Postoperative complications and visual outcomes of phacoemulsification in 103 dogs (179 eyes): 2006-2008

Objective To describe the postoperative complications and visual outcome after phacoemulsification in dogs and identify risk factors for complications. Animals studied One hundred and three dogs (179 eyes) that had phacoemulsification with or without intraocular lens (IOL) placement including foldable acrylic IOLs between March 2006 and March 2008 at Purdue University Veterinary Teaching Hospital. Procedure Medical records were reviewed and occurrence and dates of postoperative complications were tabulated. Visual status at the final recheck during the study period was recorded. Additional information including signalment, diabetes mellitus status, operative complications and factors, presence of prior lens induced uveitis, preoperative retinopexy, and cataract stage was collected. Results The majority of eyes were functionally visual (148 eyes, 82.7%) at the end of the study period. Blindness was seen in 18 eyes (10.0%) with reduced vision in 13 eyes (7.3%) at the final recheck. Postoperative ocular hypertension (22.9%), corneal lipid opacity (19.0%), uveitis (16.2%), intraocular hemorrhage (12.3%), retinal detachment (8.4%), and glaucoma (6.7%) were the most common postoperative complications seen in eyes. The odds of blindness were significantly greater (OR = 290.44) in the eyes of Boston terriers compared with mixed breed dogs and with each year of increasing age (OR = 2.00). Conclusion The prognosis for vision after phacoemulsification with injectable IOL placement is good. Boston terriers were at much higher risk for certain complications.     

Intraocular pressure in normal llamas (Lama glama) and alpacas (Lama pacos)

Objective: To determine the mean intraocular pressure in llamas ( Lama glama ) and alpacas ( Lama pacos ) using applanation tonometry. Animals studied: Ten llamas and 10 alpacas. Procedures: Intraocular pressure (IOP) was measured with a Tono-Pen™ XL (Mentor Ophthalmics, Inc., Norwell, MA, USA). Three values, with 5% variance, were recorded for each eye. Least-squares means were determined for IOP for each eye of llamas and alpacas. Controlling for age, differences between left and right eye were analyzed using anova . Two age groups were established, less than 5 years and greater than 5 years. The effect of age on IOP within each group was analyzed by linear regression. Probability values of less than 0.05 were considered significant. Results: Comparison of mean IOP between right ( n  = 20) and left eyes ( n  = 20), independent of species type, showed no differences in IOPs for llamas and alpacas. Mean IOP declined with increasing age in llamas and alpacas. Mean IOPs for 20 eyes in 10 llamas was 16.96 ± 3.51 mmHg. Mean IOP for 20 eyes in 10 alpacas was 16.14 ± 3.74 mmHg. Mean IOP for all eyes ( n  = 40), independent of species, was 16.55 ± 3.55 mmHg. The range of IOP in normal llamas and alpacas within 2 SD (95% of the population) was 14.89±18.21 mmHg. Conclusions: There was no significant difference in IOP between alpacas and llamas. Mean IOP in both species decreased with increased age.     

A comparison of anesthetic complications between diabetic and nondiabetic dogs undergoing phacoemulsification cataract surgery: a retrospective study

Objective To compare the incidence of anesthetic complications in diabetic and nondiabetic dogs undergoing general anesthesia and phacoemulsification cataract surgery. Procedure The medical and anesthetic records of all dogs undergoing phacoemulsification cataract surgery at Davies Veterinary Specialists between 2005 and 2008 were reviewed. Anesthetic records were evaluated by an ECVAA Diplomate. Dogs for which records were incomplete were excluded. The anesthetic technique, including all drugs administered in the perioperative period, was recorded. The anesthetic complications investigated included hypotension (MAP (mmHg): ≥55 none/mild; ≤54 moderate/severe), bradycardia (<60 bpm associated with hypotension) and hypothermia (esophageal temperature <36.7 °C). Where hypotension was present, the method of and response to treatment was recorded. The incidence of severe hyperglycemia (blood glucose >13.75 mmol/L (250 mg/dL)) in the diabetic group was also assessed. Results 66 diabetic and 64 nondiabetic dogs were included in the study. Diabetic dogs were more likely to develop moderate and severe intraoperative hypotension than nondiabetic dogs. Forty‐four percent of diabetic dogs had at least one episode of severe hyperglycemia whilst anesthetized. Conclusions Diabetic dogs undergoing phacoemulsification are more likely to suffer the anesthetic complications of moderate and severe hypotension than nondiabetic dogs. The increased incidence and severity of hypotension in diabetic dogs may be explained by hypovolemia secondary to hyperglycemia and resultant osmotic diuresis.     

Phaco chop technique for cataract surgery in the dog

Phaco chop is a bimanual phacoemulsification technique to remove cataracts. The technique was first presented at the 1993 3rd American-International Congress on Cataract, IOL, and Refractive Surgery in Seattle by Dr Kunihiro Nagahara. He compared the lens with a block of wood and by applying chopping forces parallel to the natural planes of the lens lamellae, as one does in splitting wood, a nucleus can be cleaved with surprisingly little force and time. Dr Nagahara used the phaco tip to impale and high vacuum to hold the nucleus while a second instrument, or chopper, hooked the equator and was pulled centrally, splitting the nucleus along its natural cleavage planes. This was a breakthrough for surgeons who had been utilizing several minutes of phaco energy sculpting grooves and bowls in a lens. Studies have shown that compared with four-quadrant 'divide and conquer', the phaco chop technique uses less phaco time and energy, significantly reducing endothelial cell damage. Other advantages of phaco chop include reduction of zonular and capsular stress because forces are directed toward an opposing instrument and the phaco tip is kept in a central 'safe zone' in the middle of the pupil. This technique has also been successfully adapted to the canine phacoemulsification procedure. The larger canine lens requires some modifications, and lenses with hard nuclear and cortical material may not be amenable to this procedure.     

Postoperative glaucoma in the Labrador Retriever: incidence, risk factors, and visual outcome following routine phacoemulsification

Objective To evaluate the incidence and risk factors associated with development of postoperative glaucoma in the Labrador Retriever following routine phacoemulsification. Methods Medical records from Labradors and a randomly selected population of non‐Labradors were retrospectively evaluated. Signalment, diabetic status, cataract stage, gonioscopic findings, presence of preoperative lens‐induced uveitis, development of postoperative hypertension (POH), postoperative glaucoma and postoperative visual status were recorded for each patient. Survival curves were developed using the Cox proportional hazards model. Results Forty‐two Labradors (66 eyes) and 199 non‐Labradors (314 eyes) were included. The incidence of POH was significantly higher in Labradors (33%) than non‐Labradors (18%). Labradors were at significantly increased risk of postoperative glaucoma and blindness compared to non‐Labradors. Estimated probabilities of postoperative glaucoma in Labradors were 23%, 25%, 30% and 35% at weeks 4, 26, 52 and 104, respectively, compared with 5%, 6%, 7% and 9% at weeks 4, 26, 52 and 104, respectively, in non‐Labradors. Estimated probabilities of postoperative blindness in Labradors were 5%, 9%, 15% and 27% at weeks 4, 26, 52 and 104, respectively, compared with 2%, 3%, 5% and 10% at weeks 4, 26, 52 and 104, respectively, in non‐Labradors. Risk factors for the development of glaucoma in Labradors included increasing age and development of POH. No statistically significant risk factors for the development of glaucoma were identified in non‐Labradors. Conclusions Labradors are at increased risk of glaucoma and blindness following phacoemulsification compared with non‐Labradors. POH and increasing age represent risk factors for the development of postoperative glaucoma in Labradors.     

A study of the morphology of canine eyes enucleated or eviscerated due to complications following phacoemulsification

This study was undertaken to describe the histopathologic abnormalities observed in canine eyes enucleated or eviscerated due to complications following phacoemulsification; to correlate these findings with the clinical abnormalities reported, and to suggest, if apparent, likely causes and effects of these abnormalities. Sixty-six canine globes or evisceration samples received for histopathologic interpretation over a 10-year period (1990-2000) were studied. All globes and evisceration samples were obtained from clinical patients examined by board-certified ophthalmologists. Hematoxylin and eosin (H&E) and alcian blue/periodic acid Schiff (PAS) stained sections were examined by light microscopy in every case. A tissue Gram stain was used when indicated. Clinical information obtained from the pathology submission form was reviewed in all cases, and obtained from questionnaires completed and returned by an ophthalmologist for 51 cases (77%). The most frequent histopathologic diagnoses were glaucoma (76%) and retinal detachment (64%). The most frequently reported clinical abnormalities in this series were glaucoma (86%) and uveitis (82%). Five problem areas were identified that appear to make a significant contribution to the failure of canine cataract surgery and merit further investigation: pre-iridal fibrovascular membranes; lens fiber regrowth; lens epithelial membranes; endophthalmitis, and the health of the corneal surgical incision.     

Pharmacokinetics of intravenous gentamicin in healthy young‐adult compared to aged alpacas

The study objective was to evaluate the effects of age on aminoglycoside pharmacokinetics in eight young‐adult (<4 years) and eight aged (≥14 years) healthy alpacas, receiving a single 6.6 mg/kg intravenous gentamicin injection. Heparinized plasma samples were obtained at designated time points following drug administration and frozen at ?80°C until assayed by a validated immunoassay (QMS ^®). Compartmental and noncompartmental analyses of gentamicin plasma concentrations versus time were performed using WinNonlin (v6.4) software. Baseline physical and hematological parameters were not significantly different between young and old animals with the exception of sex. Data were best fitted to a two‐compartment pharmacokinetic model. The peak drug concentration at 30 min after dosing (23.8 ± 2.1 vs. 26.1 ± 2 μg/ml, p = .043 ) and area under the curve (70.4 ± 10.5 vs. 90.4 ± 17.6 μg hr/ml, p = .015 ) were significantly lower in young‐adult compared to aged alpacas. Accordingly, young alpacas had a significantly greater systemic clearance than older animals (95.5 ± 14.4 and 75.6 ± 16.1 ml hr^?1 kg^?1; p = .018 ), respectively). In conclusion, a single 6.6 mg/kg intravenous gentamicin injection achieves target blood concentrations of >10 times the MIC of gentamicin‐susceptible pathogens with MIC levels ≤2 μg/ml, in both young‐adult and geriatric alpacas. However, the observed reduction in gentamicin clearance in aged alpacas may increase their risk for gentamicin‐related adverse drug reactions.