Policy implications of regional variations in eye disease detection and treatment on Prince Edward Island: a repeated cross-sectional analysis, 2010-2012.

BACKGROUND: In Canada, government insurance covers eye care services provided by ophthalmologists and other physicians. However, government coverage for services provided by optometrists, non-medical school trained primary eye care providers, varies regionally. Little is known about the impact of a funding model in which ophthalmologist services are government-insured but services provided by optometrists are not, on eye care utilization and eye disease detection and treatment. We aimed to address this question by examining geographic variations in eye care service utilization on Prince Edward Island (PEI). METHODS: PEI physician-billing data from 2010 to 2012 was analyzed across five distinct geographic regions (Charlottetown, Summerside, Prince, Queens & Kings and Stratford). The residential location of patients and practice locations of eye care providers were identified using the first three digits of their respective postal code. Age-standardized rates were computed for comparisons across different regions. RESULTS: There were six ophthalmologists practicing on PEI, five with offices in Charlottetown. Twenty optometrists practiced on the island with offices across the province. Stratford is closest and Prince farthest from Charlottetown. Age-standardized utilization rates of ophthalmologists per 100 populations were 10.44 in Charlottetown and 10.90 in Stratford, which was significantly higher than in other regions (7.74-8.92; p < 0.05). The disparities were most pronounced amongst the elderly. The prevalence of glaucoma visits was higher in Charlottetown (6.10%) and Stratford (6.38%) and lower in other regions. A similar pattern was observed for the prevalence of cataract visits. While the prevalence of diabetes visits was higher in Prince and Summerside, the utilization of ophthalmologists by people with diabetes was almost twice as high in Charlottetown (6.49%) than in Prince (3.88%). CONCLUSIONS: The observed discrepancies in vision care utilization across geographic regions were likely attributed to barriers in accessing government-insured, geographically concentrated ophthalmologists, as opposed to a reflection of the true differences in eye disease occurrence. The lower prevalence of glaucoma visits in regions farther away from ophthalmologist offices may result in delayed detection and blindness in this population. Encouraging ophthalmologists to work in other areas of the province and/or to publicly fund services provided by optometrists may mitigate the observed disparities. TRIAL REGISTRATION: Not applicable.

Survey of equine castration techniques, preferences and outcomes among Australian veterinarians.

OBJECTIVES: (1) To collect the perceptions of veterinarians performing equine castrations in Australia on techniques, preferences and outcomes, (2) to investigate veterinarian use and experience with the Henderson castrating instrument and (3) to investigate potential associations between demographics, castration methods and techniques, and complications. DESIGN: Online survey of members of the Australian Veterinary Association's Special Interest Group, Equine Veterinarians Australia (EVA). METHODS: A link to the survey was included in the EVA e-newsletter and practices on the EVA website were contacted by telephone and follow-up email. Fisher's exact test was used to determine associations between ligation and complications. A generalised linear model with a negative binomial family was used to determine associations between count response variables and categorical independent variables. RESULTS: Responses were obtained from 138 veterinarians (response rate, 13.1%) who performed 5330 castrations over 12 months. Castrations were most commonly performed in the field, on anaesthetised horses, using emasculators, via an open approach and without ligation of the spermatic cord. Estimated complications after use of emasculators were swelling (25%), haemorrhage (5%) and infection (5%). The Henderson instrument was used by approximately 10% of respondents and its use for castration was associated with fewer reports of postoperative swelling compared with emasculators (P = 0.002). Rates of evisceration with the Henderson and emasculator methods were comparable (0.43% and 0.9%, respectively). CONCLUSION: Castration preferences varied widely among survey participants. Reported complication types and rates were comparable to those reported previously in other countries. Perceptions that the Henderson instrument was associated with less swelling should be investigated further via a prospective controlled investigation.

Cataract surgery rates in Ontario, Canada, from 1992 to 2004: more surgeries with fewer ophthalmologists.

BACKGROUND: To evaluate trends in cataract surgeries in Ontario between 1992 and 2004. METHODS: A retrospective analysis of the number of cataract surgeries performed in Ontario from April 1992 to March 2005. The estimated prevalence of cataract and cataract surgeries per 1000 persons at risk was calculated. RESULTS: The number of cataract surgeries in Ontario increased from 44,943 in 1992 to 109,506 in 2004 (143.6%, 12.08% annual increase). The number of cataract surgeries per 1000 patients at risk of cataract increased from 64.6 in 1992 to 115.65 in 2004 (79%, 4.97% increase per year). This rate was strongly positively correlated with time and with the increase in the Ontario population (r = 0.920 and r = 0.922, respectively; p < 0.001). The number of ophthalmologists increased by 5.3% from 1992 to 1997 and then decreased by 2.9% by 2004. This change was not correlated with the cataract surgery rates (r = 0.475; p = 0.10). However, the number of ophthalmologists per million population decreased by 13.4% between 1992 and 2004. This number had a statistically negative correlation with cataract surgery rates (r = -0.757; p < 0.01). INTERPRETATION: There has been a significant increase in the number of cataract surgeries in Ontario despite a decrease in the number of ophthalmologists per million population.

Pharmacokinetic and pharmacodynamic effects of two omeprazole formulations on stomach pH and gastric ulcer scores.

REASONS FOR PERFORMING THE STUDY: Limited data are available on the relative pharmacokinetics and pharmacodynamics of different omeprazole formulations. OBJECTIVES: To compare pharmacokinetic and pharmacodynamic effects of a novel omeprazole formulation against a currently registered product. STUDY DESIGN: Masked 2 period, 2 treatment crossover. METHODS: Twelve clinically healthy horses were studied over two 6-day treatment periods. Horses were randomly assigned to receive a novel omeprazole paste (Ulcershield: ULS) or a currently registered reference omeprazole product (OMO). Gastric pH was measured continuously for 10 h on the day prior to commencing treatment (Day -1) and after 6 days of oral treatment (Day 5) using in situ antimony pH probes within an indwelling nasogastric tube. Plasma pharmacokinetics were determined on Days 0 and 6. RESULTS: Treatment significantly (P<0.005) increased gastric pH on Day 5, compared to results obtained prior to treatment (Day -1) and there was no significant difference between products (P = 0.773). Similarly, comparison of median hourly gastric pH (P = 0.593), mean gastric pH (P = 0.154), percentage time pH<4 (P = 0.259) and area under the time-gastric pH response curve (P = 0.734) did not discriminate between products. Both treatments resulted in significantly lower gastric ulcer severity scores (both P = 0.004), with no difference between treatments (P = 0.688). Comparison of mean log area under time-plasma concentration curves demonstrated that, although the lower limit of the 90% confidence interval was within the -20% limit for bioequivalence, the upper limit was exceeded, suggesting that the test product could have greater bioavailability than the reference product. MAIN LIMITATIONS: The small sample size, large interhorse plasma omeprazole concentrations, and low bioavailability of omeprazole impacted the sensitivity of the bioequivalence analysis. CONCLUSIONS: ULS matched or slightly exceeded OMO plasma concentrations. Both products resulted in equivalent increases in gastric pH, gastric pH profiles and decrease in gastric ulcer scores. Thus, ULS was pharmacodynamically equivalent to OMO and was associated with an equivalent beneficial effect on gastric squamous mucosal ulceration.

Oesophageal lumen pH in yearling horses and effects of management and administration of omeprazole.

BACKGROUND: In human subjects, arytenoid chondritis can be caused by chemical trauma of mucosa attributable to gastro-oesophageal reflux. Although a similar process may be involved in the aetiopathogenesis of arytenoid chondritis in horses, the oesophageal lumen pH in this species is poorly understood. OBJECTIVES: To determine if gastro-oesophageal reflux occurs in horses by characterising oesophageal lumen pH. STUDY DESIGN: Blinded, randomised, placebo-controlled, crossover, experimental study. METHODS: Luminal oesophageal pH in six yearling horses was recorded over four 24 h periods using an ambulatory pH recorder attached to a catheter with two electrodes (proximal and distal) inserted into the oesophagus. Recordings of pH were made during three management protocols. Initially, horses grazed in a paddock (Protocol A). Horses were then moved to stables to simulate sale preparation of Thoroughbred yearlings, and were given either omeprazole (Protocol B) or placebo paste (Protocol C) orally once per day. Protocol A was repeated for each horse (after a 13 day washout period) between Protocols B and C. Summary statistics described pH range and frequency of pH changes. Associations with predictor variables were investigated using linear mixed-effects models. Data are presented as the mean ± s.d. RESULTS: Oesophageal lumen pH ranged from 4.90 to 9.70 (7.36 ± 0.27 and 7.18 ± 0.24 for the proximal and distal electrodes, respectively) and varied frequently (1.2 ± 0.9 changes/min and 0.8 ± 0.8 changes/min for the proximal and distal electrodes, respectively). Oesophageal lumen pH was associated with time since concentrate feeding, activity and time of day, but not with treatment of omeprazole. MAIN LIMITATIONS: A small number of horses were used and measurement periods were limited. CONCLUSIONS: Gastro-oesophageal reflux occurs in clinically normal yearling horses. Although omeprazole had no detectable effect, oesophageal lumen pH recorded during this study did not fall within the therapeutic range of omeprazole.

Can high-resolution peripheral quantitative computed tomography imaging of subchondral and cortical bone predict condylar fracture in Thoroughbred racehorses?

REASONS FOR PERFORMING STUDY: High-resolution 3D imaging may improve the prediction and/or early identification of condylar fractures of the distal metacarpus/tarsus and reduce the frequency of breakdown injury in racehorses. OBJECTIVES: To test the hypotheses that horses suffering condylar fractures have higher bone volume fraction (BV/TV) of the distal metacarpal epiphysis, greater subchondral bone thickness at the fracture site and higher second moment of inertia in the metacarpal midshaft as identified with high-resolution 3D imaging. STUDY DESIGN: Cross-sectional study using cadaver material. METHODS: Thoroughbreds that died on racetracks were grouped as: 1) horses with third metacarpal (McIII) fractures with a condylar component (cases, n = 13); 2) horses with no limb fracture (controls, n = 8); 3) horses with fractures in other bones or suspensory apparatus disruption (other fatal injuries, n = 16). The palmar condyles of McIII and the midshaft were examined with high resolution peripheral quantitative computed tomography (HR-pQCT). Statistical analysis included logistic regression and Spearman's correlation. RESULTS: There were no significant differences in BV/TV of distal McIII and second moment of inertia of the midshaft between cases and controls. Epiphyseal bone BV/TV was greater in injured limbs of horses with any fatal limb injury (Groups 1 and 3 combined) compared with controls (odds ratio = 1.20, 95% confidence interval 1.01-1.42, P = 0.034). An epiphyseal BV/TV>0.742 resulted in a sensitivity of 82.8% and specificity of 62.5% in identifying horses with fatal limb injury. In horses without condylar fracture, increased subchondral bone thickness was associated with palmar osteochondral disease lesions in the adjacent condyle (rs = 0.65, P<0.001). CONCLUSIONS: Increased BV/TV of the distal metacarpus may have some value for identifying horses at risk of any fatal breakdown injury but not metacarpal condylar fractures. Measurement of parasagittal groove subchondral bone thickness is complicated by adjacent palmar osteochondral disease lesions. Thus, high-resolution imaging of the distal metacarpus appears to have limited ability to identify horses at risk of condylar fractures.

Catecholamines in human aqueous humor.

Aqueous humor catecholamine levels were measured in 14 patients admitted to hospital for cataract or glaucoma surgery. Norepinephrine was detected in all patients. Epinephrine was detected in one patient who had received a preoperative retrobulbar injection of epinephrine. Dopamine was not detected in any patients. The highest level of norepinephrine was detected in cataract patients with normal intraocular pressures (mean = 7.18 nmol/l).

The visual field indices in primary open-angle glaucoma.

PURPOSE: The distribution of sensitivity across the visual field, as determined by automated threshold static perimetry, can be summarized in terms of visual field indices. Such indices can be weighted for the variation in threshold at each eccentricity. The aims of this study were to determine the influence of the weighting factor, the relationship between the unweighted indices derived from Programs 30-2 and 24-2, and the relationship between the number of double determinations of threshold and the magnitude of the short-term fluctuation. METHODS: One visual field derived by Program 30-2 of the Humphrey Field Analyzer was selected from each of 60 consecutive patients with primary open-angle glaucoma. The first two fields from each individual patient were avoided. Unweighted visual field indices were calculated and compared with the Program 30-2 weighted indices using an assessment of agreement evaluated with respect to the 95% confidence limits of the population. RESULTS: The weighting function had no influence on the mean deviation, but it caused a slight reduction in the short-term fluctuation and an elevation in the pattern and corrected pattern standard deviations. There was little difference between the indices generated by Programs 30-2 and 24-2. The short-term fluctuation increased with an increase in the number of double determinations of threshold. CONCLUSIONS: The weighting function had little clinical influence on the visual field indices. The indices derived from Programs 30-2 and 24-2 were similar, and the short-term fluctuation would better reflect the intratest variability if all available double determinations of threshold were used to calculate the index.

Effects of hydrogen peroxide-induced oxidative damage on outflow facility and washout in pig eyes.

Previous studies show that hydrogen peroxide (H2O2) is present in the aqueous humor of many species and is capable of affecting outflow facility in animal model experiments. To study the hypothesis that oxidative damage to the outflow pathway may play a role in the pathogenesis of primary open-angle glaucoma, 3 mM H2O2 with 20 mM 3-aminotriazole and 1 mM carmustine (BCNU) in Dulbecco's phosphate-buffered saline (DPBS) was perfused into enucleated pig eyes at constant pressure. Baseline and experimental perfusions were done at two different pressures (7.5 and 30 mm Hg) to study the effect of pressure on the response to oxidative damage. Outflow facility in the baseline experiments (with DPBS only) was observed to increase nonlinearly with time during the perfusions, but could be linearized if plotted as a function of the volume perfused. Thus, a term "volumetric washout" (W) was introduced and defined as the fractional rate of change of outflow facility with respect to the volume perfused. This quantity was found to be independent of pressure in the baseline studies. Perfusion of H2O2 and inhibitors increased W at 7.5 mm Hg but decreased W at 30 mm Hg. These results indicate that oxidative damage increases outflow facility at normal pressure but decreases it at elevated pressure, suggesting that elevated pressure may increase the susceptibility of the outflow pathway to this form of insult.

Pointwise topographical and longitudinal modeling of the visual field in glaucoma.

PURPOSE: To develop a suitable mathematical model for the description of the pointwise distribution of sensitivity across the visual field in glaucoma. METHODS: The pointwise distribution of sensitivity at any given stimulus location for any given examination was described by a joint topographical and longitudinal model. The topographical element modeled the pointwise distribution of sensitivity using a second-order polynomial function in terms of the respective stimulus coordinates whereas the longitudinal element modeled the pointwise distribution of sensitivity using multiple linear regression in terms of the sensitivity at the given location determined at one or more previous examinations. The sample comprised Humphrey Field Analyser (Humphrey Instruments, San Leandro, CA) Program 30-2 and 24-2 fields from 49 patients attending a glaucoma clinic for an average of 3 years. RESULTS: The constant term of the polynomial correlated highly with the mean deviation and moderately with the pattern standard deviation. The goodness-of-fit between the modeled and the measured field increased as an exponential function of the number of previous examinations. The median R2 was 19.6% for the first examination and 83.6% for the sixth examination. The group median optimum percentage of error between the measured and modeled sensitivity at each test location was below 10% (i.e., less than 3 dB), increased with increase in eccentricity, was greater at the extremities of the superior field and varied as a function of the severity of the field loss. CONCLUSION: The model seems to be a promising way to evaluate visual field progression.

The long-term fluctuation of the visual field in stable glaucoma.

PURPOSE: To determine, in stable glaucoma, the characteristics of the between-examination variability of the visual field recorded with the Humphrey Field Analyser (HFA; Humphrey Systems, Dublin, CA) using the homogeneous, LF(Ho), and heterogeneous, LF(He), components of the long-term fluctuation (LF), thereby providing a technique for separating progressive loss from fluctuation in sensitivity. METHODS: The LF components were calculated using a two-factor analysis of variance (ANOVA) with replications and were determined between each pair of three successive HFA program 30-2 fields for each patient from two groups, each containing 30 patients with primary open-angle glaucoma. The interval between examinations for the first group was 6 to 9 months and for the second group was 3 weeks. RESULTS: The group mean values for LF(Ho) ranged from 1.50 to 2.19 dB and for LF(He) from 1.70 to 2.05 dB. The average difference between examinations was within +/-0.35 dB for each component, and the 95% limits of agreement for the two groups, respectively, were +/- 2.31 and +/- 2.39 dB for the LF(Ho) and +/- 2.36 and +/- 2.09 dB for the LF(He). The estimate of the 90% confidence limit for the LF(Ho) was 3.30 dB and for the LF(He), 3.60 dB. Little relationship was present between the LF components and the modulus differences in mean deviation (MD), the corrected pattern SD (CPSD), or the mean MD, mean short-term fluctuation, and mean CPSD, of the two fields. CONCLUSIONS: Estimation of the LF components and of the corresponding confidence limits yields an expression of the normal between-examination variability of two consecutive fields that can be used as a reliability index. A value outside the confidence limits indicates the necessity for a confirmatory follow-up field.

Ultrasound biomicroscopy in Sturge-Weber-associated glaucoma.

PURPOSE: To evaluate Sturge-Weber-associated glaucoma using ultrasound biomicroscopy. METHOD: Case report. Clinical examination combined with ultrasound biomicroscopy was performed in a patient with Sturge-Weber-associated glaucoma. RESULTS: In the patient's left eye, which had Sturge-Weber-associated glaucoma, a 360-degree supraciliary effusion, dilated superficial and intrascleral vessels, and an open angle were detected by ultrasound biomicroscopy. CONCLUSION: The presence of dilated intrascleral vessels and supraciliary fluid support the hypothesis of increased episcleral venous pressure as the cause of elevated intraocular pressure in this syndrome.

Beta adrenergic receptors in pigmented ciliary processes.

Beta adrenergic receptors from membrane fragments of pigmented sheep eyes were studied and characterised by ligand binding techniques after the removal of melanin. In a representative experiment the beta max (total number of beta receptors) was 394.9 fmol/mg protein. The receptor affinity (Ka) was 440 pM. The potency series of drugs to displace 125I-HYP from the receptors was timolol = (-) propranolol greater than (+) propranolol greater than salbutamol greater than practolol. beta 1 Receptors were not detected in the ciliary processes. beta 2 Receptors were the prominent adrenergic receptors present. The theory as to how beta blockers work in glaucoma, their site of action, and the potential role of beta 2 blockers for use in intraocular pressure control is discussed.

A comparison of Goldmann and Humphrey automated perimetry in patients with glaucoma.

Humphrey automated threshold perimetry (Program 30-2) was performed on 42 eyes of 25 patients with glaucoma to determine both the sensitivity and specificity of automated perimetry in detecting glaucomatous visual field defects. Automated perimetry sensitivity was 90.38%, while automated perimetry specificity was 91%. Fifty-two patients and a technician took part in a survey to determine their preference for either test. Patients generally preferred having Goldmann perimetry. The technician favoured Humphrey automated perimetry. Program 30-2 on the automated perimeter took 25% longer to perform than Goldmann perimetry.

Effect of a beta-blocker on altered body position: induced ocular hypertension.

The intraocular pressures (IOP) were measured in both eyes of 25 healthy volunteers in various body positions. One eye was pretreated with levobunolol 0.5% or placebo applied in a masked, randomised fashion, while the other served as control. IOP changes in response to levobunolol and to changes in position were significant (p less than 0.0001). However, pressure rises relative to position were not significantly different in eyes treated with drug vs placebo. Levobunolol did not alter relative changes in IOP from changes in body position. However, the overall lowering effect may offer some protection to patients with glaucoma.

Binding potencies of 3 new beta 2 specific blockers to beta receptors in the ciliary processes and the possible relevance of these drugs to intraocular pressure control.

The binding potencies of 3 new beta 2 blocking drugs to beta receptors in the ciliary processes were studied by means of radioligand techniques. The drugs studied were IPS339, ICI118,551, and Sandoz L1 32-468. The order of potency of these drugs was IPS339 greater than Sandoz L1 32-468 greater than ICI118,551. The beta 2 dissociation constants (KDs) for these drugs were 0.90 nM, 6.60 nM, and 55 nM respectively. These results are compared with those for other adrenergic agents, including timolol. The potential role of topical beta 2 blockers in glaucoma is discussed.

Glaucoma laser suture lysis.

AIM: Suture lysis is commonly performed after trabeculectomy to improve bleb function. It is often thought to be an innocuous procedure. This is the first large study to determine the safety of the procedure and compare results with a control group. METHODS: Two hundred successive trabeculectomies performed between January 1992 and October 1993 were analysed. RESULTS: Ninety nine eyes underwent trabeculectomy and suture lysis; 101 eyes underwent trabeculectomy and did not require postoperative suture lysis. The following complications were noted with suture lysis: flat chambers (13.1%), external aqueous leaks (9%), malignant glaucoma (2%), iris incarceration (2%), and large blebs (2%). All resolved with appropriate management. There was no significant difference in the final postoperative mean pressures between the lysis and the non-lysis groups. CONCLUSION: Suture lysis is not an innocuous procedure. However if managed appropriately, complications do not affect the intraocular pressure outcome.

Short-term effects of neodymium-YAG transscleral cyclocoagulation in patients with uncontrolled glaucoma.

Transscleral Nd-YAG cyclocoagulation has been reported to lower intraocular pressure (IOP) in animals, eyes and more recently in human eyes. We treated 14 patients with uncontrolled IOP using this technique. Three patients were lost to follow-up. The mean follow-up time was 12 (SD 2.6) weeks. There was a decrease in IOP in all patients. Seven had final IOP readings less than or equal to 25 mmHg (63.6%). Six patients had IOP less than or equal to 21 mmHg (54.5%). Fairly severe complications occurred in most patients. None, however, developed phthisis bulbi. Two patients had one treatment (18%), eight patients had two treatments (72%), and one patient had three treatments (9%). This preliminary study confirms that Nd-YAG cyclocoagulation effectively lowers IOP in patients with uncontrolled glaucoma over the short term.

The effect of simulated obstructive apnoea on intraocular pressure and pulsatile ocular blood flow in healthy young adults.

AIM: To investigate the effect of negative inspiratory effort, as generated by the Mueller manoeuvre, on intraocular pressure (IOP) and pulsatile ocular blood flow (POBF) in healthy young adults. METHODS: Seven volunteers with no history of systemic or ocular disease were recruited (mean age 30.7 years, range 25-40 years, M/F: 4/3). After initial instruction and practice of the Mueller manoeuvre, baseline measurements of IOP and POBF were obtained for both eyes after 10 and 15 minutes of rest, respectively, in the supine position. Thereafter, the Mueller manoeuvre was performed creating a mouthpiece pressure of -20 cm H(2)O, for at least 15 seconds followed by a 5 minute rest. The manoeuvre was repeated with a mouthpiece pressure of -40 cm H(2)O. IOP and POBF were measured 5-15 seconds into the manoeuvre for both -20 cm H(2)O (M2A) and -40 cm H(2)O (M4A) and directly upon recovery (after two respiratory cycles) from each manoeuvre (M2B, M4B). Baseline measurements were compared using paired t test, whereas manoeuvre induced changes in IOP and POBF were analysed individually using repeated measures ANOVA with Student-Newman Keuls post hoc analyses. Linear regression analysis was used to investigate a dose-response effect. RESULTS: No significant differences were found between baseline measurements so they were subsequently pooled. There was a significant decrease in IOP for M2B (-9.2%, p<0.05), M4A (-13.8%, p<0.05), and M4B (-15.6%, p<0.05), relative to baseline. A dose-response relation was found for the effect of mouthpiece pressure on measurements 5-10 seconds into the manoeuvre (M2A and M4A, r = 0.54, p = 0.045). There was a trend of increased POBF relative to baseline for all measurements; however, significance was reached for M4B only (p = 0.039). CONCLUSION: It was shown that forced inspiratory efforts as generated by the Mueller manoeuvre are associated with a dose dependent decrease in IOP and a concomitant increase in pulsatile ocular blood flow.

Is a tight patch necessary after trabeculectomy?

AIMS: To determine if post-trabeculectomy patching reduces the prevalence of shallow/flat anterior chambers and pain. METHODS: 435 eyes were prospectively randomised to either a double patch with tape or no patch with tape group. RESULTS: There was no statistically significant difference in flat or shallow anterior chamber rates or pain symptoms between the patch and no patch groups. CONCLUSION: There is no benefit to patching the post-trabeculectomy eye.