Papers by Christopher Leffler
Canadian journal of ophthalmology, Apr 1, 2019
analyzed reoperations among strabismus patients. 1 They stated that "the historical strabismus re... more analyzed reoperations among strabismus patients. 1 They stated that "the historical strabismus reoperation rate over a 21-year period was 15.7%" and hoped that their results might "benefit in the preoperative counseling of patients." Unfortunately, if a patient asks about the likelihood that he or she will require reoperation over the next 21 years, the answer is probably much higher than 15.7%. The reoperation rate in just the first postoperative year is about 7.7% in children, 2 and 8.5% in adults. 3 The only way to know the true reoperation rate over 21 years in all patients is to wait until 21 years after the last patient has surgery. The survival curve in their paper is labelled "Kaplan-Meier-like." A correct survival curve has the number of years since an individual patient had surgery on the x-axis. For instance, at the 21-year postoperative mark, the survival curve should only show patients who had surgery in 1995. Instead, the last point on their survival curve includes every patient operated on at the hospital since 1995. In reality, a patient who had surgery in 2015 (for example) will not teach us anything about the 21-year reoperation rate until the year 2036. Could the authors provide the reoperation rate at 1, 2, 5, 10, 15, and 20 years after a patient had surgery, excluding all patients who had surgery less than 1, 2, 5, 10, 15, and 20 years (respectively) before the data were collected?
Journal of infectious diseases & case reports, Sep 30, 2021
American Journal of Tropical Medicine and Hygiene, May 4, 2022
We studied all-cause mortality during the COVID-19 pandemic in 19 Indian states (population 1.27 ... more We studied all-cause mortality during the COVID-19 pandemic in 19 Indian states (population 1.27 billion). Excess mortality was calculated by comparison with years 2015 to 2019. The known COVID-19 deaths reported for a state were assumed to be accurate, unless excess mortality data suggested a higher toll. Data from one state were excluded due to anomalies. In several regions, fewer deaths were reported in 2020 than expected. Areas in
Journal of Aapos, Aug 1, 2018
To the Editor: In their article "Variability of preoperative measurements in intermittent exotrop... more To the Editor: In their article "Variability of preoperative measurements in intermittent exotropia and its effect on surgical outcome," Kim and Kim 1 assessed surgical outcomes with respect to the variability of preoperative measurements in patients with intermittent exotropia. We appreciate the authors' work; however, a statistical issue should be considered. The authors used repeated measure analysis of variance (rmANOVA) to analyze the difference in clinical course over 24 months after surgery between groups. In fact, they performed multiple comparisons. Their study considered a P value of \0.05 as statistically significant. We would like to point out that the type I error rate (alpha) may be inflated (alpha inflation) by analyzing the same datum more than once. Unfortunately, the problem of alpha inflation is frequently ignored in medical statistics. The common method of dealing with this kind of problem is to adjust the type I error rate lower than 0.05 by Bonferroni adjustment: adjusted alpha 5 alpha / number of tests. In this study, the authors carried out three comparisons for each parameter, therefore an adjusted alpha for this study is 0.05/3 5 0.016, and the null hypothesis should reject only when P \ 0.016 rather than 0.05. By this means one can ensure that the overall chance of making a type I error is \0.05. 2
Ophthalmology, Feb 1, 2023
Investigative Ophthalmology & Visual Science, May 1, 2005
American Journal of Tropical Medicine and Hygiene, Jun 13, 2022
We agree with Drs. Mattiuzzi and Lippi that excess mortality during the pandemic is not exactly e... more We agree with Drs. Mattiuzzi and Lippi that excess mortality during the pandemic is not exactly equivalent with mortality caused by SARS-CoV-2 infection. We noted that excess mortality may result from "Health system overload, delays in patients seeking unrelated healthcare … social changes such as lockdowns … other diseases, war, or environmental factors. Mortality deficits … may result from fewer injuries." We found that the excess mortality during the COVID-19 pandemic in India, through August 31, 2021, was 198.7 per 100,000 population (range 146.1-263.8 per 100,000). 2 For context, the Hopkins dataset we used reflected COVID-19 mortality of 203.1 per 100,000 population in the United States as of August 31, 2021. 2 So, the excess mortality in India is comparable with the COVID-19 mortality in countries with more robust testing. The survey that Drs. Mattiuzzi and Lippi cited does not demonstrate that delays in seeking healthcare resulted in increased mortality of this magnitude. The survey respondents obviously had not died, and the survey did not ask whether anyone in the family had died as a result of delayed care. The most disruptive lockdowns in India occurred in Spring 2020. However, the bulk of the excess mortality in India occurred in Spring 2021, coincident with the delta-variant COVID-19 wave, and to a lesser degree in Fall 2020. 2 Thus, we believe that the bulk of the excess mortality in India was in fact due to COVID-19 infection.
Wayenborgh Publishing, May 1, 2020
PurposeThe objective of this study was to quantify inter-surgeon variation in strabismus surgery ... more PurposeThe objective of this study was to quantify inter-surgeon variation in strabismus surgery reoperation rates in a large national database of provider payments, and to explore associations of reoperation rate with practice type and volume, surgical techniques, and characteristics of the patient population.MethodsFee-for-service payments to providers for Medicare beneficiaries having strabismus surgery between 2012 and 2020 were retrospectively analyzed to identify reoperations in the same calendar year. The adjustable-suture technique was considered to be available to the patient if the patient’s surgeon billed for adjustable sutures. Predictors of the rate of reoperation for each surgeon were determined by multivariable linear regression.ResultsAmong 141 surgeons, the reoperation rate for 1-horizontal muscle surgery varied between 0.0% and 30.8%. Due to the presence of high-volume surgeons with high reoperation rates, just 11 surgeons contributed half of the reoperation events...
Purpose. To determine the identity of the prototypical blind man repeatedly described by philosop... more Purpose. To determine the identity of the prototypical blind man repeatedly described by philosopher John Locke (1632-1704). Methods. Historical books were reviewed. Results. In several works, John Locke described a studious man he knew who went blind from smallpox at a young age. This man struggled to understand visual concepts such as the yellow color of saffron, the clarity of the sun, or the color of scarlet, which the man compared to a trumpet. Nonconformist minister John Troughton (1637-1681) went blind from smallpox at a young age. Troughton was a fellow student with Locke at Oxford University. Troughton's sermons quoted the exact portions in Song of Solomon (Canticles 4-6) and Revelations (chapter 18) which contain the imagery (and the association of the color scarlet with the sound of trumpets) found in Locke's writings. Thus, Locke's comparison of the color scarlet with the sound of trumpets was probably not a description of synesthesia, but rather was an attempt of a blind scholar to understand Biblical imagery. Conclusions. The struggles of blind nonconformist minister John Troughton to understand Biblical imagery probably stimulated John Locke to ponder what humans can know innately about vision, independent of experience.
Investigative Ophthalmology & Visual Science, Jun 11, 2015
Digital journal of ophthalmology, Dec 30, 2017
We present and discuss the previously unrecognized evidence for the possible introduction of cata... more We present and discuss the previously unrecognized evidence for the possible introduction of cataract extraction by aspiration into modern Western medicine on March 26, 1815, in Philadelphia, Pennsylvania, by surgeon Philip Syng Physick. On this date, he successfully extracted a cataract by suction through a tube, according to newspaper reports written by the patient, an attorney who sought a patent on the suction device. Aspects of the patient's account are confirmed by supporting evidence from the medical community and by a cataract instrument set attributed to Physick, which includes a cannula attached to a syringe. The evidence suggests that Physick was the first to reintroduce cataract aspiration to Western medicine.
Ophthalmology and eye diseases, 2016
Federico da Montefeltro (1422-1482), the Duke of Urbino, was a well-known historical figure durin... more Federico da Montefeltro (1422-1482), the Duke of Urbino, was a well-known historical figure during the Italian Renaissance. He is the subject of a famous painting by Piero della Francesca (1416-1492), which displays the Duke from the left and highlights his oddly shaped nose. The Duke is known to have lost his right eye due to an injury sustained during a jousting tournament, which is why the painting portrays him from the left. Some historians teach that the Duke subsequently underwent nasal surgery to remove tissue from the bridge of his nose in order to expand his visual field in an attempt to compensate for the lost eye. In theory, removal of a piece of the nose may have expanded the nasal visual field, especially the "eye motion visual field" that encompasses eye movements. In addition, removing part of the nose may have reduced some of the effects of ocular parallax. Finally, shifting of the visual egocenter may have occurred, although this seems likely unrelated to the proposed nasal surgery. Whether or not the Duke actually underwent the surgery cannot be proven, but it seems unlikely that this would have substantially improved his visual function.
American Journal of Ophthalmology, Oct 1, 2021
PURPOSE To describe the entry of cataract surgery into the British Isles. METHODS Handbills, book... more PURPOSE To describe the entry of cataract surgery into the British Isles. METHODS Handbills, books, and other historical sources were reviewed to determine when cataract surgery was first performed in the region. RESULTS Roman artifacts suggest that couching was performed in the British Isles in antiquity. Seemingly miraculous cures of blindness during the early Middle Ages might be consistent with couching. However, there is no strong evidence of medieval cataract surgery in the region. Cataract couching probably arrived in England by the 1560s, in Scotland by 1595, in Ireland by 1684, and in Anglo-America by 1751. Before the 18th century, cataract surgery was taught within families, apprenticeships, and mountebank troupes. Beginning in the 17th century, congenital cataract surgery permitted surgeons to tout their skills, and to explore visual perception. However, in some cases, such as the couching of the 13-year-old Daniel Dolins by surgeon William Cheselden in 1727, whether the cataracts were truly congenital, and whether vision improved in any way, remain in doubt. Beginning in the 1720s, cataract surgery began to be performed by traditional surgeons in hospitals. However, for most of the century, the highest volume cataract surgeons continued to be itinerant oculists, including those who performed cataract extraction in the latter half of the century. CONCLUSIONS Cataract surgery might have been performed in Roman Britain. Specific evidence of cataract surgery emerges in the region in the Elizabethan era. Cataract extraction was performed in the British Isles by 1753, but couching remained popular throughout the 18th century.
Journal of Clinical Medicine, Mar 11, 2020
Glaucoma is one of the leading causes of blindness worldwide, and as the proportion of those over... more Glaucoma is one of the leading causes of blindness worldwide, and as the proportion of those over age 40 increases, so will the prevalence of glaucoma. The pathogenesis of primary open angle glaucoma (POAG) is unclear and multiple ocular risk factors have been proposed, including intraocular pressure, ocular perfusion pressure, ocular blood flow, myopia, central corneal thickness, and optic disc hemorrhages. The purpose of this review was to analyze the association between systemic vascular risk factors (including hypertension, diabetes, age, and migraine) and POAG, based on major epidemiological studies. Reports presenting the association between POAG and systemic vascular risk factors included a total of over 50,000 patients. Several epidemiological studies confirmed the importance of vascular risk factors, particularly hypertension and blood pressure dipping, in the pathogenesis and progression of glaucomatous optic neuropathy. We found that diabetes mellitus is associated with elevated intraocular pressure, but has no clear association with POAG. No significant correlation between migraine and POAG was found, however, the definition of migraine varied between studies.
American Journal of Ophthalmology, Sep 1, 2017
To determine the effect of dilating drops on strabismus measurements in adults. Design: Prospecti... more To determine the effect of dilating drops on strabismus measurements in adults. Design: Prospective cohort study Methods: Patients age 18 and older with strabismus underwent a standard evaluation of ocular motility, stereopsis, and ocular alignment with alternate prism cover test by a certified orthoptist. After pupil dilation with 2.5% phenylephrine and 1% tropicamide, ocular alignment was re-measured in primary gaze at 6 meters, at 1/3 meter and at 1/3 meter with a +3.00 by a second certified orthoptist, masked to the previous measurements. The primary outcome was the mean difference in the angle of horizontal and vertical deviations after dilation in prism diopters. Results: A total of 55 patients were enrolled with a variety of diagnoses. For horizontal measurements the mean change was 0.54 prism diopters at 6 meters (95% CI-0.36 to 1.43, p=0.24), 1.67 prism diopters at 1/3 meter (95% CI-0.19 to 3.54, p=0.08), and-0.05 prism diopters at 1/3 meter with a +3.00 add (95% CI-1.65 to 1.56, p=0.95). The mean change in vertical deviation was 0.18 prism diopters at 6 meters (95% CI-0.19 to 0.56, p=0.34), 0.57 prism diopters at 1/3 meter (95% CI 0 to 1.15, p=0.05), and 0.47 prism diopters at 1/3 meter with a +3.00 add (95% CI-0.23 to 1.17, p=0.18). Conclusions: Pupil dilation does not meaningfully affect vertical or horizontal strabismus measurements in adults. Mild variability at near in younger patients is eliminated with the use of a +3.00 add.
Investigative Ophthalmology & Visual Science, May 1, 2003
Indian Journal of Ophthalmology, 2018
The objective of this study was to determine the associations of strabismus surgery reoperation r... more The objective of this study was to determine the associations of strabismus surgery reoperation rates in a large national database of provider payments with geographic region, practice type and volume, and the availability of adjustable suture technique. Fee-for-service payments to providers for medicare beneficiaries having strabismus surgery between 2012 and 2015 were retrospectively analyzed to identify reoperations in the same calendar year. The adjustable-suture technique was considered to be available to the patient if the patient's surgeon billed for adjustable sutures. Predictors of reoperation in the same calendar year were determined by multivariable logistic regression. Availability of the adjustable suture technique was not associated with reoperation rate in multivariable analysis among 5971 patients having horizontal muscle surgery (odds ratio, [OR] 0.86, P = 0.29), 2840 patients having vertical muscle surgery (OR 0.98, P = 0.93), or 1199 patients having surgery with scarring or restriction (OR 0.86, P = 0.61). For horizontal surgery, the reoperation rate was higher in academic practices (OR 1.67), as compared with community practices, and in the South (OR 2.85) and West (OR 1.92, all P < 0.001). The reoperation rate was unchanged with surgeons in the lowest-quartile of surgical volume. Among surgeons paid for horizontal surgery, 45% of surgeons in the Northeast, the West, or Florida coded for adjustable sutures, compared with 8% of surgeons elsewhere (P < 0.001). The availability of the adjustable-suture technique was not associated with reoperation rate after strabismus surgery in this large national database. Having surgery by a lower-volume surgeon was not associated with a higher reoperation rate. The reoperation rate was higher when surgery was conducted in an academic practice, or in certain regions of the country. Adjustable sutures are largely a bicoastal practice.
American Journal of Ophthalmology, Feb 1, 2016
Purpose-To determine predictors of reoperation and abnormal binocularity outcomes (including ambl... more Purpose-To determine predictors of reoperation and abnormal binocularity outcomes (including amblyopia and diplopia) following pediatric strabismus surgery. Design-Retrospective cross-sectional study. Methods-Setting: Review of a national insurance database. Study population: Children under age 18 years having strabismus procedures between 2007 and 2013. Interventions: Adjustable or fixed suture strabismus surgery, or botulinum toxin injection. Outcome measures: Reoperation or diagnosis of abnormal binocularity in the first postoperative year. Results-Of 11,115 children having strabismus procedures, 851 (7.7%) underwent reoperation. The reoperation rate was 7.4% for fixed suture surgeries, 9.6% for adjustable suture surgeries (p=0.18), and 44.9% for botulinum injections (p<0.001). Age under 2 years was associated with higher reoperation and abnormal binocularity rates (p<0.001). For horizontal strabismus, the postoperative abnormal binocularity rate was 12.8% for fixed suture surgery and 26.5% for botulinum injection (p=0.005). Reoperation rates tended to be higher with adjustable sutures (odds ratio [OR] 1.69, 95% confidence interval [CI] 0.94 to 3.03, p=0.08), or botulinum toxin injection (OR 10.36, 95% CI 5.75 to 18.66, p<0.001) and lower with 3-or 4-muscle surgery (p=0.001). Esotropia, hyperopia, and botulinum injection were independently associated with higher rates of postoperative abnormal binocularity (p<=0.005). For vertical surgeries, predictors of reoperation were adjustable suture use (OR 2.51, p=0.10) and superior oblique surgery (OR 2.36, p<0.001). Conclusions-Adjustable sutures were not associated with a lower reoperation rate in children. Younger age, esotropia, hyperopia, and botulinum injection were associated with postoperative
Uploads
Papers by Christopher Leffler