Detection of Parkinson's Disease Through Automated Pupil Tracking of the Post-illumination Pupillary Response

Parkinson's disease (PD) is one of the most common neurodegenerative disorders, but it is often diagnosed after the majority of dopaminergic cells are already damaged. It is critical to develop biomarkers to identify the disease as early as possible for early intervention. PD patients appear to have an altered pupillary response consistent with an abnormality in photoreceptive retinal ganglion cells. Tracking the pupil size manually is a tedious process and offline automated systems can be prone to errors that may require intervention; for this reason in this work we describe a system for pupil size estimation with a user interface to allow rapid adjustment of parameters and extraction of pupil parameters of interest for the present study. We implemented a user-friendly system designed for clinicians to automate the process of tracking the pupil diameter to measure the post-illumination pupillary response (PIPR), permit manual corrections when needed, and continue automation after correction. Tracking was automated using a Kalman filter estimating the pupil center and diameter over time. The resulting system was tested on a PD classification task in which PD subjects are known to have similar responses for two wavelengths of light. The pupillary response is measured in the contralateral eye to two different light stimuli (470 and 610 nm) for 19 PD and 10 control subjects. The measured Net PIPR indicating different responsiveness to the wavelengths was 0.13 mm for PD subjects and 0.61 mm for control subjects, demonstrating a highly significant difference (p < 0.001). Net PIPR has the potential to be a biomarker for PD, suggesting further study to determine clinical validity.

Conjunctival microvascular hemodynamics following vaso-occlusive crisis in sickle cell disease

Painful vaso-occlusive crisis (VOC) is the clinical hallmark of sickle cell disease (SCD). Microcirculatory hemodynamic changes following painful VOC may be indicative of future development of VOC events in subjects with SCD. The purpose of the present study was to determine alterations in conjunctival microvascular hemodynamics during non-crisis state in SCD subjects with a history of VOC. Conjunctival microcirculation imaging was performed to measure conjunctival diameter (D) and axial blood velocity (V) in 10 control and 30 SCD subjects. SCD subjects were categorized into two groups based on their history of VOC within a 2-year period before imaging (with or without VOC-H) and also based on whether there was progression in the rate of VOCs during a 2-year period following imaging as compared to before imaging (with or without VOC-P). Conjunctival V was significantly higher in SCD subjects with VOC-H than in both control subjects and SCD subjects without VOC-H (P≤0.03). Conjunctival V was also significantly higher in SCD subjects with VOC-P compared with control subjects and SCD subjects without VOC-P (P≤0.03). Assessment of the conjunctival microcirculation may be useful for understanding hemodynamic changes that lead to VOC events in SCD subjects.

Dissociations of the Fluocinolone Acetonide Implant: The Multicenter Uveitis Steroid Treatment (MUST) Trial and Follow-up Study

PURPOSE

To describe fluocinolone acetonide implant dissociations in the Multicenter Uveitis Steroid Treatment (MUST) Trial.

DESIGN

Randomized clinical trial with extended follow-up.

METHODS

Review of data collected on the first implant in the eye(s) of participants. Dissociation was defined as the drug pellet no longer being affixed to the strut and categorized as spontaneous or surgically related.

RESULTS

A total of 250 eyes (146 patients) had at least 1 implant placed. Median follow-up time after implant placement was 6 years (range 0.5-9.2 years). Thirty-four dissociations were reported in 30 participants. There were 22 spontaneous events in 22 participants; 6-year cumulative risk of a spontaneous dissociation was 4.8% (95% confidence interval [CI]: 2.4%-9.1%). The earliest event occurred 4.8 years after placement. Nine of 22 eyes with data had a decline in visual acuity ≥5 letters temporally related to the dissociation. Thirty-nine implant removal surgeries were performed, 33 with replacement. Twelve dissociations were noted during implant removal surgeries in 10 participants (26%, 95% CI 15%-48%); 5 of these eyes had a decline in visual acuity ≥5 letters after surgery. The time from implant placement to removal surgery was longer for the surgeries at which dissociated implants were identified than for those without one (5.7 vs 3.7 years, P < .001). Overall, visual acuity declined 15 or more letters from pre-implant values in 22% of affected eyes; declines were frequently associated with complications of uveitis or its treatment.

CONCLUSION

There is an increasing risk of dissociation of Retisert implants during follow-up; the risk is greater with removal/exchange surgeries, but the risk of both spontaneous and surgically related events increases with longevity of the implants. In 22% of affected eyes visual acuity declined by 15 letters. In the context of eyes with moderate to severe uveitis for years, this rate is not unexpected.

Conjunctival microvascular haemodynamics in sickle cell retinopathy

PURPOSE

To determine alterations in bulbar conjunctival microvascular haemodynamics in sickle cell retinopathy (SCR) subjects with focal macular thinning (FMT).

METHODS

Conjunctival microcirculation imaging and spectral domain optical coherence tomography (SD-OCT) were performed in 22 subjects (eyes) diagnosed with SCR. Based on evaluation of SD-OCT retinal thickness maps, eyes were assigned to one of the two groups: with or without FMT. Conjunctival venular diameter and axial blood velocity were measured in multiple venules in each eye by customized image analysis algorithms. Measurements were then categorized into two vessel size groups (vessel size 1 and 2) and compared between FMT groups. A Pearson correlation coefficient was computed to assess the relationship between retinal thickness and axial blood velocity.

RESULTS

Mean age, haematocrit, sickle cell haemoglobin type and median retinopathy score were not significantly different between the two groups (p ≥ 0.1). Retinal thickness in parafoveal and perifoveal temporal subfields was significantly lower in eyes with FMT as compared to eyes without FMT (p ≤ 0.04). There was a significant effect of FMT on axial blood velocity (p = 0.04), while the effect of vessel size was not significant (p = 0.4). In vessel size 1, axial blood velocity was lower in eyes with FMT than in eyes without FMT (p = 0.03), while in vessel size 2, there was no statistically significant difference between FMT groups (p = 0.1). In vessel size 1, there was a significant positive correlation between axial blood velocity and retinal thickness in the perifoveal (r = 0.48, p = 0.02) and parafoveal (r = 0.43, p = 0.04) temporal subfields.

CONCLUSION

Conjunctival axial blood velocity in small venules is reduced in SCR subjects with focal macular thinning.

Human bulbar conjunctival hemodynamics in hemoglobin SS and SC disease

The known biophysical variations of hemoglobin (Hb) S and Hb C may result in hemodynamic differences between subjects with SS and SC disease. The purpose of this study was to measure and compare conjunctival hemodynamics between subjects with Hb SS and SC hemoglobinopathies. Image sequences of the conjunctival microcirculation were acquired in 9 healthy control subjects (Hb AA), 24 subjects with SC disease, and 18 subjects with SS disease, using a prototype imaging system. Diameter (D) and blood velocity (V) measurements were obtained in multiple venules of each subject. Data were categorized according to venule caliber by averaging V and D for venules with diameters less than (vessel size 1) or greater than (vessel size 2) 15 µm. V in vessel size 2 was significantly greater than V in vessel size 1 in the AA and SS groups (P ≥ 0.009), but not in the SC group (P = 0.1). V was significantly lower in the SC group as compared to the SS group (P = 0.03). In AA and SS groups, V correlated with D (P ≤ 0.005), but the correlation was not statistically significant in the SC group (P = 0.08). V was inversely correlated with hematocrit in the SS group for large vessels (P = 0.03); however, no significant correlation was found in the SC group (P ≥ 0.2). Quantitative assessment of conjunctival microvascular hemodynamics in SS and SC disease may advance understanding of sickle cell disease pathophysiology and thereby improve therapeutic interventions.

Feasibility of conjunctival hemodynamic measurements in rabbits: reproducibility, validity, and response to acute hypotension

OBJECTIVE

To evaluate the feasibility of conjunctival hemodynamic measurements based on assessment of reproducibility, validity, and response to acute hypotension.

METHODS

Image sequences of the conjunctival microvasculature of rabbits were captured using a slit lamp biomicroscope under a steady-state condition, after topical administration of phenylephrine, and after intravenous administration of esmolol. Venous hemodynamic parameters (diameter, blood velocity, blood flow, and wall shear stress) were derived.

RESULTS

Conjunctival venous diameters ranged from 9 to 34 μm and blood velocities ranged from 0.08 to 0.95 mm/s. Coefficients of variation of venous diameter and blood velocity measurements were, on average, 6% and 14%, respectively. Automated and manual measurements of venous diameter and velocity were highly correlated (R = 0.97; p < 0.001; n = 16). With phenylephrine administration, diameter and velocity were reduced by 21% and 69%, respectively. Following esmolol administration, blood pressure was reduced with a concomitant decrease in velocity, followed by recovery to baseline. Venous blood velocity, flow, and WSS were correlated with blood pressure (R ≥ 0.52; p ≤ 0.01).

CONCLUSIONS

The feasibility of quantifying alterations in microvascular hemodynamics in the bulbar conjunctiva was established. The method is of potential value in evaluating microcirculatory hemodynamics related to cardiovascular function.

Immediate-release and extended-release formulations of second-generation antidepressants for the treatment of major depressive disorder in adults

Introduction

Extended-release formulations of antidepressants have been marketed as a strategy to increase patient adherence. Changes in the formulation of drugs, however, could be related to changes in efficacy and tolerability. Among second-generation antidepressants, bupropion, fluoxetine, mirtazapine, paroxetine, and venlafaxine are available in immediate- and extended-release formulations.

Objectives

To compare the efficacy, tolerability, and adherence of immediate- versus extended-release formulations of second-generation antidepressants for the treatment of major depressive disorder (MDD) in adults.

Aim

To provide an evidence base for clinicians when choosing immediate- or extended-release formulations of antidepressants for the treatment of MDD.

Methods

We conducted a comparative effectiveness review for the U.S. Agency for Healthcare Research and Quality searching PubMed, EMBASE, The Cochrane Library, and the International Pharmaceutical Abstracts up to May 2010. Two people independently reviewed the literature, abstracted data, and rated the risk of bias.

Results

Six RCTs and one observational study provided evidence about the comparative efficacy, tolerability, and adherence of bupropion SR (sustained release) versus bupropion XL (extended release), fluoxetine daily vs. fluoxetine weekly, paroxetine IR (immediate release) versus paroxetine CR (continuous release), and venlafaxine IR versus venlafaxine XR (extended release). Overall, no substantial differences in efficacy and safety could be detected. Open-label and observational evidence indicated better adherence for bupropion XL and fluoxetine weekly than for immediate-release medications. No differences in adherence could be detected between paroxetine IR and paroxetine CR.

Conclusions

Our findings indicate similar efficacy and tolerability between immediate- and extended-release formulations. Whether extended-release formulations lead to better adherence remains unclear.

Quantitative assessment of conjunctival microvascular circulation of the human eye

Accessibility to the bulbar conjunctival microvasculature provides a means to assess blood supply to the cerebral cortex and thus optimize therapeutic interventions designed to prevent or reduce the risk of cerebral vascular disease and stroke. The feasibility of a method for quantitative measurements of conjunctiva blood vessel diameter, blood velocity, and flow in the human eye is reported. The method is based on slit lamp biomicroscope digital imaging coupled with a space time image analysis technique. A sequence of conjunctiva microvasculature images was captured at a rate of 50 Hz. The images were analyzed to determine blood vessel diameter, velocity and flow. Blood vessel diameter measurements ranged between 8.7 and 24.3 microns, with a mean value of 15.5 microns. Blood flow rate ranged between 27.3 and 296.9 pl/s, with a mean value of 111.8 pl/s. The relationship between blood flow and vessel diameter was fit with a power law curve (R=0.87). The application of this technique for in vivo quantitative assessment of blood flow dynamics has potential to impact diagnosis and monitoring of various cardiovascular and blood disorders.