Marc A. Tewfik

Contour interaction in amblyopia: scale selection

It has been known for some time that visual acuity in amblyopia is higher for single letters than for letters in a row (termed crowding). Early work showed that this could not be accounted for on the basis of the destructive interaction of adjacent contours (termed contour interaction), which was shown to be, in resolution units, normal in amblyopia. We have re-examined this issue using a letter stimulus that is modulated about a mean light level. This allows an examination of the effects of contrast polarity and spatial filtering within the contour interaction paradigm. We show that the majority of strabismic amblyopes that we investigated exhibit an anomalous contour interaction that, in some cases, was dependent on the contrast polarity of the flanking stimuli. Furthermore, we show that while amblyopes do select the optimum scale of analysis for unflanked stimuli, they do not select the optimum scale of analysis for flanked stimuli. For reasons that may have to do with their poorer shape discrimination, they select a non-optimal scale to process flanked stimuli.

Contour interaction in fovea and periphery

It has been known for some time that both foveal and peripheral visual acuity are higher for single letters than for letters in a row. Early work showed that this was due to the destructive interaction of adjacent contours (termed contour interaction). It has been assumed to have a neural basis, and a number of competing explanations have been advanced that implicate either high-level or low-level stages of visual processing. Our previous results for foveal vision suggested a much simpler explanation, one determined primarily by the physics of the stimulus rather than the physiology of the visual system. We show that, under conditions of contour interaction or crowding, the most relevant physical spatial-frequency band of the letter is displaced to higher spatial frequencies and that foveal vision tracks this change in spatial scale. In the periphery, however, beyond 5 degrees, the physical explanation is not sufficient. Here we show that there are genuine physiological lateral spatial interactions, which are due to changes in the spatial scale of analysis.

Long-term outcome analysis of endoscopic sinus surgery for chronic sinusitis.

Background The purpose of this study was to determine long-term subjective outcome of endoscopic sinus surgery (ESS) for chronic sinusitis (CS) and to evaluate prognostic indicators for surgical treatment failure. Methods This is a prospective study of patients who underwent ESS for CS. Symptom assessment was performed using a visual analog scale at a pretreatment interview and then at regular intervals post-ESS for up to a 3-year period. The indicators for symptom scoring were nasal obstruction, facial pain, postnasal drip, anterior discharge, and anosmia/hyposmia. Results Data analysis indicates that ESS improves symptom scoring early on, but the effects begin to dissipate over time. Anosmia/ hyposmia is the most severe symptom overall for all patient subgroups and recurs to a greater degree 3 years postoperatively in Samters Triad sufferers (p = 0.006), asthmatic patients (p = 0.002), and those with a worse CT scan at presentation (p = 0.04). In addition, Triad sufferers who complain of nasal obstruction and anterior nasal discharge have a significant recurrence of their symptoms postoperatively (p = 0.04 and 0.001, respectively). Conclusion Individuals must be warned that ESS may not be a long-term solution for CS because of its chronic nature. Patients are relieved of their symptoms initially; however, these tend to recur over a 3-year period. Samters Triad is the strongest determinant of long-term treatment failure. Asthma also is a determinant of treatment failure, which lends credence to the notion of combined airway disease. Allergy was not a strong determinant of treatment failure in our study.

Lateral neck radiography versus direct video rhinoscopy in assessing adenoid size.

OBJECTIVE To evaluate the usefulness of adynamic lateral neck radiographs and dynamic video rhinoscopy in assessing adenoid size and the relationship of these methods to associated symptoms and thus the severity of the disease. METHODS Children with suspected adenoid hypertrophy underwent standard lateral neck soft tissue radiographs: the percentage of airway occlusion, adenoid to nasopharynx (AN) ratio, airway to soft palate ratio, and adenoid thickness were assessed by a radiologist. The percentage of airway closure was assessed by direct fibre-optic rhinoscopy in an ear, nose, and throat clinic. Associated clinical symptoms were assessed by parents using a standardized questionnaire, evaluating the severity of symptoms (snoring, sleep apnea, mouth breathing, and otitis media) to give a total symptom score out of 16. RESULTS Nonparametric statistical analysis using Spearmans correlation coefficients was performed on 32 patients. There was a weak correlation, which approaches significance, between the percentage of airway occlusion assessed by fibre-optic rhinoscopy and the total symptom score (r = .344, p = .054). However, this correlation becomes significant when the frequency of otitis media is omitted (r = .367, p = .039). There was also a significant correlation between airway occlusion assessed by rhinoscopy and the percentage of airway occlusion as determined by lateral neck radiography (r = .431, p = .014). There was no correlation between any of the measurements taken by lateral soft tissue neck radiography and total symptom score. CONCLUSION Dynamic video rhinoscopy is more accurate at assessing adenoid hypertrophy, and the percentage of airway occlusion, as estimated by video rhinoscopy, is better correlated to the severity of symptoms than are values obtained by lateral neck radiography.

Proteomics of nasal mucus in chronic rhinosinusitis

Background Chronic rhinosinusitis (CRS) is among the three most common chronic diseases in North America. The area of proteomics research is providing tremendous insight into the mechanisms of a variety of physiological processes and disease states. The purpose of this study was to evaluate qualitative and quantitative differences in protein content of nasal mucus in patients with chronic hypertrophic sinusitis with nasal polyposis when compared with control subjects. Methods A case-control study was performed in a tertiary academic center. Nasal mucus was collected from four patients with CRS and nasal polyposis as well as four control subjects. The protein content was digested using proteolytic enzymes, labeled with iTRAQ reagents, and subjected to mass spectrometry (MS) analysis. Results A total of 35 proteins were identified, many of which were related to innate and acquired immunity. Lysozyme C precursor was found to be down-regulated by a ratio (R) of 0.65 (p = 0.016) in CRS patients, as was Clara cell phospholipid-binding protein (R = 0.23; p = 0.0018), and antileukoproteinase 1 (R = 0.47; p < 0.0001). A detailed analysis and characterization of the protein isolates is outlined. Conclusion The field of proteomics has great potential in leading to a better understanding of the mechanism of the disease process in CRS. Differences in the expression of proteins related to regulation of immune cells and mediators merit additional investigation.

Polymorphisms in interleukin‐1 receptor‐associated kinase 4 are associated with total serum IgE

Background:  Serum immunoglobulin E (IgE) level is recognized to be under strong genetic control, but the causal and susceptibility genes remain to be identified. We sought to investigate the association between single nucleotide polymorphisms (SNPs) in the Toll‐like receptor (TLR) signaling pathway and total serum IgE level.

The McGill simulator for endoscopic sinus surgery (MSESS): a validation study

BackgroundEndoscopic sinus surgery (ESS) is a technically challenging procedure, associated with a significant risk of complications. Virtual reality simulation has demonstrated benefit in many disciplines as an important educational tool for surgical training. Within the field of rhinology, there is a lack of ESS simulators with appropriate validity evidence supporting their integration into residency education. The objectives of this study are to evaluate the acceptability, perceived realism and benefit of the McGill Simulator for Endoscopic Sinus Surgery (MSESS) among medical students, otolaryngology residents and faculty, and to present evidence supporting its ability to differentiate users based on their level of training through the performance metrics.Methods10 medical students, 10 junior residents, 10 senior residents and 3 expert sinus surgeons performed anterior ethmoidectomies, posterior ethmoidectomies and wide sphenoidotomies on the MSESS. Performance metrics related to quality (e.g. percentage of tissue removed), efficiency (e.g. time, path length, bimanual dexterity, etc.) and safety (e.g. contact with no-go zones, maximum applied force, etc.) were calculated. All users completed a post-simulation questionnaire related to realism, usefulness and perceived benefits of training on the MSESS.ResultsThe MSESS was found to be realistic and useful for training surgical skills with scores of 7.97 ± 0.29 and 8.57 ± 0.69, respectively on a 10-point rating scale. Most students and residents (29/30) believed that it should be incorporated into their curriculum. There were significant differences between novice surgeons (10 medical students and 10 junior residents) and senior surgeons (10 senior residents and 3 sinus surgeons) in performance metrics related to quality (p < 0.05), efficiency (p < 0.01) and safety (p < 0.05).ConclusionThe MSESS demonstrated initial evidence supporting its use for residency education. This simulator may be a potential resource to help fill the void in endoscopic sinus surgery training.

Powered Endoscopic Dacryocystorhinostomy With Selective Stenting

To compare surgical outcomes of primary powered endoscopic dacryocystorhinostomy (DCR) with selective or routine silicone stenting in anatomic and functional nasolacrimal duct obstruction (NLDO).

Ten Pearls for Safe Endoscopic Sinus Surgery

Endoscopic sinus surgery is an excellent treatment option in the management of medically refractory chronic rhinosinusitis. Continual refinements in endoscopic technique are simultaneously allowing an expanded range of applications and a lower rate of complications for this kind of surgery. However, the potential for serious complications is ever present. The sinus surgeon must always be aware of this, and actively seek to identify high-risk situations preoperatively. The technical points presented in this article should be followed to minimize the risk of complications.

Quantitative proteomics of nasal mucus in chronic sinusitis with nasal polyposis.

BACKGROUND Proteomics has been used as a tool for identification of the protein content of nasal mucus in diseased and healthy subjects. Thirty-five proteins in both chronic rhinosinusitis (CRS) and control groups were identified in a previous study by our group using conventional mass spectrometry analysis. Ten of these proteins were related to innate and acquired immunity and showed differences in expression between the two groups. OBJECTIVE To investigate the quantitative differential expression of specific nasal mucus proteins previously identified by our group using multiple reaction monitoring (MRM) mass spectrometry in patients with CRS with nasal polyposis compared with normal subjects. METHODS In a prospective case control study, nasal mucus from patients and control subjects was collected, desalted, resolubilized, and digested using proteolytic enzymes. Previously identified nasal mucus proteins with differential expression in CRS patients were targeted and quantitatively measured using MRM mass spectrometry. RESULTS Analysis of 12 samples (6 patients and 6 controls) identified 7 of the 10 targeted proteins, many of which were related to innate and acquired immunity. Quantitative analysis showed differential expression in CRS patients compared with control subjects. A detailed analysis and characterization of the protein isolates is outlined. CONCLUSION This is the first proteomics study of nasal mucus in CRS with polyposis using the MRM technique. The findings suggest that innate and acquired immunity may play a role in the pathophysiology of CRS. Future steps in evaluating the protein characteristics of the mucus of CRS patients are aimed at developing biomarkers and potentially targeted therapies.