Kaivon Pakzad-Vaezi

The feedback correct-related positivity: Sensitivity of the event-related brain potential to unexpected positive feedback

The N200 and the feedback error-related negativity (fERN) are two components of the event-related brain potential (ERP) that share similar scalp distributions, time courses, morphologies, and functional dependencies, which raises the question as to whether they are actually the same phenomenon. To investigate this issue, we recorded the ERP from participants engaged in two tasks that independently elicited the N200 and fERN. Our results indicate that they are, in fact, the same ERP component and further suggest that positive feedback elicits a positive-going deflection in the time range of the fERN. Taken together, these results indicate that negative feedback elicits a common N200 and that modulation of fERN amplitude results from the superposition on correct trials of a positive-going deflection that we term the feedback correct-related positivity.

Comparative analysis of repeatability of manual and automated choroidal thickness measurements in nonneovascular age-related macular degeneration.

PURPOSE We compared the reproducibility and mutual agreement of the subfoveal choroidal thickness measurements by expert raters and an automated algorithm in enhanced depth imaging optical coherence tomography (EDI-OCT) images of eyes with nonneovascular age-related macular degeneration (AMD). METHODS We recruited 44 patients with nonneovascular AMD and EDI-OCT images were acquired. Subfoveal choroidal thickness was measured manually by two expert raters and automatically by a graph-cut-based algorithm. Drusen area was measured using the automated software (version 6) of Cirrus SD-OCT. The manual and automated choroidal thickness measurements were compared in reproducibility, mutual agreement, and correlation with drusen area. RESULTS The mean subfoveal choroidal thickness was 246 ± 63 μm for the first rater, 214 ± 68 for the second rater, and 209 ± 53 for the automated algorithm. Intraclass correlation coefficients (ICC) and 95% confidence intervals (CI) were 0.96 (CI 0.94-0.98) between the raters, 0.85 (CI 0.77-0.90) between the first rater and the automated algorithm, and 0.84 (CI 0.75-0.89) between the second rater and the automated algorithm. Repeat scan measurement ICCs were 0.91 (CI 0.86-0.94) for the first rater, 0.96 (CI 0.94-0.97) for the second rater, and 0.87 (CI 0.80-0.92) for the automated algorithm. Manual and automated measurements were correlated with drusen area. CONCLUSIONS The automated algorithm generally yielded smaller choroidal thickness than the raters with a moderate level of agreement. However, its repeat scan measurement repeatability was comparable to that of the manual measurements. The mean difference between the raters indicated possible biases in different raters and rating sessions. The correlation of the automated measurements with the drusen area was comparable to that of the manual measurements. Automated subfoveal choroidal thickness measurement has potential use in clinical practice and clinical trials, with possibility for reduced time and labor cost.

Optical coherence tomography-based correlation between choroidal thickness and drusen load in dry age-related macular degeneration.

Purpose: Spectral domain optical coherence tomography can be used to measure both choroidal thickness and drusen load. The authors conducted an exploratory study using spectral domain optical coherence tomography to determine if a correlation between choroidal thickness and drusen load exists in patients with dry age-related macular degeneration. Methods: Forty-four patients with dry age-related macular degeneration were recruited. The drusen area and volume were determined using the automated software algorithm of the spectral domain optical coherence tomography device, and choroidal thickness was measured using enhanced depth imaging. Correlations were determined using multivariable and univariable analyses. Results: The authors found an inverse correlation between choroidal thickness and drusen load (r = −0.35, P = 0.04). Drusen load was also correlated with visual acuity (r = 0.32, P = 0.04). A correlation between choroidal thickness and visual acuity was suggested (r = −0.22, P = 0.21). Conclusion: Spectral domain optical coherence tomography can be used to assess the correlation between drusen load and choroidal thickness, both of which show a relationship with visual acuity. The measurement of these outcomes may serve as important outcome parameters in routine clinical care and in clinical trials for patients with dry age-related macular degeneration.

Optical coherence tomography in the diagnosis and management of uveitis

Optical coherence tomography (OCT) has become an integral tool in the imaging of numerous diseases of the posterior segment. The diagnostic investigation of infectious and noninfectious uveitic conditions often requires multiple imaging modalities in the appropriate clinical context. Modern OCT technology has proved useful not only in the diagnostic investigation of these conditions, but also in monitoring of their clinical course and therapeutic response. Inflammation-induced changes at the level of the retina, retinal pigment epithelium, and choroid can now easily be identified in these conditions using OCT. Prognostic information on visual acuity outcome can also be estimated based on OCT findings. Numerous OCT findings have been described in the setting of the various uveitides. Although none of these findings appear to be pathognomonic for diagnosis of specific uveitic syndromes, in the appropriate clinical context they can add a great deal of information in the diagnosis and management of uveitis.

A randomized study comparing the efficacy of bevacizumab and ranibizumab as pre-treatment for pars plana vitrectomy in proliferative diabetic retinopathy.

BACKGROUND AND OBJECTIVE To compare intravitreal bevacizumab versus ranibizumab as adjuvant treatment prior to pars plana vitrectomy (PPV) in proliferative diabetic retinopathy (PDR) with respect to parameters of surgical complexity. PATIENTS AND METHODS Prospective, randomized, double-masked pilot study of patients requiring PPV for nonclearing vitreous hemorrhage or tractional retinal detachment (TRD) secondary to PDR. Patients were randomized to receive either intravitreal bevacizumab or ranibizumab at standard doses 1 week preoperatively. Measured parameters included total surgical time, presence of TRD, intraoperative bleeding, iatrogenic retinal breaks, and use of endolaser and endodiathermy or silicone oil. RESULTS A total of 29 patients were recruited. For surgical parameters, there were no statistically significant differences between the groups in the univariate analyses. Multivariable analysis showed no statistically significant difference for total surgical time. CONCLUSION This pilot study suggests that intravitreal bevacizumab and ranibizumab are equivalent as surgical adjuvants when used as pre-treatment in patients with PDR undergoing PPV.

Conventional and Diffusion-Weighted Magnetic Resonance Imaging Findings in a Pediatric Patient with a Posterior Fossa Brain Tumor and Papilledema

We present a case report of a 21-month-old female patient to highlight magnetic resonance (MR) imaging findings associated with papilledema in a pediatric patient with an intracranial tumor. The MR findings included optic disc elevation, dilated perioptic subarachnoid spaces, optic nerve tortuosity and restricted diffusion in the optic nerve heads, all of which resolved upon resolution of raised intracranial pressure (ICP) and papilledema. The case demonstrates that both conventional and diffusion-weighted MR imaging findings can detect the presence, and follow posttreatment resolution, of increased ICP and papilledema in a pediatric tumor patient. The postoperative resolution of optic disc elevation clearly indicates the intracranial tumor etiology.

The corneal ulcer one-touch study: a simplified microbiological specimen collection method.

PURPOSE To determine if a new, single-sample device (ESwab; Copan Diagnostics, Inc) can simplify the traditional multi-sample approach to specimen collection in infectious keratitis. DESIGN Prospective, diagnostic test evaluation. METHODS In this institutional study, patients with suspected infectious keratitis meeting traditional criteria for diagnostic corneal specimen collection and culture were randomized to the order of first specimen collection method: ESwab or a sample directly plated for growth on chocolate agar. This was followed by standard samples for blood agar, Gram stain, Sabouraud agar, thioglycolate broth, and brain heart infusion broth in all cases. The specimens collected using the 2 approaches were analyzed separately by the laboratory in a masked fashion. The main outcome measure was positive growth on cultured media. RESULTS Eighty-one eyes from 80 consecutive patients were sampled. Culture positivity rate for the multi-sample method and ESwab was 70% and 69%, respectively, with a 75% agreement rate. ESwab sensitivity was 84% (95% confidence interval [CI]: 72%-93%), with a specificity of 67% (95% CI: 45%-84%). Positive and negative predictive values of the ESwab were 86% (95% CI: 74%-94%) and 64% (95% CI: 43%-82%), respectively. There was no difference in positive culture reports with respect to the order of specimen collection technique used. CONCLUSIONS The single-sample ESwab method is a more accessible and less cumbersome approach to corneal culturing for ophthalmologists, particularly those in the community setting who do not have access to the full set of traditional culture materials. Culture results using this single-sample approach were comparable to the multi-sample method.

Comparison of ophthalmic training in 6 English-speaking countries

OBJECTIVE To compare key characteristics of ophthalmology training programs in 6 different English-speaking countries: Australia, New Zealand, Canada, Ireland, the United Kingdom, and the United States. PARTICIPANTS Seven ophthalmologists with personal knowledge of all 6 systems contributed. METHODS The main features examined were career pathway, duration of training, surgical training, governing bodies, and examination structure. Data were collected from the literature, online resources, and personal experience. RESULTS Several differences were highlighted, including length of training (ranging from 4 to 9 years after medical school), number of surgical procedures such as cataracts (ranging from minimum 86 to approximately 600), and structure of fellowship training. CONCLUSIONS As trainees increasingly seek international experience to enhance their knowledge and skills, the similarities and differences between training programs in different countries have become more relevant. Some of these differences may reflect differing needs of different patient populations and different healthcare delivery systems across the globe. However, these differences should also prompt educators to more carefully scrutinize their own training system and search for potential improvements.