.2 degrees and 18 degrees. The reason for this complex response surface remains a puzzle, it cannot be explained by varying parvo/magnocellular contributions, and its possible influences on recordings in patients merit further studies.

Evaluation of three hand-held tonometers in normal canine eyes.

Tonometry, an indirect measurement of intraocular pressure (IOP), is important for the diagnosis and management of glaucoma and uveitis. The aim of this study was to compare the performance of three hand-held tonometers in normal canine eyes. Eyes from cadavers of dogs without observable ocular disease were used to compare tonometric measurements with direct manometry over a range of 7.4-65mmHg. In vivo measurements using the three tonometers in both eyes of 12 healthy dogs were compared. All tonometers significantly underestimated manometric values both ex vivo and in vivo. One tonometer showed a small fixed bias over the range of IOP, whilst the other two tonometers had a negative proportional bias. The results of this study show that differences exist between handheld tonometers across the clinically relevant range of IOP, and that all underestimate manometric measurements.

Visual outcome after corneal transplantation for corneal perforation and iris prolapse in 37 horses: 1998-2010.

REASONS FOR PERFORMING STUDY: We wanted to investigate the visual outcome of horses presented with iris prolapse and treated with corneal transplantation. OBJECTIVE: To evaluate the visual outcome of horses with iris prolapse treated with penetrating keratoplasty alone and penetrating keratoplasty in combination with overlying conjunctival or amniotic membrane grafting. METHODS: A retrospective medical records study of horses presented to the University of Florida Veterinary Medical Center for iris prolapse and treated with penetrating keratoplasty in the period of 1998-2010. Data collected from the medical records included signalment, clinical descriptions of ocular lesions, treatments, and therapeutic outcome. RESULTS: Iris prolapses in this study were caused by corneal ulcers with keratomalacia (n = 37). All horses were treated medically for infection, hyperproteinase activity and iridocyclitis, and then surgically treated with either penetrating keratoplasty alone (n = 9) or penetrating keratoplasty with either a conjunctival pedicle flap (n = 22), amniotic membrane transplant (n = 5) or amnion membrane and conjunctival pedicle flap (n = 1). The eyes were visual postoperatively in a majority of the cases (n = 24; 64.9%). Limited vision was noted in 6 eyes (16.2%), 3 eyes became phthisical (8.1%) and 4 globes were enucleated (10.8%). Graft rejection manifested as some degree of donor corneal graft opacification in all cases. Anterior synechiae were present in 48.6% of the eyes. Wound dehiscence and aqueous humour leakage were also common as post operative problems. CONCLUSION: Penetrating keratoplasty alone or in combination with an overlying graft of conjunctiva or amniotic membrane can achieve a successful visual outcome in a high percentage of horses with iris prolapse.