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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Prospective study comparing lidocaine 2% jelly versus sub-Tenon's anaesthesia for trabeculectomy surgery.

AIMS: To compare the analgesic properties of lidocaine 2% jelly versus sub-Tenon's anaesthesia with lidocaine 2% without adrenaline (epinephrine) for trabeculectomy surgery. METHODS: A prospective randomised clinical trial. 59 consecutive patients scheduled for trabeculectomy at the Toronto Western Hospital were randomly assigned to topical unpreserved lidocaine 2% jelly or sub-Tenon's anaesthesia with 2% lidocaine. Both groups received a standardised sedative consisting of midazolam, fentanyl. and/or propofol. The visual analogue scale was utilised to measure intraoperative pain. Patient comfort, physician assessment of intraoperative patient compliance, volume of local anaesthetic used, need for supplemental anaesthesia, and any complications were recorded. The two groups were compared using the Student's t test. RESULTS: The sub-Tenon's anaesthesia group and the lidocaine 2% jelly group did not vary significantly in subjective pain score (18.3 (SD 16.2) v 19.8 (12.4) respectively, p = 0.739) and surgeons' satisfaction scale (3.6 (0.7) and 3.8 (0.6) respectively, p = 0.328). Four patients required additional anaesthesia, all of them in the sub-Tenon's group. CONCLUSION: Topical lidocaine 2% jelly is as effective as sub-Tenon's anaesthesia for pain control in patients undergoing trabeculectomy. Lidocaine 2% jelly is similar to sub-Tenon's anaesthesia in patient comfort and surgeon satisfaction.

Self-inflicted corneal injuries in children with congenital corneal anaesthesia.

Severe corneal ulceration related to self-inflicted injury in the presence of congenital corneal anaesthesia is described in four boys under 2 1/2 years of age. The ulcers had failed to heal until it was recognised that the children were scratching their own eyes. The application of arm splints allowed rapid healing. Although corneal ulceration is a recognised complication of congenital corneal anaesthesia, this preventable cause of the ulceration has not previously been recognised. In two cases there were isolated recurrences which healed quickly with the reapplication of splints. All four children had good vision initially, and, although there were no overt gross development abnormalities, two had neurological signs on detailed investigation suggesting cerebellar or brain stem malformation and one had unilateral anophthalmos, talipes equinovarus, and patent ductus arteriosus. All the children showed normal intellectual development. Whether the eye scratching behaviour was the primary cause of the ulceration or merely an aggravating factor, the identification of this abnormal behaviour is important in any child with idiopathic corneal ulceration, as even in the presence of congenital corneal anaesthesia the eyes heal quickly with effective splinting of the elbows. It is therefore important to test sensation of the cornea and face and to consider the possibility of self-inflicted injury in children with refractory corneal ulceration, as in our cases there were no other consistent diagnostic features.

Systemic absorption of topically applied chloramphenicol eyedrops.

Five children under the age of 9 years had topical chloramphenicol drops administered 2-hourly to each eye for 5 to 7 days. Systemic absorption was not detected by 2 sensitive assays for the drug. The hazards of topical chloramphenicol and reports in the current literature are discussed.

Systemic absorption of topical and subconjunctival gentamicin.

Ten patients received ocular gentamicin therapy topically or subconjunctivally. Systemic absorption was not detected after topical use but was detected after subconjuctival administration. The relative safety of ocular gentamicin therapy is discussed and the literature is reviewed.

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.